I've got an 84-5 shortblock that I was considering upgrading to forged pistons and replacing the center mains with billet ones. I'm looking to get the most power out of pump gas that I can.....say 92 octane. I'm trying to stay away from an alky kit at the moment. I'm also going to keep my iron heads but get them ported. About everything else is able to be changed. What would be recommended as far as turbo, injectors, converter, ect. to achieve the most power? I know a big turbo will move more air at lower psi, but too much will cause alot of lag in the turbo( I'm thinking about one of the bigger dual BB turbo's). I hear I need alot more injector on pump gas compared to race gas with the same turbo. I also think that anything above 3200rpm stall might be a little too crazy for the street. Don't hold me to it though :biggrin: . How much power can I expect? Thank you for any help!
Power on pump gas
- Thread starter GNDreamin
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GNDreamin said:
A good set of iron heads (ie Champion's) and a roller cam will help a bunch.
Cotton sells a CPT-66bb that many have been mid 10's with. You won't see that with pump gas though. A 3200 stall *might* be a tad tight for it, but you could always try it out. A set of 60# (65 by some) injectors should do more than enough for you.GNDreamin said:
I would think on 92 octane you might be able to run some mid 11's with this setup?
If you get some ported GN1's, a cam that bleeds off some cylinder pressure (helps with detonation), ported intake, FMIC, big injectors and a big turbo, you may be able to run 17-18psi on pump gas, but the tune will be on the hairy edge. usually if you want big power with boost, you have to either run race gas, or pump gas with alky. No gettin around it really. Gotta figure what kind of dynamic compression you're getting with boost. Work on figuring what kind of power your engine will make in N/A form, and this will help you choose the turbo and everything else. The formula is
Psi/14.7+1= the pressure ratio. Then multiply that ratio times the N/A power and this is your boosted power. Or you can reverse everything to find N/A power.
For example. The TR engine realistically made about 275hp at 14.7psi.
14.7psi/14.7+1= Pressure ratio of 2.
275/2 = 137.5hp is roughly what our engine would make in N/A form. Now figure what that same engine, no other changes, would make at 23psi.
23/14.7+1= 2.56.
137.5 x 2.56 = 352hp
That pressure ratio is important when looking at a compressor map and choosing your turbo.
Lets say the stock motor, in N/A form would make 137.5hp, and now you want to modify it to make more power in N/A form, and you want to see how that would work out once you add boost.
Get the motor to make 180hp in N/A form, and add 18psi.
18/14.7+1= 2.22
180 x 2.22 = 400hp.
Whatever you do to add power in N/A form, the more pronounced the gains will be under boost. Youre making an extra 50hp with 5psi LESS boost. Naturally this formula doesnt work out perfect in the real world, but its close.
Psi/14.7+1= the pressure ratio. Then multiply that ratio times the N/A power and this is your boosted power. Or you can reverse everything to find N/A power.
For example. The TR engine realistically made about 275hp at 14.7psi.
14.7psi/14.7+1= Pressure ratio of 2.
275/2 = 137.5hp is roughly what our engine would make in N/A form. Now figure what that same engine, no other changes, would make at 23psi.
23/14.7+1= 2.56.
137.5 x 2.56 = 352hp
That pressure ratio is important when looking at a compressor map and choosing your turbo.
Lets say the stock motor, in N/A form would make 137.5hp, and now you want to modify it to make more power in N/A form, and you want to see how that would work out once you add boost.
Get the motor to make 180hp in N/A form, and add 18psi.
18/14.7+1= 2.22
180 x 2.22 = 400hp.
Whatever you do to add power in N/A form, the more pronounced the gains will be under boost. Youre making an extra 50hp with 5psi LESS boost. Naturally this formula doesnt work out perfect in the real world, but its close.
Why not alky injection. IMO, you will get far more power for the buck. I can run 20 lbs. on 93 with my PT68. We are talking low 11.00 street rim. Also if you are going to buy a lot of upgrades go ahead and get bigger stuff. You will want to go faster. Nothing like buying 2 sets of injectors. Anyway back to your question. I would go with the motron 60's. Excellent injector. Enough fuel but not too much. Go with the 67 turbo. You can always keep the boost down. Go with a GOOD lockup 3300-3500 stall. Yea it is a little wierd going up hills and driveways but other than that no problems. Go with a 218-218 roller cam, adjustable fuel reg., hotwire kit and a 340 pump. A good opened up stock intercooler should do also. Good luck on it! I would say ABOUT 500 hp.
Like DCVing said, got to go with airflow. Unless you want to bore/stroke, the alternative to more boost is more rpm. Since boost will be limited by the pump gas, then you have to flow more air, and there are only two ways to do that- more inches, or more rpm. (remember the turbo is a COMPRESSOR- high flow in, compressed to a lower flow at the discharge) But if you go with a cam that will support 6,000-6,500 rpm, you have about a 20% increase in airflow over the stock cam.
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If you want it to run low 12s on pump gas, than build it to run 10s on race gas.
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