I’ve conducted several searches on quench and it’s relationship to detonation but was unable to find anything definitive on this subject. It would appear most prefer tighter quenches (e.g., 0.039”) while some OEM specifications has acceptable quench as large as (e.g., 0.074”). Assuming the OEM specification would be your maximum reasonable quench for a performance application, is there an optimum range for quench and how quickly does it degrade once you start pushing outward toward the OEM specification? Any thoughts would be appreciated….
Thanks,
CT

 

If anything quench would reduce the chance of detonation. But there are too many variables for the purpose of detonation. It's just a miniscule part of the equation.

Not a very good example but: it's like asking if dished pistons are responsible for lower compression...well yea, they are...but there are other ways to achieve higher compression. Ie: decked block (or pistons coming past zero deck), smaller combustion chamber, and type of valves used.

But from a performance standpoint, the less quench, the more efficient the power production will be.


P

 

The tighter the quinch,the more it shoves the charge to the combustion chamber and it is compressed tighter,atomized better and the quicker the burn. The quicker the burn and by making the outlaying pockets of the cyl with less unburnt fuel, the less the chance of detionation.
It puts the explosion in a smaller area that puts more push on the piston.By speeding the burn and lessening the outlying pockets the more timing ya can run without detionation thus more power.
I have run .030 sucessfully on a tight clearence bore,steel rod engine on the street,but that is AS close as I would go.Anything between .030-.040 is real good but closer to .030 is better. I was told a long time ago by a very respected sprint car engine builder that "they run their best if the piston comes so close to the head that the wind leaves a mark on the head"(bearly kissing it) I thought he was crazy,but have learned better since. I don't know of anyone that has done a publisized study'cause that was a secret back a few years ago. I am sure it has been played with by the bigger engine builders but is not spoken about.
An engine with a tight quench is easier to tune and sounds and responds differently(better) than one with .060 quench.

 

40 seems good to me. 30 is almost "kissing"

Rich

 

Wouldn't that mean MORE prone to detonation?

one area is going to see a higher pressure which will make it more more prone to knock.

 

NO,NO,NO do some more research on the subject.

 

great explanation.

I suppose the pressure would be equal in the cylinder at all points, in theory-
but what you described makes me think more prone to dentonation.

 

Why would ya think that. Are you not familiar with how detonation happens and what causes it? Not pre ignition but detonation.

 

Boost -

I'm no engineer, but as far as I know; the way it suppresses detonation is by shoving everything into a smaller area and using the turbulence that act creates to homogenize the mixture better.

I like to get as close to .035 as I can.

 

I thought a tight quench resulted in a shock wave at or near TDC that disrupted the formation of hot spots, thereby reducing the chance of detonation. Is this incorrect?

 

Sort of. It just pushes the mixture in the quench area(close spot) to the chamber area(wide spot) in the head. When it pushes it it mixes it better and puts it in a smaller area for a faster burn=mo pop=mo HP.The faster the burn with the mixture in a small area is more complete and lessens the chance of any mixture left over for detonation.