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gr8r-x
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 08:32 Go to previous messageGo to next message
I'll just dump my 2 cents worth right now...

Why not just have the SC and turbo plumbed up to a 1-way valve? That way, if the SC is making more boost than the turbo, it'll close the valve towards it, then when the turbo boosts up, it'll close off the SC valve... You'll still have ot clutch the SC at high RPM, but it would have the desired effect.

Or, I could be completely wrong, new to the whole world of parallel-charging. Smile


Edit: Now that I think about it, it'd work well for acceleration, but decel/gear changes wouldn't work so well. Confused

[Updated on: Mon, 22 August 2005 08:35]

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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 08:57 Go to previous messageGo to next message
hmm,.. i'm not sure abotu how hot air will get.... when it is almost entirely recirculating (and about to stop) the inlet air and outlet air are same pressure (ie, both sides are compressed).. so maybe not much heat.. but then again, maybe the pulsations (which cause the heat anyway) will still put heat in..
it would be just as easy to recirculate the air after the IC as well...

there may still be a need for a wastegate, but then again, if you size the turbo right, you may not need one...

the thougth is that if you want it to come on between 4000-5000, and you already have a motor pumping 12psi, you effectively have maybe a 3L motor turnbing the turbo.. and since the compressor is not actually flowing huge amounts of air, (and we are no longer relying on the compressors output to spool the turbine) we can have a much much larger turbine than usual, so it won't choke up high.. a small wastegate would be good insurance and allow some boost control tho.


Tricky, thats how i see it Smile


with just a one way valve only, since the SC is PD, it will always provide a constant volume unless you throttle it... so then when you shut it off, you have a sudden decrease in air volume and thus pressure. if you keep SC spinning, it would work fine. but i wanna shut it off Very Happy.

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Mr DOHC
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 09:51 Go to previous messageGo to next message
this is the most insightful thread i have ever rad on toymods, shame on u all Rolling Eyes

have u thought about a few idle speed control motors {stepper motors} to control the throttles

heat in freewheeling SC:
hmmmm, what a pop off valve to vent nay hot air once the throttles are closed
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tricky
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 09:55 Go to previous messageGo to next message
oldcorollas wrote on Mon, 22 August 2005 18:57

it would be just as easy to recirculate the air after the IC as well...


this could be even easier, depending on where you stick the SC bracket. So basically you could have T3 after the IC? There could be some weird convection interference flow issues with feeding cooled air back to the hot side, but the feedback transition, in reality would probably be pretty quick.

Quote:

there may still be a need for a wastegate, but then again, if you size the turbo right, you may not need one...


fo shizzle ma nizzle! I'd be putting one in whatever I was doing. Good, cheap insurance.

Quote:


if you keep SC spinning, it would work fine. but i wanna shut it off .


I wonder how T1 would stand up? at full turbo boost, there'd be some pretty industrial strength sucking going on.

In reality, the parasitic losses incurred in spinning the SC past it's efficiency range would probably outweigh the advantage of using a huge turbo for unrestricted high RPM use. Not clutching the SC would all but defeat the purpose of twincharging.
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Lukass
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 11:59 Go to previous messageGo to next message
Maybe the blow off valve reference is confusing. I'm thinking along the lines of a bleed valve, this does all your boost controlling. Approaching the end of your superchargers efficiency (around 12-14 maybe) you need the turbo to be producing that as well to make the transition smooth. This excess is bled off until the SC shuts off. To make your truly linear boost curve this bleed valve needs to be smart enough to work off RPM. The turbo can produce as much boost as it wants, you just bleed off what you don't need.
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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 12:24 Go to previous messageGo to next message
Mr DOHC wrote on Mon, 22 August 2005 19:51

this is the most insightful thread i have ever rad on toymods, shame on u all Rolling Eyes

have u thought about a few idle speed control motors {stepper motors} to control the throttles

heat in freewheeling SC:
hmmmm, what a pop off valve to vent nay hot air once the throttles are closed


hmm... steppers and electronics would be absolutely awesome, but i'm afraid i have NFI how to set up the control side of it..

and i want a system that is easy for anyone to set up.. not just nerds Razz (like me Wink )... actually, MS2 has a stepper controller onboard.. would be easy to change the code (as it's in C... well.. for a nerd Razz )

once all throttles are closed?? there has to be a fully sik blowoff valve somewhere, that operates in the normal manner..

it would be relaitively easy to measure the rate of the air heating up using either a conventional air temp sensor (the camira ones react fairly quickly) or an unsheathed K type thermocouple... or even a precision temp sensor (LM35DZ??)

you could suck a loss and vent some of the recirculated air.. but if it recirculates after the IC (to keep SC cooler) then not much point.. hmmmm hmmmmmmmmmm
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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 12:38 Go to previous messageGo to next message
Lukass wrote on Mon, 22 August 2005 21:59

Maybe the blow off valve reference is confusing. I'm thinking along the lines of a bleed valve, this does all your boost controlling. Approaching the end of your superchargers efficiency (around 12-14 maybe) you need the turbo to be producing that as well to make the transition smooth. This excess is bled off until the SC shuts off. To make your truly linear boost curve this bleed valve needs to be smart enough to work off RPM. The turbo can produce as much boost as it wants, you just bleed off what you don't need.


sorry, but i consider any bled off air to be wasted energy.. you had to use energy to make it, so you may as well keep it Wink

you could do it that way tho... but you have to have a bleed valve that can bleed off the entire contents that the SC processes... lets see... at 1 bar boost, (on 1.6L) thats 1.6L per engine rev... sayy 5000rpm.. 8000L of air per minute. thats a fair bit of air.....

i think by recirculating the air, with the SC shutdown system regulated by manifold pressure, you get to kep the air, and the transition is smooth.. it's kinda self-regulating.. if it shuts the SC down too much, pressur edrops, and the SC throttle opens up again.. etc..

regarding last point, it's not so much as what the turbo wants, as that we want to use every last bit of air.... no point doing all this if you are not going to run it to the ragged edges of staying together Evil or Very Mad the only time i forsee that you would want to bleed off any air is during gearchanges... even during cruise, if you can recirculate air the turbo is pushing, back thru the SC, (maybe in this case T1 and T3 could be seperated slightly??) combined with wastgate, you will never need to bleed any air except on quickly closed throttle
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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 12:46 Go to previous messageGo to next message
tricky wrote on Mon, 22 August 2005 19:55

this could be even easier, depending on where you stick the SC bracket. So basically you could have T3 after the IC? There could be some weird convection interference flow issues with feeding cooled air back to the hot side, but the feedback transition, in reality would probably be pretty quick.

I wonder how T1 would stand up? at full turbo boost, there'd be some pretty industrial strength sucking going on.

In reality, the parasitic losses incurred in spinning the SC past it's efficiency range would probably outweigh the advantage of using a huge turbo for unrestricted high RPM use. Not clutching the SC would all but defeat the purpose of twincharging.


hmmm.... well, you are feeding probably hotter air than ambient, to back before the SC... so you have IC cooled air mixing with ambient air, so it should be ok i think.. at worst, the hot air takes up more volume and the SC has less drag as it is moving less mass of air? yeah, i think even if the air had to go past the IC... when the turbo is boosting, the IC and manifold already are full of compressed air, so it is just the distance from T3 to the SC inlet that is an issue..... if you think of a 4AGZE, the SC sits below the inlet manifold anyway, so the pipe may only be 20cm long.... hmmmm neat!!!

well. the good thing about vacuum is that there is a limit.. ie 1 atmosphere = 14.7psi... if you had a sayyyy.. 60mm throttle.. thats.. 4.38sq" = 64lbs = 29kg of force on the throttle... hmmmmmm would you wanna regularly load a throttle shaft with 29kg??? would it bend the shaft?? more importantly, would it casue it to stick???? that could be a serious issue!!i'm glad you brought it up... Shocked

totally agreed on last point... there still is a mechanical limit to what a motor can handle.... and every bit of friction or losses savd means more RWkW Very Happy mmm kW

[Updated on: Tue, 23 August 2005 07:57]

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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Mon, 22 August 2005 12:54 Go to previous messageGo to next message
Mr DOHC wrote on Mon, 22 August 2005 19:51

this is the most insightful thread i have ever rad on toymods, shame on u all Rolling Eyes





oh yeah.. it's about time to start taking toymods back to the good 'ol (boys) days where tech was actually technical and all these conversions and mods were thrashed out before a spanner turned...




ok it wasn't really like that Razz, but a good discussion on a fundamental level is a good thing to have from time to time.. gets ppl thinking

[Updated on: Tue, 23 August 2005 07:31]

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Henn
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 01:01 Go to previous messageGo to next message
tricky wrote on Mon, 22 August 2005 19:55

oldcorollas wrote on Mon, 22 August 2005 18:57

it would be just as easy to recirculate the air after the IC as well...

There could be some weird convection interference flow issues with feeding cooled air back to the hot side,

The convection effects would be SFA, things would get mixed up and get to the same temperature quick in any case. Plus the effect would be negligible compared to the other things happening.

And yes, the good thing about vacuum is that you can't get more than 1bar below atmospheric, so there is a limit to how much you can suck. Whereas there is no limit to pressure so you can blow as hard as you like. So it is dangerous having throttles after turbo/SC, but before they are pretty safe.

I think the worries about heat buildup of the air circulating in the inlet is not so important, if you are driving a car as it should be driven it will be sucked into the engine quick smart. Plus a freewheeling SC will add very little heat.

Hen

PS, yes it is good to see a tech thread that actually taxes the brain and has a solid basis rather than starting with "my cousin said..."
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Henn
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 01:04 Go to previous messageGo to next message
PS I am a fair nerd (yes, it's pretty bad, Eng and Comp Sci degrees) so I get into the whole electronics side of things. Plus I have an uncle who is a total guru and sets me straight if I ever get too stuck. So doing it with fly by wire throttles may be possible

Hen
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Merudo
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 01:28 Go to previous messageGo to next message
Henn wrote on Mon, 22 August 2005 16:31

Superchargers get very inefficient once they start spinning too fast. This puts a big drain on engine power for little gain, especially when the turbo could be producing the air instead for very little loss.

Hen




well can't it just be in parallel and after a certain rpm the clutch on the supercharger simply disengages, meaning the drag the supercharger is placing on the engine is eliminated?


edit: just ignore me. I dont know what I'm talking about.

[Updated on: Tue, 23 August 2005 01:32]

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RobertoX
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 02:00 Go to previous messageGo to next message
Henn wrote on Tue, 23 August 2005 11:04

PS I am a fair nerd (yes, it's pretty bad, Eng and Comp Sci degrees) so I get into the whole electronics side of things. Plus I have an uncle who is a total guru and sets me straight if I ever get too stuck. So doing it with fly by wire throttles may be possible

Hen



Hmmm... I think this calls for a state space analysis of the system to really nerd it up Wink

Then some sort of tunable microcontroller to get things working
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M.W.P.
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 02:35 Go to previous messageGo to next message
I have actually been thinking about twincharging control for a long time now.

My thoughts are that it would probably be easier to use a bleeding valve to remove the pressure instabilites around the SC->Turbo switch over than using the valves that control the SC/Turbo flow.

Ie, create a BOV with electronic control.
This with the control of the turbo wastegate should allow for good enough control to smooth out the boost spike problems.

Itll also allow for the ability to make "enhanced" BOV functions that can sense any aproaching TB closing, reducing backpressure and therefore increasing the chance of earlier spooling.

This would need a very custom ECU, but thats why im interested in this as i can build and program them Wink
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 02:55 Go to previous messageGo to next message
Admittedly I haven't read the whole thread, but what exactly is wrong with just having a turbo feeding a PD blower geared for low boost (say 5psi)? The blower moves a fixed volume of air, and that volume of air can be at any pressure. If it sees 15psi on the inlet side you should get (15psi * multuplication factor) on the outlet side. I suppose you still get the disadvantage of extra heat generated by a roots-type blower, but if it's geared for low boost (hence low rpm) it should be so bad.

That's my random thoughts on the subject anyway. It just sounds so much simpler than playing around with valves and transitions and electronic doo-dads. Much simpler piping too. Smile
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VeeP
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 03:57 Go to previous messageGo to next message

old corolla

im pretty sure that 0psi of boost gives the engines capacity in air every revolution. . . . .

otherwise, what does 0psi give?

remember boost pressure is comparative to external pressure - its not absolute.


Also, why not save yourself the effort of the pipework, and have the supercharger blowthru the turbo and progressively block off the supercharger pipework as the turbo became more efficient than the turbocharger?

And uhh, im pretty sure just dumping the magnetic clutch is more than capable of giving a smooth transition. . . .


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Corona RT142
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 04:01 Go to previous messageGo to next message
VeeP wrote on Tue, 23 August 2005 13:57


progressively block off the supercharger pipework as the turbo became more efficient than the supercharger?


Fixed
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 04:04 Go to previous messageGo to next message
VeeP wrote on Tue, 23 August 2005 13:57


pretty sure that 0psi of boost gives the engines capacity in air every revolution. . . . .

No, only one intake stroke every 2 revolutions. So 1.6L at 1bar boost gives 3.2L every CYCLE which is 2 revolutions.

VeeP wrote on Tue, 23 August 2005 13:57

And uhh, im pretty sure just dumping the magnetic clutch is more than capable of giving a smooth transition. . . .

I disagree, have a read of some of the above stuff. Dropping the clutch without throttling/bypassing will cause a big drop in manifold pressure. However it would be interesting to see how long this lasted.

Hen
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tricky
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 04:17 Go to previous messageGo to next message
oldcorollas wrote on Mon, 22 August 2005 22:24

Mr DOHC wrote on Mon, 22 August 2005 19:51

this is the most insightful thread i have ever rad on toymods, shame on u all Rolling Eyes

have u thought about a few idle speed control motors {stepper motors} to control the throttles

heat in freewheeling SC:
hmmmm, what a pop off valve to vent nay hot air once the throttles are closed


hmm... steppers and electronics would be absolutely awesome, but i'm afraid i have NFI how to set up the control side of it..

and i want a system that is easy for anyone to set up.. not just nerds Razz (like me Wink )... actually, MS2 has a stepper controller onboard.. would be easy to change the code (as it's in C... well.. for a nerd Razz )



That'd be the easy bit! bring on the armchair analysis!!
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berad
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 05:37 Go to previous messageGo to next message
VeeP wrote on Tue, 23 August 2005 13:57


old corolla

im pretty sure that 0psi of boost gives the engines capacity in air every revolution. . . . .

otherwise, what does 0psi give?

remember boost pressure is comparative to external pressure - its not absolute.


Also, why not save yourself the effort of the pipework, and have the supercharger blowthru the turbo and progressively block off the supercharger pipework as the turbo became more efficient than the turbocharger?

And uhh, im pretty sure just dumping the magnetic clutch is more than capable of giving a smooth transition. . . .





because this is not what he is trying to achieve , something different that has never been done before that anyone knows of.
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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 07:56 Go to previous messageGo to next message
VeeP wrote on Tue, 23 August 2005 13:57



And uhh, im pretty sure just dumping the magnetic clutch is more than capable of giving a smooth transition. . . .



if you think that then you have completely misunderstood any of my analysis...

a supercharger, because it is positive displacement, MUST move it's internal volume of air per revolution. there is no way around that. when you switch it off, it stops pumping air.

how quickly do you think it will take for a turbo to suddenly produce an extra 8000L of air per minute???

say at 1.6L, 5000rpm, the SC is making 14.7psi (8000L of air/min), and the turbo has just spooled up enough so it can produce 14.7psi of pressure too.... it will be moving almost ZERO volume!!! if it was moving same volume of air as SC, then you would have 44psi!!! (ie 16000L/min) and then turning off SC would drop it from 44psi boost to 14.7psi boost... (from 16000 to 8000L/min)
i fail to see how that is a smooth transition Wink


and boost can be regarded as absolute pressure, just most people cannot comprehend it as easily, which is why most ECU's have 1atm as 0boost and 0vacuum... i prefer to work in absolute pressure terms, as then you know exactly where you stand in terms of volumes...

yup... who here (or anywhere) has designed a smooth, simple to control, parallel SC/TC system?? if it has been done then all this idle chatter is pointless.. but afaik, it has not been done to the level i would be proud of. we can do a quick and dirty way in an afternoon, but it'd still suck Razz
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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 08:05 Go to previous messageGo to next message
M.W.P. wrote on Tue, 23 August 2005 12:35

I have actually been thinking about twincharging control for a long time now.

My thoughts are that it would probably be easier to use a bleeding valve to remove the pressure instabilites around the SC->Turbo switch over than using the valves that control the SC/Turbo flow.

Ie, create a BOV with electronic control.
This with the control of the turbo wastegate should allow for good enough control to smooth out the boost spike problems.

Itll also allow for the ability to make "enhanced" BOV functions that can sense any aproaching TB closing, reducing backpressure and therefore increasing the chance of earlier spooling.

This would need a very custom ECU, but thats why im interested in this as i can build and program them Wink


you mean to vent the air to atmopshere? or vent the SC air to before the SC? venting all the air the SC pumps is wasting the power that it took to actually create it, ie whatever the SC's crank loss is. venting to before the SC is similar to my idea anyway?

i think that it may be better to set soemthing up with mechanical control, but perhaps use an EBC to accurately control the pressure to the mechanical actuators, than to use purely electromechanical actuators.. esp since wategate actuators are easy to get...

then again..

if some of you boffins out there can design a stepper motor controller system to control, that can reference TPS and a couple of pressure measurements (using motorola MAP sensors?).. then we could be in business Wink (not literally Razz)
how much force can steppers motors exert (against air pressure and return spring pressure)? how fast can they move? and how accurate could they be for a sub-90deg movement?

how easy would it be to have the characteristics programmable??

i do have a motorola MC68HC09 (sp?) programmer Wink they are pretty cheap and easy to reprogram from scratch (if you have a compiler Sad ) the MS code has been written in both assembler and C already....

hmmmmmmmmmm..... but this takes away from the DIY junkyard approach... but then again... it could start a whole new MS-like community of crazy bastards wanting to run stupidly big turbos on tiny poor little engines Evil or Very Mad Evil or Very Mad Evil or Very Mad

[Updated on: Tue, 23 August 2005 08:12]

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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 08:31 Go to previous messageGo to next message
thinking a bit more abotu the SC recirculation....

with SC only, the air going in is at 1bar, the air going out (we will assume) is 2bar... (well actually, it is still 1 bar, just that when it gets into the system post-SC it becomes 2 bar as there is less space for it to occupy)

when the turbo starts pumping air.. the air to be recirculated will be at 2bar (absolute) before T3, but between T3 and T1, the air must be at 1bar.. if it is higher than 1bar, the air will escape back past T1 and back into the SC intake tract..... so the SC is still pumping 1bar air into a 2bar system.. but the source of the air is from the pressure side....
so the amoutn of air going into the system is still the same, AND the SC crank losses are still the same.. since it is not freewheeling...

the only way to reduce the SC losses is to have the input and output air at the same pressure, and then it will be freewheeling as such, and only have friction losses...

when T1 is closed and T3 is open, this will be the case.. but i think the transition of T1 and T3 needs more thought based on a volume/pressure/flow point of view

as it stands, T3 bleeds2 bar air at a rate that keeeps 1 bar pressure between T3 and T1, and we will still have the SC pumping losses. these losses will only be reduced when T1 is closed enough so that the SC intake air (between T1 and T3) is higher than 1atm,which can only be the case when T1 is closed... if we close T1, so we have a higher SC intake pressure, the SC still pumps more air, at a lower pressure differential, but the input to the system is zero... so the SC may as well be off....

maybe there will be a small period of time (i hope it is small, otherwise we are not accelerating fast enough Razz ) whereby we can almost close T1, accept the loss of air past T1 back into the intake tract, BUT, the slight reduction in manifold pressure is offset by the gain by the reduced pumping pressure of the SC...

so in fact, to make the crank output smooth, we DO need a SMALL dip in the manifold pressure, but only enough to compensate for the reduction in SC losses.... i would guesstimate roughly that we can gain about.. what?? 20hp/15kw in pumping losses by increasing the SC intake pressure..

at 5000rpm, this equates to about....7.9Nm.. which on a 1.6L motor is about 0.73 psi..... so we could have a 0.73psi loss from reducing the air input to the system, and yet still have the same crank output...
again... when we turn the SC off, if we do so in such a way that results in a 0.73psi loss, we have same crank output...

or said in a different way, if we don't do anything to reduce pumping losses of the SC before turning it off, we can still have an instant loss of almost 1.5psi, but STILL have the same crank output...... which means that we can stil have the SC contributing some air to the system (ie 40hp worth) and when we turn it off, as long is it doesn't upset the turbos compressor flow, we have smooth crank output...

just more fodder for thought Wink

Cya, Stewart



and to ppl just joining the thread, please go back and read all the posts to get up to speed Very Happy TIA..
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 08:33 Go to previous messageGo to next message
oldcorollas wrote on Tue, 23 August 2005 17:35


you mean to vent the air to atmopshere? or vent the SC air to before the SC? venting all the air the SC pumps is wasting the power that it took to actually create it, ie whatever the SC's crank loss is. venting to before the SC is similar to my idea anyway?


Yes, vent the air to atmo, or back into the sc/turbo inlet.
You only do this during the sc->turbo stage to smooth the transition out, not as a way of turning off the sc (use the clutch for that).
But the exact setup would depend on how the sc & turbo were configured adn what order/system you wanted them to run in.

Quote:


if some of you boffins out there can design a stepper motor controller system to control, that can reference TPS and a couple of pressure measurements (using motorola MAP sensors?).. then we could be in business Wink (not literally Razz)
how much force can steppers motors exert (against air pressure and return spring pressure)? how fast can they move? and how accurate could they be for a sub-90deg movement?


This would be the interesting part for me (i am a elec engineer).
Though i enjoy doing the mechanical stuff just as much.

Working out the control mechanics stuff (like the servos) would be quite difficult, but it can be done.

Quote:


how easy would it be to have the characteristics programmable??



Depends on how much time you want to spend on the software.
Getting it to work is one thing... making it easily usable is another.

Quote:

i do have a motorola MC68HC09 (sp?) programmer Wink they are pretty cheap and easy to reprogram from scratch (if you have a compiler Sad ) the MS code has been written in both assembler and C already...


I would probably do the whole thing off a laptop to begin with.
Easier to program and test with.
When working, itll be easier to work out whats required to move it onto a dedicated ECU.

Quote:


hmmmmmmmmmm..... but this takes away from the DIY junkyard approach... but then again... it could start a whole new MS-like community of crazy bastards wanting to run stupidly big turbos on tiny poor little engines Evil or Very Mad Evil or Very Mad Evil or Very Mad



It still can be done backyard DIY style.
I designed & built an ECU similar to the MS based on a AVR here at home... i just never got around to writing the software for it.
It just takes time, knowledge and a few $$s.

I wont be attempting anything like this myself for a long time though.
The 1UZ into RA28 will keep me busy for a long time yet.

[Updated on: Tue, 23 August 2005 08:40]

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tricky
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 08:33 Go to previous messageGo to next message
oldcorollas wrote on Tue, 23 August 2005 18:05


if some of you boffins out there can design a stepper motor controller system to control, that can reference TPS and a couple of pressure measurements (using motorola MAP sensors?).. then we could be in business Wink (not literally Razz)
how much force can steppers motors exert (against air pressure and return spring pressure)? how fast can they move? and how accurate could they be for a sub-90deg movement?

how easy would it be to have the characteristics programmable??

i do have a motorola MC68HC09 (sp?) programmer Wink they are pretty cheap and easy to reprogram from scratch (if you have a compiler Sad ) the MS code has been written in both assembler and C already....

hmmmmmmmmmm..... but this takes away from the DIY junkyard approach... but then again... it could start a whole new MS-like community of crazy bastards wanting to run stupidly big turbos on tiny poor little engines Evil or Very Mad Evil or Very Mad Evil or Very Mad



Well, in the prototyping phase, I think a mechanical approach is significantly cheaper, and easier to instantiate, but in the modern age, an electronic system would be much more tuneable.

As far as stepper motors are concerned, they come in all shapes, sizes and mechanical ratings. The step (in degrees) varies between motor models, but many are more accurate than you could imagine! The controllers are easy enough to make (I knew my electronics engineering units would serve a purpose!), and some highly versatile models are available from Jaycar in kit form.

The controller you design directly relates to the versatility of the motor, and you could do it a couple of ways. You could reference from, say, an ECU signal, or a pressure signal, or a separate microcontroller setup as a "boost control unit" dedicated to the twincharge setup which would complement a basic ECU.

I think doing this in the latter fashion, following the proven success of the mechanical prototype, OEM type smoothness and reliability could be achieved.

Now I am in my zone! Laughing An entire world filled with numbers, hypotheses, perfectionism and eternal contradiction! I likey this discussion! Cool I come to toymods as a break from uni assignments and I end up dedicating thought to the exercise! Laughing
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 09:00 Go to previous messageGo to next message
MWP, have a read of my last post.. i think i just proved that it doesn't make much difference if you vent to ATM or to after T1...

venting to after T1 makes the actual closing process a little easier i think... hmm, that may all come down to how the valves are actuated, and what 'logic'is used to change their position...

hmmmm also showed that we aren't saving power by recirc.... maybe in that case, just closing T1 would be enough?? but then we have even higher pressure differential across the SC, so we would get some whopping great losses (well more.. imagine each time the lobes opened after pulling vaccum thru, we have 0.6L of 2bar air rushing to greet them...mmm can you say heat!!)


my only concern with laptop is that it is not real time based (unless you did it in linux of course Razz) and this is something you would not want a half second hang time while bill gates does his shit...
i guess there are heaps of micro-controllers and PIC's that could work.... i would want only one IC to be doing all the controlling.. so you can apply logic to all of the valves/gates at the same time...

hmm, so we are sort of making a sooper-dooper-EBC then? hmmm.... then again, if we had wastegate actuators, we could just use the EBC's, but i foresee the need to actuate the throttles with no pressure to make actuators work... hrmmm..


Tricky, i agree, esp after playing with megasquirt, electronic stuff is soooo much easier to play with.. cool Very Happy, heh heh, is amazing what uni degrees can be used for Wink

well, we would need a stepper for each throttle.. although from comments, maybe a wastegate could easily be used for T2.. so sayy two stepper motors, 90deg max movement, maybe 1 or 2 deg steps? doesn't need to be too fancy.. force?? enough to be able to open/close a valve against a lot of pressure..

mech engs? does a throttle plate experience a turning force when a pressure is applied against it? to me it seems like maybe a minimal turning moment due to slightly different amounts of air getting around the edges but.... still needs enough force to keep em closed/push against the spring pressure keeping them closed...

i would want them commanded by a microcontroller (twincharge-ECU) that takes into account TPS position, manifold pressure and IC pressure (for controlling SC pressure with throttle and at cruise Wink ), and maybe pressure between T3 and T1.. but thats about it really.. esp if T2 is a wastegate.. so 2 steppers, 3 pressure measurements and one TPS... the pressure and TPS are just 0-5V sensors, so thats easy to work with...

maybe we can do that one also, so maybe 3 steppers, and 4 pressure measurments..

so either:
2 stepper outputs, 4 x 0-5V inputs.. or
3 stepper outputs, 5x 0-5V inputs.

damn, is sounding easier all the time Razz then all thats needed is to be able to set up tables and a LOGIC path to determine what opens how much when (ie stepper position vs pressure/TPS) and also things like testing stepper home position (tho if they are spring closed, the initial position could be set to home position), a commented program that is easy to change for laypeople (ie me Razz) with absolute pressure units and sensible variable names... noice!!

i would rely on the driver not to be doing things when cold etc, and the ECU to correct for manifold temps..


hmm, MS2 has a stepper motor controller onboard, you could look into that chip.. it's SMD, but is compact and there may be a legged version

heh heh, all it takes is time, coffee beer, and pizza Razz

in fact, if electronic control of steppers could be set up, then the whole thing with decel and cruise becomes very easy.. you could just set either turbo (for highway) or SC (for city) and things like that.....

i think the basic idea of the throttles above can be used for all conditions.. and i guess the idea of this thread was initially to pick flaws in the system, and secondly to discuss operation logic....

thanks fellas Very Happy we are makin progress!!
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 09:30 Go to previous messageGo to next message
oldcorollas wrote on Tue, 23 August 2005 18:30

MWP, have a read of my last post.. i think i just proved that it doesn't make much difference if you vent to ATM or to after T1...

venting to after T1 makes the actual closing process a little easier i think... hmm, that may all come down to how the valves are actuated, and what 'logic'is used to change their position...

hmmmm also showed that we aren't saving power by recirc.... maybe in that case, just closing T1 would be enough?? but then we have even higher pressure differential across the SC, so we would get some whopping great losses (well more.. imagine each time the lobes opened after pulling vaccum thru, we have 0.6L of 2bar air rushing to greet them...mmm can you say heat!!)


It doesnt really matter where it goes, as long as its before the last compressor.
Yes, it would be wasted energy, but it would only be open for a fraction of a second if done properly.
Most of the control could be done via the turbos wastegate.
The bleed would only be there to remove and small crossover surge.

Quote:


my only concern with laptop is that it is not real time based (unless you did it in linux of course Razz) and this is something you would not want a half second hang time while bill gates does his shit...


It could be done in Windows quick enough, but yes, i would use Linux.
Even injector timing (much faster than would be required for this) could be done on a windows box if careful.
Comparativley, engine timing stuff is VERY slow compared to what a PC can easily handle.

Quote:


hmm, so we are sort of making a sooper-dooper-EBC then? hmmm.... then again, if we had wastegate actuators, we could just use the EBC's, but i foresee the need to actuate the throttles with no pressure to make actuators work... hrmmm..


Well you could do the actuation stuff with pnumatics if you really wanted Wink

Quote:


well, we would need a stepper for each throttle.. although from comments, maybe a wastegate could easily be used for T2.. so sayy two stepper motors, 90deg max movement, maybe 1 or 2 deg steps? doesn't need to be too fancy.. force?? enough to be able to open/close a valve against a lot of pressure..


Hrm, i would try worm drive geared servo's for this first.

Quote:


in fact, if electronic control of steppers could be set up, then the whole thing with decel and cruise becomes very easy.. you could just set either turbo (for highway) or SC (for city) and things like that.....


Yup, would be pretty cool coming up with profiles for hills driving, city driving, econo, etc, etc.

I wanna hear the cool sounds this engine is gonna make Shocked Shocked
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 10:07 Go to previous messageGo to next message
M.W.P. wrote on Tue, 23 August 2005 19:30


It doesnt really matter where it goes, as long as its before the last compressor.
Yes, it would be wasted energy, but it would only be open for a fraction of a second if done properly.
Most of the control could be done via the turbos wastegate.
The bleed would only be there to remove and small crossover surge.


I wanna hear the cool sounds this engine is gonna make Shocked Shocked


I think i mis-understood what you meant then...

hmm, sucks that we will be losing that much air from system... and that the energy is wasted, but i envisage this will occur between about 4-5000rpm... a 1bar boosted motor won't spend a long time between those revs...

my idea of venting from after SC to between T1 and T3 was that then we could have simple mechanical control between the two, and so when T3 opens, T1 closes... but if it is all electronically controlled......
oh, and for controlling SC boost below WOT when turbo is not spooled... hmmm dammit....

maybe it is better to vent from after the IC to before the turbo???? but then we have the SC pulling vacuum which is not good... hmm... any ideas??


heh heh, it's going to (QUICKLY) go WHRRRRRRRRRRR as the gilmer drive spins the SC, and then it's gonna go WHOOOOOOOOOOOOOOOOOOSH as the turbo quickly spools and hits 30psi Very Happy

Evil or Very Mad

[Updated on: Tue, 23 August 2005 10:38]

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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 11:07 Go to previous messageGo to next message
ok, more vague thoughts.

if you don't throttle SC input, you have massive pressure/volume drop when it turns off. not good.

if you bleed off the air to atmosphere then you lose air and have parasitic loss still, and you still need some way of stopping air flowing backwards through it.

if you throttle SC input only, then you pull a vacuum between the SC and T1, which increases parasitic losses of the SC, but you lose no air from pressure side of system (but it is still reduced). the losses will almost double as you have twice the pressure differential across the SC, and when you switch the SC off, you will temporarily have air flowing backwards thru the SC, reducing the manifold pressure.. will pulling high vacuum at high rom be bad for SC seals??

if you throttle SC and recirculate air to maintain 1atm between T1 and SC, you reduce the mech loss of above to just the normal amount, but you lose air from the system which has been compressed....... but you now have a smooth way of throttling the SC input...


hmm... so the difference in the last two is..
with no recirc, higher mech losses, some backflow when SC stops.
with recirc, lower mech losses, system is already equalibriated when SC stops.

and if you just bleed air off, then you need someway to quickly stop air loss thru the SC when it turns off...

so i misunderstood some of the previous posts, and also didn't think the system thru enough yet Razz


i guess this hinges on the mech losses of a PD supercharger..
i am assumning that a higher pressure differential will result in higher losses, but maybe this is not the case if it is pulling against a vacuum???

anyone know?
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 11:45 Go to previous messageGo to next message
I would use a servo for the actuation, you can get surprising amounts of speed and accuracy out of them

I was thinking about this a few years ago when I saw some article about a twin charged corolla, and I got bored today so I drew this up, just a thought, kind of using a 'gate' sort of thing... The turbo and supercharger pressure difference could sort themselves out (by pushing on either side of the gate) and when the turbo starts to win a bit the SC clutch could be turned off. That's what the position sensor is there for, so the 'black box' knows when to turn off the SC clutch (turning it on again would be another problem Smile ). In this case the turbo would start to close the gate and the SC pressure would increase and possibly create a pulsing effect as the gate closes up then the SC pressure builds up. The clutch could then be turned off.


anyway, looks like this:


http://www.geocities.com/robert_ae86/Super_operation.jpg


http://www.geocities.com/robert_ae86/Turbo_Operation.jpg


It could have some sort of springing mechanism that pushes the gate to one side or the other (ie so its not just flapping about in the middle) to hold a better seal and that sort of thing

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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 12:36 Go to previous messageGo to next message
oldcorollas wrote on Tue, 23 August 2005 20:37

o
i guess this hinges on the mech losses of a PD supercharger..
i am assumning that a higher pressure differential will result in higher losses, but maybe this is not the case if it is pulling against a vacuum???


Yeh, i was wondering about this earlier too...
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 12:38 Go to previous messageGo to next message
This is a very ley question and so far removed from the previous posts but with all the talk of minute power losses and restrictions on the intake side of things, how do you plan to vent exhaust gases efficiently?

I'm not exactly up to speed on wastegates but can you flow all the exhaust gases produced by a supercharged engine through even a massif external wastegate without restriction? And the wastegate would have to be progressive proportionate to the throttling of the supercharger wouldnt it?

Also, the last CAD drawing seems to be the most logical setup surely as it allows the most progressive transition from SC to turbo as the valve is opening as the turbo slowly spools up. This, to me (which isnt saying much), looks to be the perfect system if you could decrease the SC's output proportionately to the turbo's increasing out put. (I.e manifold pressure could be kept at say 15psi if when the turbo is pumping 2psi the SC is pumping 13psi etc..) Is there any way of gradually reducing the superchargers out put without bleeding air off. Altough maybe you could do it by just bleeding the air off. I dont know because while i can comprehend this discussion (barely) i can hardly contribute anything useful. Sorry if i have misunderstood anything or made it too general hahah

Very Interesting Though Rolling
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 12:40 Go to previous messageGo to next message
Oh.... there is a kinda simple solution to all of this (i think).

Parallel the SC & Turbo, put a TB before both, have a one-way valve after both.

So:

                 == turbo == one-way valve =========
in == TB == split                                   join == IC == intake
                 == supercharger == one-way valve ==



Having the TB before everything would remove the problems with surge on changeover.... i think...

The obvious disadvantage is the long intake path with the IC after the TB.

[Updated on: Tue, 23 August 2005 12:42]

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RobertoX
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 12:49 Go to previous messageGo to next message
Hi there nudes, whilst that drawing may seem logical if you look at the turbo and the supercharger producing a fixed amount of pressure at some rpm, thus giving a smooth transition unfortunately it wouldnt work like that.

The supercharger will produce a higher level of pressure if it is restricted on its outlet (because it displaces a fixed volume of air per revolution, as oldcorollas has explained already this is the key to understanding the operation of the PD blower).

It still could work afik with some careful control....


EDIT: SC throttling added... This might help in the transition of turning off the supercharger. It would still however have the increased drag caused by throttling the SC as previously described.

http://tekcities.com/robert_ae86/SC_op_with_throttle.jpg

http://tekcities.com/robert_ae86/T_operation_wThrottle.jpg

[Updated on: Wed, 24 August 2005 23:08]

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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 13:02 Go to previous messageGo to next message
One thing to think about is turning off and on the electric clutch of the supercharger at high revs, as you come back down with the revs the boost from the turbo will drop and the SC will start again, if you throttle the charger it will slow down even more, ive been able to stall a motor by shutting the throttle on the inlet side of a sc12 charger and shread belts by doing it at a few revs and also slowing things down by throttling the outlet side.
I would guess it will distroy the clutch or snap the input shaft of the blower in this setup, maybe thats why it done in series so the super charger has a good volume of air spinning the internals not to cause too much of a problem.
Toyota recomend 2500rpm max for switching a already free spinning SC.

[Updated on: Tue, 23 August 2005 13:07]

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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 13:14 Go to previous messageGo to next message
If you're wondering how to do this, call Darryl at Screamin Performance.

He's done it on 4AG powered Corolla.

02 4284 6674
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 14:03 Go to previous messageGo to next message
Fr3aK wrote on Tue, 23 August 2005 23:14

If you're wondering how to do this, call Darryl at Screamin Performance.
He's done it on 4AG powered Corolla.
02 4284 6674



done what? series or parallel? how did he do it? what psi are we talking etc? good for him...get him to post his ideas here Very Happy , or at least find out from him if it was series or parallel, and what order, and where were the control points.


RobertoX, i had the same idea a while ago.. problem is again, that the SC moves fixed amount of air, and turning it off wil cause pressure drop... you could throttle it but then we are back at the same point.. since the wastgate/throttle is acting like a one way valve anyway.

fwiw, i think Berad had a good idea that he _should_ be posting in the series twincharging thread... similar to brett_celicacoupe's idea, but simpler.. possibly the way the nissan march does it...


Nudes,
venting exhaust?? well, it goes into the turbo manifold, tries to spin the massive turbo, and then goes into dump pipe..

the turbo will provide shiteloads more air than the SC, and the turbine is sized bigger than usual for this size engine (ie as a 3L instead of a 1.6) so it will still have top end flow, and only a small wastegate needed..

and i guess the whole point of the SC is to spool the massif turbo... Very Happy

yar, the way to regulate the SC without bleeding off air is to throtle it's intake, but i think that this may actually result in higher losses than if the SC actually pumps the air and it is bled off!!! sonce there will be a higher pressure differential across the SC.. can't throttle the SC output, it will destroy any throttle you put there because of PD.. re-read (one of) my recent earlier posts about the losses with the different ways

MWP, one way valve for SC is effectively on or off due to the PD nature of SC..


NickZ, thats a bloody good point no-one has mentioned..... so if you suddenly close the throttle on an SC, then the force required to turn it suddenly goes up (confirming that it uses more power to turn pulling a vacuum) and kills belts.... hmmmmm

so we DO actualyl need to recirculate air back to the front of the SC, if only to allow it to frewheel to the point where we turn it off....

if T1 is closed but T3 is open (so air is free to get to the SC input) and we turn it off, then the SC can continue to freewheel because there is no pressure differential across it (well, there will since the recirc air is cooler)... maybe the recirc air chould be from hot side (ie before IC) so that when it turns off, there is no temp or pressure differential across SC??

re: turnng SC back on, there would be an elec lockout such that the SC ONLY turns on at a given throttle%.. maybe 20-30%?? so on gearchange when motor slows, SC is off, and probably not still moving fast(tho it might be??) i wonder what rpm is safe for the SC to turn back on?? is it the differential between the pulley and SC speed??

hmm.. maybe series IS the best way to go Razz

regardless, i like the idea of making parallel work....

maybe we can aim for a toymods dyno day in future where we test out turbo, vs series, vs parallel, vs SC12/14, vs lysholm Wink

now THAT would be interesting
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 14:17 Go to previous messageGo to next message
Fr3aK wrote on Tue, 23 August 2005 23:14

If you're wondering how to do this, call Darryl at Screamin Performance.

He's done it on 4AG powered Corolla.





so is that a free commercial ad or what Razz heh heh
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 15:03 Go to previous messageGo to next message
oldcorollas wrote on Tue, 23 August 2005 23:33


NickZ, thats a bloody good point no-one has mentioned..... so if you suddenly close the throttle on an SC, then the force required to turn it suddenly goes up (confirming that it uses more power to turn pulling a vacuum) and kills belts.... hmmmmm


Hence why all factory SC cars have the TB before the SC.

The more i think about my idea in the ascii diagram above, the more i like it.

The only electronic control that would be needed it a standard EBC and somthing to turn off the SC when the turbo spools up.
[/quote]
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 15:51 Go to previous messageGo to next message
i think he was referring to shuting the throttle on the INLET side of the SC...that this shreds belts...
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 16:43 Go to previous messageGo to next message

i still dont understand why you would want to persevere with a system that uses a shitload of piping and at least 3 or four control poitns with teh possibilty of a recirc unit too.

What do you propose this system will gain over a series SC/turbo system.


Henn -

thanks d00d, i meant to say 1 cyccle not one revolution Very Happy


oldcorolla -
you sorta confused me when you said that a turbo producing 14psi might move zero volume but a supercharger at 14psi has to move all its air volume. How does that work, a supercharger moving real slow might be making 14psi, but speed that same supercharger up and the pressure after it will increase all else being equal. So how does a turbo and SC differ in pressure/moved volume?
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Re: PARALLEL Twincharging, lets make it work Tue, 23 August 2005 18:20 Go to previous messageGo to next message
VeeP wrote on Wed, 24 August 2005 02:43


i still dont understand why you would want to persevere with a system that uses a shitload of piping and at least 3 or four control poitns with teh possibilty of a recirc unit too.
What do you propose this system will gain over a series SC/turbo system.
Henn -
thanks d00d, i meant to say 1 cyccle not one revolution Very Happy
oldcorolla -
you sorta confused me when you said that a turbo producing 14psi might move zero volume but a supercharger at 14psi has to move all its air volume. How does that work, a supercharger moving real slow might be making 14psi, but speed that same supercharger up and the pressure after it will increase all else being equal. So how does a turbo and SC differ in pressure/moved volume?


it might look like a lot of piping but it can be made very compact... SC and turbo are on opposite sides,
for a series, it has to go to turbo, then across to SC, the forward to IC, then acrossat the front, then back across to the plenum on the oposite side... thats three trips across the engine bay.

for parallel, the turbo can go straight from the outlet to the IC, across the front then into plenum... this is where the most power is made.. when turbo is on full boost.. this is just one trip across the engine bay.
the SC goes from SC, across to turbo outlet/IC inlet, and then follows same path... ie two trips across engine bay... the bypass is from plenum to SC.. luckily (as mentioned previously) the plenum is directly above the SC, so the bypass pipe might only be 20cm long.....

so the parallel actually has LESS piping and less pipe volume than the series one Wink and a more direct path for the high power turbo inlet path Very Happy

i dunno what advantage it will have apart from keping SC output at lower temps perhaps?, and reducing the length of the path from turbo to plenum.. and also increasing efficiency of turbo piping (less length/bends = less friction losses)

as for complexity, yes it is more complex, and that's why it is interesting.


okay..
go to here and play the little movies near the top
http://club.corrado.free.fr/prepa/eaton/eaton.htm

the SC is a positive displacement air pump, meaning that each revolution, it Positively... Displaces.. the set volume of air. ie Definitely Moves the air... what goes in comes out _unchanged_. the compression occurs in the plenum itself...

you could kind of think of it like..... hmm... positive displacement is like filling a bucket with water using a cup. each time you you fill the cup with a set amount, and each time you pour out the same amount.. thats positive displacement....

if you ke filling the cup and pouring it out, you will keep moving water..

same goes for the SC, if you keep turning it, it will keep moving air, no matter what.. it doesn't get compressor stall or anything, it just keeps moving air....and the reason is that there is no way for the air to go back, since the lobes seal against each other...


now a turbo.. a turbo is just a fan... have a look at the impeller of a turbo.. there is actually a path for the air to go backwards thru the turbo... if the turbo is not moving fast enough, and there is too much pressure in the turbo outlet, air WILL go backwards..... it is only the movement of the blades, and the throwing of the air from the middle of the turbo to the outer edges that causes compression... think of a turbo like a merry-go-round (or a gravitron ride Razz ).... if it's not moving you can easily move to the centre, but if it is spnning quickly, it's hard to move from the outside to the middle as you are being thrown outward.. but if you try hard enough (have enough pressure Wink) you can get there...

so basically a turbo is like a fan.... if you take a normal room fan, or PC fan or whatever, and covr the exit with a piece of cardboard, the air between the cardboard and the fan will be slightly higher pressure than the surounding air, but there is NO flow.... if you moved the fan really fast, you could get some compression of the air, but no flow still...

in a turbo, if the outlet is blocked, the air is still trying to be thrown outwards, but it has nowhere to go, so the pressure increases, but there is no flow... of course there is a point at which the impeller will experience stall/cavitation,

try blowing air back thru a turbo with your mouth.. and then try doing the same with a supercharger.... which one is harder???


hmmmm, lets make it arbitrarily simple example. you have a motor that uses 1L of air per revolution.
an SC making 1 bar boost means it moves 2L of air per engine rev, so the outlet air is compressed 2:1. since the SC and the motor are mechanically linked, and the SC and the engine (alo a positive displacement air pump Wink) move fixed amounts of air each time, regardless of what speed the engine goes (assume 100% efficiency in everything), there will ALWAYS be 1 bar boost...

a turbo does not move a fixed amount of air, the faster it spins, the more air it moves and it throws it out with greater force..... at low rpm, the turbo compressor is moving LESS air than the engine needs, so air is SUCKED thru the turbo... at some higher rpm, the turbo is spinning more, and so it will cease to become a restriction, and is effectively freewheeling... at higher rpm, the compressor is moving fast enough to spit air out with enough force/velocity to be more than the engine requires, and so you start making boost.... the amoutn of air move increases with the square of the compressors impeller speed...

hmm.. i guess it's hard to explain....i guess a vacuum cleaner on BLOW mode is similar as it uses a centrifugal compressor.... if you cover the end of the pipe, you feel the pressure, but there is no flow... you can probably hold your hand on the end for a while as the pressure will only increase until the compressor cannot provie any more force to the air, and flow stops.. but there is still pressure..

if the vac had a PD device moving air, you put your hand over the end and each revolution of the pump puts more air in... the pressure gets higher and higher and higher since there is nowhere else for it to go...eventualy either your hand comes off or the pipe explodes Wink



geez, i can't explain it any simpler than to say that, at a given fixed speed:
a PD SC is a Fixed Volume-Variable Pressure device.
a Centrifugal Compressor is a Fixed Pressure-Variable Volume device.

you could also search for it on google Razz

ummm
http://www.lextreme.com/centrifugal_supercharger_diagram.jpg

http://www.lextreme.com/roots_blower.jpg

http://www.lextreme.com/twin-screw-diagram.jpg

[Updated on: Tue, 23 August 2005 18:25]

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Henn
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Re: PARALLEL Twincharging, lets make it work Wed, 24 August 2005 00:14 Go to previous messageGo to next message
Gee, this thread has become so long and convoluted I can't find the things I'm trying to quote any more.

There is no torque applied to a throttle plate due to pressure differences across it. Otherwise they'd be sucked open (or further closed) all the time due to manifold vacuum.

And closing a throttle on the inlet side of an SC while it is spinning fast should cause no problem. I do it all the time from 7000rpm (engine, not sure what that makes at the SC shaft), SC clutch still engaged and throttle fully closed. No snapped belts and no rooted SC.

Hen
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NickZ
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Re: PARALLEL Twincharging, lets make it work Wed, 24 August 2005 03:42 Go to previous messageGo to next message
henn, maybe so.
I have had 2 snapped front shafts on sc12 superchargers
but a standard system has bypass built into the standard piping
After building a 4K-ZE and braking belts and superchargers, yes it can work but does put a large load on the blower shutting the inlet side.But i have seen it working and many people get away with it.
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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Wed, 24 August 2005 03:51 Go to previous messageGo to next message
ahh the ol' internal ABV???? that is kinda what we are doing here, but on a larger scale... one that can take full SC output...

hmm.. i'm getting confused with all this as well Wink
maybe time to go think in a dark room....
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Fr3aK
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Re: PARALLEL Twincharging, lets make it work Wed, 24 August 2005 05:06 Go to previous messageGo to next message
I posted the number because you're all sitting there scratching your heads with a confused look on your face. Razz

I do agree though, i think it'd take the fun out of it if you called him and got the answer straight away...

Parallel from memory, but i could be wrong.
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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Wed, 24 August 2005 05:56 Go to previous messageGo to next message
Fr3aK wrote on Wed, 24 August 2005 15:06

I posted the number because you're all sitting there scratching your heads with a confused look on your face. Razz

I do agree though, i think it'd take the fun out of it if you called him and got the answer straight away...

Parallel from memory, but i could be wrong.


sigh.. there had to be someone who completely misses the point Wink

just because your mate did it one way, does NOT mean it is the easiest, or best, or most efficient way. as is being shown here, there are many different ways to twincharge, both series and parallel, and each has there own drawbacks or benefits. what some ppl would at first think is a good idea ( for zample throttling SC intake with no bypass) may turn out to be not the best solution (since it increases mech losses)


since you are so sure that this guy has the best solution for parallel twincharging, can you call him today and ask him abotu the details. then post it here and we can discuss whether or not it actually is the best way...

actually, maybe it is better if someone else does it.. a bit of impartiality never goes astray... any volunteers?? i can call from my computer at home but i am never home during aussie work hours....

if he is unwilling to share his ideas, then he either is not confident about it, or thinks there is some big secret to it (in which case he can go... something.. himself Razz )

i think it will be even more fun to analyse his method of twincharging and actually see if it is better than the other series or parallel ideas...


now that you have posted the number.. someone has to call.. even if just to wipe the smirk off your face Evil or Very Mad Razz Razz jk Wink
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oldcorollas
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Re: PARALLEL Twincharging, lets make it work Wed, 24 August 2005 05:59 Go to previous messageGo to next message
and also be interesting to hear a mechanic explain the function of the system, in terms of volumes, pressures, losses, and where inefficiencies are recovered Wink

SOMEONE CALL!!!!! Very Happy
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Fr3aK
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 06:49 Go to previous messageGo to next message
I don't know who the guy is who had it done. It was just a random car in a random shop (at the time).
I was only in there for a ECU pin diagram for my car.

I don't give a rats' about this forced induction setup (or promoting that particular workshop), but i thought it'd be somehow beneficial to call a guy who's actually done it for some pointers.
I mean sure, you could probably improve on his methods but the point is: he's done it. Have you?
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oldcorollas
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 07:05 Go to previous messageGo to next message
settle grettle, i'm just muckin around Wink

nope, i haven't done it, but i have thought about it.. which is a lot more than many ppl do before they do mods Razz

fwiw, i will not have a permanent twincharge setup on my car. i know what i want and how to get it..
this is initially just a thought experiment to work out the best way to do it... basically because all the info on the net so far doesn't come to a decent conclusion, nor do they actually do any kind of indepth analysis..

it's usually, "well my mates budgies uncle did this, and it worked so why bother trying a different way"... a bit of thought goes a long way....

so anyway, are you going to call or does someone else have to Razz

Cya, Stewart
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Fr3aK
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 07:33 Go to previous messageGo to next message
oldcorollas wrote on Wed, 24 August 2005 17:05

basically because all the info on the net so far doesn't come to a decent conclusion, nor do they actually do any kind of indepth analysis..


That's why i posted a real life person who'd done it.

oldcorollas wrote on Wed, 24 August 2005 17:05



so anyway, are you going to call or does someone else have to Razz



I already said i don't give a rats.
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oldcorollas
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 07:55 Go to previous messageGo to next message
Fr3aK wrote on Wed, 24 August 2005 17:33

oldcorollas wrote on Wed, 24 August 2005 17:05

basically because all the info on the net so far doesn't come to a decent conclusion, nor do they actually do any kind of indepth analysis..


That's why i posted a real life person who'd done it.

oldcorollas wrote on Wed, 24 August 2005 17:05



so anyway, are you going to call or does someone else have to Razz



I already said i don't give a rats.



Laughing Laughing Laughing Laughing

many ppl have done it, and most do it in a fucked way... surely this guy is not going to break the mould Razz if most of the ppl who have twin chrged actually thougth about their setup, they would have done it differently (is the whole frickin point)

well, stop posting then.. sheesh..
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berad
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 08:13 Go to previous messageGo to next message
haha i think its time for these ideas to start being tested on an engine Razz... just to shut a few people up.. ill be trying this in the not to distant future but not paralell but as far as i know the idea im using hasnt been documented or hasnt been done for 1 of 2 reasons , 1 its stupid , or 2 as oldcorollas has said noone thinks about there mods
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Enchanter
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 10:27 Go to previous messageGo to next message
Geez this thread get the mind ticking over.

Is it possible to "throtle" the rpm of the supercharger, as the simple fact of disengaging the supercharger will give a spike in power as the engine is freed up and so would destroy the entire point of this thread, ie smooth transition.

As the engine rpm increases the supercharger needs to be "throtling" down.

Its almost as if the supercharger needs to be run off an electric motor, variable stage clutch or even a lockup torque converter type situation but in reverse ?????

or I could be entirely full of it Very Happy
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oldcorollas
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 11:10 Go to previous messageGo to next message
no no, you are right on the money.. a mechanical variable setup could be difficult, but if we could vary the amount of lockup with the elec clutch...

problem is that the force required to turn the SC changes..


now if you could set up the clutch as a stepper motor, and program it to increase the amount of "slip" as the turbo kicks in.,.....
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Enchanter
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 11:33 Go to previous messageGo to next message
I dont know how a CVT works but there may be a clue there, anyone know ??

Could it even be viable to continue the running of the supercharger and not turn it off, just keep it running at its optimum rpm ??

Starting to sidetrack perhaps .....
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oldcorollas
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 12:32 Go to previous messageGo to next message
this is one for the electromechanical boffins out there...


if you completely engage the elec clutch, you kill belts (perhaps)


is it possibly that by applying a decreasing 12V PWM signal to the electromagnetic clutch would decrease the holding force, and so allow the SC to slow down????

i rrealise that the normal holding power of the clutch must be high enough to hold the whatever power ppl are putting thru it (like 60hp!!), but at some point, it will start to slip....

in this case, you could just use effective one way valves, and electromechanically slow the SC...

the PWM required could be worked out via a lookup table of pressure and rpm i guess...

thoughts?? could it work???
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Henn
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 12:50 Go to previous messageGo to next message
Slipping the SC slutch to slow it down would generate LOTS of heat (difference is RPM across the clutch multiplied by the torque being transferred) and I'm sure it would kill the tiny little clutch very quickly.

Hen
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oldcorollas
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 13:38 Go to previous messageGo to next message
Henn wrote on Wed, 24 August 2005 22:50

Slipping the SC slutch to slow it down would generate LOTS of heat (difference is RPM across the clutch multiplied by the torque being transferred) and I'm sure it would kill the tiny little clutch very quickly.

Hen


oh.. from the SC'S lump'o'metal (thats a technical term Razz) mow movign within the clutch's electromagnetic field?? i'm a bit sketchy when it comes to how energy and heat are transferred with magnetic stuff...... been a while since i learned it (oh bugger... a decade!!! sheesh)

any way to reduce it??

wait a minute..... if we are using PWM, and the current is turning on and off, there it should be generating much less heat than if we were trying to move against a full current??

any way to extimate the amount of heat generated?? assume that we wanna smlow it down between about 4-5000rpm, the max torque of the SC there is maybe 30hp or sayy 20kw... (hmm, 20kw is a fuck off big room heater!!! hrmmmmm)
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doityourself
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Re: PARALLEL Twincharging, whatever.... Wed, 24 August 2005 13:57 Go to previous messageGo to previous message
this may not make any sense but.... My excuse for this is I woke up at 5:50 am

How about using the SC to speed up the air that between the turbo manifold and the turbo, effectively bringing it on boost really quickly I even have a pic
but I don't know how to out it on.
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