What is pefect comp. for turbo?

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CRseX84

Senior Member
hey guys my 91 siR is gona be at my house in 4 days, im doin a full rebuild to it, for turbo. im planing on running like 13boost. im getin new rods, pistons, and getin the head and block squared and milled, now when i give it to the machine shop to square the block and stuff i can tell him i want a exact comp and he will mill my head to give me the comp i want. what is the perfact comp for my JDM siR with 13boost? iv heard 9.5:1 is real good. but wut do u guys think? thanks for the help.
Tyler
 
Originally posted by xyswany@Jan 3 2004, 04:34 PM
9 to 9.5 is ideal.
Edit: what turbo are you running?

:ditto: althought type R's react well to turbos...id still go 9ish for a built turbo motor....
 
i wil be getin a T3 most likly... so low 9's?? or mid??
 
what are you going to tune with?

for a low boost setting (IMO, 13 psi is low), i'd go with 10:1. the in-vacuum power difference will be quite consideredable. lots of street cars run this CR.

keep in mind that 13 psi will most likely need a hondata unit or better. the vafc hack tops out around 10, fmu's just below, and you're going to need a 3-bar map sensor to go above 11, neither of which an fmu or vafc support.
 
Originally posted by CRseX84@Jan 3 2004, 05:31 PM
hey guys my 91 siR is gona be at my house in 4 days, im doin a full rebuild to it, for turbo. im planing on running like 13boost. im getin new rods, pistons, and getin the head and block squared and milled, now when i give it to the machine shop to square the block and stuff i can tell him i want a exact comp and he will mill my head to give me the comp i want. what is the perfact comp for my JDM siR with 13boost? iv heard 9.5:1 is real good. but wut do u guys think? thanks for the help.
Tyler

milling the head will raise the compression ratio. if I were you instead of milling the head I'd get a 2mm cometic head gasket to lower the c/r.

also I would check your compression per cylinder. if your it's no more than 185-190psi per cylinder then it should be ok to turbo. anymore though and you'll probably be seeing detonation, especially on 13 lbs. of boost. which pistons/rods were you planning on using? 9.5:1 is good.
 
eagle rods and JE pistons, i might change my mind on the pistions to some other brand, and i was plaing on getin the hondada setup
 
Originally posted by pissedoffsol@Jan 3 2004, 10:49 PM
here's a good deabte...

i followed the link and all i found was a debate - no deabte in the entire post. :unsure:
 
Personally i dont think there is a "Perfect" Comp. for turbo. Rely on power goals to get you there and compensate P.S.I. for compresstion to get you to your power goals. Lower Comp. will hold boost better and longer.. but the higher it is the better throttle response you will have...Just like NotUrAverage_Si said, I think 9.5:1 is a 'good but not perfect' CR. You have to decide that for yourself when you determine your power goals!
 
yea wit the 13boost i wana get near 300hp, somthing like 175+ would be good enough. im dropin $7k into the rebuild so im hoping i can get the hp that high. wuts some other bad ass turbo pistion brands that are respectabel?
Thanks
Tyler
 
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