I calculated the air densities between summer and fall/winter and the percent gain in amount of air being injested in the engine. At 90 deg F and R.H. of 65% at sea level the air density is apprx. 1.144Kg/cu.meter. At 40 deg and R.H. of 40% at sea level the air density is approx. 1.247 Kg/cu. meter..

So what does this mean? It means a roughly 9% increase in air flowing thru the engine with a corresponding increase in power assuming all engine losses are linear..Drivetrain etc..

 

Uh...yea. Most people know this. That is why there are "Correction Factors" built into Dyno software.
I did some calculations of my own, do you know that the farther down you press the pedal on the right, the faster the car goes?

 

LOL..Tell that to some of these drivers out here in GA. They seem to think it's the pedal on the left, as much as they keep their feet on the damn thing

 

Wow...nice smart-@$$ remark. That was actually good information for those of us who don't sit around with our slide-rules calculating air-density all day long. Next time, think before you post.

jpc350z, thanks for the info.

 

Good post jcp350z....yeah I knew the colder the more power, but I sure as hell don't know how to come up with those figures.....good job.

Do you have a formula for that?

 

I think a VERY rough estimate that I heard once is 1 crank hp for every 7 degrees drop in temperature.

Obviously this is not the actual number, because it's actually a percentage based upon your current HP output/compression/altitude/volume and a billion other factors etc...etc...yada yada yada. So it all basically means that if you bought a kia spectra and it was zero kelvin outside you'd have yourself a real monster.

 

+1.

i knew the idea, just never sat down to calculate it all out.

 

+1, great information!

 

with this information i shall now die with my life complete.

 

Wow. Your 2nd post and already you're mocking people who went to some trouble to post information that others find useful. Not a great start. Why was this necessary?

 

Maybe he was trying to be humorous and it didn’t come out very well. Might I add you car looks kick a@@

 

Hard to give the benefit of the doubt to people who are from "Milky Way"...

And thank you!

 

+1... you can get seriously hurt for making comments like that where i come from

 

The formula is : AD= [( 0.34844 X P) - h(0.00252xt-0.020582)]

AD = Air Density (kg./m3)
P = Air Pressure (m bar)
h = Relative Humidity (% rh)
t = Air Temp. (deg. Centigrade)

 

Hey that's good info. jpc350z but can I ask why you get more power. I understand that as the density increases, for a fixed volume the mass increases:
m = V * P
so you have a higher mass flow rate.

But why more power (I know you do get more, but why) is it:
a) to do with more mass of air thus relatively less mass of fuel thus effectively running leaner?
b) to do with the MAF sensor detecting more mass of air and thus sending a higher voltage so more fuel is put in by the ECU too?
c) none of the above?

Forgive my ignorance but I'd like to know

 

The MAF measures the increased mass of air flowing into the intake and tells the ECU what to expect. The ECU alerts the fuel system to get ready for a slug of air by increasing the fuel delivered to the cylinders by increasing the injector duty cycle..The o2 sensors help keep the fuel ratio safe by also alerting the ECU as function of RPM as well as other factors..Simple but reasonably accurate explanation..

 

b) + o2 sensor closing loop, then.

Thanks for explaining.

 

Sorry for the leaving out the denominator