Bimmer32

In my previous cars both v6 and v8, I have noticed that when the AC is ON, the performance of the car, particularly in acceleration, is slightly diminished. It is more noticeable on the v6 than the v8.

I've tried this on the 545i also, and do noticed a slight (very slight) lag on the acceleration. When the AC is off, the car responds noticeably faster.

So the question is, how much hp/torque does the AC take from the engine? Both on the V6 inline and the v8? I don't buy the answer that an AC compressor doesn't affect the engine performance even on a v8 unless someone can show it to me on a dyno.

EBMCS03

3-5hp is my guess.

znod

It's an unknown to me. But, I always assume about 20 HP. The cost in relative HP was very large, for example, on my (gone) 94 RX-7. Our compressors don't have clutches so I think the loss is somewhat proportional to, maybe, temperature. I know that if you turn our compressors off it actually takes a while to be completely free of the compressor's HP consumption. These thoughts pretty much sum up my lack of knowledge on the issue you raise. I'd like to hear more.

Jeffs

donv: 20HP???? are u kidding me???

I don't know how much so i cant comment.....but 20 seems liek ALOT to me.....where did u get that info??

m5lover

i never notice that ac would swallow up hp
i know that ur rpm increases with ur ac and lights on..

ipse dixit

AC robs the car of about 5-15 hp.

Each accessory in a car uses rotary power - each accessory is turned to perform it's function, whether it's an electrical component (the alternator or compressor for A/C) or a fluid displacing component (the water pump and power steering pump). They all have a pulley which takes power from the crankshaft pulley via a belt.

All of these components use horsepower, horsepower that is lost. Power that could be making the car faster.

m5lover

so when ur flooring no ac,no lights,no music?

znod

Definitely no AC if you are flooring seriously.

znod

It is a very crude estimate based on past experiences with a variety of cars. And, note that above I said:

"It's an unknown to me. But, I always assume about 20 HP. The cost in relative HP was very large, for example, on my (gone) 94 RX-7."

In general, note that if one can feel a difference with the AC on versus off, then that difference might be worth .2 sec in the 1/4--which, by rule of thumb, would translate into about 20 HP. I could feel the loss of the 94 RX-7 so well that it felt like the AC was consuming 50 HP. But, of course, the rotary is a low-torque engine at many RPM. I'll nose around and see if I can find anything more definitive.

EDIT: I haven't been able to find anything "official" yet. And, I added some new info above.

BetterMakeWay

I agree about the ac. It should be off when flooring it...but loooooooooool the lights/muzic/seat heater makes me laugh...................

No music please, if u race at night, lights off, that way u'll win for sure