WallyP

"It ain’t so much the things we don’t know that get us into trouble, it’s the things we do know that just ain’t so."
A. Ward

Which is more dangerous to a high-performance engine - pre-ignition or detonation?

Some interesting reading...
http://www.contactmagazine.com/Issue...ineBasics.html

Any comments from those who have destroyed an engine?

SeanR

Great read Wally, thanks.

worf928

+1. I remember reading this when (actually before) I was tuning the Twin-Screw. It is however, worth reading again!

the flyin' scotsman

thx Wally.......gr8 information.

danglerb

Good read, makes me wants to run out and increase my flame rate or something.

Mrmerlin

Thanks Wally it was nice to go back to school for a refresher.

JEC_31

I played with Mazda wankel rotaries for a while. One little detonation ping = shattered apex seals = most of the engine is now scrap. The long, thin, and narrow squeezing-down combustion chamber makes for uneven mixture distribution and the lean spots at the "tail" end can cause game over, much like the pre-ignition described. Boosted rotaries have to run very rich and have stellar heat removal to survive long. The running joke was the photoshopped "Check Engine" light into a "Change Engine" light.

I kinda wish the author had delved into the "wedge" design combustion chamber we have on 16v 928s (and 944s). I fully grok the 32v chamber dynamics but am weak on the wedge.

oups59

Thanks for sharing.

davek9

Thank you for sharing!

jpitman2

On the ignition thing....recently watched a clip about Don Garlits , talking about his life in dragsters. At one stage he was given a new model Chrysler engine to run, but he couldnt get near what he needed out of it, seemed to be a lemon, doing all the normal hot up work. So he thought, I will destroy this POS, and send it back as a dud. He started advancing the ignition in a big way, thinking it would detonate or something bad - it started performing like it should, and the more he advanced it the more competitive it got. Mopar just got the timing wrong.
jp 83 Euro S AT 55k

IcemanG17

great article......I wonder how our engines rate in terms of "fast burn"....since the older 16V engines ran quite a bit of timing, probably not very fast....but the later 32V engines didn't run much timing at all....