S/C on 12:1 motor with 110 race gas?

[DREGSZ]

Hi all, I'm thinking about ways to get more power for my race motor. It is a destroker, 377, 12:1, forged bottom end with 220 Prolightning heads, and demon carb. I run it on a full race '88 vette in various road race series here in CA. Can I run a blower with 12:1 compression and 110 race gas safetly? or am I doomed to detonation with 12:1 compression? Thanks Evan

[AKS Racing]

Doomed to detonanion, due to the high s.c.r. Best to purpose build the shortblock for the intended application. Are the heads aluminum? If not, the heads and carb will only add to the reasons why not to SC at this high s.c.r.

Aaron

[Baldturbofreak]

Well, how do you/ your sanctioning race body feel about methanol? Most badass blown alcohol drag cars start with 11-1 or better then pump 20psi of screwcharger boost on it.
It's also may be possible to use vp116/intercooler/and water-methanol injection with low boost (under 6psi). MY first crack at the turbo setup was just a hair under 11-1 (hypereutectics!) with 7psi intercooled on pump gas. But only ONE mistake in the fuel curve spelled DOOM for this motor's ring lands

[Baldturbofreak]

It is a destroker, 377, 12:1, forged bottom end with 220 Prolightning heads, and demon carb.
I run it on a full race '88 vette in various road race series here in CA.

What is the rod length? how hard do you twist it? (rpm) Long rod high rpm motors don't have time to detonate. If you has it cammed to run from say 3500-7500+ rpm then it is feasable to run a low boost system. Remember, compression ration has a PROFOUND effect on how much BHP per CU/psi. That is the higher the compression (detonation aside) the more power you get from each pound of boost.
According to this calculator http://www.turbofast.com.au/TFcompB.html
with a 377, 12-1, 93% VE and 6 psi (non intercooled) it states that boost compression will be 15.4-1 and recommends 111 octane.

[DREGSZ]

This is a road race application for NASA Vette Viper Challenge.
Forced induction is allowed in the VX class.
I turn 5000-7500 rpm for 30 minutes solid all out, per sprint race. my rods are 6.2, Eagle H Beams, Eagle Crank and JE pistons, all forged. Pro Lightnig AL heads, 220 runners, 66 custom CNC chambers.
I don't think I can run more then 110 octane gas, addidives are unlikely.
I'm at or near sealevel for all but 2 races, (one at Reno, one at Fontana).
I expect I would need an intercooler for the demand I place on the motor.

[Baldturbofreak]

An intercooled procharger (D1), plus a smg water injection kit would do well in your application. you must remember that boost goes up the square of rpm for centrifugal compressors, so some calculations for pulley size are in order for that kind of Rpm. keep boost below 7 psi with the water/methanol injection kicking in at 3-4 psi. That will keep you safely out of detonation even on the hottest days with 12-1.
Sounds like a screamin combo. the long rods will help out with octane tolerance (due to increased dwell time at TDC) as will you cnc'd alum heads.
You didn't mention cam specs, but I imagine a solid roller with some square lobes are in place :cheers: That will keep you from building much low speed cylinder pressure before boost comes on(at like 4500). Just take a look at your cam card for the lobe separation. 112-114 would be ideal to keep from losing to much out the exhaust. One of those knock sensor kits would be cheap insurance as well. :chevy

[BoostManiac]

If you truly want to benefit from the extra cost, complexity, heat, and weight of a supercharger, you need to run more than 3-4 psi boost. You shouldn't be much beyond 10:1 even for relatively low boost applications IMO. Even that would be a case where you need to carefully limit boost, your compression ratio is effectively doubled with forced induction. Most FI production cars are more in the 9:1 range, which can allow very high boost with proper tuning.

[krivera]

ok i have a question...now i know a little about SC a EFI but what about a carb do you get splashing in the bowls in the carb how do you control that?

[Baldturbofreak]

Nope you put the whole carb in a pressure box. Vortech, ati both make one. Then fuel is boost referenced 1:1.