HP/torque to PSI ratio

[scottw03]

I was wondering how much HP/torque each PSI is equal too. I assume that if you increase boost from 14 to 18 psi you gain HP/torque, so how much per PSI? Anyone know? Obviously there are other ways of gaining HP as well (exhaust, intake, etc....). Thanks guys.

[jaymzx]

There are rules of thumb, but I can't say there is a definate formula. The NGC PCM manages power output based on several variables in realtime, in addition to long-term fuel trim values, etc. In a nutshell, every car is different, depending on the weather, too.

[Gishdream]

some people say 1#=10 HP, I think its more like 7hp for the stock turbo.

[scottw03]

thanks, that is more towards what I was looking for, not that I didn't appreciate your response jaymzx. You bring up a very valid point that depending on where you live and weather conditions it can greatly effect the performance of the car. I just wanted to get a general rule of thumb for how much each psi equals. Until I can find a dyno around here to test my car at I would atleast like to estimate the horsepower. Thanks guys for the replies.

[Gishdream]

but agian if its out if its "efficiancy" the # will go down, TQ will normally go up but only b/c its pushing more hot air.

[ENDUROS]

And keep in mind each dyno is different too. There are alot of different manufacturer's out there and each dyno is different especially on how they calibrate hose power and torque. If you use the same car on each dyno with the exact same paramaters (cold/hot runs, air flow during a pull, etc.) you'll get a different number for each dyno. Because of this its almost impossible to get an accurate measure of each psi to power ratio. It is rather tedious to measure power increases with the same dyno because of engine heat range changes (depending on weather and ambient temps), and not every dyno has a fan or ducting to blow air on the intercooler (or if they do they have cfm's of different rates), etc. All of these factors will change the final numbers for sure. Whoever posted above that psi to power ratios are rule of thumb was so increadibly correct. Today's dynos are basicly the manufacturer's best guess and nothing more. To get the most accurate result, I recommend using a single dyno and measure the engine temp and ambient air temp before doing your first pull. Then, do the work you intend to do, remeasure engine and ambient air temps (make sure they match exactly the temp readings you took on your base pull) and go for a second pull. This will give you the most accurate numbers possible. If the temps vary, even slightly, it will change the results of the test. Hope this helps.