first off, im planning on being NA. im getting a bottem end kit and was wondering which compression pistons to get. if higher compression means more power, then the 12.5 would be best, but is there some con to having higher compression? also, i heard that porting & milling the head increases the compression, therefore power, so if i plan on doing this in the future, should i get a different compression with the bottem end kit? thanks.

'98 Eclipse GS - The slow screamer.

Mods? If God wanted us to mod cars, he would make aftermarket companies. Oh wait... yeah i better get to work on that.

I cant think of any cons except it would limit how much you could go with a turbo. Yeah, if you mill your head you can achieve the same result, so if you milled to 12.5 compression, than got 12.5 compression pistons you would be running 15.5 compression, which indy cars dont even do!!! SO if you milled you would just need 9.5 pistons. Of course you could run 14 compression and tell me how it is. As for power increase, its around 4% per point more of compression, so about 12% more power.

but you have to be carful about detonation.




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so since im getting the bottem end kit anyway, i should just get the 12.5 pistons and not worry about milling the head?

'98 Eclipse GS - The slow screamer.

Mods? If God wanted us to mod cars, he would make aftermarket companies. Oh wait... yeah i better get to work on that.

Don't mill the head, it causes to many problems. 10.5's will run a good pump gas, 12.5's will require a timing retard. Every increase in compression gives you 4% per point as a rule of thumb.

Gary

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will it cause it to retard timing with high octane? Just wondering... Also take into consideration that you'll be changing the power band. I'm guessing it going to be super top end power. So you'll have to learn to drive in the upperpowerband. Might want to find a way to increase the rev limit also so you can get more power. Unfortunately there is no ecu out for out cars yet

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If i'm not mistaken running high compression will give a lumpy idle too.. like having some nice cams.

but also that 4% rule of thumb.. that's just for the compression.. and higher compression is one of those nice mods that makes more power when combined with other mods.. like some 'bigger' cams, P&P head, better exhaust/intake and such.

so in other words, get 12.5 for your car, unless you are gonna boost high and use cheapo gas. Then get some 10 1/2's. is there an 11? What do you all got? and isn't stock like 8?

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so can i get 12.5 if i always use 93 octane and not have to worry about getting a timing retard or will i need one regardless?

'98 Eclipse GS - The slow screamer.

Mods? If God wanted us to mod cars, he would make aftermarket companies. Oh wait... yeah i better get to work on that.

yeah if you go 12 you'll need the msd ignition w/timing adjustments.

1998 dodge avenger 4 cyl AT
Mods are:
Not enough

Some of the Neon guys with stock ECU are running 12.5:1 with no timing retard. But with an upgraded ECU they run around 8 degrees retard. With that compression, I would suggest a good ignition and the timing retard just in case. I plan on a knock sensor when I go to high compression to be safe and for tuning sake.

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