Increasing compression

[94_Rolla_Guy]

Hello, i have been looking into this but i haven't come up with too many firm opinions, i thought i would run it by people here.

I have a 7A-FE that runs stock 9.5:1 compression on 87 octane, i want to increase the compression to 10.5:1 compression by using pistons with a smaller dish. the question is will this run properly on 91 octane?

The other question i have is will the ECU adjust to the 10.5 compression, or am i going to have to add a Piggy-back system to re-tune my fuel?


I have a older 8point SAFC on the shelf at home that i could use if needed would that work if needed

Also, finally will the ignition timming be ok or will i have to do something about that?

Thanks for any help, im not looking for anything definative just looking for some opinions!

[Tommy]

10.5:1 compressionw will run fine on 91, my GTI had 10.5-1 compression and it ran fine on 87 actually.

As far as tuning? not sure it would be necessary, but a stand alone system never hurts, you're timing should be ok, maybe retard it a few ticks, but you probably want to upgrade the ignition system to something with a little more juice, stronger coil and a MSD would be good.

[Toysrme]

91 octane = nobody knows
retuning = no. Only in extreme cases.




Why are you jumping compression? Are you planning on doing other things? Jump one pointn in compression would be worth a who 2-3-4 horsepower without doing anything else.

[TTercel]

4AGE Top end FTW

[94_Rolla_Guy]

It wouldn't just be extra compression it would be a mild P&P and a valve job, and maybe some sorta cam work later, without the cam work id like to see maybe a 15% gain?

I would do a GE head conversion only issue is that i don't think i can make the GE distributor work with the 7A-FE ECU the problem being the 7afe ecu pulls its RPM and cam postition off the distro....