Shawn McKenzie wrote:11:1 is not pushing it with today's tuning abilities. Factory cars come over 11:1 now: Honda S2K 12.4:1, E46 M3 11.8:1, the new BRZ has 12.2:1, the RSX came just over 11:1 from the factory. All #'s are IIRC, but they should be pretty close.

My little 1.8L @!#$ shaker is 10.5:1.

well here is the thing without newer designed fuel and head setups don't expect to go over the 11:1 mark easily all out the hondas referenmced run direct inject which puts fuel pressure upwards of 70psi and has an overall better design, so keep that in mind as well, 2013 is def not same as the hardware in the 90's. I can see 11:1 working, with some doing, for how long? noone knows.

After some thinking and reading and some quik math-balpark stuff- I think 10.5:1 with .010 off the block an 0.20 off the head should be about 11.1, then spin that stupid little mp45, but i don't know how much i trust that 45 in a DD with mo cooling options mite be better off adapting the 62 onto it

Honda just recently started direct injection, however they've been running high comp for years...

once again... Its ALL IN YOUR TUNE... You can run 12:1 N/A in a J all day long on 93 octane with a good tune, and the motor will last for as long as you maintain it (so long that none of the parts on the motor are defective)..

I echo what Kyle said. Its all in your tune and parts selection. Also remember the guys who do the 086 head swap have something like 11.3:1 CR on a STOCK bottom end with no problems when properly tuned. So if your building the whole bottom end you should have no problem running on 11.5:1 properly tuned, even on a daily driven car. If I was going to build an NA motor, which I was until 2 weeks ago, I wouldn't go less then 11.5:1.


PSN ID: Phatchance249

It all depends on the cams you use that determine what compression you use. Smaller cams as ld9s to the LD2 would be ideal 11-1 or less since the psi would be higher and LG0 or bigger needs higher cr because these cams loose psi in cylinders.

You are wrong.. as your rpms increase with bgger cams so does your compression. This is how a lot of people use highr cr pistons and shaved heads in circut racing. Because when they do a cr test it won't show high cr on thee test because the valves are overlapping. But at higher rpms there is many things that come into playbut over all your cylnders have more air forced into them.... resonating effect is what ii believe it is called.

Well this is why smaller cams are better with low rpms. They buikd up more tq at lower speeds. But yes dynamic cr is the word I was looking for.. thank you for correcting me. ..

wait what test are we talking about... i have all three of the things listed, and on a compression test, i'm sitting around 260 psi across each cyl...

yeah, i'm leaning to the 11:1 hahaha, but still not sure, I do want to go boosted....even if it is just the limited mp45 thats fine, but it be nice to do more. Def want pump gas no matter what. i checked my supposedly stock motor...185 psi across all cylinders, lowest 180-181, odo shows 160k. but I just don't know yet...with the boost and shaving the head and block....you guys think that 11:1 are gonna be ok if I end up running 15psi? I'm only going all out if I get bit by the j-virus again, if not prob just gonna push the mp45-umm whats this max out at again? 8psi? o without getting so hot you can cook on it that is, i'm gonna drive this thing hundreds of miles at a time.

i got some 2.3 made to work in a 2.4 that are cut to raise compression.


97cavalier