moehp

Remarkably, a search on the term "dynamic compression" returned zero results, so I am posting.
Are there any quideline printed anywhere that advise on max dynamic compression with different octanes, etc.?
For instance, a dynamic calc on a sea level GSR with 9:1 pistons and 15 psi of boost shows something like a compression ratio of 17:1 - what octane is required to make that setup manageable at that boost?

Muckman

iTrader: (2)

Thanks for attempting to search but you need to search the archives to get the good stuff.

https://honda-tech.com/zerothread?id=1744189
https://honda-tech.com/zerothread?id=1655407
https://honda-tech.com/zerothread?id=1170939
https://honda-tech.com/zerothread?id=964239
https://honda-tech.com/zerothread?id=700677

NJIN BUILDR

http://kb-silvolite.com/articl...id=36

Do a little surfing around on this site.It's based on domestic v8 stuff but it still applies.There is a dynamic compression calculator there to.

moehp

Thanks for the links, but they all dealt with discussions about dynamic compression in general and, its relationship to static, etc., particularly as to NA motors. My question centers on the variable introduced with FI. I did some more searching, including archives and am still coming up short.

A chart like that provided in the link by NJIN BUILDR http://kb-silvolite.com/articl...id=57 suggests that if I build my motor with 9:1 pistons, I can only safely run 6 lbs of boost before putting the dynamic compression at 12.7:1. Going to 12 lbs boost with the same motor, puts compression at 16.3:1. 18lbs boost puts Dynamic CR at 20:1.

pulling timing, adding fuel, cooling air, etc are all factors, I know, but what's the dynamic CR cap generally with FI honda engines and 93 octane?

turboteener

I am too lazy right now to run the numbers, but my static compression is 11.5:1 and I am running 13-15 psi. So figure that is acceptable. I haven't had any issues.

moehp

Thanks - the chart stops at 11:1, but extrapolating a bit it looks like you are running an end compression of about 23:1 when at 15psi. What octane do you run at 15 lbs boost?

turboteener

93 pump gas. Now if i were racing on the track I might go to something like 100 just to keep the heat in check on the long straights.