Ideal Compression for Centri

[97snakebite]

Going to start buying parts for a build and was curious to whats the best compression for a Centri?? im running a p1sc thats seeing 12lbs with a 3.7 pulley:banana: but i wanna push this p1 pretty far.. i know 8.5-1 is what most boosted guy run but i still want to maintain a good low end #s..any suggestions..keep in mind im in CA and only have 91 and E85 as an option

 

[CBelleperche]

I've seen guys on E85 run as high as 12:1 compression, but again that's E85. With a fully built motor you would have no issue running around 10:1.

 

[CBelleperche]

On 93 pump gas that is

 

[Brutal Metal]

go with an 11 cc dished piston..

 

[97snakebite]

On 93 pump gas that is

I should add that im in CA and we have crappy 91... but i was thinkin about going e85 because it everywhere here!!


ps main post edited

 

[corysmach1]

When my motor blows im going 11:1 comp with e85 and 12 psi.....with that being said for sure go e85 and at least 10:1 it will have great throttlw response.....if i recall didnt you car make 500 on stock motor? If so has it blown up yet?

 

[itSSlow98]

Id do 10:1 on E85 personally. Just keep in mind your fuel syetm will need to be addressed with E85.

 

[98 Saleen Cobra]

If running E85 all the time I'd do 10:1, if you even think you'll be running 91 at somepoint 9:0-9:5 with around 12psi.

 

[1QUICK10TH]

If e85 is every where you would be crazy not to do it. Id go 10:1 with e85

 

[01yellercobra]

9.5:1 here and I was running 14psi. On 91 octane.

 

[vic_s197]

Im in the same boat but with a d1sc. Im stuck between 10.0:1 or 10.5:1 on my 3 valve. E85 im prolly gunna go with. Im making 525 rwhp on stock bottom end too.

 

[CBelleperche]

I'd say go 10:1 all day long with E85 and don't look back! Taking mine tomorrow for the E85 tune, my tuner expects north of 700 rwhp... Safely because of the cooling effects of the ethanol. It's a no brainier.

 

[97snakebite]

When my motor blows im going 11:1 comp with e85 and 12 psi.....with that being said for sure go e85 and at least 10:1 it will have great throttlw response.....if i recall didnt you car make 500 on stock motor? If so has it blown up yet?

haha no not yet... my tuner want me to dial it back so i got a 3.9 to take her down to a safer level... + im not always boosting her around and it hasnt hit the track yet with that power:beer:

 

[97snakebite]

alot of good feedback on the E85 and 10:1 sounds like thats the route.. if anything i can do the 9.5:1 and go both E85/91

 

[98 Saleen Cobra]

What does AED want to do with it is the real question lol

 

[97snakebite]

I'd say go 10:1 all day long with E85 and don't look back! Taking mine tomorrow for the E85 tune, my tuner expects north of 700 rwhp... Safely because of the cooling effects of the ethanol. It's a no brainier.

what are your supporting mods if u dont mind tellin

 

[IUP99snake]

I have 10.3:1 with a P1SC running about 11-12 lbs of boost with a 3.7" pulley and a power pipe. Granted, I don't have forged internals so Im limited with how much "peak" HP I can make, around 450 to be safe, but the higher compression makes a huge difference in the lower rpm's off boost, not to mention throttle response and fuel economy.

I'd say you can go 1 or 2 points higher in compression with a centri than a roots or twin screw because the centri only makes boost at the higher rpm range.

Detonation is a lot easier to manage with other techniques than compression ratios, which are fixed for the life of the engine. I'd say, go with a higher compression ratio and have it tuned right. You can also benefit from E-85 or meth injection to keep detonation at bay.

If I were to build a new forged motor running more boost, I'd probably go somewhere around 9.5:1.

 

[fst86410]

Mine is 10:1, but I wish I'd gone higher. Mine is on E85 made 680hp on the last dyno with 16psi of boost, at 6k rpm and a fresh motor. Going to get a retune and lean on it a little harder 7500 to 8k rpms and see what happens.

 

[Black*Death]

Mine is 10:1, but I wish I'd gone higher. Mine is on E85 made 680hp on the last dyno with 14psi of boost, at 6k rpm and a fresh motor. Going to get a retune and lean on it a little harder 7500 to 8k rpms and see what happens.

What heads are you running..I think stock springs will only handle 7200 RPM's?

Don't break anything...

 

[fst86410]

Ported navigator with comp springs and crower stage 4 cams.