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Registered:
July 2003
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New stepless throttless valvetrain
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Tue, 01 July 2003 04:06
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At http://www.pattakon.com a new Continuously Variable Valve Actuation system is presented, with working prototype photos, plots and animations (even stereoscopic ones).
It is like Honda's VTEC or Toyota's VVTLi, just with infinite steps starting from zero (and not only two).
Any engine, racing or normal, can be improved as the torque can be about constant from very low revs to the top allowable revs. But this is not "the" important.
The fuel economy and the lower pollution with improved driveability, are.
Hybrid car seems for the moment a solution just because present heat engines are not working in real life as effectively as in the lab. The new system can change existing and future engines in order to operate as if they were always in their best revs and load.
In just five minutes the animations and the plots in the site can change the way engineers are thinking about the present internal combustion engines.
We need your comments and objections.
Thank you
Manolis Pattakos
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I supported Toymods
Location:
sydney.au
Registered:
August 2002
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Re: New stepless throttless valvetrain
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Tue, 01 July 2003 06:16
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wow
this post seems to confuse me. maybe its the engrish like grammar?
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: New stepless throttless valvetrain
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Tue, 01 July 2003 08:30
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it looks like an interesting idea, although i think there are a few issues to be resolved.
1. on the valve opening graphs, there is a flattening of the curve near max lift... this would not be good for spring haronics at high rpm... as an analogy, think of clipping of an amplifiers output and it's effect on speaker cones...
2. what longevity could be expected on the components under 'real' driving conditions... that small rod (and the ball ends) seems a little flimsy for the things i would like ti to do...
lets say 9-10000rpm, with seat pressure of 80lbs and nose pressure of 240lbs. at high revs that part would have to be rather stout, especially in compression.
looks like a nice design, but i would like to see a more stout design capable of higher revs, incorporation of more of a roller type design (that stick is a bit wussy), and also not have it as a throttle, but more of a variable lift/duration.
interesting that someone from greeve would send ideas to a car club list.... nice designs tho..
if you want to make a head for a toyota K type enigne i'll be glad to try it 
Cya, Stewart
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Registered:
July 2003
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Re: New stepless throttless valvetrain
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Wed, 02 July 2003 09:33
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| oldcorollas wrote on Tue, 01 July 2003 18:30 |
it looks like an interesting idea, although i think there are a few issues to .... a toyota K type enigne i'll be glad to try it
Cya, Stewart
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Hello from Greece.
The flattening of the valve opening graph at max lift is only because the cam lobe profile was selected to have a specific simple form, for demo reasons.
The real cam profile of the prototype is shown many times in the “Theory, images and photos” page of the site, and the resulting valve lift graph is quite different than the demo one.
The top curve could be, according the profile of the cam lobe, even a pure sinusoidal curve. We have already an easy method to calculate and create the necessary cam lobe profile in order to achieve any desirable valve opening graph. Just note that even with a pure sinusoidal top curve, the lower curves are somewhat deformed, but there the inertia loads are very light in comparison.
The expected longevity of the mechanism in “real” driving conditions is better than the conventional valve train system.
The normal car operates most of its “life” in low revs and partial loads, where the new system operates actually unloaded, as the valve springs are only partially compressed. Compare this case to the idling (or low revs) operation of the conventional engine having the 80lbs/240lbs valve seat pressure you mentioned. The cam lobe has to compress completely the strong springs, while the timing belt or chain has to provide the necessary “impact” torque.
No matter how strong the valve springs are, you can rotate at idling (which means 0.15 to 0.2 mm valve lift) the camshaft of the new system (with the timing belt removed) easily, just by your small finger. Try the same in a conventional head.
The new system is loaded as the conventional system only at its maximum valve lift operation. And this maximum valve lift is necessary only at “high revs with full load”. Anywhere else the new system operates with lower loads than conventional.
On the other hand, if by “real” driving you mean racing use, things are not significantly different. Any moment you operate the engine at lower than maximum revs or at partial load, the valve springs, valve seats, cam lobes, timing belt and the rest components of the valve train system take a short or long ‘breath’ that extends their life and delays fatigue.
By the way, what is the percentage of time that a racing engine operates at its maximum revs with full load?
The small ‘push rods’ with the spherical ends, do seem weak.
But their 4 mm diameter, their 25 mm length form center to center and the 6 mm diameter of their spherical ends could easily change to 8 mm, 25 mm and 12 mm without changing the basic design.
In practice the small ‘push rods’ gave no indication that they are overloaded.
Just compare the contact ‘surface’ between the small spherical end and the corresponding hemispherical cavity to the case of Toyota Celica GTS (or VVTLi), where the rocker arm and the top valve stem have an actually point or line contact. Surface contact against line or point contact.
Thanks
Manolis Pattakos
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: New stepless throttless valvetrain
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Thu, 03 July 2003 05:05
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| manolis wrote on Wed, 02 July 2003 19:33 |
The flattening of the valve opening graph at max lift is only because the cam lobe profile was selected to have a specific simple form, for demo reasons.
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ohh oki.
| manolis wrote on Wed, 02 July 2003 19:33 |
The expected longevity of the mechanism in “real” driving conditions is better than the conventional valve train system.
The normal car operates most of its “life” in low revs and partial loads, where the new system operates actually unloaded, as the valve springs are only partially compressed. Compare this case to the idling (or low revs) operation of the conventional engine having the 80lbs/240lbs valve seat pressure you mentioned. The cam lobe has to compress completely the strong springs, while the timing belt or chain has to provide the necessary “impact” torque.
No matter how strong the valve springs are, you can rotate at idling (which means 0.15 to 0.2 mm valve lift) the camshaft of the new system (with the timing belt removed) easily, just by your small finger. Try the same in a conventional head.
The new system is loaded as the conventional system only at its maximum valve lift operation. And this maximum valve lift is necessary only at “high revs with full load”. Anywhere else the new system operates with lower loads than conventional.
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thats a very good point, would reduce the valve train loading quite a lot.
| manolis wrote on Wed, 02 July 2003 19:33 |
By the way, what is the percentage of time that a racing engine operates at its maximum revs with full load?
The small ‘push rods’ with the spherical ends, do seem weak.
But their 4 mm diameter, their 25 mm length form center to center and the 6 mm diameter of their spherical ends could easily change to 8 mm, 25 mm and 12 mm without changing the basic design.
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i don't actually know, but they would be at high revs for about 1/2 the time...
if the exposure to high rpm and load will not cause significant wear, then it might last...
as an example, in my road car (1.3L) cruising is at about 4500rpm, and when driving hard the rpm stay between 5000 and 8000rpm... although i don;t always drive hard, it is this time that will cause the most damage.
as far as the pushrod size, i think the OHV pushrods in my motor are about 5mm diamter, but hollow, so i guess your dimension may not be too bad. i would be concerned with the wear of the contact points at the ends tho... what happens when maybe 0.5-1.0mm of wear has occurred? are the parts rebuildable?
a couple more questions. how do you turn the lever part to achieve the different lifts? electric motor wuth screw thread? how loaded are these parts?
anbd finally, do think this sort of system could be retrofitted to an OHV type design? ie replacing conventional rocker arms with something similar to this?
Cya, Stewart
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Location:
Montrose, VIC
Registered:
May 2002
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Re: New stepless throttless valvetrain
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Thu, 03 July 2003 10:16
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Sure, I love it, in fact I want one - but isn't it rather similiar to what is already offered by BMW on their V12 engine?
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Location:
Sydney
Registered:
July 2002
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Re: New stepless throttless valvetrain
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Fri, 04 July 2003 03:18
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This is all very interesting. I was wondering how it could be done. I've been interested in getting some cams that were tuned for a specific rpm band, with this it could be tuned for that rpm band, but still work at others.
Are there any real applications for it? I saw you made a prototype. Is this going to go into production for a specific (I'm guessing new) engine?
Can you retrofit it to older engine heads? Can we send you a set of heads and you set it up ready with completely WILD cams at full load, but bugger all at low load?
I've had my car idling at 340rpm on 4 cylinders (its a v8). If this could be done all the time (on all 8 cyl), that would be pretty cool. And of course the benefits of lower fuel consumption and emissions.
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Registered:
July 2003
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Re: New stepless throttless valvetrain
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Fri, 04 July 2003 04:15
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[quote title=oldcorollas wrote on Thu, 03 July 2003 15:05 ... replacing conventional rocker arms with something similar to this?
Cya, Stewart
[/quote]
Hello from Greece.
Do not compare the diameter of two push rods to see which one can carry heavier load. Your pushrods is "weaker" than the small pushrods of the prototype just because they are many times longer, thing that make them easier in bending.
I hope you mean wear of 0.05 to 0.1 mm and not 0.5 to 1 mm.
Normally, even the 0.05 mm wear is excessive.
The valve actuators/adjusters (the small cylinder on the top of the valve stem) and the small push rods are so small, cheap and simple pieces that they will be replaced when necessary. They are like the replaceable shims of conventional engines.
The control of the valve lift is done by the rotation of the control shafts. As the accelerator pedal is pressed, a string (the previous “throttle string” or “throttle wire”) is pulled and the control shafts are rotated. When you leave the accelerator pedal, the control shafts return in their idling position immediately, just by the action of the normal valve springs. This is all. The accelerator pedal is heavier, of course. But the response is so direct you cannot believe.
In the prototype the brake pedal is also heavier as there is no vacuum in intake manifold to amplify the force applied by driver’s foot on brake pedal.
Always there is the option of “drive by wire”.
Or you could use some kind of “servo” (electric, hydraulic etc) to lower the necessary force on the accelerator and brake pedals.
And of course the prototype had to be as Spartan as possible.
As regards the OHV designs, the proper position of the VVA system is between camshaft and pushrods, if there is room there.
But the more parts and joints between cam lobe and valve stem, the worse the total accuracy.
So it seems easier and more effective the application of the system in OHC engines and even better in DOHC, 4 valve per cylinder engines.
Thanks
Manolis Pattakos
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Location:
Sydney
Registered:
July 2002
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Re: New stepless throttless valvetrain
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Fri, 04 July 2003 04:28
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I never thought of the affect to the vacuum brake line.
With the wire needed to actuate the system, it would be better (that I can see) if it was controlled by load or MAP by the computer and a servo instead of throttle. Throttle cable may be an easyer and cheaper way to implement it though.
What do you mean by "the prototype had to be as Spartan as possible"? Sounds as dodgy as a dingo's donger (joke).
Again, can it be done for any other specific engine? When does mass producing start?
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Registered:
July 2003
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Re: New stepless throttless valvetrain
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Fri, 04 July 2003 07:32
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| mrshin wrote on Thu, 03 July 2003 20:16 |
Sure, I love it, in fact I want one - but isn't it rather similiar to what is already offered by BMW on their V12 engine?
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There are many differences between BMW’s valvetronic and the new system, even if both are continuously Variable Valve Actuation systems.
Valvetronic changes the lift of the valve together with the duration of the valve opening. For instance if you choose 1 mm valve lift, you get also 40 degrees valve duration. If you choose 8 mm valve lift, you get also 180 degrees valve opening duration. But if you like 1 mm valve lift with 180 degrees duration, it is impossible.
The valve opening also happens at about 100 degrees after TDC, so you absolutely need an improved additional continuous VVT of wide angle (they call it double vanos) in order to move the valve opening near to TDC at short valve lifts.
You need also additional strong restoring springs, one per valve.
You need also drive by wire and relevant electromotors, otherwise the engine cannot operate.
You need also a strong CPU and software to coordinate the subsystems involved.
And besides all these, valvetronic cannot control the exhaust valves, but only the intake ones.
Valvetronic includes a good number of parts (for instance it uses two reciprocating rollers per valve) and a good number of interfering joints conveying the motion from the cam lobe to the valve.
But if you try low revs with full load, the system is confused, as what is necessary is short valve lift (i.e. 1 mm) AND long duration (i.e. 180 degrees). Finally it necessarily works as a conventional valvetrain system (i.e. 6 mm valve lift with 150 degrees duration), losing the benefits it claims it offers: “extreme turbulence and swirl” and “perfect homogeny” due to the passing of the mixture through the narrow opening between valve and valve seat.
On the other hand, if you try to operate the engine above 6000 rpm, again there is problem, as the mechanism cannot operate safely there (heavy parts, high friction, wear concentration points etc).
The case becomes strange:
On one hand, a VVA system seems theoretically the perfect tool to make an engine operate efficiently in a wider range of revs, compared to conventional.
On the other hand the BMW’s valvetronic VVA mechanism itself restricts the operational revs range, at low lifts due to inherent design characteristics, at high revs due to its strength, its internal friction, its inertia loads and its excessive wear.
So, even though BMW’s valvetronic is an absolute commercial success offering better economy, lower pollution and improved drivability than conventional and two step VVA systems (like Honda’s VTEC, Toyota’s VVTLi, Porsche’s Variocam Plus etc), it does have a lot of weaknesses and limitations.
If a continuously VVA system could combine the power output of Honda’s S2000 VTEC (120 PS per litter in normal production) with the economy, drivability, easy starting, low pollution etc of BMW’s valvetronic (if possible without additional supporting systems like VVT, CPU, network, drive by wire, electromotors etc) then it would be a very good system indeed.
Thanks
Manolis Pattakos
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Registered:
July 2003
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Re: New stepless throttless valvetrain
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Fri, 04 July 2003 07:35
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| HKSPete wrote on Fri, 04 July 2003 13:18 |
This is all very ... of lower fuel consumption and emissions.
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Applying the new VVA system in normal 4 valve per cylinder engines, and using just one wild cam lobe per pair of valves, it is actually like having infinite cam lobes (from wild to ultra “soft”) and use the best according instant operational conditions.
We plan to apply the system in a 16 valve straight four, 1.8 litter new Ford Mondeo engine. We have to remap injection and spark advance, as the operation of the engine is completely different. It seems necessary also the substitution of present intake manifold with multi body throttle system (but without the throttles). Then we will evaluate the result and proceed.
In our future plans is the retrofit of older engine heads. But we are not yet ready.
What we are trying to achieve are engines offering at high revs “power per litter” similar to the best VTEC or racing, and simultaneously offering the drivability, the economy and the low pollution of the best “family” car engines.
In other words, we are trying to achieve “substantially” constant torque from extreme low revs to the rev limit of the engine.
Thanks
Manolis Pattakos
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Registered:
July 2003
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Re: New stepless throttless valvetrain
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Fri, 04 July 2003 07:49
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| HKSPete wrote on Fri, 04 July 2003 14:28 |
I never thought of the affect to the vacuum brake line.
With the ... engine? When does mass producing start?
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Spartan means as simple as possible.
I preffer in the prototype a heavy accelerator pedal with a string immediately rotating the control shafts than a drive by wire system which needs electromotor, control, adjustment etc. In the prototype we wanted to see how the basic VVA system behaves.
Yes the system can be done for any DOHC and OHC engine. It also can be applied to some OHV engines, but it is not so easy neither so accurate as in DOHC.
When? Not yet.
Maybe before the end of the year.
For now we have just one prototype.
Thanks
Manolis Pattakos
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