How much does summer heat affect HP

[quinthawk]

I have a maggie with 3.6 pulley, headers and an airraid intake. I went to
the track, temps were upper 80's with 75% humidity, my best run was a 12.5 @112+ (2.0 60ft time). I was on the stock pzeros. I was hoping to hit about 115 mph. All cars seemed slow. A 2010 camaro ss auto with an intake and tune ran 14.1 @101, DA was well over 3000. A 2010 Challenger with intake and tune ran 14.5 @ 97. Was it the heat slowing me down?

[bi11ymc]

Heat kills horse power. Check out this thread and compare notes

[alfie43]

Originally Posted by quinthawk

How much does summer heat affect HP

An answer in two words: Big Time. Regardless of what type of induction and fuel delivery you have, i.e, forced induction, carburetor, FI, etc, we all have experienced how cooler temps make our cars run stronger. This is especially evident in the northern climates. Back in the 70s when I did a lot of drag racing, my ETs in Oct were .10 -.20 faster than my midsummer ETs...especially if I tuned it for the cool dense air.

I have had my Maggie on my Camaro for only a couple of months now, but I have already noticed that a forced inducted engine seems to be even more affected by excessive heat and humidity. More affected than a normally aspirated car.

My brother who has been driving several blown Mustangs since the early 1990s, says, "Watch when early November arrives, your car is going to run like King Kong."

Maybe someone else here can explain the science of why this happens to a greater degree on S/C engines.

Alfie

[bi11ymc]

Just a wild guess, but I believe it has to do with the density of the air. Cooler air is more dense, therefore more air per cubic inch, and more air allows for more fuel in the cylinder before combustion. More air and fuel, more power.

[2010 SSRS]

wish this damn heat and humidity would go away.

[Luvpilot]

Originally Posted by bi11ymc

Just a wild guess, but I believe it has to do with the density of the air. Cooler air is more dense, therefore more air per cubic inch, and more air allows for more fuel in the cylinder before combustion. More air and fuel, more power.

Zactley

Altitude works the same way.

I don't even like running mine hard with our 110+ temps. I've seen as high as 118 on the temp sensor already. I can only imagine what my IAT's are under full boost

[SGOS252382]

Heat and humidity + altitude are a killer.

3000' DA is worth about .5 sec and 4-5 mph in trap speed (NA). Supercharged/Turboed cars are "usually" not affected as much by the altitude.

But there are other factors like a heat soaked engine (pulling timing), etc that can affect your times.

[bi11ymc]

Originally Posted by Luvpilot

Zactley

Altitude works the same way.

Closer to see level, higher air density. More power.

How does the humidity affect the air? I am guessing water in the air also hinders combustion.

So, I guess the best place to drag race is in the desert (dry air) in the winter time at night (cold air) at sea level (dense air)

[alfie43]

Originally Posted by bi11ymc

Just a wild guess, but I believe it has to do with the density of the air. Cooler air is more dense, therefore more air per cubic inch, and more air allows for more fuel in the cylinder before combustion. More air and fuel, more power.

Yes, that's the line of logic that I was thinking. Back when I raced, we used to run the carb a little richer for the cooler temps...more dense air...it needs more fuel, right?

I didn't want to "pontificate" unless I knew for sure. Besides, my old science prof might be reading. What am I thinking? At my age, he has passed away by now.
Alfie