Air Temp and performance ?

[jackfit]

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

 

[Hib Halverson]

What your son says is generally true however, because your 66 w. L79 has a carburetor and no electronic controls and his WRX has electronic engine controls and EFI, for your car to run best on a really cold day or a really not day might require changes in carb jetting, depending on what the base jetting was.

So, given the above question and assuming that the current jetting was selected as a compromise for local atmospheric conditions, I'd say the engine will run best on a 60 deg. day. On a 90 deg. day it might be a little rich and on a 30 deg day it might be a little lean.

 

[jackfit]

Thanks for the great reply

What your son says is generally true however, because your 66 w. L79 has a carburetor and no electronic controls and his WRX has electronic engine controls and EFI, for your car to run best on a really cold day or a really not day might require changes in carb jetting, depending on what the base jetting was.

So, given the above question and assuming that the current jetting was selected as a compromise for local atmospheric conditions, I'd say the engine will run best on a 60 deg. day. On a 90 deg. day it might be a little rich and on a 30 deg day it might be a little lean.

Good information for me and others who may read this post.

Thanks for making a choice on the "degree day" based on question and assumptions.

Jack

 

[mashinter]

"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

my guess:

performance: 30* because air will be denser (more oxygen for CID).
fuel economy: 90* if drag (warmer bearing lube, warmer tires, lower air density, but no A/C!) will be lowest.

Bill