Octane and Compression Ratio...SCHOOL ME

[Black1987Stang]

I'm building an all forged 331 stroker with twisted wedge heads, trackheat intake, trickflow stage 2 cam or a comp xfi stroker cam, and all the usual. It has 9.8 to 1 compression with a .040 gasket and the parts that are in it. Will I be able to use pump gas no problem? Like 91 or 93 octane? It will be tuned with a wideband and Tweecer R/t

 

[NIKwoaC]

9.8 to 1 is nothing, 91 or higher will handle that easily. Make sure you have your timing set right and it doesn't run too hot and you'll have no problems with it. I've seen cars with much more compression ratio run fine on pump gas, and even though they have knock sensors and systems that can compensate, many newer cars run more compression ratio than that from the factory.

 

[squeak93]

I run 11.1 on 93 (91 works if stuck w/o) w/o any problems. i can tell its pretty touchy on the tuning but can be done with ease.

 

[Black1987Stang]

K thanks, now would it be too much for an S-trim with a stock pulley or a single turbo on like 7-8 psi?

 

[vtecwho]

you should not have any problems pushing 10lb boost with that combo. your cr is getting up there but with a good tune that the tweecer can get you, you should be ok.

i guess that im running about 9.5 to 1 cr and i have plans on going to 8lb and im not expecting any problems with 91 octane and a good ol tweecer tune.

eric

 

[Vipersix]

Be advised that with 7 lbs of boost your final compression will be 14.5:1, well above the recommended limit for pump gas. You may run into detonation problems.