i want something to bump up my compression ratio a bit be4 i go ls/vtec. would this be a good choice. i think it will put me a about 11.4-1. can i run 91 octane with this. what else woul di have to do to install this besides new headgasket? thanks

 

i believe that you have to have the piston end of your connecting rods machined to accept the CTR piston. you should be able to run 91 if you do conservative tuning. it'll give you a decent increase in torque. run higher octane if you can afford to, think of it as cheap insurance

 

actually, if we're talking about p30 pistons (which I believe is the same as CTR when my memory serves me), your compression in a b18b1 is going to be closer to 11.9:1 - the c-speed racing calculator is off unless you put the deck height as 0 - according to what I've been told by those apparently in the know.

I'm still trying to find out if that 12:1ish compression is plausible on 93 octane (I'm guessing that by you having 91 that you're in the midwest in a high elevation area). I'm sure it's possible with retarded timing, but full timing ? doubtful to me, 12:1 is mega high, heck, 11.4:1 is still pretty high for a street car.

- Nathan

 

i used the bojangs calculator, and on a stock b18b bottom end with CTR pistons @ 81mm bore , 3 layer headgasket, b18b head, CR is 11.6:1

Now if you did a gsr head like you were indicating, with a .25 over bore ctr piston, and a 2 layer headgasket, you CR would be 12.84:1 . that is way too high to be suitable for 91 octane gas.

Your best bet would be to get P30 pistons @ stock 81 mm bore and run everything else b18b untill you swap on the gsr head. you will have a 10.98:1 CR and then when you swap on your gsr head with a 3 layer headgasket, you will be at 11.78:1... better yet would be a b16 or itr head. that would give you 11.5:1 which is better for lower octane gas.

HTH

 

ok what octane woul di have to run with the ls/vtec with ctr pistons? whats the highest they sell at gas stations? or woul di have to get gas elsewhere.

 

they highest pump octane available to me is 94. I can go to the airport and get 116, but that stuff is hella expensive. If you cant get high octane gas, dont build a crazy high compression motor. The low octane fuel will detonate under high compression so wither you have to addd more fuel or retard the timing a lot. 11.5 is probably the best for 91... if you can get your hands on anything higher like 93 or 94, then you could run a higher compression bottom end

 

will i need new rings. i noticed u said oversized with ls/vtec setup. can u just run regular for now without tuning? how much power increase could i expect

 

regular size ctr pistons i mean

 

no... but you should replace the rings anyway... when we built my buddy's ls/vtec with CTR pistons (b16 head) we re-used his rings... not a good idea.

Get new rings...
-Mike

 

I am running LS block with ctr pistons and a b16 head and yielding a compression around the 12:1 range. It fully retarded to be able to run on street gas and still is ify. To run high compression be prepared to invest some money in gas. I've found running 2 gallons of 110 with a 9 gallons of 91 works pretty well for me. Good Luck. BUMP FOR HIGH COMPRESSION N/As

 

iight 93 octane with ctr pistons and rings in a stock ls motor. untuned...need anything else

 

bump for answers. i have head that i have to bore my motor to 84mm to run the ctr pistons?

 

stock bore is 81mm... CTR pistons come in 81mm or 81.25mm you dont need to bore your cylinders, you just need to do a light hone to get the crosshatch. its not a good idea to break in new pistons and rings on shiney cylinder walls

 

what would the compression be if u did the CTR pistons on an all ls motor...that is what my plan is, so i would just like to know.

 

thanks. compression would be in the 11.5:1 range...how do i hone? lol

 

https://honda-tech.com/zerothread?id=350173
https://honda-tech.com/zerothread?id=262069
https://honda-tech.com/zerothread?id=1031058


also do a search under ''honing'' in archives... i found 64 other threads