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Old 06-10-2006, 01:11 PM   #20
Matt Monson
Scooby Guru
Member#: 832
Join Date: Jan 2000
Chapter/Region: RMIC
Location: Teh Ghetto Garage, CO
99 2.5RS, '85 911
'73 914 and 2012 BRZ


Originally Posted by tzedek
Great write up, I have to disagree about high compression motors though. You said that anything north of 11.2:1 will need race gase and engine mangement. While I agree that those things would be great with the high compression, some of the locals here run hybrid engines with 12:1 c/r on 93 ocatane with stock ecus. Those motors run great, and have lasted well. My build is going to be high compression on 93 octane, but I plan on using a s-afc or e-manage. Just my opinion though, great thread!
Realistically, this is going to vary greatly by location. This is because both available local octane and altitude influence this. I consider 11.2-11.4 to be a good safe limit as a generalization. Beyond that, as he alluded to, running some sort of EM is the best approach. If one were to make the blanket statement that 12:1 CR was safe on pump gas, there would be guys out there who had engines go south on them because they were misadvised...

Great compendium of info. Really my only suggestion would be to trying and get some clarity regarding dyno's. In your power to weight ratio section, you make reference to a certain WHP level that will be equal to a WRX. Without knowing both the stock NA and WRX power levels on that same dyno, it's a meaningless number. I make 150whp on our local Dyno Dynamics dyno, and more like 170+ on a Mustang. I was handing WRX's their arse back when I was in the 130's. The only point is that it's all relative, and like my CR comments, it something where making gross generalizations gets into questionable territory with respect to accuracy...
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