Air Temp and performance ?

[Jack P.]

My son and I where out in my 66 L79 , air temp 24*, top down, and the following discussion came up about performance and air temp.

Son said he has a 420hp plus WRX STI mod. Subaru rice burner.

"cool temp allows cars to have better performance and gas mileage."

My question? All conditions being the same : humidity, clear day ,etc. race car, drag car issues not apply (tire friction etc)

Which day would my 66 get best performance and gas mileage ?
(car timing mapped for 2500 - 3500 rpms 50 *) without any adjustments for each day

30*
60*
90*


Which day and why?

Jack

[John H.]

Re: Air Temp and performance ?

Jack -

Rule of thumb is a 1% power increase for each 10*F reduction in intake charge temperature.

[Clark K.]

Re: Air Temp and performance ?

I have been told my performance dynomometer technicians that there is an air temperature correction factor used when you dyno your engine. The cooler the ambient (existing) air temperature, the more power.

I believe that is because the air is denser at colder temperatures, more oxygen molecules per given volume of air. -Clark

[Michael W.]

Re: Air Temp and performance ?

Jack -

Rule of thumb is a 1% power increase for each 10*F reduction in intake charge temperature.

Key words are 'intake charge temperature' which may or may not move in lock stay with ambient temperature.

[Rich G.]

Re: Air Temp and performance ?

A standard for performance in aircraft piston engines is 59F (15C) and 29.92in of pressure. I would assume it's similar for dyno results. Cooler and higher pressure is better than hotter and lower pressure.

[Jack P.]

Re: Air Temp and performance ?

Thanks for the info. So which day is the best , all things being the same?
30,60,90 ? no adjustments to carb or timming

Jack

[Michael W.]

Re: Air Temp and performance ?

Much like the leading brand of adult comfortware- Depends.

Was the carb jetted for the 30 degree or the 90 degree day?

[Jack P.]

Re: Air Temp and performance ?

Much like the leading brand of adult comfortware- Depends.

Was the carb jetted for the 30 degree or the 90 degree day?

It was jetted at some factory in Holley Land. I have not taken it apart since buying it new, a couple of years ago. It is the proper Holley for the L79.

So, we don't know what we have ,

Jack