What's the average HP gain per LB of boost?

[87WE4BOOSTED]

I know there's alot of different variables that plays a part in this equation, but I would like to hear what some people gain per lb. I think mine gains 23~25HP per psi.

 

[turbokinetic]

A rough estimate I have used is based on the % increase of manifold absolute pressure. It is a rough estimate but gives a "ballpark" figure.
Boost + 14.7 PSI = manifold pressure (absolute)

Lets say you have a 200 HP engine at 10 PSI boost.
To go from 10 PSI to 15 PSI:

10+14.7 = 24.7 psia original pressure
15+15.7 = 29.7 psia new pressure

29.7/24.7 = 1.2 so you have 1.2 times original manifold pressure. Manifold pressure is a good indacator of engine torque, so you can estimate at the same RPM, going from 10 to 15 PSI will have 1.2 times the power.

1.2*200=240 so an estimated power of 240 HP at new boost level.

I'm sure there are other more accurate formulas taking into account more variables. But for quick and dirty calcs, this works.

Sincerely,
David

 

[bison]

Stock heads/cam 0-15hp per 1psi. Better heads/mild cam 0-25 per 1psi. Really good heads/aggressive cam, raised CR, purpose built for power. 0-35hp per 1psi. The ones that show the most have everything working together between 6500 and 7000rpm. I put zero to whatever but you could actually go backward in power increasing the manifold pressure.

 

[Eric Stage I]

I find it's typically 3-4% more HP per PSI until you hit some efficiency wall for that particular engine. So a stock engine might only see 10HP/PSI, but a 700HP engine might see 30HP/PSI. This looks like its similar to what you guys have seen also.

 

[87WE4BOOSTED]

Better heads/mild cam 0-25 per 1psi.

I think this is where I fall in.. I'm getting ready to stuff all the springs in the exterenal gate and apply an electronic boost controller and start tunning for 23~25 PSI. Just wanted to see if I was in the ballpark. Hopefully with a medium aggresive tune (23~25psi, 21* in 1/2 - 3/4, 93 w/alky) I can pull off 25~30hp. We shall see soon enough.

Thanks guys!

 

[bison]

I think this is where I fall in.. I'm getting ready to stuff all the springs in the exterenal gate and apply an electronic boost controller and start tunning for 23~25 PSI. Just wanted to see if I was in the ballpark. Hopefully with a medium aggresive tune (23~25psi, 21* in 1/2 - 3/4, 93 w/alky) I can pull off 25~30hp. We shall see soon enough.

Thanks guys!

I would expect that with iron heads. With race ported aluminum heads you would be around 72-73lbs/min@25psi. It will probably take 28-29psi to get to that point with iron heads. From 25-29psi I only picked up 5-6lbs/min of mass flow on a 9:1 stock stroke with the really good heads. Power went from about 655whp to 697whp. Mass flow went backward after that. With the iron heads I'd expect the same at 32-33psi but then again you have about 7% more displacement so you might see it run the turbo out around 31psi at sea level. Btw the 62cea and 65f1 ex wheel are a great match of wheels. The potential is almost the same on the two.