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Re: Reliable DCR Calculator?
[Re: polyspheric]
#1349977
12/12/12 02:12 AM
12/12/12 02:12 AM
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Joined: Nov 2012
Posts: 264
Farmington Hills, MI
BPBP440
OP
enthusiast
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OP
enthusiast
Joined: Nov 2012
Posts: 264
Farmington Hills, MI
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Quote:
There are 2 major differences:
1. you have to know the nominal intake closing point. The .020" and .050" are useless, and the K-B correction is a vague guess (based on Vizard's estimate of 30° effective duration diff between lashed and .050").
2. the ratio of variable heats (the exponent in th formula) will vary all over the place between about 1.2 and 1.4 depending on water jacket temperature, compression ratio, EVO point etc. No engine you can buy runs 1.4, the best guesses are 1.25 to 1.3.
BTW: DCR is now a buzzword (yes, that 15 year old at the magazine rack uses it), but it does very little of practical value.
Sure, a simplified calc is never a substitute for a full blown combustion model. Indicated mean effective pressure, kernel formation, flame propagation, mass fraction curve, etc. are all thrilling topics, but when I go talkin that talk to the 15 year olds at the magazine rack, they just look at me funny. 
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