telemakhos

Does anyone notice that one very hot days when their AC is running there is a noticeable drag on the engine and when standing beside the car, it is very loud ? Didn't have any of this on my old E.

Mine is a 3.5 2011 and I wouldn't expect the AC load to be noticeable when driving given the engine power.

dfordham

No. I live in the desert southwest where 100 degree days are common. I find both the engine and the A/C to be superb. Never notice any effect of the A/C on the engine when inside.

If you're outside the car it is normal on any car to be able to hear the A/C cycle on and off and hear an apparent short drag on the engine. And, yes, the A/C can be quite loud from outside.

Regards,
Don

telemakhos

Thanks for the reply. I even notice the difference at the gas pedal. I actually have to push down more to get the car going when the A/C is on. It is as if the brakes are partially on!

Hmmm... time for a check up at the dealer.

WEBSRFR

Does anyone know how much HP is drained by the engine?

telemakhos

Found another thread discussing this topic.
https://mbworld.org/forums/s-class-w...s-c-being.html

The loss should not be noticeable.

WEBSRFR

Great find! Thanks for posting. SO apparently only about 5-10 hp and less than 10 torque. Good to know. So my habit of turning off the AC to get maximum power on rare occasions is apparently meaningless. Good to know.

I bet you loose more power by rolling down the windows than turning on the AC.

ttoE550

I don't know about the E class specifically, but at least three cars (Porsche, Toyota, and Subaru) I owned were designed to automatically shut off the AC compressor briefly with high demand on the engine. With the Subaru, it was very noticeable when the AC compressor would turn off - it was also very noticeable when it would turn on.

konigstiger

Check your PM

K-A

I don't notice any difference to power output/performance with the A/C on. I even don't notice any MPG decrease with it on.... in fact, my best MPG's have happened with A/C on, as odd as that sounds.

Nuru

Same for me too. I noticed some very good mpg with the AC on and going up hill

telemakhos

My issue is only at speeds less than 25 mph. At normal driving speeds, no noticeable drag and the mileage does not seem to take a hit. At low speeds on very hot days it feels like I'm driving through mud. Weird.

Arrie

At 75 MPH my AC lowers gas mileage by about 2.5 MPG.

Nuru

Hmm, with the larger engine the AC should have less effect than it will on a E350? I might get a 1 - 2 mpg diff, depending on how long I maintain a steady speed. If I have a lot of instances where accelerate and decelerate (SP?), I will notice a drop in mpg, steady speed almost no drop in what I get at speed.

Arrie

Engine size should have nothing to do with how much MPG you lose with A/C on. Turning the compressor at a given speed takes the same amount of energy regardless of how big the engine is that turns it.

I have tested for this many times and it seems 2.5 MPG is what I lose at 75 MPH speed, at least this is what the car computer shows.

Nuru

Actually, a larger engine should be capable of handling more due to its additional HP and torque. A 4 banger wold suck eggs big time with the units on the E550. They hopefully size the compressor units to the engine, otherwise if they used the same compressor on all, you would notice much larger mpg decreases as the engine size and associated HP varies.

dfordham

They definitely don't size the compressor based on the engine size. Would you want someone saying: " I wish I had bought an E550 'cause this air conditioner just doesn't cut it."?

Regards,
Don

Arrie

Again, turning the A/C compressor at a given speed takes the exact same amount of energy regardless of the size of the engine that runs it.

If there are differences in the amount of MPG you loose for the A/C then it is related to differencies between the A/C compressors and/or the charge level of the system.