Cool relative horsepower calculator

[manzano]

Hey all

Ever wonder why your car seems to pull harder in certain weather?
Here's a link to a site where you can punch in the variables and find out just how the weather (and altitude, if applicable) is (are) affecting your engine's performance.

http://home.sprynet.com/~rshelq/calc_hp_dp.htm

Just check your favorite online weather source to get the info you need, and this calculator will show you current relative HP (100% being baseline)

It's really cool, and you'll be amazed how baro pressure and humidity (dew point) can influence power.

Cheers,

Manz

[T4 Primera]

Hey thats cool. Do you think it'll work for turbo applications i.e. input boost pressure and various temps etc?

[manzano]

T4,

Yea, it will work for turbos.

Atmospheric pressure at sea level is 14.7 psi. That's (1) atmosphere.

If you are running 7.3 psi boost, it's like you stuck the weight of another 1/2 atmosphere on top of your car.

So, divide your PSI boost by 14.7 and get you multiplication factor you need

7.3 / 14.7 = .5

so you have in effect created an atmospheric pressure (1) + (.5) or 1.5 times that of normal pressure at sea level.

So get the barometric pressure and multiply times 1.5
If baro pressure is 30.00, your adjusted (boosted) baro pressure will be

30.00 * 1.5, or, 45.00


and remember, the intake temp will be higher due to compression, so raise the ambient temp some. As to what amount, it depends on if you have an intercooler, air temp, etc. So unless you have a temp sensor that gives you temp in f or c, you'll have to guess.
If you don't have any idea, enter outside (ambient) temp * 2.

Now you've got everything you need.