Does quench affect power?

[NewbVetteGuy]

Does quench matter? How much.?
How much quench clearance is enough.?
Does low rpm (eg stock engines) require tighter quench clearance than high rpm. to be effective?

VERY good questions.

My take on what I THINK I know:

1. "Does quench matter"/affect power? Yes. But helping to reduce ignition advance requirement and allowing an engine to run a higher cylinder pressure when octane limited without detonation. Achieving an appropriate max squish velocity at peak HP RPM is the goal and quench is one of the variables impacting it.

2. "How much?" An advanced sim that takes into account max quench velocity and calculates ignition advance requirements take that as one of the inputs could, on a given engine estimate how much less ignition advance is required with best-case quench vs. worst case quench... In HP? -Not a clue; quite interested in a potential answer to this one. (Seems like an answer in HP @ HP PEAK RPM would involve a LOOOOOOOOOT of variables.)

3. How much quench clearance is enough? Enough to get the max squish velocity at the desired peak HP RPM to 15-20 m/s on the engine in question-according to Blair; 15-30 m/s according to TSR, I've seen David Redszus quote 25-30 m/s in one place and I think 25-35 m/s in another thread.



Adam

[David Redszus]

You guys are getting all lost in the math. tech, theory

Not lost at all. Finally finding our way with quantified understanding. It helps leave the dreams and folklore behind. And always has.

KISS .

Really? What word does the second letter S stand for? It ain't Smart.

I recomend not falling down the deep rabbit hole of technical theory and exoric engines far
removed from a SBC and other relevent 2valve push rod engines.

Understanding theory is what allows us to understand how any engine works; not just obsolete (but cheap) SBC engines.
Who really cares about pushrods, and old 2 valve, single cam, slow moving antiques?

All the theory doesn't matter until you test this stuff,
on real relevent running engines.

Test all you want; there is always some value in testing what we build and hope will work.
But testing will never improve any product except if we break it and then build it better.
The development process is called: "Trial and error, and error, and error, and error, and error."

I'm simply too old to use the inadequte methods we were taught long ago.
We have the money, but we are running out of time.

[JES]

.034 be done

[skinny z]

.034 be done

Now, this isn't my thread, however that was my question when I started following.
Is .034" doable?
Physically, obviously yes. But operationally?
What's your opinion on running as close as .034" in a Vortec headed (RHS aftermarket), steel rods, 4032 forged pistons and a RPM ceiling of 6500? Maybe 7k.

[JES]

I know it's. 002 different, but I run a .036 at 7200 RPM with same material and no problem. I think your combination will peak a fair amount lower.

[skinny z]

I know it's. 002 different, but I run a .036 at 7200 RPM with same material and no problem. I think your combination will peak a fair amount lower.

Peak is yet to be determined but certainly not 7200.
We've run .036" with a hypereutectic piston and a peak RPM of 7k.
Never taken it apart since assembled but there's no indication of any trouble.
As for that quench being effective or not is difficult to say as there's never been an A to B comparison but this latest iteration is the strongest for that car to date.
Thanks.

[RDY4WAR]

There's other factors like the piston weight, rod length, and stroke that must be considered.

A 4.00" stroke with a 6.00" rod and 600 gram piston will have 5,193 lbs of upward inertia at 7200 rpm.
A 3.25" stroke with a 6.25" rod and 400 gram piston will have 2,658 lbs of upward inertia at 7200 rpm.

A 4.00" stroke with a 6.00" rod and 400 gram piston will have 3,462 lbs of upward inertia at 7200 rpm.
A 3.25" stroke with a 6.25" rod and 600 gram piston will have 3,987 lbs of upward inertia at 7200 rpm.

[JES]

For what it's worth. The combination I had was an SRP 4032 Piston that was 420 Grams, plus the rings pin and clips, don't remember those numbers. 5.7 Scat, proComp rod for strokers, 5.7 length on a Scat std weight 9000 cast crank. Externally balanced.

[frnkeore]

I've been following this, from the start and not much has been said about thermal expansion of the rotating assy vs block, so I did some research on it. As a machinist, I have had to deal with expansion rates, on various metals and know that when you mix different metals, you have to take that, into account.

Please correct me if I get anything wrong.

This is based on the following:
Expansion rate of cast iron = .000006 per inch, per deg (F in this data) Temp increase of 132° over 68F
ER - 4340 steel = .0000068 - Temp increase 232F
ER - 2618 alum = 2618 .0000125 - temp increase 200F

deck ht = 9.00
Crank w/rod =7.75 (1.75/6.00)
Piston = 1.25 CH

Difference of Rotating assy length over deck ht of block = .0082. .00065 less for 4032 pistons

[RDY4WAR]

Add .005" for rod stretch at 7200 rpm.

Add another .005" to cover rod and main bearing clearance.

Add .010" for piston rock.

.0082" + .005" + .005" + .010" = 0.0282"

[skinny z]

Is this to say then that an .034" target clearance, measured in a static state obviously, may be reduced to .006" when at speed?
.034" - .028" = .006"
Provided the criteria of those given dimensions are in line with a given build.
On a similar note, would a ten thou piston rock be an extreme example?

[F-BIRD'88]

Is this to say then that an .034" target clearance, measured in a static state obviously, may be reduced to .006" when at speed?
.034" - .028" = .006"
Provided the criteria of those given dimensions are in line with a given build.
On a similar note, would a ten thou piston rock be an extreme example?

So would a .068" clearance be reduced by that same factor? at speed. so .040" . Is that effective quench clearance at speed?

[skinny z]

Is this to say then that an .034" target clearance, measured in a static state obviously, may be reduced to .006" when at speed?
.034" - .028" = .006"
Provided the criteria of those given dimensions are in line with a given build.
On a similar note, would a ten thou piston rock be an extreme example?

So would a .068" clearance be reduced by that same factor? at speed. so .040" . Is that effective quench clearance at speed?

The reduction would be the same amount obviously.
What's an effective quench at speed or statically is open to debate it seems.
Where I end up is still open ended as not all of the variables have been determined.
That'll be later.
That's about all I have to say or contribute at this time.

[nitro2]

Bear in mind if the piston is just barely kissing the head at WOT, it is only doing so at TDC overlap. It's not kissing the head at TDC combustion.

If you close the throttle at high rpm then the piston could touch the head at both TDCs, instead of just TDC overlap.

[F-BIRD'88]

The moment of max piston-rod stretch "elastic" at rpm, happens @ a bit after TDC.