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Does quench affect power?

General engine tech -- Drag Racing to Circle Track

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LotusElise
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Re: Does quench affect power?

Post by LotusElise »

Bigchief632 wrote: Thu Sep 22, 2022 10:25 am That's my point it's not 15hp, it's minimal. Set it to .040-.050, and call it a day. Thread over, lol
I varied the injection location, injector size, injector pattern, EOI and fuel pressure, which opened a 10 % power influence on a 2-Liter NA-engine. Squish and it's consequences on the design made a 1.5 %-point in thermal efficiency on an industrial engine, which gave the customer an almost 20,000 Euro benefit per year, now, at actual gas prices, even more.

I am convinced forums usage is on a wider range, from read and take till understanding and learning on the one hand, vice versa also. Don't you think so too?
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310 hp@8200 rpm
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Re: Does quench affect power?

Post by ClassAct »

hoffman900 wrote: Thu Sep 22, 2022 10:33 am
Bigchief632 wrote: Thu Sep 22, 2022 10:25 am
hoffman900 wrote: Thu Sep 22, 2022 9:10 am

Most of what I quoted is NASCAR, which applies to most any two valve engine :roll: . 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.

I think that’s what the OP and 632 were getting at Bob. What’s the power gain from say .050 to .040 to .030 going to be. I understand there is no hard and fast rule but I have tested going from .060 to .035 and if the compression didn’t change there was so little power gained it’s not worth it IMO. That testing costs a boat load of money and luckily a customer paid for it all or I would have never bothered.

I’m all for expanding my horizons (and I work on that daily) but not all of us have an F1 budget. Or a NASCAR or Pro Stock budget. So we take what we can learn from them and use it when we have the cash and time to test it out.

I shoot for .050-.040 quench and send it, unless the customer is will to crack open the wallet (straight cash) and do the testing.
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Re: Does quench affect power?

Post by RDY4WAR »

It's always puzzled me why people join technical forums or groups and then question anything that remotely steps outside the box. How dare you deviate from the way things were done 50 years ago. lol

My personal favorite is those who say "Trust the engineers at the OEM." You mean the engineers that spend 10x more R&D on meeting fuel efficiency targets, passing emissions standards, and shaving $5 off the production cost of each engine? Sometimes that works in our favor such as precision ring design and hone roughness to improve ring seal. They did it for fuel economy, we adopted it to make more power, but it's still stepping outside that box.

Discussions like this are great to have. We also acknowledge that it's highly circumstantial and subjective, but that's what makes it so fun. At least for me anyway. I could go on for hours about subjective mess that 99.9% of people couldn't care less about.
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Re: Does quench affect power?

Post by hoffman900 »

ClassAct wrote: Thu Sep 22, 2022 11:03 am
hoffman900 wrote: Thu Sep 22, 2022 10:33 am
Bigchief632 wrote: Thu Sep 22, 2022 10:25 am





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.

I think that’s what the OP and 632 were getting at Bob. What’s the power gain from say .050 to .040 to .030 going to be. I understand there is no hard and fast rule but I have tested going from .060 to .035 and if the compression didn’t change there was so little power gained it’s not worth it IMO. That testing costs a boat load of money and luckily a customer paid for it all or I would have never bothered.

I’m all for expanding my horizons (and I work on that daily) but not all of us have an F1 budget. Or a NASCAR or Pro Stock budget. So we take what we can learn from them and use it when we have the cash and time to test it out.

I shoot for .050-.040 quench and send it, unless the customer is will to crack open the wallet (straight cash) and do the testing.
Right but you can apply that train of thought to anything. For a hobbyist street strip type situation, nothing matters. Just slap together or buy one of the many combinations out there. 95% of the time it’s just about showing up somewhere for these guys and slapping each other on the back over some beers and send it down the drag strip once in a while. This is fine, this is good, it’s what keeps the entire industry afloat. But if this is you, then why even be here or make your participation in these forums a “well that’s well and good you fancy smarty pants guys, but that doesn’t help me”. It does if you read the information and think about why and what is happening, but people don’t want that. They just want to be told a number, slap it together, and be mad that it’s a few hp or doesn’t make any more power but maybe uses less gas for that power, because they don’t understand why.

I pull bits and and pieces together and we apply it to old engines for racing and these things ideas and thought exercises work. Do you go about it the same way? No. Is it developed to their degree? No. But it gets you headed in the correct direction.
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Re: Does quench affect power?

Post by ClassAct »

hoffman900 wrote: Thu Sep 22, 2022 11:10 am
ClassAct wrote: Thu Sep 22, 2022 11:03 am
hoffman900 wrote: Thu Sep 22, 2022 10:33 am

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.

I think that’s what the OP and 632 were getting at Bob. What’s the power gain from say .050 to .040 to .030 going to be. I understand there is no hard and fast rule but I have tested going from .060 to .035 and if the compression didn’t change there was so little power gained it’s not worth it IMO. That testing costs a boat load of money and luckily a customer paid for it all or I would have never bothered.

I’m all for expanding my horizons (and I work on that daily) but not all of us have an F1 budget. Or a NASCAR or Pro Stock budget. So we take what we can learn from them and use it when we have the cash and time to test it out.

I shoot for .050-.040 quench and send it, unless the customer is will to crack open the wallet (straight cash) and do the testing.
Right but you can apply that train of thought to anything. For a hobbyist street strip type situation, nothing matters. Just slap together or buy one of the many combinations out there. 95% of the time it’s just about showing up somewhere for these guys and slapping each other on the back over some beers and send it down the drag strip once in a while. This is fine, this is good, it’s what keeps the entire industry afloat. But if this is you, then why even be here or make your participation in these forums a “well that’s well and good you fancy smarty pants guys, but that doesn’t help me”. It does if you read the information and think about why and what is happening, but people don’t want that. They just want to be told a number, slap it together, and be mad that it’s a few hp or doesn’t make any more power but maybe uses less gas for that power, because they don’t understand why.

I pull bits and and pieces together and we apply it to old engines for racing and these things ideas and thought exercises work. Do you go about it the same way? No. Is it developed to their degree? No. But it gets you headed in the correct direction.
I agree 100%.
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Re: Does quench affect power?

Post by Tartilla »

F-BIRD'88 wrote: Wed Aug 31, 2022 7:18 pm I suspect that at higher engine rpms WOT the realized anti knock benefit of squish will deminish as the air flow has plenty of swirl. tumble energy.. But quench head cooling benefit may be a different story.
Aparently on (street) supercharged engines the ease of being able to simply lower the compression ratio (by say just adding a extra head gasket) out weights the (loss of) squish benefit, on roots street strip pump gas engines.
(Relative modest boost) (low cr)

The position of the spark plug has a big effect also.
More central is always better.

IMO most of the benefit is realized at lower rpms.

If emissions and driving fuel mileage efficientcy was a priority you'd think the OEM's would employ this on every OEM passenger car engine...
Supercharged cylinders will have more air volume to start, so thicker quench will have higher pressures. IVC and SCR dependant of course.

At high RPM, a larger quench deck may not be able to expel all the air in time, and may create localized high pressure zones. Essentially, how fast can you push a gas? Like pushing a rope up the hill.

When watching valve spring dynamics on high speed cameras, they do things we don't normally think of. The high speed dynamic world is like a foreign entity.

Compressing A/F mixture at 7500 RPM is much the same.

I expect the pressure on top of the piston to increase as it gathers the intake charge on the compression stroke. How fast can that pressure change affect the total cylinder volume as it rises? Not to mention the velocity of that charge as it c0mes up into the chamber. There is likely a lot of turbulence. The quench may align it to be more effective.

There is probably a limit before turbulence becomes a limiting factor to flame front burning.

There has been some thought that using no more quench than is required. The law of diminishing returns.

DV has mentioned the quench deck on the TDC exhaust stroke, can create issues for the exhaust valve if the quench to valve angle is too sharp, and cannot make the transition to the port opening,bowing over the valve to over demand the plug side of the valve curtain.
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Re: Does quench affect power?

Post by Tom Walker »

This thread has became a very entertaining and informative discussion starting from a question at first that I thought would not last more than a few pages.

I appreciate all who have added such thought provoking ideas and experiences. You guys are some of the brightest:)
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Re: Does quench affect power?

Post by LotusElise »

Tartilla wrote: Thu Sep 22, 2022 4:01 pm At high RPM, a larger quench deck may not be able to expel all the air in time, and may create localized high pressure zones. Essentially, how fast can you push a gas? Like pushing a rope up the hill.
That's a good question. What I know from at least 3 racing series that the design of the squish height and area is done to the extreme. Biggest possible area and lowest operated squisch height of almost 0.0 mm. DTM, STW, BTCC, NASCAR (according the Video) and Formula 1 NA engine (e.g. BMW P80) run very low squish height's which would calculate in enormous squish velocities.

If you look into scientific papers to that topic you see a lot of ongoing in Diesel and Otto lean combustion engines as well as some motorcycle engines. Only a few of those match the conditions and chambers of the mentioned extreme squish approaches. Here the tenor is like, squish is added to tumble or swirl as squish is a short time but very intense supporter to get down the ignition delay reduced and the 0-15 % mass fraction burned time down, which is a good control lever arm of cyclic variations. That is important in emission related engine at low, mid and high load and low engine speeds. Here the Authors report of limits, even distinguishing effects of ignition initiation.

A high revving engine is not comparable to that application, as inertia of the mixture is accounting for some loss as well as tumble, swirl and hybrids of this get of less efficiency as I wrote in a previous post. So we need to take everything we can take to keep TKE adopted to the necessary flame speed (e.g. 10,000 rpm, 86 mm bore, 0.7 ms of time gives roughly 61 m/s on average). The incoming mixture speed is around 0.2-0.6 Mach, where peak is around peak valve lift. That means a lot of TKE potential lays in the incoming impulse. Therefore intake runner, port and valve seat design have a huge effect on what is coming as well as valve timing (reverse flow). To preserve this energy and to dissolve it into micro turbulence (= TKE) is one of the tasks of the combustion process designer. Effects from tumble, swirl and squish are way less in potential, one cause why critical pressure drop over the intake port throat at boosted engines (= Mach 1 possible at overcritical pressure ratio) don't really count on those supporters as the most TKE comes with port flow at even lower engine speeds. Of course much of it get lost during compression, only a few will build up TKE, therefore spherical chambers can have advantages on boosted engines.

NA engines are less blessed with intake impulse, keeping it high is essential for combustion process design. Every supporter is necessary, but as impulse is lower not every is useful in terms of efficiency. Squish is the cheapest, but also the shortest. What it does at least on all engine intake concepts is to push mixture, especially fuel, to the mid, which is very important when fuel separation is an issue on a mixture process. Once I've tested the ID injectors (5° fuel beam) and lost immediately 7 hp at best EOI of it compared to an OEM double spray pattern with single cones of 30° and a 6 whole each pattern. Lambda went greatly lean with the ID's. It just meant a greater portion of fuel run just through the engine as mixture homogenization efficiency went down significantly. Squish didn't help here. Obviously all systems have to be optimized, none has potential laying around and come up with it just when there is a demand. I can't say higher squish velocity would have helped here to get again more fuel into oxidation action, maybe you guys have experienced differences on that.

Regarding the acceleration inertia of air at e.g. 10,000 rpm, we have 2nd Newton's law. To keep it simple I've assumed the squish velocity must be double of the average speed at squish inner ring as max. happens around 12° BTDC and must reach flame at a proper progress, about 50 % mass fraction burned, assuming combustion start is around the same as max happens. The force to accelerate the total ring mass is around 83 N on a 86 mm bore, 4 mm depth squish ring and a proper squish height mixture to model the continuous ongoing squish flow from 30 to 0 degree BTDC. The available force on the crank is significantly bigger and FMEP (that force is lost on crank not on PMEP) won't see much of it. The bigger part of force is created by compressing the inner ring mixture. Here my model is simplificated most, as here calculated it only at 2 mm squish height, assuming it to be a compromise of the integral'd force by the moving piston. Finally 187 N, which also comes from the crank. So about a 270 N/piston, which is reducing the negative acceleration force during piston slow down into TDC position, and therefore increasing a bit FMEP. If combustion is slower and IGT more advanced the force of course increases, so this represents an thumb value for the best case condition. What I conclude from that is the force is available to get this done, but it is clear the TKE need to be increased at a relevant radius from spark plug center. So higher is better in terms of squish velocity to get a higher "throwing distance" for the relevant TKE effect as the impulses in the main center of the chamber are also not from bad adults. From that standpoint of time window demand the squish design may be pushed to the extreme as knock doesn't play that role, as time is quite short on rational IGT, also here retarded IGT's but optimal 50 % MFB (= shorter delay) helps to improve FMEP as well as IMEP.

If squish can support this, why not pushing it to the extreme?!
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Re: Does quench affect power?

Post by ptuomov »

"The incoming mixture speed is around 0.2-0.6 Mach, where peak is around peak valve lift. That means a lot of TKE potential lays in the incoming impulse. Therefore intake runner, port and valve seat design have a huge effect on what is coming as well as valve timing (reverse flow). To preserve this energy and to dissolve it into micro turbulence (= TKE) is one of the tasks of the combustion process designer. Effects from tumble, swirl and squish are way less in potential, one cause why critical pressure drop over the intake port throat at boosted engines (= Mach 1 possible at overcritical pressure ratio) don't really count on those supporters as the most TKE comes with port flow at even lower engine speeds."

While I basically agree, I'd make the following addition. I see tumble and swirl as ways to preserve this "port energy" in very large eddies until combustion. I see squish as a way to add additional kinetic energy to the charge and as a way to time the breakup of the large eddies preserved in tumble and squish. I personally think this is a useful way to think about the issue.

One possibility is that squish itself is not a particularly important from pure energy perspective but can be used to precisely time the breakup of large tumble or swirl eddies in some engines.

In terms of boosted engines, they do definitely have denser mixture and thus more energy in the flow. However, they also have much lower geometric compression ratio requirements. I see a lot of those engines running great with a spherical dish that preserves the tumble the best but doesn't produce an appreciable squish.

With normally aspirated engines with apparently tight squish, it's possible that the designer was prioritizing a high geometric compression ratio and compact combustion chamber (so minimum piston dome) and the result produces a geometry that has tight squish clearance even though high squish velocity was never an important design consideration. Instead, tight squish is mostly just a by product of those two more important design considerations.
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Re: Does quench affect power?

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LotusElise wrote: Thu Sep 22, 2022 10:58 am
Bigchief632 wrote: Thu Sep 22, 2022 10:25 am That's my point it's not 15hp, it's minimal. Set it to .040-.050, and call it a day. Thread over, lol
I varied the injection location, injector size, injector pattern, EOI and fuel pressure, which opened a 10 % power influence on a 2-Liter NA-engine. Squish and it's consequences on the design made a 1.5 %-point in thermal efficiency on an industrial engine, which gave the customer an almost 20,000 Euro benefit per year, now, at actual gas prices, even more.

I am convinced forums usage is on a wider range, from read and take till understanding and learning on the one hand, vice versa also. Don't you think so too?
I agree with you. I just find it ridiculous that these threads go for 18+ pages. We all know there is some benefit. It's been known for many decades. We have a very small window to work in for what we are building. Most guys on here now are working on old junk, that it really doesn't matter. Think it's a coincidence that fel-pro makes head gaskets .039 thick for most applications, and we "zero" deck blocks, and all piston manufacturers base their compression heights on "zero" deck? Nascar teams have spent a lot of time testing this to save a few gallons of fuel over a 500 mile race to maybe get an extra lap or 2 to strategically time their pit stops and can be an advantage. The average guy on here, is going to see +/- a few hp mainly from the extra compression, and reduce bsfc's slightly which will help a little for fuel consumption, but probably not even measurable, and it can reduce the engines total timing requirement that will gain maybe a few more due to reduced what I call, negative tq. Picture trying to start a heat soaked engine that has to much total timing. And it cranks hard. That's what's fighting the engine when it needs more total timing to make max power, but once running, obviously the engine over comes that resistance very easily and you don't even notice. So, if you can make the engine make it's max power with less total timing, it will make a few more.

And now, your typical sbc, bbc, mopar, buick, olds, ls, etc, we have a MAYBE +/- .020 to play with. How much difference between MAX benefit and most benefit, if you say end up .010-.020 away at max rpm so the piston doesn't hit the head. +/- a few, almost can't even measure the difference. No need for 18 pages of discussion, it's not rocket science here.
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Re: Does quench affect power?

Post by juuhanaa »

Just thinking, if it doesnt make that big difference, then there is power hidden or something that perhaps we can do different :) how about crazy slow lobe and better combustion chamber/piston shape?
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Re: Does quench affect power?

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juuhanaa wrote: Fri Sep 23, 2022 9:39 am Just thinking, if it doesnt make that big difference, then there is power hidden or something that perhaps we can do different :) how about crazy slow lobe and better combustion chamber/piston shape?
You don't think that has been beat to death over the years?
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Re: Does quench affect power?

Post by travis »

From my point of view, I appreciate the lengthy discussions of things like this. As the OP :wink: this has not only answered my question, but also filled in some blanks and connected some dots on other bits and pieces that I already knew. So for those of us that aren't professional engine builders or racers, this is good educational stuff.

I've learned more from this site in the last few years than I have in the last 20 years of building engines, and I try to use this information on everything new I build. I believe this is why my engines come out better than in the past. And I don't build what most on here build...quite the opposite in fact.
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Re: Does quench affect power?

Post by juuhanaa »

Bigchief632 wrote: Fri Sep 23, 2022 9:54 am
juuhanaa wrote: Fri Sep 23, 2022 9:39 am Just thinking, if it doesnt make that big difference, then there is power hidden or something that perhaps we can do different :) how about crazy slow lobe and better combustion chamber/piston shape?
You don't think that has been beat to death over the years?
They say lift the valve as far as you can, but damn piston didnt have valve pockets.. Crazy cylinder pressures and big ass headers may have been beat to death, but it puts smile on my face 🤭

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Re: Does quench affect power?

Post by LotusElise »

juuhanaa wrote: Fri Sep 23, 2022 9:39 am ...how about crazy slow lobe and better combustion chamber/piston shape?
You mean slow on valve lift, in such a way that scavenge phase get the name worth and lift harder later with the aim to let the piston design need no valve reliefs?

Two things why this won't be the optimum:
  • cam lobe design need very consistent acceleration, once you begin slow it is hard to get it back without going to the edge on materials, you would loose lift potential and duration, seating is one of the most sensitive moments for cam designers, the profile before dictate what it needs in the end to seat the valve smooth so that bounce is reduced to min. at high engine speeds. Otherwise we need even more FMEP eating valve springs. A smooth but stepped lobe profile isn't good for the wear and the dynamics of the valve and valvespring. What you do wrong in the beginning can only be healed with higher valve spring forces in some portion. Nothing we want have for highest power output everywhere.
  • TDC valve lifts of 5-7 mm are typical for NA engines in the 4-valve field. If you go lower you loose in the midrange engine speed. At 10,000 rpm you still see 3-4 mm@TDC with a R/S-ratio of 1.7 and a 86 mm stroke and a 13:1 CR in a 50 ccm head that means still touching the piston without reliefs
I fear this is not leading to the holy grail. I talk about 100 ftlb/liter torque. I've reached already with my first attempt in NA racing 104 ftlb/liter peak torque (almost 209 ftlb peak torque on a 2-Liter NA engine) and from 4500-8200 rpm over 96 ftlb/liter. I know to get there and still searching on ways to take that level to higher engine speeds for the next attempt I am working on.
DAMPFHAMMER engine:
2000 ccm, Honda K20 NA engine
4000 rpm bandwidth of at least 192 ftlb
310 hp@8200 rpm
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