Highest CR on 93 Octane
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From: Chi-Town Western Burbs
Highest CR on 93 Octane Like the title...What would be the highest SCR I could run for 93 Octane pump gas? I tried searching came up with a bunch of hits that were useless. Thanks in advance....
BS
BS
I would like more info on this as well. Although I believe it would have a lot to do with the DCR as well. And maybe combustion chamber shape. Is there a known limit? At what point does using a methanol kit become a good idea?
Barking Spud, This is what they are talking about.
SCR = static compression ratio. The physical difference between combustion space volumes at bottom dead center and top dead center.
DCR = dynamic compression ratio. The compression ratio actually produced during operation. It is a fine tuning of sorts on the SCR. It varies with cam timing, intake manifold tuning, RPM, and load.
You could have a high SCR that convention says won't work on pump gas but with a long duration cam that bleeds off compression at low engine speeds your DCR is lower so it works great. Find a knowledgeable engine builder and or cam grinder. Comparing cam specs for others compression ratios will give you a guideline. If you're just wanting the highest safe number that will work with street cams then the answer is stock.
Vernon
SCR = static compression ratio. The physical difference between combustion space volumes at bottom dead center and top dead center.
DCR = dynamic compression ratio. The compression ratio actually produced during operation. It is a fine tuning of sorts on the SCR. It varies with cam timing, intake manifold tuning, RPM, and load.
You could have a high SCR that convention says won't work on pump gas but with a long duration cam that bleeds off compression at low engine speeds your DCR is lower so it works great. Find a knowledgeable engine builder and or cam grinder. Comparing cam specs for others compression ratios will give you a guideline. If you're just wanting the highest safe number that will work with street cams then the answer is stock.
Vernon
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From: Chi-Town Western Burbs
Originally Posted by Manic Mechanic
Barking Spud, This is what they are talking about.
SCR = static compression ratio. The physical difference between combustion space volumes at bottom dead center and top dead center.
DCR = dynamic compression ratio. The compression ratio actually produced during operation. It is a fine tuning of sorts on the SCR. It varies with cam timing, intake manifold tuning, RPM, and load.
You could have a high SCR that convention says won't work on pump gas but with a long duration cam that bleeds off compression at low engine speeds your DCR is lower so it works great. Find a knowledgeable engine builder and or cam grinder. Comparing cam specs for others compression ratios will give you a guideline. If you're just wanting the highest safe number that will work with street cams then the answer is stock.
Vernon
SCR = static compression ratio. The physical difference between combustion space volumes at bottom dead center and top dead center.
DCR = dynamic compression ratio. The compression ratio actually produced during operation. It is a fine tuning of sorts on the SCR. It varies with cam timing, intake manifold tuning, RPM, and load.
You could have a high SCR that convention says won't work on pump gas but with a long duration cam that bleeds off compression at low engine speeds your DCR is lower so it works great. Find a knowledgeable engine builder and or cam grinder. Comparing cam specs for others compression ratios will give you a guideline. If you're just wanting the highest safe number that will work with street cams then the answer is stock.
Vernon
Thanks Vernon...I will have a chat with my engine builder....I'm not looking for something too well behaved on the street......But, I do want to run readily available pump gas though.
Trending Topics
Originally Posted by yak
DCR is what matters most. I would say that 8.7 drc and no more than 12.0 scr with a good tune. btw, where in the western burbs are you?
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From: Chi-Town Western Burbs
Originally Posted by Ari G
CR is nothing you can calculate accuratly to go with octane number,has to do with so many variables
hmmmm....I hope my engine builder has a better answer than that.....
Originally Posted by NoGamesLS1
I am running 12.5:1 SRC with a trex on CA 91 so you could run a bit more on 93
Teching In
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From: Grand Rapids, MI
Originally Posted by 8ty8 LS1
is there a formula to calculate DCR? and or SCR? thanks.
http://members.uia.net/pkelley2/DynamicCR.html
SCR is pretty easy to calculate by hand, it's just volume at BDC over volume at TDC. DCR is much more difficult to calculate though as it takes into consideration valve timing, rod length, as well as the volumes from the SCR calcs. Definitely tedious to do by hand. If you search for DCR calculator on google you will find plenty.
Originally Posted by 2fast97Z
my old lt1 383 was 12.5:1 and i ran 93 and it was a daily driver and tuned by madz28..never a problem
How big of a cam did you have? I wonder if the guys with the Trex are getting away with it because by nature it bleeds off a lot of compression?
A local guy is in the high 13s:1 compression and he runs a mix of 104 and pump gas depending on the weather but he also has a Trex.
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Originally Posted by Ferocity02
.. If you search for DCR calculator on google you will find plenty.
