mingster

with 92 octane gas? I have my eyes on those 10 extra ponies...

Schatten

define...."safely." =D



I really dunno, but if you are in a state like Indiana, where the gas is more additive-junkola than real gas, then I would suggest not.

mingster

[QUOTE]Originally posted by Schatten
[B]define...."safely."

cdelena

250 PS = 246.58 horsepower

Would you really teardown the top of the engine (big installation cost) for 6hp and a chance to test your knock detector?

BB AP1

Usin JDM pistons will raise your compression a bit more but it won't work on 94 Octane gas...

ultimate lurker

Absolutely. First, Honda gave us 11:1 to provide some leeway for bad gas or even the emergency requiremtn to run lower octane. However, with a good combustion chamber design, 11.5-12:1 compression is well within reach on 92-93 octane. I've run 11.5:1 on a B18C1 engine (modified) with no problems whatsoever. Toyota runs the Celica GTS at more than 11:1 compression ratio as well.

Basically, you remove some safety margin, but as long as you don't run lower octane and keep your knock sensor, you'll be fine.

As another example think about the effective compression ratio on a supercharged S2K running 6 lbs of boost.

That said, it isn't worth the effort to pull the head just for a compression ratio change. If you plan on changing cams (which means you've done half the job required for pulling the head) or plan on porting the head, then go ahead and up the compression.

UL

Takashi KazuMori

If you can get 100-octane, you can try. Not betting on it to have no problems. Export and local engine parts differ frequently with the slightest difference sometimes unaware of the common tuner.

Luis

I have though about this frequently.

Chris, it's not clear to me that ROW S2000 have 240HP and not 240PS. If that is the case, then you do get an extra 10PS.

I would also be weary about taking conclusions just by looking at the CR. The final cylinder pressure is also dependent on variables other than CR. So a 12CR maybe fine for one engine but not so good for another.

This said, I'm convinced that the thinner headgasket that JDM versions sport are the basis for their increased power, and that Honda was playing it safe in the ROW markets. For instance, in some countries in Europe 98RON is simply not available (Italy comes to mind).

This is a mod I could do for less than 500USD. and in the S2000 you usually have to pay much more to get 10 extra PS.

My question is (I know, I've asked this before, sorry!): Is opening up the top end a risky undertaking? (like in "my motor was never the same... " )

Patch

Doing a head removal with the motor in the car is a PITA any way you look at it. It takes me over 3hrs to get to the bolts - then again I keep a notebook next to me and label anything that will hold a tag. But ;-), 10 more ponies is tempting. To be on the safe side (for poor pump pee), I would bump the FP up 2-4lbs. Rent an hour on a dyno and adj the FP to peak and then add in the safety margin.

Be sure to wrap pantyhose around the radiator "in" to catch the old head gasket shavings which fall into the block when you scrape.

cdelena

I can only go by what is published.. any dyno reports tell little since there is no reports of a JDM car and a ROW car being measured on the same dyno.

As far as the risk of the change.. it simply depends upon the mechanic. I have swapped heads on cars (with simpler valvetrains) many times without problems so that tells you it is not that hard. But it would be prudent to use a mechanic that is experienced with Honda/VTEC and the swap.