a1snag

Does any body know the formula for HP loss from air temperature?

MechaniX_034

Depends on where you want it from man, basically when intake air gets hotter the molecules are not packed as closely, so less O2. But there's like power loss from cylinder temps rising because of poor insulation as well as power loss from heated air being drawn or forced in.

Thermodynamics is a pain, heat is everywhere in the engine bay, what we need to do here is isolate the parts of the engine and its ancillaries which will lose you the most power, and see what we can do about making the situation a little better.

If you want intake air temperature only, it starts to get interesting, because it depends on a lot of factors, like intake velocity, plenium volume, runner length, whatever else. Dunno man this is like the beginning of the mother of all threads.

Visionz

Moving to the engine forum.... rolleyes.gif

a1snag

At the air intake, Dyno people should know this conversion. I think it's

HP loss from heat = HP / 10 x 3% x (air temp degrees - 72 degrees)

My memory isn't what it use to be. hehe

[ August 23, 2002, 07:26 AM: Message edited by: a1snag ]

Koreandude

hmmm, is that right? Very Interesting

If my order of operations are correct...
plugging in 113hp and 98 degrees Fahrenheit

HP loss from heat = HP / 10 x 3% x (air temp degrees - 72 degrees
HP loss from heat = 113 / 10 x 3% x (98 - 72 degrees
HP loss from heat = 113 / 10 x 3% x (26)
HP loss from heat = 113 / 7.8
HP loss from heat = 14.487179487179

It seems like a bit much but who knows. Maybe we can try to fully insulate all the components of an engine and see if it works!

[ August 23, 2002, 09:40 AM: Message edited by: Koreandude ]

a1snag

I think it would be easier to insulate the air intake system. Nitrous is another way to cool the intake charge.

BTW, your math is correct.

Angelos

Every 11 degrees C down you gain a bloody 1hp!!!
Practical way to learn about the importance of cool air..

Frostbyte

HP Loss from heat = HP / 10 x 3% x (air temp degrees - 72 degrees)

HP Loss from heat = 113 / 10 * .03 * (98 - 72)
HP Loss from heat = 11.3 * 0.03 * (98 - 72)
HP Loss from heat = 0.339 * (98 - 72)
HP Loss from heat = 0.339 * (26)
HP Loss from heat = 8.814

Stupid infix notation smile.gif

is it temp in C or F or K or what? (I hope not kelvin smile.gif )

with HP instead of kW i assume it's F?

a1snag

YES, it's F. Sorry about that

Koreandude

hmm dude, you can't first can't divide 113/10.. you're suspose to work the paranthesis first (order of operations rule) then computate what's in the denominator of the fraction then divide the numerator by the denominator.
Geeez, now i sound like my math teacher in 7th grade. sorry dude! tongue.gif