hey guys
just got an a15 which is stock. I have added twins and extractors. I want to know how much compression you can run naturally aspirated? Is it worth going over 10.1? Is it true you need to shave the head around .08" to acheive this compression?
Any help will be great
thanks

NA isn't the problem, you can run 12:1 if you have a really high octane fuel.

if you had 110 octane fuel all the time build it 12:1 it'll be loads of fun. On pump gas, you'd want to have it lower. What is it? 9.5:1 seems to come to mind.

In Oz where the standard pump fuel octane rating for these cars is 95...we can get away with 11:1 I'd say.

E.g the Honda S2000 runs about an 11:1 comp ratio ( a little more advanced than a A12).

I few skylines I know are running 12:1 (on boost) on 98 octane fuel.

Well that should make it about as clear as mud for you.....

On 95 RON fuel 10.2 CR and on 98 10.6CR is aabout the limit.
Plenty of info in the search button :)

I stand corrected....got to stop hanging out with those ricer boyz.

Just for interest sake.
We in South Africa have 93 octane fuel.
Shell has recently launched 95 but are a little bit more expensive than the 93 octane.

We always had 106 octane leaded racing fuel. Recently I saw in a magazine that the 106 leaded racing fuel are going to be replaced with 98 unleaded racing fuel. What a bummer.

I think performance and dragrace times are going to drop now.

Don't bother to compare Octane Ratings from different countries, or from different time periods. They are measured differently. We get 87 R+M/2, which is about 90 measured the old way.

Anyways, the new cars can go over 10:1 because of the superior engine managment systems (fuel injection, lambda sensors, and most importantly: Knock sensors). Don't try this on your old carbureted cars, kiddies.