Cal Club Autocross Forums

Being the automotive question go-to stud that I am, my friend asked me yesterday whether changing the fan position on the A/C in his car changed the mileage he'd get. I told him that the A/C motor connected to the engine is either on or off, and when it's on, it draws power from the engine (I'm talking about a mechanical system, of course, not the newer electrical ones). Changing the amount of air blowing into the cabin wouldn't affect that operation. The only difference would be the amount of power required to run the fan at a higher speed, which wouldn't significantly affect his mileage. Was I correct?

More air has to be cooled, so the compressor has to run more often.

Liberal arts major?

Steve Ekstrand wrote:More air has to be cooled, so the compressor has to run more often.

Liberal arts major?

You got it, baby! Science schmience!

Me too.... But I took a couple of physics classes so someday I could at least figure out a few good things to ask Marshall.

Steve Ekstrand wrote:More air has to be cooled, so the compressor has to run more often.

Liberal arts major?

Volume of air per second crossing the cold-side condenser means the coolant returns to the compressor carrying more heat.

Tell him if he drives faster it will make up for running the interior fan.

Bob Beamesderfer wrote: Volume of air per second crossing the cold-side condenser means the coolant returns to the compressor carrying more heat.

Tell him if he drives faster it will make up for running the interior fan.

replace volume flow rate with mass flow rate, condenser with evaporator, and coolant with refrigerant and you would be correct.

I assume the second part is sarcasm?

Marshal (as usual) has it nailed.
For an easy experiment try turning your AC on and off while coasting.
It is amazing how much drag it puts on the car.
Way back when Hondas were significantly underpowered I used to put a vacuum cut out switch on the compressor clutch, to get max horsepower at full throttle.

I called the AC on my 318 BMW Negative Turbo

Marshall Grice wrote:

Bob Beamesderfer wrote: Volume of air per second crossing the cold-side condenser means the coolant returns to the compressor carrying more heat.

Tell him if he drives faster it will make up for running the interior fan.

replace volume flow rate with mass flow rate, condenser with evaporator, and coolant with refrigerant and you would be correct.

I assume the second part is sarcasm?

Oh, no I was dead serious.

John Prosser wrote:Marshal (as usual) has it nailed.

not sure who that marshal guy is, but i believe technically Steve nailed it.

Marshall Grice wrote:

John Prosser wrote:Marshal (as usual) has it nailed.

not sure who that marshal guy is, but i believe technically Steve nailed it.

Hey, I learned something from your explanation [mass vs. volume]; the other stuff I knew but brain-freezed on the nomenclature. Never took physics, barely passed chem.

Diss the nomenclatura!
Refuse to speak their language!

Marshall Grice wrote:not sure who that marshal guy is

He's the law around these parts.

Kurt Rahn wrote:

Marshall Grice wrote:not sure who that marshal guy is

He's the law around these parts.

Hah!

Sebastian Rios wrote:

Kurt Rahn wrote:

Marshall Grice wrote:not sure who that marshal guy is

He's the law around these parts.

Hah!

I hope he doesn't declare Marshall law

Marshall Grice wrote:

John Prosser wrote:Marshal (as usual) has it nailed.

not sure who that marshal guy is, but i believe technically Steve nailed it.

Marshall suffers from the same problem I do, when people write our names with a single trailing L, they usually drop the one that's pronounced and keep the silent one by mistake.

But, it's all fun and games until someone loses an i.