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-   -   dumb question on max compression ratio (http://forums.pelicanparts.com/911-engine-rebuilding-forum/999356-dumb-question-max-compression-ratio.html)

Harpo 06-12-2018 05:02 PM

dumb question on max compression ratio
 
Good evening Pelican

What is the highest CR on a single plug with pump gas?


Thank you


David

chrismorse 06-12-2018 06:54 PM

It Depends...
 
Fuel octane ratings vary. here in kalifoania, 92 is about it and that is with alcohol. We cannot buy "pure" gas unless we swear a blood oath, in writing, that such criminal fuel will NEVER be used on the highway.

did someone get bought off on that one???

To a lesser extent, it depends on the cam duration, overlap and the ability of the engine to go over 100% volumetric efficiency, (dynamic compression).

Still pissed off,
chris

racing97 06-12-2018 07:39 PM

10:1

Schmierung 06-12-2018 08:57 PM

10.5:1 with carbs and, most importantly, S + cams. The overlap reduces the dynamic compression. Single plug.
In MI, you may be able to get away with milder cams. My euro 3.0 has SC equivalent cams stock and 9.8:1 stock, pump gas, single plug.

Harpo 06-13-2018 03:53 AM

I'm still on the fence weather I want carbs or ITB. I have absolutely no idea about what Cams I want other than I have no intention on racing so nothing too aggressive.

Thanks

David

safe 06-13-2018 07:13 AM

Quote:

Originally Posted by Harpo (Post 10071730)
I'm still on the fence weather I want carbs or ITB. I have absolutely no idea about what Cams I want other than I have no intention on racing so nothing too aggressive.

Thanks

David

Well tuned carbs vs well tuned ITB / EFI:

https://www.youtube.com/watch?v=aj-Z33MO2Gk

Quite interesting.


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