Gannet

What's the suggested quench for a 4.125" bore run at 16 psi?

KCS

iTrader: (20)

Normally, for a naturally aspirated or nitrous engine, you can set quench distance at about .040" and be okay.

However, on a boosted engine, some people have claimed that larger distances (.050-.100") actually help make more power.

Gannet

Now that's very interesting. I wondered if it might be different for a FI engine, which is why I asked.

Anyone have any comments as to why this might or might not be true?

jmm98LS1

iTrader: (28)

A lot of the big nitrous guys are saying the same thing....running .080"+ gives a bigger tuning window and makes more power than the tighter stuff NA motors usually run. I'm not smart enough to know why though.

KCS

iTrader: (20)

If I had to guess, I would think it helps to "tame" the combustion in this type of application.

With a super/turbocharged engine, the cylinders are much more densely packed with fuel and air, and the combustion is a lot quicker. Imagine lighting a brush fire in the desert, versus a dense forest. Which fire speads quicker?

I would guess, that the crevices in the quench area cause peak pressures to be a lot higher than the rest of the chamber, probably inducing detonation. That could probably even explain why the Hemi chamber is the standard in T/F and T/A classes, as there is basically no quench area at all.

I'm probably wrong though. lol

helicoil

iTrader: (104)

I will run the quench around .060" on alot of BBC N20 engines I do for the reason of minimizing the speed at which the burn across the chamber/piston heads takes place. The 'theory' is it helps control detonation, if that is possible on a N20 engine. I have also had good luck on 400 shot and bigger BBCs with the larger combustion chambers - 115cc and up. Sometimes to good/small of a chamber design and quench can promote too fast of a burn and make it more of an explosion than a slow burn leading into detonation.

I would assume these things would apply to the LS engines.....

I did my 403 Procharged engine at .041" quench because I didn't want to spend for special thickness H.G.'s and it was fine at 14-15 psi - pump gas and meth - when I tore it down. It didn't like more than 16* WOT.

Would have been interesting to play with the quench (open it up) and run it again to see if it would tolerate more timing.