Heat and performance. Myth or fact?

So there is a discernible difference driving my truck when it’s a 40° Brisk morning or 110 hot summer afternoon like today. I’m not sure exactly but if there is an actual spec difference I would say probably a solid 15 hp decrease. I don’t know or understand the physics on how that works if someone could explain it I find it interesting and it would be appreciated.

 

Yes. There is, sorta.

Cold, dense air is great and is easier on the cooling system. But, warmer air means a faster warm up with less time on enrichment and cooling systems are more efficient in heat exchange when there is a greater temp difference.


Still on my bike with a simple EFI, it definitely eats better on cold days.

 

Look up air density and it will explain it pretty well. You also have the drag from your AC and you're engines fan sucking up more power when its hot.

https://airdensityonline.com/2016/10/why-air-density-is-important/

 

Colder air is more dense than warm air. Effectively, more air (because it’s more dense), and more fuel to match, end up in the compressed in the combustion chamber of a naturally aspirated engine, and more power is made.

You should try going for a rip at -20 or so, Bud. (Any colder, and your drivetrain fluids and tires get stiffer and rob too much.)

 

In addition to this, you'll also notice a difference in MPG. Even without winter blend gas and with proper tire pressures you can expect to lose a couple of MPGs in cold weather.

 

I gain litres/100 km instead.

 

Anyone whose tried a takeoff in a single engine plane on a 100+ degree day with near full tanks on a field with a couple of thousand feet elevation knows why air density is important, and has the stained underwear to prove it

 

Hot High and Humid.... not a good combo..

 

I don't know why gas is more flammable at 200 degrees compared to 0 degrees but I think most everything is. All that cold air going in the engine doesn't burn gasoline very well. A thermostat keeps the engine temperature up there but very cold air doesn't help the burn. Might have something to do with how well the gas vaporizes at different temperatures.

 

That must be why cold air intakes (CAI) are so popular with the scientifically challenged.

 

I too notice this but its science and just gotta deal with it

 

Was talking to a mechanic while back and he said that there is a limit how benifical cold air is. He said the Cooler the air, the better it is for the car performance and mpg wise untill you get down to about 50f degrees. And colder and it’s worse for the engine.

 

You want your fuel warm because it vaporizes easier as the temp increases, to a point. You don't want vapor lock. You want cold air because it's more dense and has more O2, thus is more explosive.

Science is a cycle of observation, hypothesis, testing, data analysis and reporting so that others can repeat the tests; not just believing what you're told. Thousands and thousands of tests have been done that prove cold air is better for engines and that's why turbocharging enthusiasts utilize intercoolers to get the really hot air temp down to a usable temp before it's forced into the intake manifold.

https://www.aet-turbos.co.uk/turbo-tech-101-what-is-an-intercooler-and-how-does-it-work/

 

really all there is to it.

 

Warm air is less dense and has lower wind resistance so mileage is better.

 

I’m trying to bring a “luke-warm Air Intake” to market and am looking for investors.

“have the best of both worlds with the LWAI”

 

That's why carb heat is a dash panel control on every IC engined aircraft worth talking about.

Must be scient terriffic!

 

To help vaporize your fuel in the carb. See my post above about about fuel vaporizing better at higher temps. Catch up.

Edit: It also helps keep ice crystals from forming in there and blocking fuel.

 

Oh! there is more! Humidity! some people have used water injection to aid performance. (Watch for valve erosion)

JATO is the ticket!

 

Catch up indeed

Carb heat does not effect fuel temp // jeesh!