Temperature question for the Engineers/Physicists here

[bobalu]

When evaluating engine performance at an ambient temperature (outside, not in a controlled condition), does the Humidex index matter? Here in southern Ontario, air temperatures are reported along with the humidex, so the ambient temperature may be 82 degrees for example, but will feel like 92 degrees with the humidex. I guess what I'm asking, is does a mechanical engine care about the Humidex? Or is 82 degrees 82 degrees (ie: only humans are affected by the humidex). Just wondering. :6:

 

[Hoople]

does the Humidex index matter?

Not so much the "index", but the % of water certainly does. I do know that the more dry the air is, the more Oxygen there will be in the air. And the more O2 there is,, the better.

The place to find the real scoop on your question is the NHRA Funny car guys. Those guys have to know the complete low-down on Temp,, Humidity,,altitude etc when it comes to performance because just 1 or 2 points off could mean total destruction to the engine..

 

[kemo]

I would say that an engine likes cool humidity. An engine runs best in cool damp weather. Fuel is condensed in cool weather meaning that you are getting more fuel at cooler temps. When I was a kid we would make up cool cans. We would coil copper tubing and insert it into a can and hook the tubing into the factory fuel lines, we would then pack the can with ice and go racing.
Ken

 

[Jack Klarich]

Take your bike out at midnight for a good cool run and feel the difference in the throttle, Yep they like cool air IMO

 

[bobalu]

O.k., I think I understand the answer. I didn't think about the dragsters Hoople, thats a good source you suggested.

Thanks for the answers guy's.

 

[Dr.Evil]

When evaluating engine performance at an ambient temperature (outside, not in a controlled condition), does the Humidex index matter? Here in southern Ontario, air temperatures are reported along with the humidex, so the ambient temperature may be 82 degrees for example, but will feel like 92 degrees with the humidex. I guess what I'm asking, is does a mechanical engine care about the Humidex? Or is 82 degrees 82 degrees (ie: only humans are affected by the humidex). Just wondering. :6:

As stated above, the heavier air is better for combustion. But to answer another part of your question, the heat index was created for humans and our ability to self cool by perspiration, the more water in the air, the less cooling effect and the hotter we feel. This index has no effect on mechanical or inanimate objects. Although we feel cooler at 60 mph in damp air, so it may be if we are moving the moisture helps with cooling.

 

[bobalu]

As stated above, the heavier air is better for combustion. But to answer another part of your question, the heat index was created for humans and our ability to self cool by perspiration, the more water in the air, the less cooling effect and the hotter we feel. This index has no effect on mechanical or inanimate objects. Although we feel cooler at 60 mph in damp air, so it may be if we are moving the moisture helps with cooling.

That is exactly what I was asking. Thank-you Dr. for your excellent answer!