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I have read about this sort of calculation mostly with the two stroke crowd.
I did read where professor Blair explained the calculations needed to use this
with four strokes. I believe this will become common in the years to come.
With one of the iron head SBC engines I'm using for combustion testing, the
squish to bore ratio is ~36%. The engine RPM is between 5000 - 7500. I run
the piston down in the hole 0.025", this gives me the option of adjusting
squish clearance with a head gasket change. Some of the common thickness
are 0.015", 0.026" and 0.040". I'm currently running the 0.015" gasket for a
squish clearance of 0.040" at assembly or ~0.010" at max RPM. Unfortunately
the compression ratio changes along with each head gasket reducing the
benefits of the test.
This is a combination I have been working on for several years, my goal is
> 12:1 compression (iron head 23 degree SBC) on 93 octane premium fuel,
actually I think I'm there now. I'm thinking the MSV is relatively high with
this combination, so high that can causes combustion problems. My first
attempt with this engine was poor combustion and detonation limitation with
100 octane requiring ignition retard. Eventually I modified the engine and
opened the squish clearance and eliminated the problem. After several
variations of engine modifications, I'm now able to test different ignition
advance curves with out detonation on 100 octane, progress. Soon I will
be weening it off the 100 octane to 93.
Knowing MSV would be a big advantage with this testing. I have read of
maximum levels of squish velocity before problems arise, your software
would eliminate some of the guesswork. Please tell us more.
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