weather wise for performance:

hot and dry
or
not so hot and very humid?

Just wondering...

https://www.s2ki.com/forums/showthread.php?...?threadid=27362

this is my DC dyno results... my question above is not related to the below one.

Anyone care to guess why even though the car is running a bit more lean, it didn't make any more power after the header went in?

thanks,
-Shing

 

Seriously, I think both situations are bad. Don't know any other way to justify that. I think of course the best situation is cold air with no breeze or wind on fine night. That's probably the best time when the car performs as it's very peak.

 

Cold air increases the density of the fuel charge and hence the force of combustion. If these are your only two choices......move.

Utah

 

Hahaha, yeah that's the only two I get this time of the year.

-shing

 

Id be curious if the humidity would act like a water injection system (a detonation deterrent)

My cars run much stronger here at sea level and not so hot but humid compared to Az, hot and dry.

 

Phoenix is at 1200ft above sea level, too, which may be part of the difference. Tucson, Flagstaff and Sedona are all much higher.

 

Well learned a few things today,

-Humidity content displaces oxygen per volume (bad)
-At lower altitude not only is the air more dense but its at a higher pressure and is forced into the engine harder (good)
-As we know hot air's density is less (bad)
-Barometric pressure also affects performance (just like altitude) and in non-EFI cars with carbs, changing jets would be necessary for racing, because the A/F mixture can change with the pressure. EFI cars can usually adjust within set parameters.

So go to a drag strip at sea level on a cold night when its really dry with a high pressure front coming through

 

I don't think that this second part is true. The absolute pressures throughout the engine change relative to the ambient air pressure. If ambient goes up by .1psi, so will the pressures all through the intake, engine and out the exhaust.

The only way that air would be 'forced into the engine harder' is if there was a greater difference in pressure between areas of the intake/exhaust; these differences in pressure are based on flow rates and resistance to flow, not on the absolute ambient air pressure.

 

Is it not true that the Dynojet corrects based on the weather conditions ("SAE Corrected HP"). ?

Wesmaster

 

Sure, they correct for air density (altitude, temperature) variations. My point was that higher ambient air pressure increases density, but it does not force more air flow through the engine.