90sc35thann
Registered User
I know our compression ratio is about 8:1. I was doing some thinking and does anyone have an idea how this is affected by the increase in volumetric efficiency under boost? I am more curious than anything.
ECR = [(Boost PSI/14.7) +1] x static CR.
And the stock static CR is 8.2:1, not 8:1, IIRC.
That calculation leaves a lot of things on the table.
I understand why you are dividing by 14.7 (pressure at sea level), but why add "1" ? Is that how you adjust for absolute pressure?
That calculation leaves a lot of things on the table. It's not the same as 17:1 N/A. The volume of any gas is relative, and so since the air is under pressure prior to entry into the cylinder, the end result is not the same.
I totally agree with that. I know you can't bump up compression to 17:1 on an NA motor and get similar performance Vs. forced induction. My brain was just spinning some stuff around with things I read and I wasn't sure if there was some type of funky calc out there for something like this. Curiousity more than anything.
THATS UNDER FULL BOOST DON,T THINK THESE MOTORS WOULD LAST LONG AT 17 TO 1
LIke CMAC said though Boost and compression ratio are independent. I positioned my question improperly. I was more curious about how much the volumetric efficiency is typically increased via an M90 sitting on top of our engines. Obviously there are many factors but was curious about the average gain.
LIke CMAC said though Boost and compression ratio are independent. I positioned my question improperly. I was more curious about how much the volumetric efficiency is typically increased via an M90 sitting on top of our engines. Obviously there are many factors but was curious about the average gain.