Ford Mustang Forums banner

1 - 1 of 1 Posts

128 Posts
Discussion Starter #1
I have this posted in the SVT DOHC section and Supercharger section with no luck, so im throwing it in here.
my cobra has a 11.3:1 compression ratio. so when i supercharge it obviously my ECR is going to be even higher and more awesome. making the equation even more critical... I want to run 5-8psi, depending on this equation, my tuner (a very trusted speed shop, and very vetted tuner) uses the fallowing equation:

sqrt((boost+14.7)/14.7) * CR = ECR
sqrt = square root
boost = psi of boost
CR = static compression ratio of the motor
ECR = effective compression ratio

But, i find 2 others out thru the web:
Final Compression Ratio (FCR) = (Boost / 14.7) + 1) x CR
Boost = Maximum Boost
14.7 = Psi. at Sea Level
CR = Engine Static Compression Ratio

i cant locate the third right now (i am deployed and the internet is acting up), but all 3 give you VERY different numbers. i want to think its the 1st one because i want to believe that they wouldnt be building cars for the last 30 years with extremely innacurate compression ratio equations. thanks for the help
1 - 1 of 1 Posts