Does quench affect power?

[ptuomov]

I know by far not all engines in essential racing series in Europe, but spherical heads are very rarely used in the late 90'ies till today. Hemi-heads are much more popular in the US, maybe they survived longer there. What I know is that flat head, wedged heads and roof chamber heads are used today in the V8 market. Are there spherical heads still there? Maybe the V2 engine of Harley-Davidson?

I think that (hemi)spherical heads belong to historical racing classes.

However, I think the modern analogy to "hemi" head is wide included valve angle. Normally aspirated four valve heads have been getting narrower and narrower valve angles, both to keep the high compression ratio combustion chambers reasonably compact without a piston crown and because the port angles and flow around the valve heads is now designed to preserve the flow kinetic energy as tumble. So in that sense even the hemi analogy of wide included valve angle is dead.

What's interesting to me is that even in forced induction heads designed for low geometric compression, the designers keep the narrow valve angle head and put a shallow spherical dish on the piston. If wide valve angles would make sense somewhere, it would be with low geometric compression forced induction engines -- but no, those seem to be gone too.

[juuhanaa]

Finnish the most popular racing class in its competive form, Lancia Fiat TC engine is still number one.

Folkrace is also a class where the rules are open i should say, so that reason i wont call it a piece of s*** "hemi". I know only little about quench, or mixture motion things, so that historical engine was just a side note from the racer...

[ptuomov]

Finnish the most popular racing class in its competive form, Lancia Fiat TC engine is still number one.

Folkrace is also a class where the rules are open i should say, so that reason i wont call it a piece of s*** "hemi". I know only little about quench, or mixture motion things, so that historical engine was just a side note from the racer...

That’s a claimed series for, what, EUR 3000? That’s 1/20 of the price of one piston in top level racing.

[LotusElise]

From Randy Gillis (formerly of JE Pistons, now at Racetec. Also ‘piston_guy’ on here):

I did the first "tapered" or conical dish pistons...Several dimensions were changed and those changes had a very clear affect on performance. One critical aspect was the width of the "perimeter squish band"

Yeap, I've experienced that also with flat or small head volume wedge heads. The industry use those since almost 40 years, and combine this with swirl and squish. On roof top chamber this won't work because of the CR demand, except inclined angle is low, CR demand is low and the bore as well the stroke are huge, just because the volume get to big.

I was involved in 5 combusiton process developments using those, we say "Linsen-" or "Topfbrennraum", where the outcome was always similar, a wider squish ring and a more deep bowl to gain back the volume of the combustion chamber to the spec'd CR. These configuration work very well, but are only possible and rational if there is room to play. The former socalled "M-Brennverfahren" of MAN, which was an extreme of that was well known. It was an approach to integrate the prechamber of the Diesel chamber into the piston as spherical with a smaller radius at intrance combared to the bowl radius. Designed for low pressure-rate (silent Diesel) these had awful CO emissions as much of the Diesel sticked to the spherical wall. Just as a side story when someone ride this horse to extreme .

https://youtu.be/rBZCnG1HwDM (starting at 39:00)

Very nice, thanks for sharing. That active operated 0.1 mm squish height is riding with big balls

[juuhanaa]

Finnish the most popular racing class in its competive form, Lancia Fiat TC engine is still number one.

Folkrace is also a class where the rules are open i should say, so that reason i wont call it a piece of s*** "hemi". I know only little about quench, or mixture motion things, so that historical engine was just a side note from the racer...

That’s a claimed series for, what, EUR 3000? That’s 1/20 of the price of one piston in top level racing.

when i started it was only half of that. Ask some ex world rally champs how competive class it is

[ptuomov]

Porsche 4-valve turbo engines, AMG/MB M139 2L turbo, Koenigsegg V8, etc. I believe they have spherical dish pistons with a band that’s not matched with the head to produce squish. But they of course do break up the tumble into smaller turbulent eddies as the combustion chamber gets compact with the piston coming up.

Those are all emission driven combustion process designs. Fast combustion is a NOx production lever arm, which is not the aim in todays EURO 6d+ compliant engines. You can't put them in a row of high performance engines. If they design it just for track it would look a bit different.

I agree with you on the general point that when interpreting other people's designs, one needs to understand what the binding and expensive constraints were.

In the case of the M139 engine that was released in 2014, I believe that the most binding constraint to making even more torque at higher rpms was cycle to cycle combustion variability, particularly pre-ignition/super knock that was traced back to oil droplets being drawn into the charge. I recall reading this from somewhere back in the day.

[Bigchief632]

So have we figured out how much it affects power yet? 13 pages, no definitive number, just a bunch of theory and I thinks and it seemed to helps.

[ptuomov]

So have we figured out how much it affects power yet? 13 pages, no definitive number, just a bunch of theory and I thinks and it seemed to helps.

On what kind of engine? 2-valve wedge at 6000rpm or 4-valve pent roof at 11000 rpm?

[Bigchief632]

So have we figured out how much it affects power yet? 13 pages, no definitive number, just a bunch of theory and I thinks and it seemed to helps.

On what kind of engine? 2-valve wedge at 6000rpm or 4-valve pent roof at 11000 rpm?

On anything. The majority of the guys on this site are referring to 2 valve domestic stuff, except for hoffman, who always quotes formula 1 stuff for some reason. Lots of theory for something that is minimal at best. And works the opposite in many cases based on the theory that no one has been able to define except for simulators that never seem to match, and a bunch of formulas that don't seem to apply to anything.

[RDY4WAR]

There's been less complex topics go 20+ pages. This one is just getting started.

[skinny z]

I believe the original question was "Does quench affect power?".
It would appear the answer is most definitely yes.
However by how much and in which direction is different questions altogether!

[hoffman900]

So have we figured out how much it affects power yet? 13 pages, no definitive number, just a bunch of theory and I thinks and it seemed to helps.

On what kind of engine? 2-valve wedge at 6000rpm or 4-valve pent roof at 11000 rpm?

On anything. The majority of the guys on this site are referring to 2 valve domestic stuff, except for hoffman, who always quotes formula 1 stuff for some reason. Lots of theory for something that is minimal at best. And works the opposite in many cases based on the theory that no one has been able to define except for simulators that never seem to match, and a bunch of formulas that don't seem to apply to anything.

Most of what I quoted is NASCAR, which applies to most any two valve engine . If you want to make an engine as efficient as possible, and extract every last drop of chemical energy out of gasoline, run it to 0.1mm (in a firing engine, accounting for stretch, thermal expansion, etc) The NASCAR teams and OEMs spent tens of millions of dollars figuring that out. Dr. Randolph literally gave that information out for free. So did Randy talking about piston shape. Also, the one Honda white paper I linked literally was a 2 valve hemispherical type chamber where they experimented with different squish pad shape / tapers. This information is not only out there and not only free, but is already in this thread. I don’t really see where the debate is.

If you want a number, let’s just pull 15hp out of the air, because that’s how most people define gains “+20 camshaft, +10hp intake”, and yes I’m being facetious. The real answer in science and engineering is “it depends”.

Are people interested in learning or do they just want to be told what to do? You don’t need a forum called “speedtalk” to do the latter or need to muck up a discussion where people are trying to talk this through.

[LotusElise]

In the case of the M139 engine that was released in 2014, I believe that the most binding constraint to making even more torque at higher rpms was cycle to cycle combustion variability, particularly pre-ignition/super knock that was traced back to oil droplets being drawn into the charge. I recall reading this from somewhere back in the day.

Juup, I've mentioned similar earlier in my posts to this that a too high squish velocity can lead to low pressure squish ring, which can suck oil from the fireland and liner wall. The M133, released in 2013 (M139 was released in 2019) does operate on peak cylinder pressures of up to 160 bar, which is quite similar to that what I've worked on. The combustion process design was taken from the M270 base engine, the so called BlueDirect process, includes stratified low load, lambda 1 mean load and turbine temperature driven enrichment at WOT as well as ignition and injection cycling during one stroke, depended on load and engine speed. That design for the combustion process management goes quite along with the NEDC. RDE was that time no issue .

We saw many irregular combustion phenomena: oil induced pre-ignition, random but heavy knock (up to 300 bar cylinder pressure) and other stuff. At that BMEP or peak cylinder level the integrity and flex of the liner and piston plays a big role. Mercedes was/is using an Aluminum-Alloy system on the block architecture as well on the liner, the latter I am not too sure, just the base block uses Alu there. If there is too much flexibility in the liner system oil issues are programmed and affects of course the combustion. We made simulations of the block structure during operation and measurements, which made clear the system, which was designed with lower cylinder pressures in mind, but still within the spec'd range, that torsional tension and bending forces de-shape some liners, especially at the corners. This lead to oil management issues, which couldn't be measured, that engine has the lowest oil consumption on the market, but if tiny oil droplets get burned, the effect can be huge, especially in a homogeneous mixture combustion regime.

Pre-ignition and many other irregular combustion phenomena are predominately happening in lower engine speed and under high load conditions. If those happen in higher engine speed region the heat management likely show issues. Because in that cases the self ignition delay is shortened by massive temperature increase, e.g. due to highly retarded WOT IGT, which can lead to glow knock or pre-ignition. In that case it is clear that is no race engine . At the Green Hell these cars perform not bad, but the Honda Type R was with significant less power (-100 hp) 5 s faster. That speaks for it self . If you would have seen the Honda Type R engine (K20C1) in detail, it's not the engine alone, responsible for that success . Looks like a VW EA113 2-Liter turbo engine, which we actually use for our 1200 hp drag Audi Quattro - like a loooooooooot of work .

[Bigchief632]

On what kind of engine? 2-valve wedge at 6000rpm or 4-valve pent roof at 11000 rpm?

On anything. The majority of the guys on this site are referring to 2 valve domestic stuff, except for hoffman, who always quotes formula 1 stuff for some reason. Lots of theory for something that is minimal at best. And works the opposite in many cases based on the theory that no one has been able to define except for simulators that never seem to match, and a bunch of formulas that don't seem to apply to anything.

Most of what I quoted is NASCAR, which applies to most any two valve engine . If you want to make an engine as efficient as possible, and extract every last drop of chemical energy out of gasoline, run it to 0.1mm (in a firing engine, accounting for stretch, thermal expansion, etc) The NASCAR teams and OEMs spent tens of millions of dollars figuring that out. Dr. Randolph literally gave that information out for free. So did Randy talking about piston shape. Also, the one Honda white paper I linked literally was a 2 valve hemispherical type chamber where they experimented with different squish pad shape / tapers. This information is not only out there and not only free, but is already in this thread. I don’t really see where the debate is.

If you want a number, let’s just pull 15hp out of the air, because that’s how most people define gains “+20 camshaft, +10hp intake”, and yes I’m being facetious. The real answer in science and engineering is “it depends”.

Are people interested in learning or do they just want to be told what to do? You don’t need a forum called “speedtalk” to do the latter or need to muck up a discussion where people are trying to talk this through.

That's my point it's not 15hp, it's minimal. Set it to .040-.050, and call it a day. Thread over, lol

[hoffman900]

On anything. The majority of the guys on this site are referring to 2 valve domestic stuff, except for hoffman, who always quotes formula 1 stuff for some reason. Lots of theory for something that is minimal at best. And works the opposite in many cases based on the theory that no one has been able to define except for simulators that never seem to match, and a bunch of formulas that don't seem to apply to anything.

Most of what I quoted is NASCAR, which applies to most any two valve engine . If you want to make an engine as efficient as possible, and extract every last drop of chemical energy out of gasoline, run it to 0.1mm (in a firing engine, accounting for stretch, thermal expansion, etc) The NASCAR teams and OEMs spent tens of millions of dollars figuring that out. Dr. Randolph literally gave that information out for free. So did Randy talking about piston shape. Also, the one Honda white paper I linked literally was a 2 valve hemispherical type chamber where they experimented with different squish pad shape / tapers. This information is not only out there and not only free, but is already in this thread. I don’t really see where the debate is.

If you want a number, let’s just pull 15hp out of the air, because that’s how most people define gains “+20 camshaft, +10hp intake”, and yes I’m being facetious. The real answer in science and engineering is “it depends”.

Are people interested in learning or do they just want to be told what to do? You don’t need a forum called “speedtalk” to do the latter or need to muck up a discussion where people are trying to talk this through.

That's my point it's not 15hp, it's minimal. Set it to .040-.050, and call it a day. Thread over, lol

We’re all not building street strip engines here or are interested in that.

A bunch of you need to expand your horizons. Why are you even here and posting in this thread? Like, if you guys want to build historic engines with like 20% brake thermal efficiency, have at it. It’s fun, but this discussion is probably not for you.