I'm planning on running a T-76 turbo at about 15-20 psi on pump gas, 92 octane. I was going to put my compression ratio at around 8.8:1 Do you guys think this is wise? Can I get away with more compression? I really don't want to blow up this motor and will dyno tune it safely.

I'm looking for a reality check here. I'd love to hear some suggestions or what CR and boost level you guys are running on pump gas. I'm ordering the pistons tomarrow. Thanks in advance.

 

i spoke with c motorsports about this, and after talking to them i have decided to go with trick flow heads to get compression down to 8.4:1 ...im gonna be running two master power t-70's ...so were probably talking right about the same boost/power levels...they basically said if your running pump gas, the lower the better...mine will be a street car with only occasional track use...so im going as low as possible

 

I am putting my C/R @ 8:4.1 as well the lower the better...you will make more power.

 

I called a few companies today and they all suggested 8.5 - 9.0 :1, leaning towards the 9.0 side to get better street responce.

 

The lower the better if you want to try to run 20psi on pump gas. Did you ever look at the CR of factory hi-boost setups?

Rich

 

I just ordered my pistons and when I get my heads done (they are bare) to 64cc's, the compression ratio will be at 8.4 to 1. I am plannig on running anywhere from 15 to 20 pounds.

 

Hmmm. Think about your statement. What do you mean? have you felt 600rwhp at 5000 rpms? How about 700rwhp at 5000rpms?

Most of the time, you cannot tune 20psi on pump gas even with a FMIC on 92 pump gas. Unless you have the timing cut back so much that you could make the same power at like 25 degrees and 14 psi. (those are just general numbers).

I would go 8.25:1 and look into reverse dome pistons.

 

Agree and would even go lower if possible. I am at 7.8:1 and am happy as a clam.

Rich

 

Well, I went to a 34cc dish piston. That should get me right around 8.6:1 that should get me pretty good up til around 15psi on pump gas. If I need more boost then I guess I'm gonna have to go with some octane booster or race fuel. 15psi on the street should be plenty though, don't you think? If......um, when....I feel I need more I'll figure it out from there. Maybe a set of afr's will be in order then.

 

-34cc? thats a big dish...why dont you just go with -24 and some trick flow heads or AFR's? trick flows price is very reasonable...i just picked up an unassembled set for $700 ...with the -24cc dish, it puts it at 8.4:1 ...-34cc dish is an option, just expensive for custom pistons

 

Actually it's going to cost me about the same for custom pistons. Its nice when you know people that know people And my chambers just got cc'd they are 60cc and flow about 250 on the intake side. So I could dump another grand into Tricflow heads and end up the same place that I'm at now which doesn't make any sense to me. Besides the Trickflow heads only have a 62cc chamber(some ads say 64 ) so I'd still need a really big dished piston. I could go with AFR's but those things will set me back like $3k with intake and everything, so that's out of the question.

 

Sounds like a good move. Folks generally push for too much engine compression.

rskrause, 7.8:1 no kidding. Meaney is right around there.

I am 8:1 on paper, max of 8.2:1 I think.