supercharger compression ratio

Jaym14 · Feb 28, 2009

I'm considering adding a supercharger to my set up. 331 stroker built by DSS racing... forged internals, 10-5-1 compression. I don't really want to pull my motor apart to lower my compression ratio... but also want to keep running pump gas (93-94 octane)

What would be the safest amount of boost I can run before detonation becomes an issue?

I've read 5-6lbs should be no problem, but others have suggested I can go as high as 9lbs.

Which kit would be appropriate? Intercooling? I'm looking to pick up around 100 HP

claytucc3 · Feb 28, 2009

I tend to a live a little more on the conservative side. i would stay away from 9 lbs. I am planning on throwing around 9 lbs on my motor and I have a 306 with a 9:1 comp. Vortec makes a kit that is around 6 lbs without an intercooler.

rbonella · Feb 28, 2009

Jaym14 said:
I'm considering adding a supercharger to my set up. 331 stroker built by DSS racing... forged internals, 10-5-1 compression. I don't really want to pull my motor apart to lower my compression ratio... but also want to keep running pump gas (93-94 octane)

What would be the safest amount of boost I can run before detonation becomes an issue?

I've read 5-6lbs should be no problem, but others have suggested I can go as high as 9lbs.

Which kit would be appropriate? Intercooling? I'm looking to pick up around 100 HP

I agree with clay, I have a 357 windsor with 10.5:1 compression and I was told by many professionals not to go higher than 6lbs. with 92-93 octane pump gas. Boost can be addictive so staying @ 6lbs will be the hard part. Your motor should react pretty well to that little amount though...ez 100 hp. You could slways have the chambers in your heads opened up a bit to lower your compression which I have considered.

KamiKaziDK · Feb 28, 2009

Port out the chamers a little if you want, can also buy thicker head gaskets Paxton has a 5-6 lb kit, and so does vortech. I think the vortech kit is like 1800 bucks and adds 75 hp on a stock engine(supposedly)

parrish5o · Feb 28, 2009

Yeah, I wouldn't go with anything over 5-6lbs of boost. Even with that small of an amount I believe it may be pretty harsh on a motor with that much compression, I wouldn't expect to see it last near as many miles as if it were naturally aspirated. Then again I have always ran nirtous and am by no means an expert on boost. Trying to learn more though, I really want a turbo on my car. For not that is out of the question since I am running 11.5:1 compression. When I eventually rebuild my motor it's going to be in the neighborhood of 8.5:1 or 9:1 with alot of boost.

BYRDPE · Feb 28, 2009

I would go with ~6-8lbs with a meth injection system for added insurance.

Bullitt347 · Feb 28, 2009

Try to avoid thicker head gaskets. By raising the head even a small amount, you ruin the quench of the combustion chamber and end up killing the flow of the head and burn (flame front) characteristics of the chamber. You can open up the combustion chamber to pick up a few cc's and unshroud the valves, but it takes about 10 cc's of chamber volume to drop 1 point in compression. (average)

Cobra_Dusten · Feb 28, 2009

BYRDPE said:
I would go with ~6-8lbs with a meth injection system for added insurance.

meth is a ****ty band aid for a street driven car.
keep the boost in a safe range, make sure you good fuel, get the right plugs, and keep your timing in check.
Best of all, get a good tune done with it.

Cobra912 · Feb 28, 2009

I'm gonna be running a 6lb Paxton 1220SL on my 331 with similar compression, +mods.......

87AODGT · Feb 28, 2009

really I believe just keep it intercooled and under 10 psi and you should be perfectly fine as long as its tuned right. if you're running a vortech with the aftercooler kit you should be golden, especially if you run redline water wetter and some ice in the recovery tank you should be more than alright

Jaym14 · Feb 28, 2009

Thanks for all the responses. Based on all of your advice in addition to my research I think that I'm going to look for a set-up with approx 5lbs of boost with an intercooler. I have the anderson PMS tuner so keeping things in check shouldn't be a problem. All things considered, I think I should be totally safe and pick up around 125 hp with this set up.

This leads me to my next question..... What kit should I get?

SC-trim.... Paxton Novi.....??? Which Intercooler????

90lxcoupe · Mar 1, 2009

Get a custom cam made up with alot of overlap so it will bleed off compression and you can safely run boost that way.

there is a guy on turbomustangs.com that is running 15psi with 1.5:1 compression with a t-76 with no problems, he told me that the secret is getting a cam with the right overlap. He is running no meth injection and pump gas.

KamiKaziDK · Mar 1, 2009

90lxcoupe said:
there is a guy on turbomustangs.com that is running 15psi with 1.5:1 compression

1.5:1!!!! Good lord, how does he stay running???

supercharger compression ratio

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