Does quench affect power?

[Elroy]

MBE and others hav been doing it for quite a while. I’ve said for a looooooooooooooooong time that a soft(er) chamber is better NA in most cases.

Why do you think that is? Are there softened, quenchless chambers at the top tiers of NA motorsports?, like Nascar, Prostock, Comp Eliminator etc. ?

It seems like the evolution of things all and all have ended up at the opposite. But I of course haven't seen it all

[RDY4WAR]

I've seen a Pro Stock DRCE 3 head/chamber and have a piston here on my desk. I'll reach out and see what I can or can't disclose to bring some resolution to this discussion.

[hoffman900]

MBE and others hav been doing it for quite a while. I’ve said for a looooooooooooooooong time that a soft(er) chamber is better NA in most cases.

Why do you think that is? Are there softened, quenchless chambers at the top tiers of NA motorsports?, like Nascar, Prostock, Comp Eliminator etc. ?

It seems like the evolution of things all and all have ended up at the opposite. But I of course haven't seen it all

I’m a nobody to dismiss MPE but NASCAR and designs with OEM level of involvement, which include a lot of R&D, measuring cylinder presssures, etc all do not use a softened approach.

F5838C11-71E5-4FCB-BAF6-3A2FEE26DE26.png

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

The only thing I can think of, is that drag racers are not chasing efficiency at all so with the excess fuel they run in the engines, it may need a “softer” approach, where NASCAR, IMSA, etc applications, etc are not only worried about power, but part throttle efficiency and fuel mileage. The OEM race programs and NASCAR teams have gotten there based on widespread use of in cylinder pressure testing equipment.

Looking at a NASCAR chamber in the last ten years, they’re compact, with a lot of squish, and near flat top pistons.

[RDY4WAR]

I've seen a Pro Stock DRCE 3 head/chamber and have a piston here on my desk. I'll reach out and see what I can or can't disclose to bring some resolution to this discussion.

There's no softening of the chambers in Pro Stock either. The piston I have here has some slight marking to the quench areas from the piston ever so slightly kissing the head. There's also a mark where the valves kissed the piston.

[hoffman900]

I've seen a Pro Stock DRCE 3 head/chamber and have a piston here on my desk. I'll reach out and see what I can or can't disclose to bring some resolution to this discussion.

There's no softening of the chambers in Pro Stock either. The piston I have here has some slight marking to the quench areas from the piston ever so slightly kissing the head. There's also a mark where the valves kissed the piston.

I think drag racing has lagged NASCAR / OEM type development by a lot, but from what I have heard, in-cylinder pressure measuring is pretty common now in Pro Stock, where it wasn’t so much even ten-fifteen years ago.

Also, carburetors are pretty common in drag racing, and there is a lot of raw fuel / large droplets floating around, which also may have some to do with it too. Just look at this:
https://youtu.be/7Iq1B-2paCs . This is why the last port injected F1 engines were chasing 200 bar injector pressures (100 rules stipulated) and reached average particle size in the 17micron range. So there might be some “horses for courses” going on here.

[David Redszus]

Squish velocity, both before TDC and ATC, are critical to the combustion process.

But squish is not merely a matter of piston to head clearance. Squish area and shape must be considered along with
inlet temperture and rpm.

Tumble does not survive for very long, usually not even up to TDC, due to the chamber shape.
Swirl can and does survive longer, even longer to assist flame propagaation. It comes at the expense
of chamber filling.

Squish has twin turbulent peaks; one BTC and one ATC to assist flame propagation.

When an engine demonstrates large cycle to cycle variances, it is difficult to measure incremental improvements.

[hoffman900]

Squish velocity, both before TDC and ATC, are critical to the combustion process.

But squish is not merely a matter of piston to head clearance. Squish area and shape must be considered along with
inlet temperture and rpm.

Tumble does not survive for very long, usually not even up to TDC, due to the chamber shape.
Swirl can and does survive longer, even longer to assist flame propagaation. It comes at the expense
of chamber filling.

Squish has twin turbulent peaks; one BTC and one ATC to assist flame propagation.

When an engine demonstrates large cycle to cycle variances, it is difficult to measure incremental improvements.

David,

In regards to tumble decay, you may want to read SAE Paper 2018-01-0366 ‘The Development of a New V6 3.5L Turbocharged Gasoline Engine”. It sticks around more than you think and also has two peaks, with one as it approaches TDC.

It’s about the development of the Toyota engine that had 442lb ft of torque, 420hp, and had a thermal efficiency of 37%, while meeting emissions and warranty standards.

[NewbVetteGuy]

Food for thought, many high level na engines are using "softened" chambers and make more power and are less sensitive to timing.

Source / examples?

I’ve said for a looooooooooooooooong time that a soft(er) chamber is better NA in most cases.

Is it actually that a soft(er) chamber with less max quench velocity is better in most cases, or is it just that there's an ideal max quench velocity and once that ideal max quench velocity is exceeded (and the rate of cylinder pressure rise gets too fast) that that particular engine combo benefits from a softened chamber, which brings the max quench velocity back under the max quench velocity "speed limit"?


My current understanding is that quench velocity is quite similar to max intake port speeds, and that more is better up until you reach the upper "speed limit" and after that more is worse and sometimes you need to slow it down with things like chamber softening to get below the "speed limit". (There's a Blair quote on the max quench velocity "speed limit" range at HP peak RPM (I think David Redszus has quoted an overlapping but slightly different value, too), I think I have squirreled away in some notebook, that I should be able to find...)


Adam

[hoffman900]

Source / examples?

I’ve said for a looooooooooooooooong time that a soft(er) chamber is better NA in most cases.

Is it actually that a soft(er) chamber with less max quench velocity is better in most cases, or is it just that there's an ideal max quench velocity and once that ideal max quench velocity is exceeded (and the rate of cylinder pressure rise gets too fast) that that particular engine combo benefits from a softened chamber, which brings the max quench velocity back under the max quench velocity "speed limit"?


My current understanding is that quench velocity is quite similar to max intake port speeds, and that more is better up until you reach the upper "speed limit" and after that more is worse and sometimes you need to slow it down with things like chamber softening to get below the "speed limit". (There's a Blair quote on the max quench velocity "speed limit" range at HP peak RPM (I think David Redszus has quoted an overlapping but slightly different value, too), I think I have squirreled away in some notebook, that I should be able to find...)


Adam

There may also be some bore size considerations going on here. The 98-100mm bore size of the 20,000rpm F1 engines could only be made to have good combustion with injection pressures of over 100bar. Some of these V8’s are pushing 130mm+ bored and are using carburetors. I could see there being issues.

Again, like a lot of things, I think there is a lot of horse for courses and it depends on the application.

[hoffman900]

If anyone wants a fun read, this is a good one and goes beyond pressure sensor testing:

Study on Combustion Monitoring System for Formula One Engines Using Ionic Current Measurement

A combustion monitoring system has been developed by applying ionic current measurement for malfunction diagnosis and combustion management of Formula One engines. In this system the spark plug’s center electrode acts as an ion probe for ionic current measurement, which eliminates the need for additional sensors. The system allows the onboard monitoring of each of the cylinders for their combustion status under all operational conditions. The accuracy and reliability has ensured that the technology can be effectively used for the management of Formula One engines with car-to-pit communication carried out via telemetering. It is capable of various types of controls including detection of misfire, hesitation, detonation and the lean-burn condition. In addition to these points, this paper reports on the relationship between the spark plug center electrode configuration and the absolute quantity of ionic current.

https://www.hondarandd.jp/point.php?pid=365&lang=en
(And it’s free)

This is the kind of stuff that would help inform what works and what doesn’t, and why.

[RDY4WAR]

I've seen a Pro Stock DRCE 3 head/chamber and have a piston here on my desk. I'll reach out and see what I can or can't disclose to bring some resolution to this discussion.

There's no softening of the chambers in Pro Stock either. The piston I have here has some slight marking to the quench areas from the piston ever so slightly kissing the head. There's also a mark where the valves kissed the piston.

I think drag racing has lagged NASCAR / OEM type development by a lot, but from what I have heard, in-cylinder pressure measuring is pretty common now in Pro Stock, where it wasn’t so much even ten-fifteen years ago.

Also, carburetors are pretty common in drag racing, and there is a lot of raw fuel / large droplets floating around, which also may have some to do with it too. Just look at this:
https://youtu.be/7Iq1B-2paCs . This is why the last port injected F1 engines were chasing 200 bar injector pressures (100 rules stipulated) and reached average particle size in the 17micron range. So there might be some “horses for courses” going on here.

Pro Stock engines are port EFI.

[Carnut1]

I've seen a Pro Stock DRCE 3 head/chamber and have a piston here on my desk. I'll reach out and see what I can or can't disclose to bring some resolution to this discussion.

There's no softening of the chambers in Pro Stock either. The piston I have here has some slight marking to the quench areas from the piston ever so slightly kissing the head. There's also a mark where the valves kissed the piston.

The marks that show the quench kissing the head is damn near perfect quench. The rod stretch needs to be taken in to account at max rpm.
Thanks, Charlie

[hoffman900]

There's no softening of the chambers in Pro Stock either. The piston I have here has some slight marking to the quench areas from the piston ever so slightly kissing the head. There's also a mark where the valves kissed the piston.

I think drag racing has lagged NASCAR / OEM type development by a lot, but from what I have heard, in-cylinder pressure measuring is pretty common now in Pro Stock, where it wasn’t so much even ten-fifteen years ago.

Also, carburetors are pretty common in drag racing, and there is a lot of raw fuel / large droplets floating around, which also may have some to do with it too. Just look at this:
https://youtu.be/7Iq1B-2paCs . This is why the last port injected F1 engines were chasing 200 bar injector pressures (100 rules stipulated) and reached average particle size in the 17micron range. So there might be some “horses for courses” going on here.

Pro Stock engines are port EFI.

I was talking about softened chambers working in NA Sportman applications. Found a MBE video where they talked about it.

[juuhanaa]

I've seen a Pro Stock DRCE 3 head/chamber and have a piston here on my desk. I'll reach out and see what I can or can't disclose to bring some resolution to this discussion.

There's no softening of the chambers in Pro Stock either. The piston I have here has some slight marking to the quench areas from the piston ever so slightly kissing the head. There's also a mark where the valves kissed the piston.

The marks that show the quench kissing the head is damn near perfect quench. The rod stretch needs to be taken in to account at max rpm.
Thanks, Charlie

The rod characteristics needs to be taken in to account at development stage, but i could imagine the quench kissing need some testing to get it right

Screenshot_20220908-215242.jpg

[hoffman900]

If you guys want another one to learn about combustion in a motorsports application, this is a good one:

Combustion Diagnosis of Formula One Engine Using Micro-Cassegrain Sensor

Combustion diagnosis of a Formula One engine during wide open throttle (WOT) acceleration and deceleration operations was performed using a micro-Cassegrain system.
The air/fuel mixture (A/F) in each cylinder was measured, which helped in the development of controls to minimize the torque loss due to unstable combustion.
In transient conditions where acceleration and deceleration are performed repeatedly, the air/fuel mixture around the spark plugs becomes too rich or too lean, and results in unstable combustion. In addition, the air/fuel mixture formation is different inside each cylinder.
The fuel distribution to each cylinder needed to be controlled to a high degree of accuracy, and to do this, a highly responsive air/fuel ratio sensor (LAF sensor) is required.

https://www.hondarandd.jp/point.php?pid=616&lang=en

They were also looking at flame propagation speed and cyclic variability as well.