Planning to strenthen the bottom end of my motor going 156mm long rod and forged piston. Can't decide on 9:1 or 10:1 my builder is saying 10:1. Fuel will be E85 normally and Q16 at the track. Boost will be 30 on E85 and 36.5 on Q16. Turbo will still be my AMS 37R. What do you recommend and why?

 

if you are going to be running e85 go with a 10.0 motor!

 

ill say 9:1

 

Is there a reason you are saying 9:1

 

9:1 will allow you to run more boost and have a better tolerance to Knock, At the cost of Engine responce.

10:1 Good low end responce, helps spool. But will be boost limited...Boost will make more HP then compression in most cases.


This is not a scientific observation, but running high compression does tend to shorten the lifespan in a engine IMO. Think of it as boost you can never turn off...because no matter the RPM you will have higher Cylinder head pressure all around.

 

Now if this car has a standalone and will run only the fuel/boost you mentioned...10:1 can work might be pushing it on E85...but then again i myself never ran that CR with boost and E85.

 

10:1 and high boost seems to get it done.

The real question is what turbo?

Lucas' car runs 10:1 on E85 and made 506whp on a stock turbo and got 12k street miles/race miles.

Paul runs 10:1 and VP import and 44+psi of boost and makes between 1050 and 1117 depending on turbo.