I was wondering for those who either have had experience or have a reliable source for the info. have ran a CR of approx. 11.5-7 on 91 octane (Cali folks)? My Gsr head is milled .030 and I'm debating whether I should use the US or Jdm R pistons. Im not too sure what my CR is currently (many members on this board give different numbers from 10.4 to 10.8 from a .030 mill...) so who knows, but if I were to run Jdm pistons it would be 11.4 or 5 then I'm not sure what that .030 would raise it up to. Also anyone know if this runs into clearance issues? Sorry for the long post, I'd like to make sure before ending up doing something regretful. Thanks guys.

 

i think 11.5 is safe...just get a J&s. BTW what is your setup anyways?


[Modified by Type Goch, 8:15 AM 9/2/2001]

 

J&S Safeguard.
[Modified by Type Goch, 9:16 AM 9/2/2001]


[Modified by Type Goch, 9:16 AM 9/2/2001]

 

11.5:1 would more than likely be a good stoping point with 91 Octane..Try the USDM ITR pistions if you don't want to worry about to High of a C/R but then again the JDM ITR's would'nt be to bad.. Like eveyone else said get the J&S to be on the safe side

 

I would get the safe guard no doubt because its not worth it if it start pinging and such. But 91 octane will make me never want to move to CA ever. My car does ok on 93-94octane here. But it runs even better and smoother on 98-100octane when I can get it here..but it's high.

IMO I would kind just stay with 10's in compression to be on safe side because who knows they could drop it another octane point..which could not be any good at all if your on the boarder line with 11.5. Buts thats just me I rather play it safe then with a messed up motor. But I guess you could use octane booster too.

 

Thanks for the replys everyone. So what about the mill of .030? If I were to use US itr pistons which would boost up Cr with a gsr head to maybe around 10.9, how much more would the .030 raise up the comp.? Thanks again.

 

i currently have 11.5:1.. im at 16 degrees timing though..so i dont chance it..vp 103..or 91 with some nos octane booster

 

So octane boosters will help? I know its been said that they dont give hp gains, but they will help if one has high compression?

 

I am running 11.3 to 11.4 CR with 91 octane gas right now. I have to add a bottle of NOS octane booster in every tank of gas. I am not sure if I can run without it, because Yoshio programmed my ECU for 94 octane gas!!

 

if you use those boosters, you better have a lifetime supply because those things only raise the octane points like .xx

 

The new celica gts has 11.5 to 1 comp. So you should be fine.