Just recently decided to built my engine, power goal is 800 hp with possibility of maybe going for more down the road. I'm looking at all the current forged piston offerings and all the different compression ratios from 9:5.1/10:0.1/10:2.1/10:5.1. The car is currently on E85 w/stage 3 fuel pumps and Doc race IM w/750cc inj. Had a talk to a reputable engine builder and he recommend go with the higher compression piston cause of the fueling and my power goals. Wondering what are you thoughts on what compression ration go with and is there anything else I should be taking in consideration. Really appreciated your help.
High compression or low compression... can make up my mind?...Need pros help
- Thread starter STE92
- Start date
When a lot of people are wrong doesn't mean they are right.
Usually its a good indication to look at the manufacturer, and you see a clear trend on DI engines, CR is going UP. I know they are doing it mostly to comply with emission regulations, but still.
Add to that E85, and you have absolutly no reason to lower CR. Altho you might want a closed deck if you increase CR and go for big numbers.
I'm no pro, but this is my opinion.
Usually its a good indication to look at the manufacturer, and you see a clear trend on DI engines, CR is going UP. I know they are doing it mostly to comply with emission regulations, but still.
Add to that E85, and you have absolutly no reason to lower CR. Altho you might want a closed deck if you increase CR and go for big numbers.
I'm no pro, but this is my opinion.
I think the majority of built N54 engines in the last few years have gone with 10.5:1, actually. I know at least most of the vendor cars and big builds I've seen have. You're running e85, have a reasonable power goal and the engine builder even said to go up. You've got nothing to lose and itll help you hit 800whp with less work.
If you were going to try to break hp records with it or turn it into a tube frame chasis trying to run 7s and planning to run a gigantic turbo at 40psi with spray, then I'd say go lower. But you'll be hitting a nice whp number that people have run stock blocks at for shorter periods of time, so go up!
If you were going to try to break hp records with it or turn it into a tube frame chasis trying to run 7s and planning to run a gigantic turbo at 40psi with spray, then I'd say go lower. But you'll be hitting a nice whp number that people have run stock blocks at for shorter periods of time, so go up!
Oems go higher cr for fuel economy and emissions, not power.
I vote for lower cr than stock, but not too much lower. Why would you make an engine that is already sensitive to knock and octane even more so? Seems counter intuitive. I see plant of pros for decreasing, but none for increasing.
I vote for lower cr than stock, but not too much lower. Why would you make an engine that is already sensitive to knock and octane even more so? Seems counter intuitive. I see plant of pros for decreasing, but none for increasing.
Raise it for ethanol. If you want to make bigger numbers on lower octane fuel (like pump gas), drop it. If it's a mix, keep stock or slightly lower. I'm out in AZ so if I wanted a built motor (not yet....) I'd probably drop it so the car is still worth driving on our lousy ACN91.
