Quench Explanation

[Mad Dart]

I was under the impression that Quench is the distance of the closest part of the piston in relationship to the chamber in the head, whether it is Flat, Dish or Dome.


Can some of you experienced motor guys answer this question.

Thanks in advance.

 

[demon seed]

Oh this should be good info. MOPER where are you.:-D

Terry

 

[1wild&crazyguy]

You're centralizing the burn/mix around the plug/valves, squishing it toward with force getting a more faster complete burn.jmo

KB pistons says...

A single side tight quench is a very important combustion enhancer that an engine builder can use to speed flame travel. What quench does that doesn't happen with high swirl or tumble chambers is TDC drive. A normal ignition system starts a small flame about 30° before TDC that burns relatively slow. The piston stops just short of hitting the cylinder head, a blast of air is forced from the quench area through the previously lit flame front. The flame front is driven through the chamber, increasing the chamber burn rate sufficiently to build maximum cylinder pressure early after TDC. The old way to get maximum cylinder pressure early was simply to run 40° of timing. The problem with the old way is that a long slow burn is more affected by hot spots, fuel distribution, spark scatter, chamber temperature, and general cylinder-to-cylinder variation. Don't forget the negative torque component of 40°.

 

[moper]

I was under the impression that Quench is the distance of the closest part of the piston in relationship to the chamber in the head, whether it is Flat, Dish or Dome.

What we refer to as "quench" is the distance between the top surface of any piston, and the portion of the chamber roof, furthest from the spark plug and is kind of a slang term now. It's not the same as piston to head clearance although on a quench-built engine it is usually the closest those two parts get. Quench is really the effect as the KB site says and the quench distance is what you are refering to. Dishes, domes, and flat tops, and open or closed chambers all bring thier own variables to the build if you want to build to maximize the quench effect.

 

[Longgone]

I`ve always heard of the word "squish" used in place of what is now referred to as quench. Squish was created when the flat area of the piston and the corresponding flat part of the combustion chamber, closest to the piston, squished the fuel/air mixture into the expanse of a wedge shaped combustion chamber. Like moper said, things like hemispherical combustion chambers and pistons with domes or reliefs will make another set of variables.