I see why he'd want to use the 11.4:1 compression instead of the CTR.

It'll give him a lot of tuning options so that he can bring the cams on lower in the RPM range and stay on pump octane.

Makes perfect sense.

 

I've seen steve talk about using B16 pistons and not CTR pistons.

Chris - considering CTR pistons and Toda B's.....

 

B16a pistons can be either PR3 or P30. P30 pistons are from the JDM b16a that has 10.4:1 CR, PR3 come from all US B16a's or 1st gen JDM B16a's that are 10.2:1 CR. I've read that there have been some people that have measured CTR pistons and there is a big difference design between a ITR, B16, GSR piston vs. CTRs. CTRs actually will sit taller in a block and will yeild a higher CR than most people think. I think I remember hearing CR with a B18C5 and CTR pistons with stock bore is closer to 12.4:1, according to Omniman.

 

WTF people.

CTR pistons in an otherwise stock b18c5 yield 12.4:1 and 12.8:1 compression. (81.25mm Oversived pistons)

Please don't talk about compression if you don't know. Most of the compression calculators do not take all necessary variables into consideration.

CTR Pistons = PCT.

quote from omniman -

stock type-r motor with ctr pistons
head Gasket 2.8cc big vol= 488.3cc
piston dome vol. 6.3cc small vol= 39.2cc stock type-r=12.45
camber vol. 44cc
deck height .25mm 1.3cc
cyl vol. 449.1cc

b16 pr3 pistons, b18c type-r pistons and b16b ctr pistons all have a different compression height. the pr3 pistons have the smallest and the ctr pistons have the biggest. with type-r in the middle

 

Arent stock s2k's compression up there. So I dont think there would be much problem with running them on daily driven cars.

 

You have to advance the timing WAY out there, its not very streetable unless you have an excellent tuner and its STILL pushing it. It would also be advisable to have some octane booster or higher octane gas at almost 13:1.

They are different engines - you can't compare like that.

And - the s2000's stock compression ratio is 11.7:1. ITR is 10.6:1. 2004 S2000 is 11.0:1

That's not exactly 12.5 or 12.8.

 

i've heard that 12.5 is jsut about the limit for 93 octane if you tune it just perfect

 

Yes...that's the general rule of thumb, if tuned properly.

 

I am currently using JDM ITR pistons at 81.25mm with a spoon Headgasket this yeild's 11.6:1 compression perfectly safe for pump gas on a daily driver.

 

That's the key - and there aren't a lot of tuners out there who take the time to be perfect....