[Diy_efi] boosted compression ratio

[Nick Starai]

I'm currently rebuilding my project Honda. Wondering what kinda CR you
guys would recommend. My engine management system is a modified OEM ECU by
Hondata. I will have full control of fuel/timing map and boost through an
electronic boost controller. I also have a knock sensor with individual
cylinder retard.

Some specs that may help: 1.95l aluminum head and block. The head has a
factory port/polish. The engine will run somewhere around 20psi through a
garrett t3 .63 a/r stage 3 / t04e 57 trim .60 a/r to reach my goal of
400whp. Will be run on 93 octane pump gas. My previous build was 8.8:1 as
I was able to put a shelf pistons in for cheap. I want to choose ideal c/r
for this next rebuild and will get custom pistons. It sounds like 9:1 (not
much different then 8.8 )is a reasonable median for street drivability
while still allowing a decent amount of boost. I've read many many heated
threads of high compression moderate boost vs. low compression high boost
merrits and it seems to boil down to around 9. Obviously higher cr will
make more power all things equal, but there is probably a ratio that is
more desirable for my street setup. I wouldn't hesitate putting in some
10.0:1 or 9.5:1's and running 20psi, I'm just trying to get a feel for
what everyone else in thinks is reasonable. I know that tuning will be the
key, but I don't know if 10:1's will be able to run decent timing at
15-20psi on 93 octane. I will have access to an inertial w/ wideband
initially. I'm just wondering what some of the experts on this list would
recommend for a street boosted custom application. Any advice? Thanks.

Nick Starai


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