N/A motor build help

[Magana559]

im really not blowing smoke out my ass, my tuner had a ls with pct pistons. he said the had about a 13.6:1 and it ran on 91 pump with no problem.

 

[K2e2vin]

No no, it was regarding the PCT argument. PCTs in GSR are around 13:1 but that's not far off(small differences are normal presuming variances in measurement), but that also wasn't part of the argument(the thread was just to show how CH can severely affect compression ratio).

What compression you run has more to do with it the overall compression figure, as combustion chamber shape/bore makes a huge difference. The motor I'm building right now, I'm actually aiming for 13.9-14:1 compression(pistons are pretty much flat top/slightly dished). Theoretically, a smaller bore helps control detonation better hence able to run higher compression.

 

[5speed]

stick with 12 compression pistons, dont matter what kind, you'll be fine at 91 92 octane..do head work to it..i'd stick with itr cams or toda spec...the thing is you HAVE TO GET A TUNE!!!!! if you want to be safe and fast TUNE.

 

[CAFROG]

I would think that anything over 12:1 compression is a risky venture on pump gas. Too many people tell me so. Not to say it can't happen (like Magana stated about his Tuner's experience) But I can't see it being okay for the long term DD. But cool part would be you could put some high octane in (I can get 107 for $7.99/gal....ouch) and get some serious results. If its a race car....I'd run the high compression too.

 

[K2e2vin]

hint hint, E85

High compression is risky, especially if there's variances in fuel quality. I plan on running flex fuel(Megasquirt is the only ECU that supports this at the moment) but from what I gather it's similar to 104-105 octane gasoline.