Trying to do lots of research before I start my N/A buildup of my 1990 prelude si(b20a).

In the rare case I can find any sort of numbers, they seem to be contradictory.

So I thought I'd pose the question to yall-running 91 or 93 octance(what I can get here in san antonio), what's the maximum compression I could run?

I'd prefer to just use pistons, and not mill the head any, seeing as how I haven't found a machine shop I trust here at home. Plus, with pistons, I should know my exact compression ration.

 

from what i have gathered the max compression you could run is not really the best to run on the streets. I beleive you could go as high as 12.8 on 91 octane w/ a good tune however some would argue that 12.1 is the most suitable..

 

But 12.8 on 91 or 93 even if its driveable with a "good tune" there is still a compromise somewhere. People who tune these 12+ compression cars on pump gas for a living know alot better than I do but it just seems to me, if you can run full timing and an optimum AFR on an 11:1 motor on 91--I feel like it would make more power and be more reliable than a 12.8:1 motor on 91 that is running rich AFRs and pulled back timing. Also there are so many factors to consider. Do you live in a flat or hilly area? Do you have air conditioning? Is it going to be very cold or very hot when you are driving? Do you often carry alot of passengers? Is this in a heavy or light car? How do you plan to drive the car? How good is your cooling system?


Modified by d16dcoe45 at 11:42 AM 11/28/2006

 

I have 12:1 and only use 100 octane unleaded. I would LOVE to be able to mix it or even run straight 93--but not if I have to negate the advantages of high compression to do so. And what you can get away with in a short drag race, is different than on the street where you might have to go up a big hill, in 95 degree weather in 3rd gear with 4 people in your car. That is what a manufacturer has to worry about so even on a permormance car it has to be able to do that plus some extra without detonating enough to damage the motor. That is why you rarely ever see above 11-11.5 on a production car--except some of those direct injected Audis run 12.5 on 87 or 89 octane.

 

bump for good answers