I recently purchased some 10.0:1 comp pistons for Mahle 87.25 bore, and will have them installed soon. I plan on runnin N/A for most of the summer, maybe purchasing a turbo later on. My buddies are hackin me for not getting 9.0:1, but the dude thats doin all the machine work says its not about how much boost you run. 10.0:1 with 12 lbs on race gas is the same as 9.0:1 with 19 lbs on race gas. Its just what are you willing to sacrifice. Plus I have a Hondata S200 and we're planning on runnin alcohol injection when I turbo it. Did I make the right move?

 

A friend of mine that has built several high HP turbo'd v8's recommends low comp with high boost. Take that at about what its worth.

Tuning 10.0 comp pistons would be more difficult with less margin for error on a turbo motor (which shouldn't be a problem if you're not doing your own tuning). You'll be able to spool a slightly larger turbo with the higher comp or benefit from a slighty quicker spool.

As far as whether you made the right move, there's no real answer for that. There are so many options out there that nearly anyway you go there are parts to compliment your setup. I'd say since you already bought them go with it. No need to spend extra money on more pistions.

 

Anybody else?

 

about a year ago there was an article in SCC. they were comparing two boosted cars (SRT-4s i think), one with slightly more compression and less boost. the car with more compression and less boost ended up making more power than the other. with the higher compression you will get a better quench area, which will give you more powerful, more efficient, and quicker combustions. you will be better off with higher compression and very good tuning. don't be tempted to turn up the boost though! and make sure you get an oil cooler too so you don't overheat your oil/engine.

 

9:1 is on the low side. with that outside of boost, its gonna feel sluggish. tuning is what really matters.

 

Well. An RSX we have in the shop is running stock 11:1 compression at 14lbs of boost. 93 octane here in Houston.

Fully tuned. 375whp. Runs great.

No long term tests though. Only a couple months in, but from what I'm hearing, the cars that have actually been tuned are running strong and long tern with up to 12lbs of boost.

Take it for whatever it's worth.

 

I would think that a car with higher compression and less boost would also have a better powerband, and more torque throughout the curve than a car with lower compression and higher boost which would have a higher peak hp.

However anything is possible with good tuning. So don't worry about having 10.0:1 compression.

 

Well unfortunately Mahle won't have the 10:1 pistons til mid-July, and since I've waited since April, I'm gonna go with the 9:1 and run a nice little turbo setup in a month or so. Not my initial plans, but like my buddy said, I have all Crower valvetrain thats setup for turbo including the Stage 2 turbo cams, and those are best utilized by boost, and boost alone. I'll let you know how things work out.