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Removing squish band to help reduce det? WTF...

8K views 30 replies 10 participants last post by  Cord 
#1 ·
A friend just got excited with the dremmel and was wondering if it's a good idea to 'smooth' out those ugly flat surfaces on the cyl head of the RB26

Then he sent me a page from the JUN website and I was gobsmacked:eek:

Would anyone here do this on a lightly modded skyline? (not talking 1000bhp cars with standalones etc)
 
#27 ·
Hugh Keir said:
I have heard it said that the initiation of the flame is more affected by the AFR than the flame front speed ...
Many people mistake misfires for ignition deficiencies, even when they really are AFR-related.

There is a maximum flamefront speed for a given fuel and charge density. Going leaner or richer slows it down. After about 3 AFR points it slows down a lot more steeply.
That's one of the real reasons that people find out experimentally that it's safe to run very rich. Without realising it they are slowing down the flamefront, effectively retarding the ignition.
 
#28 ·
Hugh Keir said:
the quality of the cooling system will have a great effect on detonation.

Water wetting agents in the cooling system might also have their place in keeping combustion temps in check with payoff in detonation reduction and resultant increase in ignition timing
Funnily enough, the same people who I quoted in my post made a big deal about the "GT" head cooling system like you see on some top GTRs.

They made their own though.
 
#29 ·
Pavlo said:
Exactly.

which should increase peak cylinder pressure and perhaps increase likely hood of det for a give PR or TP (just one example).
Paul
PCP, although significant, is not the only factor in the propagation of detonation.
 
#31 ·
Nice picture Steve.

That head is very similar to what we do, but I don't remove quite as much squish as that on the intake side.

Have to agree with Hugh on the det detection tho, with the correct equipment it is quite easy to hear it, even on engines well past 700hp.

Steve, what do you mean by the "GT head cooling"?
 
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