Originally posted by Chris Hightower:
What is the highest compression ratio that SVT cams and valve unshrouding can use? 12:1? 12.5:1? Say with 93 octane and some crazy ECU prog (ADC)


Originally posted by fastcougar:
12:1 with a great tune ... I wouldn't go any higher on 93/94 gas.


Not even remotely close!!!

Even the hybrids can't really run optimum timing on most pump gas.

I would say 10.5 to maybe 11 to 1 on good 94 octane can run best timing. Weather permitting. (SVT cooling system, 160 t-stat, OAT with WW or Evans coolant, et cetera are all a must either way!)

I could get the 10.3 CR 2.5L to best timing on 92 octane plus booster (real octane not the POS over the counter stuff or about 93.5 pump) or just straight 92 octane in cold weather. In hot weather I had to back the timing off a little even with octane booster.

Compression is not going to gain you much power though.
Figure maybe 1% over a 9.8-10.1 CR engine. That alone is a waste of money to just buy forged pistons & need engine balancing for!

Even if you went 12 to 1 and ran 104-110 octane race fuel you are only going to see a 4 maybe 5% (8-12 crank) increase in numbers. Good luck paying for race fuel every fill up!

High CR, pump gas, and optimum timing do not mix very well.

2000 SVT #674 13.47 @ 102 - All Motor! It was not broke; Yet I fixed it anyway.