Effective Compression Formula

(Boost PSI / 14.7) + 1 X existing compression = Effective Compresson

(8/14.7)+1X11

In an S2000 at max boost on a Vortech your effective compression is 16.98+ to 1.

Anyone else familiar with this formula?

thanks fltsfshr

 

hunh?

 

Vic A friend of mine just finished supercharging a bmw gave me this formula. He was commenting on the stress FI puts on our motors at 11:1.

In an earlier correspondence with Aquamist water injection people, they told me that my compression running 8psi of boost was at 13.5 or so to 1.

My neighbor says thats wrong. He gave me this formula. I'm trying to see if anyone else knows anything about it.

fltsfshr

 

It looks good to me from an engineering point of view. Make sure you mutiply the compression ratio by the quantity (1 + boost/14.7). So the formula is
(1+Boost(in PSI)/14.7)*CR

 

So you add the plus one to the boost psi and then diviide by atmo?

the way he gave it to me was boost psi/14.7 then plus 1 =1.544 times compression 11 = 16.98 effective compression

your way is boost psi 8 +1=9/14.7 = .6122 times comp 11 = 6.763

are you sure you didn't misstype Jon?

fltsfshr

 

fltsfshr-
Operator precedence. "/" has higher precedence than "+", so you'd do the "Boost(in PSI)/14.7" before adding 1. You should come up with the same answer.
Your equation above is actually wrong:
(Boost PSI / 14.7) + 1 X existing compression = Effective Compresson
Because you would do "1 X existing compression" instead of what you really want to do. You'd need to group it w/ parentheses like this:
((Boost PSI / 14.7) +1) * existing compression = Effective Compression

 

I've never pretended to be a mathematician. thats the way the formula was given to me. All i care about is which is the correct answer. Please put in the proper form and please do the math for me boost is 8psi compression is 11:1

thanks

fltsfshr

the answer is 16.98+ to 1 I think

 

For 8 psi if boost effective compression does work out to be 16.98

 

Almost 17:1 effective compression, given the equation above.

 

wow no matter how I did it it came out to 16.98 plus a fraction...hmmmm you must be using new math lol...thanks for the help

now how can i apply this to make the world a better place?

fltsfshr