Posted by alloy_625 on September 21, 1998 at 23:39:48:
Racetech had a bunch of articles on group C engines. In particular, it mentioned that the Toyota engine didn't have any quench and ran a dished piston. I seem to recall some hints that you might have worked on that project and I was wondering why they gave up "free octane" as you put it if indeed you had a hand in designing it. Also, the Nissan engineer mentioned using a laser to do flow vis on a single cylinder through a window to map the swirl, stuff we've done for boundary layer analysis, but still pretty damn cool. Any involvement in that? How about the notion that tumble flow is difficult to achieve at F1 speeds as suggested by another article? And while I'm beating on the topic of quench, is there any reason why the pistons for the SOHC 1.6 on the hybrid site appear to have asymmetric valve reliefs (or am I going blind) and why didn't you machine some quench pads onto the pistons and corresponding reliefs on the head as NITRO mentioned doing a while back?
Posted by NITRO on September 22, 1998 at 08:50:29:
In Reply to: TOO/NITRO buncha questions posted by body on September 21, 1998 at 23:39:48:
First on the sohc and dohc pistons, the valve reliefs are symmetrical
only with respect that there are two on each side of the piston. The intake
and exhaust reliefs are not the same diameters or the same depths. The
reliefs exist only because attempting to "soften" a production based engine
where the valve angles are fixed and grinding a cam profile that the rocker
can follow on the intake side which would allow the valve to return to
a seated position at tdc on the overlap cycle is impossible (or simply
cost prohibitive). I'm not sure that you have noticed that the dome prortion
is much larger on the inlet side of the piston to help create the exhaust
bias, and the flats or quench areas extend (out of the top of the block)
so their clearance with the "dished" quench areas of the head is minimal
(the quench "gap" is slightly less than on a head/piston with deck level
"flats"). This is a poor mans way of solving the resessed deck or quench
areas of the head.
Regarding the Toyoda Group C engine you read about: Was this a turbo or N/A engine, and you must remember two things. First don't believe everything you read (and see) in magazines, and you must also understand that there are typically several R&E programs that take place in parallel prior to a down select.
We have never dealt with Nissan on (flow related matters), and their use of lasers is not unique, however, there are "better ways" of looking at the mixture in the cylinder than laser measurement.
As we really have never been proponents of "tumble flow", it's good if Nissan can't achieve it. To ENDYN working to achieve tumble is like trying to achieve negative lift on the wings for an airplane that you also want to fly. Tumble falls into what T.O.O. has often described as "random turbulence" , and due to the nature of the motion, using tumble does not provide a homogenous cylinder mixture that we feel is conducive to a rapid controlled burn.
I hope I've properly addressed all of your questions, if not, post again and we'll give it another try.
Posted by alloy_625 on September 22, 1998 at 13:23:33:
In Reply to: Re: TOO/NITRO buncha questions posted by body on September 22, 1998 at 08:50:29:
WRT SOHC piston, I was wondering if one of the intake valve reliefs was larger than the other, not the asymmetry between intake and exhaust (ie is TOO playing stagger cam tricks here). For the quench, I think I see where you might have milled some clearance for the piston at the periphery, you guys are too tricky. It's sort of hard to see all the piston detail in the two pictures but I'd be happy to accept one in the mail =) 87mm please.
Could you talk more about soft heads? You/TOO have mentioned what you're trying to achieve, but never much on how you actually implement it. From your statement, it would appear that it's difficult to do, but still it would be interesting.
On the Toyoda engine, I think they were talking about an RV35 or 36, but I don't have it handy. It was a turbo engine with Toyota divided inlet turbos and four wastegates! I usually buy the magazines for the pictures, unfortunately they almost never show the guts. Say, TOO mentioned ceramic liners a while back, have you guys had any experience with the GKN squeezeform liners?
Posted by NITRO on September 22, 1998 at 14:46:38:
In Reply to: NITRO more questions posted by body on September 22, 1998 at 13:23:33:
The notion of the soft head is what T.O.O. created in his efforts to
develop engines which could run at higher power levels without detitonation.
They were cracking a lot of exhaust valves, when T.O.O. met Michael May
on a program they were both involved with...the General Dynamics Electrosonic
fuel induction system. Micheal had sucessfully built his "Fire Ball" cylinder
head for application on some water cooled VW's. The stacic CR was 16-1,
and the engines made more power than stock, ran on unleaded fuel, produced
fewer emmissions, got better mileage, and did not detonate.
The "Fire Ball" head squeezed all the mixture into a combustion chamber that only housed the exhaust valve and the spark plug.
Based on what May had shown, T.O.O. used the same principal but threw swirling the inlet mixture into the mix, as well as using the shape of the piston and chamber to maintain or accelerate the swirl, and also move the swirling mass to the exhaust side of the chamber where he also placed the spark plug. The heads were listed in the Ford SVO catolog as the "Super Swirl" heads, however, subsequent testing revealed that, not only did the engine make torque that was "questioned at the time", but you could retard the spark and gain additional power and the fuel consumption was about the same as a 2ltr. engine, except this engine made well over a thousand HP in doing so. The spark could be advanced to the extent that the crank should have hit the dyno room floor, but it would not detonate....it'd lose some power, but that was all. You could also run the fuel curve max rich to so lean that people didn't want to watch....but no detonation, simply a slight loss of power. The name "Soft Head" came from one of the people observing the tests, because the engine exibited such a wide window for tuning and you couldn't blow it up by missing the proper tune-up.
In combinations where the head locations are already designated by the casting, you do the best you can. If staggering the inlet opening allows you to more effectively create swirl (combined with the port configuration), rest assured that T.O.O. will employ any means possible. The biasing of the piston dome toward the inlet side is to create a pressure differential, which will force the mixrure to the exhaust side. Do not forget that those pistons are for a blower engine, and if you want to force the mixture and burn to a certain area, you sure can't do it with a flat or dished top piston = the dome = high static CR for boosted engine, which normally = trouble, but if you can "soften" the sensitivity, perhaps the engine won't realize that you can't do that, and run detonation free, and also be more forgiving on fuel mixture....beginning to get the picture??
In 1986 T.O.O. had developed the means to sample the mixture in the cylinder when the piston was at BDC on the inlet stroke, and what he found was a shocker. Although we were running leaner mixtures than books said were possible, we'd always thought that is was due to having a homogeneous mixture in the cylinder due to the inlet swirl, but the mixture was layered, so as the upper few % were 12-1, the next 10% was 14-1, and as you went deeper the mixture continued to get progressively leaner, with the last 30% far less than 20-1. You can't light mixtures that lean with a plug, but the fact that the upper layers were richer, the ignition was easy, and each layer could progressively light each other. The burn was progressive, and very thorough, and very fast requiring little ignition advance.
So what T.O.O. created with his "Soft Head" was really a simplistic form of stratafied charge combustion with no pre chamber.
T.O.O. has worked with ceramic cylinders since 1984 when the government requested his participation in some programs. As I do not know where the status is, all I can say is that the friction coefficient was near 0 and the ceramic was able to absorbe heat and then reflect it back into the cylinder for additional power, and the engine required no cylinder cooling what so ever.
I hope I've provided some info that will get your head going even faster than it already obviusly is..I have to go............keep it up.
Posted by NITRO on September 22, 1998 at 20:36:48:
In Reply to: Hmmm...I can see where the notion of running just air as fuel came about. Seems feasible... and didn't Oldsmobile or Mitsu actually create an all ceramic 4-banger in a concept car back in the mid 80s?? I could've sworn... n/m posted by body on September 22, 1998 at 18:11:55:
There have been several engines with primary components made of ceramics
during the last 15 years, and some as you noted received publicity. The
program T.O.O. worked on was a "black project", and, as I said earlier...I
do not know if I can talk about it or not. Sometimes these programs take
50 years before the DOD feels the public has the "need to know". I'll ask
T.O.O. about the status.
Burning air....We'd like to think that it came from one of our projects, but.............in a since, part of the process did. The notion was part of an attempt to design engines that could allow a "craft" to take off from a runway and "fly" to orbit, and fly back.
The original program (which has been de-railed (financially) many times by government spending cut-backs, used rocket propulsion. We proceeded to ram jet, and from there to scram jet in efforts to cut some of the polution that both liquid and solid fueled rocket engines produce.
During the mid to late '80's T.O.O. was contracted by the Livermore Labs. to build engines that they could test gas formulation with to allow their Cray computer to analyze in a government funded program to produce a non polluting gas supplement which would eliminate detonation. The program was not very successful, considering that it lasted two years, however, at the end T.O.O. machined a "special" combustion chamber/piston combination and sent it to them with instructions to test when they had time. They tested it and quickly found that regardless of how close they moved the head to the piston, they could not induce detonation. This had considerable signifigance as pressure had previously always caused detonation, but this application did not. T.O.O.'s notions of the "shape" quickly grabbed attention, and from that point on he's been consulting and building "special" shapes that will produce detonation (pulse detonation) and shapes that will not. The fact that the "shape" could play such an important role in the character of the "burn" started engineers working on alternate fuels that previously were not acceptable, and we've not come to the ability of having the technology and "shape" necessary to burn only air as fuel. This does create some adverse gasses, however, it allows engineers to design air/space craft that don't need huge fuel tanks, and thus can reach orbital velocities quicker and also carry greater pay loads.
So, perhaps the Soft Head did point things, but it's hard to say. T.O.O. has always maintained that anytime we think we're the only ones working with certain technologies, we're setting ourselves up for a big surprise, because there are so many people working on similar things world-wide, it's crazy to think that you're the only one, and, of course, there's T.O.O.'s philosophy that there are many ways to skin a cat, and, therefore, there are many different combinations which can produce the same or similar results.
And with the "few" distractions here, people can't see why it takes so much time to spit blower kits out! ! !
Posted by The Demon on September 23, 1998 at 00:05:24:
In Reply to: Re: A Lot Of Hot Air ! ! posted by body on September 22, 1998 at 20:36:48:
A concept that's fascinated me recently is...well, it might be old news or something that's already been done...but the idea of something I think is like a form of perpetual motion. I think the sr71 took advantage of this concept with its movable engine cones...where at certain speeds, the cones would move in and out to direct the air into the engine. But I was wondering if it would be possible to produce a shape or a variable shape that can take advantage of the air it's cutting through and just literally "ride the wind." So at a certain velocity, the object can alter its shape to produce a flow of air over it that will propel it forward with no need of propulsion from an outside source. Maybe this is too far-fetched...? Hmmm...to make it automotive-related...maybe the same concept can be applied to engine components or maybe even a whole car's shape or....
Just going off,
Posted by NITRO on September 23, 1998 at 06:29:29:
In Reply to: Re: A Lot Of Hot Air ! ! posted by body on September 23, 1998 at 00:05:24:
The spikes in the front of the engines on the SR-71 are there to prevent
supersonic air from entering the engines. The SR-71's engines are of the
conventional turbojet with afterburner variety, and as the speed of the
craft increases, the size of the inlet opening must decrease, or the engine
simply will not work.
If you look at the inlets on the F-111, F-14, F-15 you will notice that several have "splitter plates" which separate the inlet from the fuselage and prevent boundary layer air from entering. The inlets also can change area by use of a spike or simply rotating a portion of the inlet to close off a good portion of the area, which prevents supersonic air from entering.
A cheaper fighter that's still quite revolutionary is the F-16. It has a fixed area inlet which is optimized for around 500 mph which is typical dog-fighting speed. The fixed inlet also weighs a lot less, and probably reduces the cost of the plane by at least $1mil. The F-16 also can fly very close to mach 2 without having the engine inhaling supersonic air. This is accomplished by the placement of the inlet relative to the raydome or nose of the craft. When the F-16 exceeds the speed of sound, the shock wave developed by the nose acts as a flow diverter and the almost all the supersonic air is deflected past and under the inlet. It's a relatively good performer.
There are and have been variable area inlets that were "smart", but none has ever been good enough for production aircraft.
So now you know what the "cones" are for....they do look bad-ass on the SR-71, and when you see them, you know that they're "serious business".
Posted by alloy_625 on September 23, 1998 at 00:13:20:
In Reply to: Re: A Lot Of Hot Air ! ! posted by body on September 23, 1998 at 00:05:24:
There are some projects out there in academia (and perhaps in top secret black labs too =) on smart surfaces that can identify certain conditions and then adapt to optimize some metric, in this case vortices that contribute to drag on airplane wings. In a nutshell, you detect local high-drag areas, change the surface and make sure it runs off somewhere else to play. To stay on topic, I guess you could do this on a car, don't think anyone could afford it...
Posted by alloy_625 on September 23, 1998 at 00:09:20:
My head's sort of stuck on backwards now so you'll have to go gentle when I get something wrong, but let me see if I'm on the right track here.
Using the analogy that an engine is a glorified air pump, our job is to pump in some air, prepare it, and then burn it doing some useful work in the process. For a given amount of energy, there are a lot of ways we can use it, quickly, slowly or somewhere in between. "Conventional" wisdom these days would seem to be the pentroof chamber, centralized plug, multiple valves etc. Given what you guys appear to be able to do (well I never have seen it with my own eyes =) with "antiquated" technology ie Pro-Stock, one has to start wondering. If I'm understanding this correctly, you are foregoing the easy to ignite, rich mixture with centralized ignition that generates a flame front that conceivably spreads radially in some uniform manner for a (as you put it) progressive flame front that propagates from one end to another generating a pressure wave that is in some sense controllable wrt speed and pressure. At the same time, you are using a "single" outlet system ie closed intake valve at TDC, to regulate the cylinder pressure and work done on the piston. The exhaust profile then serves to meter or dribble out the amount of combustion energy needed to keep the motor together and perhaps serves to inertially suck some intake in for the next cycle? If the above is correct, then the implication is the combustion space merely (haha) needs to be designed for optimum flame front propagation and exhaust flow meaning compression ratio and AFR become somewhat meaningless assuming pre-ignition doesn't happen as that would ruin your day. Does this mean you organize the mixture so that the leanest areas are in the "hot spots"?
If the above is right in any sense, does this mean old two-valve heads with the plug near the exhaust are better in some sense since it's easier to push the charge near the plug and exhaust? My photocopy of the old articles doesn't show the pistons clearly enough to see what they're doing.
Posted by BigWigVW on September 23, 1998 at 16:32:58:
In Reply to: NITRO: lukewarm air posted by body on September 23, 1998 at 00:09:20:
On normally aspirated engines, as in Pro-Stock like mentioned above, how does not opening the intake valve until after TDC affect the cam duration and the engine's powerband? Does the gain you get either in additional CR or in more efficient burn offset the loss in how much air the engine could draw in with the shorter duration cam? Along that same thought, do you then have to increase the valve opening rate to help compensate for the loss in duration? With solid lifters like we have in our aircooled VWs, weíre somewhat limited on cam ramp rates.
Itís not totally clear to me how the FireBall head mentioned in the thread below or T.O.O.ís subsequent design would reduce the chance of detonation. If itís possible to explain here, please elaborate a little on how chamber shape and detonation are related.
I guess what Iím getting at is this. On a VW race motor, if I was to get a cam that had a delayed intake opening until after TDC, and then get a domed piston such that it effectively filled the combustion chamber on the intake side, and angle my plug toward the exhaust valve, so that what I was left with was seemingly outrageously high CR and a tiny combustion area focused on the exhaust side, would I be able to go out and crush the current Pro-Stock Volkswagen record? Thatíd be cool.
Thanks for any answers to the real questions above.
Posted by NITRO on September 23, 1998 at 18:53:15:
In Reply to: Re: delayed intake & combustion chamber shape posted by body on September 23, 1998 at 16:32:58:
On ProStock engines we do open the intake valve prior to tdc, but only
a minimal amount, and once the crank is at tdc we open the inlet valve
at the same velocity the piston is moving down from tdc, then about 12*
atdc the cam "slams" the valve open, as the piston is out of the way at
that point. The entire cam event is short, as the inlet ports flow close
to their maximum at only 50% lift. This allows one to configure the combustion
space to a more optimum shape = deep valve reliefs on the inlet side are
You must remember that the quality of combustion, not the flow rates, cam size, or any other support system is what rotates the crank. If you can produce a broad pressure curve that focuses the peak pressure past tdc, you mechanically and geometrically are doing good.
Creating a bias burn is also very effective. We always smile when we see no carbon coloration on the inlet side of the chamber and piston.
I can't make this any more simple than T.O.O. has: If you consider all the fuel and air molecules as pieces of charcoal, and a conventional chamber places them all in a circle. Light the center piece and time how long it takes to burn all the pieces. Then take the same number of pieces and configure them into a sphere (smaller area) and somehow light the center piece again and time the burn...which takes longer.
The purpose in compressing all or as many as possible fuel and air molecules into a "sweet spot" is to expose more to the flame front for at least a moment, and once you have them all burning you have created a more efficient burn than could be achieved if the air/fuel molecules were "all over" the combustion space. Get the picture??
When T.O.O. designs chambers and pistons for any application Turbo, N/A, etc., he never determines a specific mechanical CR. He designs the chambers to create the "soft burn" and the CR is what ever it is. On programs where we supply sealed engines, we normally never check the CR, as it's meaningless to us, and also to the engine. The shape is everything.
Posted by BigWigVW on September 23, 1998 at 10:08:53:
In Reply to: NITRO: lukewarm air posted by body on September 23, 1998 at 00:09:20:
Hey Alloy_625 or Nitro or whoever, I've read with interest the posts below about headflow and combustion chamber dynamics, but from lack of experience on my part, not knowing what alot of these things look like makes it tough to grasp some of these concepts. What is some good reading material on the subject? I saw Alloy_625 mention Racetech atricles - what's that?
I'm particularly interested in combustion chamber techniques that could be applied to 2-valve single-plug chambers, such as the aircooled VW head.
Thanks for the interesting discussion so far. Looking forward to more.
Posted by NITRO on September 23, 1998 at 11:27:21:
In Reply to: Re: My Head hurts! posted by body on September 23, 1998 at 10:08:53:
Most of the larger book store chains carry a reasonable collection of books relating tothe subject, and there's also Classic Motorbooks which generally always has ads in Road and Track and other mainstream sports car magazines. They may be on the internet as well.