i live in denver its about 5500ft up here, the best gas we can get is 91 octane, is 12.5:1 CR gona be to high? im only gona use a vafc, fpr, and wideband to tune it.

ide like to keep it streattable, im also planing on running m24x rocket cams

(ctr pistons in a gsr aprox 12.5:1CR) or (jdm itr in a gsr aprox 11.5:1CR)

 

if you use ctr's you will probably detonate, i have seen no detenation with 12.9:1 compression roller waves on 92... but thats with roller waves, whole different design.

 

Running that octane with 12.5 compression and having the timing at 16 btc. I it will knock. If I was you and all I could get a hold of is 91 octane. I would go with the JDM GSR pistons. You're only going to make like 1 or 2 percent more using the 12.5 pistons.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revhard92si &raquo;</TD></TR><TR><TD CLASS="quote">Running that octane with 12.5 compression and having the timing at 16 btc. I it will knock. If I was you and all I could get a hold of is 91 octane. I would go with the JDM GSR pistons. You're only going to make like 1 or 2 percent more using the 12.5 pistons. </TD></TR></TABLE>

jdm gsr pistons?????

why

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Blind Fashion &raquo;</TD></TR><TR><TD CLASS="quote">i have seen no detenation with 12.9:1 compression roller waves on 92... but thats with roller waves, whole different design.</TD></TR></TABLE>

 

jdm gsrs are 10.6 if i remember correctly

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 555R &raquo;</TD></TR><TR><TD CLASS="quote">jdm gsrs are 10.6 if i remember correctly</TD></TR></TABLE>

that's what i thought..this guy is gonna use rocket m24x cams...
needs some compression

 

Remember a chunky cam can possibly aid in taming the dynamic compression down a bit.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by oMekoneDC2 &raquo;</TD></TR><TR><TD CLASS="quote">

(ctr pistons in a gsr aprox 12.5:1CR) or (jdm itr in a gsr aprox 11.5:1CR)</TD></TR></TABLE>


?

 

I ran 12:5:1 compression on OEM pistons and 91 octane. You should be fine.

 

12:1 is alot, if those cams are big enough u could bleed some of the extra compression off, esp with some cam gears. U might be able to get away with it, just retard the timing and give it overlap.

 

the air up here is also really thin, people are telling me that will help in running a high cr?

 

why dont he just go with ctrs, which would come out to about 12.3 or you could go with what i have, jdm itr pistons. i like them and the compression is like 11.6 in my lsvtec.