Power Decrease with A/C on, how much is normal?

[Nick1994]

On the Beetle I notice a power/acceleration decrease when my A/C is on. It's not dramatic but it's definitely noticeable. The reason I'm asking is because lately my mileage has gone down to only around 33-34 mpg last tank from 37-38.

 

[dlundblad]

The AC compressor is causing more resistance and its normal to hear mileage suffers while the AC is on. It is noticeable in my Jeep too.

 

[Mr Nice]

A/C use usually equals less gas mileage.

OT: Did you get flywheel issue resolved ?

 

[dishdude]

Odd, I'd think with the low end torque that a diesel has you really wouldn't feel a power loss with the AC.

 

[Nick1994]

The car used to get 37-39 with A/C though, could be something else causing the low mpg though, just trying not to narrow it down.

 

[Nick1994]

Originally Posted By: Mr Nice
A/C use usually equals less gas mileage.

OT: Did you get flywheel issue resolved ?

Flywheel issue was sort of resolved. I was assured by the service manager that with all of the documentation with my flywheel issues that even out of warranty if the flywheel explodes VW will take care of it. Nothing left I can do.

 

[Nick1994]

Originally Posted By: dishdude
Odd, I'd think with the low end torque that a diesel has you really wouldn't feel a power loss with the AC.
It's definitely got lots of low end torque, and it still has plenty of power and I don't have problems with passing with the A/C on or anything like that, but it's just that it's noticeable.

 

[eljefino]

Remember that AC load is per minute, not per rev, so the compressor turns harder (CCOT) or with a longer duty cycle (normal) when the RPMs are down, so it's a double whammy.

When I sit at a light in neutral I'll kick it up to 2500 RPM when the other guy gets the yellow, to "catch up" on the cooling so there isn't a big slug of slowness when I get the green.

 

[fdcg27]

Depends upon the car.
With my old BMW, you can really feel the difference.
With the Hondas we've had, not so much.
You could tell the difference on our old Vulcan Aerostar mainly by the increase in pinging under the right conditions.
Drove some miles in an old Civic VX, and the AC button was a virtual speed brake, but this was a fuel economy special Civic with very tall gearing.

 

[dlundblad]

When was your fuel filter replaced last? Our TDI Jetta went through them every 20k it seemed.

 

[pitzel]

I've never noticed it on my fuel injected GMs in either mileage or performance. Although the ECU does command the AC compressor off during periods of high power output from the engine. And the ECU bumps up the idle slightly simply so the engine doesn't shake quite as much with the incremental load of the AC compressor applied.

 

[Nick1994]

Originally Posted By: dlundblad
When was your fuel filter replaced last? Our TDI Jetta went through them every 20k it seemed.
I changed it at around 160k-161k so maybe 11k on it

 

[Merkava_4]

It's supposed to be a noticeable difference but not dramatic.

 

[4D-56]

I sure feel it in my 4cyl Honda. A K&N panel filter helped and an experiment with premium gas (while it was cheaper) helped even more, to the point where it no longer made a difference.

I just have to rev it more and know that the Mobil1 is doing its thing.

 

[Rand]

some cars use a variable displacement compressor some fixed.

I'd say 10% lower fuel economy with a/c on is normal.

 

[abycat]

I notice it in my car quite a bit. feels like 20ish horsepower is gone. Never noticed with my big v-8's. All my other vehicles didn't have ac.

 

[Kuato]

Originally Posted By: Nick1994
Originally Posted By: dishdude
Odd, I'd think with the low end torque that a diesel has you really wouldn't feel a power loss with the AC.
It's definitely got lots of low end torque, and it still has plenty of power and I don't have problems with passing with the A/C on or anything like that, but it's just that it's noticeable.


Running the AC costs power, period. Doesn't matter how much power you have, it is reduced with AC use.

 

[Nick1994]

Originally Posted By: abycat
I notice it in my car quite a bit. feels like 20ish horsepower is gone. Never noticed with my big v-8's. All my other vehicles didn't have ac.
Wow, I guess I didn't think of that. The cars I'm comparing it to is my grandpas Jeep (190hp) and grandmas Trailblazer (273hp). My car only has 100hp so I guess it's probably normal.

 

[Andy636]

Our 20 yo Daewoo has an interesting feature that cuts off AC when you need all the juice that the poor 1.5 L engine can deliver. Kicks in when the traffic light goes green or when you step on it more aggressive to overtake someone.

 

[OneEyeJack]

I've been driving a Prius on my current project and the a/c is not connected to the engine. In fact there is no accessory fan belt or serpentine belt on this engine.

Because of the energy recovery system I'm having a hard time figuring out what the hit is when using the a/c.

The only hit I can see is when you are parked for a long time and have the climate control set to a low temp on a hot day. The engine will start every now and then and run for a few minutes. That's the hit.