Turned the AC on for the first time today. Pulling away slowly in first gear, hit the AC button and the engine really bucked then was fine. Is this normal? I also notice a rise in RPM at idle.

Jim

 

I don't know about a bucking, but there is a definite thump, hesitation, bang whenever the A/C compressor engages. It's especially noticable at lower speeds.

 

If you are trying to engage the clutch like you normally do, yes its normal. The engine is under load with the AC on, so you will need to give it more gas to take off than with the AC off.

 

Thanks. "Bucking" is an old term for "hesitation". I was at low RPM so I will be aware of that in the future, as the engine almost stalled. It seems to take the compressor a few seconds to wind down after the car is shut off. At first I could not figure out what was going on. The mini talks some getting use to in some regards.

Jim

 

most all cars will notice a slight hesitation or "buck" on the engine when you turn the A/C on. This is because it's an extra load on the engine (as someone else suggested). This isn't unique to Mini's, it's common on most all cars. You're asking the engine to work harder by turning an extra motor when the A/C is on. For maximum performance and maximum gas mileage turn A/C off. Yet for maximum comfort on a hot day you'll want to use the A/C.
Higher RPM is normal as well (as the engine is working harder to turn the A/C motor).

 

this will be debated for ages.
Windows down and AC on is not necessarily a gas killer compared to the drag/loss of efficiency in aerodynamics of the windows rolled down. It's negligible.

Also, there have been recent studies that show A/C greatly increases air purity as well.

The debate goes on...:D

 

i didn't say anything about rolling down the windows ...yes rolling down windows will cause a certain amount of drag.

so will:

-carrying a mattress on top of the car
-towing a bunch of crap behind the car
-a plastic bag that has become stuck to the front of the car while driving on the freeway
-using the Mini to bring the Christmas tree home

 

Mythbusters seemed to have debunked the myth on Ford Escapes. They took two out to a track, put 10 gallons of gas in each. Turned the AC on high in one, and the windows down on the other. The one running the AC ran out of gas first

 

how fast were they going

 

LOL

You act as if rolling down the windows is an exceptional case. People turn on the AC when it's hot. If they're not going to use the AC and it's hot, they're going to roll down the windows. That's a given.

 

Actually, on Mythbusters they had inconclusive results:

On the first Mythbusters show on this, the car with the AC on and windows up Mythbusters performed better than the car with the AC off and windows down.

Computer-based mpg measurements:
11.7/11.8 with A/C on and windows up
11.7/11.8 with A/C off and windows up
11.3 with A/C off and windows down

So, according to the computer, it's better to use A/C on with windows up.

Then they revisited this test and had completely the opposite results when they tested 5 gallons of gas going 45mph. Jamie driving an SUV with A/C on and Adam driving an SUV with windows down.

Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate.


So the debate rages on!