i have a 89 honda crx that im building and i recently put 12:5:1 compression pistons in the block with shot peened rods and knife edge crank theres more but thats not the point. i was just wondering if i can run 91 octane gas with that compression with a good tune for dail driving?

 

you might be able to. but it really depends on the tune. im running about the same compression but im running 100 octane.

 

thanks

 

didn't have that much success on 12.5 on pump gas. learned my lesson. will never do it again. don't care how it's tuned. not safe.

 

12.5 on 91 is probably not safe. 93 would be better

 

bad tank of gas is all it takes...

 

12.25:1 on 91 here. I wouldn't do it again either - unless it was a track car.

 

Would 12.5:1 be ok on a good tune and 93?

 

You should have Sunoco stations. They carry 94 octane.

Who will do your tuning? Send them an e mail and ask.

 

Well it depends on alot of things. The important number is not your Static compression. That calculation is useless in the real world. What matters is you dynamic compression. This is largely affected by your cams, the shape of the pistons etc. You have tools to help you combat pre-detonation like octane, tuning, adjusting the cam gears etc. If you're that worried about comp, I'd just run a 3-layer Headgasket as cheap insurance to bring that comp slightly down, and get a GREAT tune on the car and you'll be set. I ran

12.5 comp with ENDYN rollerwave pistons everyday to work on 91. But that was with a tune by Locash.

 

I am not sure what your goals are, but if I was building daily driver for 91 oct (or 94 for that matter) I would keep it under 11.5:1.
Given same gas at 11.5 one can catch up on timing what they would give away in compression (if they went to 12~), and that motor will last without much upkeep...

 

i have 2.0 with 12.5 compression with hondata s200 and it runs great with 91 oct. i even ran 12's with 91 oct. it all depends on your tuner.

 

Runing 12.5 CR with CTR pistons in a C5 block with BC4+ cams on 93 octane for almost 20k miles now, daily driven. Tuning is the key.

 

I guess it depends on where you live. With the gas here in the Mid-Atlantic, I'm keeping my Endyn Rollerwaves at 11.7:1 with Crome Pro

 

12.5 on pump is really questionable. i would really suggest not doing it, even with a tune. my 12 to 1 build for a daily has really got some of the builders questioning whether or not it will be able to do ok. either way. that was my .02 keep up updated on the outcome

 

they sell suzuki gsxr1000's in ca and they are 12.5 comp and run off of 91oct. all day with a warranty. its all in the tune.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18avtec(A!!M0TOR) &raquo;</TD></TR><TR><TD CLASS="quote">didn't have that much success on 12.5 on pump gas. learned my lesson. will never do it again. don't care how it's tuned. not safe.</TD></TR></TABLE>

 

what do u guys think about 12:5 on a b20vtec set up?

 

good luck keeping the stock sleeves from crackin.. i would sleeve the b20 if youre runnin 12:1 or higher comp.

 

Why run such a high compression? Not unless you have big and long duration cams that call for it. Remember its the combination of a lot things on your engine that will make it work.

 

is there anywhere in the bay area that carries 93 octane?

and a 3 layer head gasket would bring my compression down a little right?

 

it is all about the tune and machine work. at 12.4:1 i could run 89 with not so much go but great mpg. and run 92 making 214whp on b81c with bc-4's

 

its do able but your on such thin ice any detonation or problems with be pretty much catistrophic too your motor. If u got the money for hours on the dyno go for it

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by _eoN &raquo;</TD></TR><TR><TD CLASS="quote">Runing 12.5 CR with CTR pistons in a C5 block with BC4+ cams on 93 octane for almost 20k miles now, daily driven. Tuning is the key. </TD></TR></TABLE>

got dyno chart??? would like to know what kinda power ya making...

 

on california 91 octane, its not gonna happen unless you DETUNE it.

in the end, youll make less power than if you stayed 11:1 which will give you a larger window for tuning and using THAT to gain you power.

whereas 12.5:1 youll need to richen it up and back off the timing to where its not really a performance gain but instead a hinderence