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Location:
Lost in the K hole
Registered:
May 2002
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 ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Mon, 11 October 2004 14:59
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ive been doing a fair bit of resarch and maths on ITB manifold design and dimensions and id like some feedback on what ive come up with.
(If possible Id also like anyone who's done a 3sge in a similar fashion to describe their assembly... the similarities would make excellent comparisons)
anyway, a stock 2jzge setup looks something like this:
total valve area = 16.08 cm^2
port area at head/manifold join = 11.29 cm^2
a few cm up the manifold runner, the area expands dramatically (almost a step function) from this 11.29 cm^2 to 18.85 cm^2 and this continues up into the stock plenum.
now, im trying to design a nice, harmonically tuned, high velocity, individual runner intake manifold, to suit....
- redline around 8500
- power band from say 6700 to 8200
- rod stroke ratio of 1.75:1 (thus the desire for higher velocity intake style)
- cams not figured out due to trying to sort out intake velocity caharcteristics and cyl filling properties - please contact me if you can help describe this to me 
- desire around 110-120hp/L
- do NOT want a 500rpm power band 9000rpm gutless screamer of an engine!! would still like to maintina some sembelence of tourque in the lower rpms (hence details paid to good inatke design)
im proposing individual 45mm throttles at ~15cm from the valve face (edit - is there data or recommendations on distance from throttle to vlave??). the area of each throttle would be 15.97 cm^2 (close enough to valve area of 16.08)
this is based on my understanding that the throttle area should be as close to the valve area as possible.
not only this though, but such a port cross sectional area I calculated to produce peak torque around 7000rpm. the emphasis placed on tuning cross sectional port area for tourque band seems quite significant. as a consequence, im lead to believe that i should try and maintain this cross sectional dimension all the way from the throttle to the valve??? which means id need to do some serious work on the 11.29 cm^2 bottle-neck witnessed at the head/manifold interface??
(alternatively is there some advantage to narrowing the port at this point, and increasing the intake velocity, venturi style, and simply maintinaing this 16 cm^2 area along the rest of the port length?)
back to the 45mm port and throttle, mean intake velocity at 8500rpm is around 22m/sec - i figure thats fine. comments?
beyond the throttle, ive read that a taper in runner diameter, up to a factor of 1.3x or 1.4x valve area is the way to go. thus id be aiming for an expansion from 45mm at the throttle to around 52mm by the end of the runner. thoughts? (bellmouth would expand again on top of this 52mm)
regarding length - ive found VERY little accurate information on calculating harmonic lengths. however, one calculator suggested that for a tuned rpm of 7000-8900rpm a 16" total port length would be appropriate for 2nd harmonic resonance...
...this seems quite long!!
of all the itb manifold setups ive seen, not many have i noticed to be 16" in length!! perhaps they are halving (or some other multiple) the harmonic length and accepting the lower energy of the resonance??
its all a bit much in one post, but i kind of needed to write it all down to atleast get it clear on paper. my apologies...
...now if anyone can add some useful insights, suggestions or information to what ive just spat out, please speak up!
and as i mentioned earlier, if youve built an ITB setup for a 3sge (or a 2jzge!) id be interested in what youve done, what interesting things you noticed while tunig it, and what suggestions youd have to make...
cheers guys!
ed
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Mon, 11 October 2004 15:13
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fwiw, you can calculate your own harmonic length using standard theory. the speed of sound will that close to room temp (and easily found) compared to the higher speed of sound in hot exhaust gas (making it more difficult to accurately calculate).
i have a vague recollection that havign a continually tapering intake is ideal, so that the charge continually. but smoothly, increases in velocity.
something i've been thinking lately is that using the valve head area is not exactly correct.. the air only has the open spce between valve and seat to flow ie valve circumference x lift. which lift you choose to use? maybe mid to 2/3rds?
just a quicky, why are you aiming for second harmonics, not 1st harmonics? second will give lower, but wider peak, and less negative effects either side, but where will your 1st harmonic occur in rpm?
mmm tis late.. think later 
Cya, Stewart
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Mon, 11 October 2004 15:16
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hmmmm...
perhaps i take it back. maybe a 16" runner length isnt that whacky afterall. maybe ed got his maths right for once
question - is the intake port of the 3s (at the point where the manifold meets the head) normally oriented at such an angle - or does this pic imply serious port work?? id love to see what theyve done inside there. would certainly clarify my questions regarding homogeneity of port Xsectional area in the transition from runner to head port
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Mon, 11 October 2004 15:23
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stewy - i agree on the continuous taper. and i do plan to continue the taper proximal to the throttle - but i felt i should leave that out for now as it wouldve just confused the above monologue further 
the closure of the stock/existing port area, however, does seem excessive! thats a 30% reduction in area over just a few cms, which then expands again rapidly (back to 100% original size) in the valve bowl area.
i dont get it
perhaps its just an artefact from going from the round runner to oval port?? room for improvement?
ed
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Location:
Adelaide
Registered:
September 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Mon, 11 October 2004 21:25
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FFFFFFFFFFFFFFFFAAAAAAAAAAAAAARRRRRRRRRKKKKKKKKKKK KK MMMMMMMMMMEEEEEEEEEEEEEEEE 
I have no idea Ed, but I'll dig around my library and see if I can find a reference of any use
Cheers
Michael B
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Location:
Adelaide
Registered:
May 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Mon, 11 October 2004 21:43
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The runner configuration on the TODA engine is reasonably optimal, but from memory they had to elevate the ITBs by a huge margin, due to the design being for FWD, where the 3S is rocked back. Otherwise the throttles wouldnt clear other bits in the engine bay.
From memory (been a good year or so) the last time i looked at a 3S they didnt have a huge intake angle, and it looked relatively similar to a 4A. So judging by the 4A intake tracts (which were designed for RWD), which i have included a picture of below, im lead to believe that the 3S angle is suboptimal.
From everythign ive read, the 4A tracts are pretty optimal for their design, and use only an 8" tract from butterfly to valve, although its effective 14" at WOT.
On the 2JZ (or is it the 3S) with the reduction of intake size around the head entrance, i believe this is suboptimal for a high rpm power band, but more beneficial for lower end torque. Mainly due to higher intake velocities etc. It was the same principle behind the whole TVIS system. Personally i would be wanting to enlarge the head porting to around 13-14cm^2
Anyway, thats just my thoughts.
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Location:
Adelaide
Registered:
September 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Mon, 11 October 2004 22:15
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Bill Sherwood might be your guy.
Another thought is to look at what the BEAMS 3S-GE does, as they pump out pretty good power and rev like the bejesus, and Bill may be able to provide you with some detail in this area as he has one of these in his Fraser Clubman
Cheers
Michael B
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Location:
Gold Coast
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Mon, 11 October 2004 23:10
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Ed, the only person I know here who has done extensive tuning on a 3SGE who visits this forum is Glenn Booth.
Glen has experimented by varying inlet lengths, diameters/intake & throttle plate; ditto with exhausts & cams.
My combo was the result of what I could either make or buy for cheap, so they would be far from optimal (& do not follow any trend from what I can gather) but seem work well for my application.
I'd try Glen.
I'm happy to provide my specs, but they do not follow any mathematical or theoretical formula and therefore may not be of much use to you.
I've seen Bills site, and he has some great gear, but it doesn't appear he's got to the stage of experimenting as described above. I'm sure he knows someone who has though??
Cheers
Steve
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I supported Toymods
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Location:
Canberra
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Tue, 12 October 2004 05:25
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I used an engine analyser to optomise the inlet setup for a friends 4AG rally motor and the runners wound up fairly long:
This was set up for midrange torque rather than pure top end though.
IIRC, it was about 14" from trumpet to valve, which is almost exactly the length Toyota put on the factory inlet....
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I supported Toymods
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 13:05
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Just as an aside, with my 2JZGE running 48mm throttles, extractors and standard internals, the peak power shifted up the rev range. Peak power is made at 5500rpm with the standard motor, yet mine peaked at 66-6700 (but sharply dropped off thereafter). The best gains were with the torque - tractive effort (as a surrogate of torque) was flat from 3000 right thru to 6000 rpm. The distance from the valve to the throttle plate is approximately 250mm (80 + 170), and the distance from the throttle plate to the bellmouth is 120mm. I didn't deliberately pick these - it's just how it worked out with the bits I had.
I haven't played with throttle diameters, but I suppose if you really wanted, we could put it on a dyno and you could see what the pressure drop across the throttles is. For what it is worth, that 400hp 2JZGE runs 55mm throttles. I don't have enough space in the engine bay to lengthen the trumpets without modifying the inner guard.
Anyway come have a look when you get here.
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Location:
Brisbane
Registered:
February 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 13:38
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ed: are you considering placing the injectors up-stream of the butterflys? as per the TODA engines?
my (limited) understanding of this would be some improvements in upper-rev ranges at the expense of some low rpm drivability/torque?
am curious as to how much extra their placement would add/subtract to power output in for your preferred power band.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 13:51
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one of the most interesting threads for ages
when thinking about these things i like to try and seperate the port velocity and port length as seperate entities..
port length is (almost) controlled by harmonics alone.
port velocity is (almost) controlled by the port/runner diameters and tapers etc etc.
well thats what i think anyway...
the other approach in my head is that velocity is what fills the cylinders, and harmonics are what give you the extra little bit (like 5%).. if you have bad velocity but good harmonics, it's still a bad motor.
if you have good velocity, but bad harmonics, then you are probably only goign to be down a max of 10%(?) on what you could get...
for bens runners, giving good mid range, they are probably doing more for velocity than harmonics..
i dunno... harmonics need a lot of energy (read, RPM) to get them working hard. F1 get maybe +25-30% from harmonics, and bikes maybe 10-15%, but below 10,000rpm, maybe there is not enough energy to make massive differences...
i realise why you are doing it, and i feel the same way (make it the best it can be for what it is)...
anyways, just thought i'd add a few thoughts (with no scientific backing )
Cya, Stewart
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 14:45
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chuck - yes im considering staged injection on this manifold  its apparently worth just a few ft/lbs in the upper rpm's
dave - im not convinced that the 'pressure drop' hypothesis is the correct method of determining intake assemblies. infact im pretty bluntly against the whole idea. the whole history of head porting and such seems to have been built around the rubric of "hog it out until it flows like a big steel pipe" - and in the end you have very little pressure drop, and the head flows like haides.
however we all know that abs flow figures mean very little these days, and its all about the quality of the flow, the velocities, swirl, and the harmonics that are present in a real operating engine.
perhaps for a 'single rpm use only' engine, yes, 9000rpm and ports and throtles that just flow big numbers might be adequate. i suspect that is the story with that 400ps 2jzge w/ 55mm throttles. looking at the intake and given that size throtte, i doubt itd do much other than be a whingy, useless, undrivable engine until the whole lot hit 9000rpm, and just screamed its tits off.
i dont want that
from everything ive calculated, i *think* ive got my port X area sorted correctly, and that is supportive of the idea of a 45mm throttle (no i didnt start out trying to justify the throttles i have, i honestly started from scratch!). it may not be the 'ultimate' in terms of peak power and abs flow capability, but, fucking engines, compromises a plenty.
i know that a dyno and several goes with different setups is the final solution. but im sure you can understand the pursuit to get somthing 'close to right' in the first instance (even if it all turns out to be shit, and i end up starting from scratch following dyno session #1)
if nothing else, learning the maths id fun hehehe
and yeah - thanks to all who have contributed so far (even if i didnt directly address your points.) ive read this all a few times over the last day or so, and have just been chewing on it before replying. your imput is appreciated - its hard to muster good discussion on stuf like this.
oh - also, check here for further discussion:
http://pforums.company-hosting.com/forums/showthre ad.php?t=67181367
cheers
ed
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 14:58
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stewy - i agree completely on the velocity thing... hence my concentration thus far on port X area. witness the 'small' 45mm throttle in comparison to some engines getting around. im even thinking of filling and reshaping the inside of the runners (of the stock manifold ill be cutting and modifying) with some kind of resin to keep the size down in some sections.
the ports will not be hogged out, but i may open up the 'bottle neck' section described earler in order to keep the X area somewhat constant - this is a long way from the valve bowl though - so wont stuff around with velocities too much right up behind the valve. short of cleaning up the short side radius and the bowl transition, (and other casting dags and machine edges) i think ill be leaving the inlet reasonably alone.
as for harmonics - two things seem important, length and dia
length is as discussed, and still debatable (hehehe - would you use the open pipe harmonic formula, or the 'one end open, the other closed' formula?? both situations exist with the valve opening and closing!! where do you want the node!!??)
the other question is - would it be an idea to place the throtle plate at the position of the middle node?? i think it would! for the tuned rpm i think it would have some impact - albiet a minor one! but it all counts (if not just in my anal mind!)
now dia seems to be the BIGGEST factor, formula one designs refer to it over and over (more so than length) yet i can find SFA real data on it. i found the odd calculator, and the outputs make sense to me... but i hate blindly following a bunch of numbers. thoughts?
phew...
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 15:04
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| Bill Sherwood wrote on Thu, 14 October 2004 00:48 |
You can see they're rather short. It's missing the inlet trupmets but we make our own and they're about 10mm long.
The length isn't too critical on the variable inlet cam engines, though you should pick a rough optimum.
I wrote out an answer to the original question on Performance Forums as well.
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thanks bill, i replied to your post in PF
might i just say "thats damn short". my head has trouble reconciling all the different approaches different designers/builders have, and yet they all have excellent outcomes. so much conflicting data 
*grumble*
i agree though, VVTi would make life just that litle bit more barable!! damn old technology! maybe i 'should invest' in a VVTi head one day....
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 15:06
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Ed - Echoing what I wrote in the Perf Forums thread, make you diameter so that you get 290 - 300 ft/sec average airspeed at max revs. You're also looking for a mach number of between 0.3 and 0.4 odd. Around the middle seems good.
I like to keep the throttles as far away from the engine as possible, to reduce any turbulence they might make in the inlet system. It also reduces the effect of making the inlet shorter at part-throttle. (note where the butterflys are on the Fraser engine)
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 15:07
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Yep, I like short inlets!
FWIW the new 4AFE screamer that's going together oh-so slowly will have an inlet from valve-to-trumpet of less than eight inches.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 15:30
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that intake velocity is unachievable bill
with the 45mm throttle body, velocity accross the plate is only 75ft/sec @ 8500rpm @ 100% VE
even at the bottle neck in the port, the velocity only gets up to around 105ft/sec
im not sure how the hell youre getting those numbers??
maybe if i add up all the velocities from all 6 runners simultaneuously we can get 450ft/sec !! 
little help?
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 15:40
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i cannot comprehend how you can get an intake velocity of 300ft/sec
calculating cfm(183 in^3 in whole engine):
Airflow rate = (cid x rpm x 0.5 x Ev) / 1728
per cyl, cid is only 30.48
so @ 8500rpm and 100% VE were only getting 75cfm
lets work out req Area (X) for 300 ft/sec
(75/60)/X = 300
X = 0.004166 ft^2
X = 0.6 in^2
where on earth are you going to find a port of X sectional area of 0.6 in^2 ???
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 15:40
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It's from the formula ->
Runner velocity = (piston velocity x piston area) / inlet runner area
well, that's what my theory book tells me ...
Does that work for you?
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Location:
Lost in the K hole
Registered:
May 2002
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 15:45
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Nah, peak - that's how you get the 290ft/sec odd.
Download a copy of Engine Analyser Pro from www.performancetrends.com and have a good read of the manual.
It's mostly theory stuff, but there's some very interesting reading in it.
Also install the program and send me an email.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 15:50
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roger that
not at 2am though. i should learn to sleep properly. im switching this off now. ill do some quickmaths in bed, but be damned... i gotta reset this body clock!
thanks again bill
cheers
ed
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Location:
Adelaide
Registered:
September 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Wed, 13 October 2004 21:36
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I haven't been able to really contribute, but am learning heaps.
Keep up the good work Dr Ed.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 01:34
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"i make learning FUN!" - strongbad of strongbadia
anyway... recalculated velocities using bills method:
if max mean piston velocity at 8500rpm is 4777 ft/min
drumroll please....
intake velocity across the 45mm throttle is 286 ft/sec! bingo! this is also the cross sectional area (and heance intake velocity) of most of the port (not including the bottle neck region) and is also the surface area of the valves 
yet another piece of data that fits in perfectly with the proposed design.
(now to contemplate the consequences of a max mean piston velocity of 4777 ft/min!!)
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Location:
Adelaide
Registered:
September 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 02:08
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| ed_ma61 wrote on Thu, 14 October 2004 11:34 |
"i make learning FUN!" - strongbad of strongbadia
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Ke ?
| ed_ma61 wrote on Thu, 14 October 2004 11:34 |
(now to contemplate the consequences of a max mean piston velocity of 4777 ft/min!!)
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What sort of speeds are on engines like the Beemer M5 at the redline of 8500rpm ?
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 02:26
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| bbaacchhyy wrote on Thu, 14 October 2004 12:08 |
| ed_ma61 wrote on Thu, 14 October 2004 11:34 |
"i make learning FUN!" - strongbad of strongbadia
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Ke ?
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http://www.homestarrunner.com/sbemail58.html
as for piston speed, 4777 ft/min is FAST, but i think doable and sstainable with material selection. bimmer piston speed, i dont know
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Location:
Tasmania
Registered:
April 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 02:49
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Hi,
Try to find some pictures of 2 litre supertourer engines. They peak and cut at 8500rpm.
You'll find that the supertourers used 2 injectors per cylinder. One of these injectors was fitted close to the head, and another was not part of the inlet manifold and fired straight down the trumpet/ram-tube (was mounted as part of the airbox). "Good for top end" was the answer to my question when I asked the Audi (I think) mechanic.
This thread is sounding very interesting!
Cheers,
Justin
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Location:
Adelaide
Registered:
September 2003
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 03:09
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| ed_ma61 wrote on Thu, 14 October 2004 12:26 |
| bbaacchhyy wrote on Thu, 14 October 2004 12:08 |
| ed_ma61 wrote on Thu, 14 October 2004 11:34 |
"i make learning FUN!" - strongbad of strongbadia
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Ke ?
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http://www.homestarrunner.com/sbemail58.html
as for piston speed, 4777 ft/min is FAST, but i think doable and sstainable with material selection. bimmer piston speed, i dont know
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Can't access that site  from work.
The Bimmer M5 has a 92.0mm Bore x 75.2 stroke and max power of 373kW @ 7750 rpm, and is redlined at 8300 !!!
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I supported Toymods
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Location:
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May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 04:15
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dave, what mean peak velocity numbers have you been quoted by piston manufacturers?
i know 4000 ft/min is the established norm for basic components, but what of quality forgings etc?
cheers
ed
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I supported Toymods
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Location:
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 05:06
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| gianttomato wrote on Thu, 14 October 2004 14:27 |
over eleventy billion hp...".
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There is that magic figure again....
Is that like one of those fancy numbers like Fibonacci (sic ?) or is it a Tomatonacci Number !!!
The guide that I would use would be to look at some of the stuff used by serious racers and stuff like TRD as GT has recommended. I wonder what the peak speed is for a V8Supercar engine at their imposed redline of 7500 ? I believe that the 350 Chev has a stroke of 92mm, so is the V8Supercar the same ?
Cheers
Michael B
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I supported Toymods
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 05:32
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Interesting.
It seems that all of the engines that are being discussed have a rev peak and stroke that is similar, despite completyely different origins and configuerations !!!
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Location:
wangaratta
Registered:
May 2004
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 12:21
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i have not contributed as it is clear that there is far more knowledge already out there than i can provide  , but my god, this post is GOLD!!!!
i should really print this off and frame it, i dont think ive read anything like this anywhere other than those hard to find tech documents and journals, let alone a net forum.
i think i speak for a lot of people here, that this is THE
SHIT
thanks for the interesting and mind boggling read guys.
and by the way ed, u better keep us up to date with how this thing goes, we wanna see some NA supremacy again
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Location:
Montrose, VIC
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 12:54
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I've been keeping quiet here so far (as I figured I'd likely make a fool of myself!), but, has anyone got anything to offer on knowledge of multi throttle intakes for turbo engines? I'm going to have a go at one soon, and would like to see what others can offer me!
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Location:
South Australia
Registered:
July 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 14:51
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So what is more important in calcuating an approximate redline - the peak piston speed or the average piston speed? Surely there are more important factors though, like skirt length, oil/compression ring surface area, harmonics/rod strength???
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 15:17
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| FWDboy wrote on Fri, 15 October 2004 00:51 |
So what is more important in calcuating an approximate redline - the peak piston speed or the average piston speed? Surely there are more important factors though, like skirt length, oil/compression ring surface area, harmonics/rod strength???
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Average piston speed, though as far as I know the shorter the rod (I.e. rod-to-stroke ratio) the higher the piston accelerations for a given stroke. So in that respect a longer rod should be easier on the pistons.
As far as the limiting factor, it's often the rod bolts. Twin-cam multi-valve engines often aren't limited by the valve gear with regard to max revs as they'er much lighter than a two-valve, and even more than a push-rod engine.
Some engines get bad harmonic in the cranks at certain revs, so that's an area to stay away from, others might even have the oil pump fail before anything else.
But for our purposes it's usually the rod bolts.
Always change them, every rebuild.
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I supported Toymods
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I renounced punctuation
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Thu, 14 October 2004 21:25
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The theoretical critical rpm (for a single cylinder engine) is dependent upon the rod length to stroke ratio (as Bill alluded to) as this takes into account piston acceleration, but I can't find the formula.
Practical limitations have changed over the years. In the 50's, bearing technology was the major limitation, but nowadays definitely rod bolts (for us mere mortals anyway). Valve actuation and control was a major issue for F1 manufacturers as they pushed their limits.
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Location:
Lost in the K hole
Registered:
May 2002
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 00:22
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| boxh34d wrote on Thu, 14 October 2004 22:21 |
my god, this post is GOLD!!!!
i should really print this off and frame it, i dont think ive read anything like this anywhere other than those hard to find tech documents and journals, let alone a net forum.
i think i speak for a lot of people here, that this is THE SHIT
thanks for the interesting and mind boggling read guys
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all i can say is: this is exactly why turbos are *cheating*
mrshin - from my understanding, ITBs on an FI engine becomes simply an issue of throttle response. other aspects of port tuning etc etc are reasonably irrelevant in FI use.
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Location:
Lost in the K hole
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May 2002
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I supported Toymods
Location:
Perth
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May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 00:39
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| ed_ma61 wrote on Fri, 15 October 2004 08:22 |
all i can say is: this is exactly why turbos are *cheating*
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Riight, cheating. You're just looking at it from the wrong perspective. You're improving the efficiency of the intake in this thread, the turbo is improving the efficiency of the entire engine by utilising a wasted resource. Sometimes the option to just turn up the boost isn't available, and you have to look at maximising the efficiencies of other things
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Location:
Lost in the K hole
Registered:
May 2002
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 00:50
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| ed_ma61 wrote on Fri, 15 October 2004 08:46 |
if the turbo boys put this much effort into their BOV selection, then maybe i'd give em a bit of credit...
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Don't pigeon hole us Dr Ed Not all of us want to neglect the finer points of extracting the little bits.
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Location:
Lost in the K hole
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May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 00:51
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notice how i edited it... you caught me!
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I supported Toymods
Location:
Perth
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May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 00:56
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Oh yeah, I had to copy and paste from my e-mail! "Hey, thats not what he originally wrote..."
Just making sure that you realised there are some people who ain't just going to wind it up 1psi and toast the air some more, or bitch about how my BOV doesn't flutter or make a big enough "ppsshht". My little baby turbos, high-flowed or not are only going to make so much power before I need to look at optimising further what i've got.
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I supported Toymods
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Perth
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May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 01:00
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And besides, I'm reading this thread aren't I?
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Location:
Lost in the K hole
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May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 02:35
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QUESTION re the above graphs...
the throttle plate appears to be the termination point of the intake wave functions the only way that makes any sense to me is if the throttle is closed, or only partially open, which doesnt quite work with the model operating at 9000rpm.
thoughts?
also, anyone have any thoughts further to my idea of placing the throttle plate at the node of the intake wave? looking a little more closely at the TODA 3S engine, the throttle plate is almost exactly 1/2 way along their l-o-n-g intake runner.... leading me to believe that the runner is tuned for 2nd harmonic, and that their throttle is located at the central node.
just an idea
ed
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Location:
Sydney
Registered:
July 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 02:45
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That gif file(s) is awesome. Now I know what MilesB has been talking about with port scavenging etc.
And how important it is to get the waves to match up.
Thing is, this is very specific isn't it. Like specific RPM (piston timing), very specific cam (when the ports open/close).
So you'd really have to define an RPM band that you want it to be in the sweet spot (intake/exhaust tuned for) then build it ALL to be at that point.
How wide would the RPM band be for the sweet spot? Are we talking 100/200 rpm and a bell curve away from it?
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Location:
Sydney
Registered:
July 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 02:55
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| ed_ma61 wrote on Fri, 15 October 2004 12:35 |
QUESTION re the above graphs...
the throttle plate appears to be the termination point of the intake wave functions the only way that makes any sense to me is if the throttle is closed, or only partially open, which doesnt quite work with the model operating at 9000rpm.
thoughts?
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The different diameter in pipes would definately change the form of the wave, but I don't think it would push it back completely like it looks like its doing without being completely closed.
The wave won't be in the belmouth as it'll have no where to bounce back from. It'll be where the biggest restriction is.
The return wave on the intake track is a considerable amount smaller than the first wave.
... my thoughts.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 02:59
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| SupraPete wrote on Fri, 15 October 2004 12:45 |
So you'd really have to define an RPM band that you want it to be in the sweet spot (intake/exhaust tuned for) then build it ALL to be at that point.
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thats exactly what building an NA is all about 
you can build the system to have a power band as narrow or as broad as you want it pete. down to a few 100 rpm is possible. the narrower it is, the higher the efficiency and peak output will be. conversely, if you accept a lower peak, youll have a wider available power band. its all a big compromise... hence the introduction of VVTi, TVIS, ACIS and all that stuff.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 03:01
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pete, waves DO bounce off the open ends of pipes
at WOT that whole graph should be alight with waveforms right up to the very tip of the pipe
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Location:
Sydney
Registered:
July 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 03:11
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| ed_ma61 wrote on Fri, 15 October 2004 13:01 |
pete, waves DO bounce off the open ends of pipes
at WOT that whole graph should be alight with waveforms right up to the very tip of the pipe
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So whats the point of that image if its not at WOT??
And yes, the waves bounce of "open ended pipes", but what about flutes? I thought one of the reasons for flutes (appart from getting as much surface area as possible) is that wave bounce would be reduced considerably.
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Location:
Sydney
Registered:
July 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 03:14
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My theory: The reason why grammaphones produce more noise than normally is because there isn't (sound) waves coming back towards the end point, they're all exiting the fluted end.
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Location:
South Australia
Registered:
July 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 03:19
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Must hit books at uni.... *sigh*
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Location:
Sydney
Registered:
July 2002
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Re: ITBs & Port X-Sectional Areas + Lengths : Your Thoughts....
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Fri, 15 October 2004 03:21
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| ed_ma61 wrote on Fri, 15 October 2004 13:01 |
at WOT that whole graph should be alight with waveforms right up to the very tip of the pipe
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Looking at the diagram again. It makes more sense if the little square was the end of the runner with open air (constant pressure) on the left and the intake runner on the right.
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