A/C sucking power... - The Unofficial BMW M5 Messageboard (m5board.com)

plisken · 30th June 2004, 07:32

I've been using my A/C more and more now that we are in the height of summer, well it has been a little warmer lately

Anyway, I've been noticing that if I run with the A/C on for around 45 minutes or so, it really starts to suck power from the engine, in that that car generally feels much less responsive. I know that if the engine is being used to drive the pump/compressor, then some of it's power is being used to do so, so I always expected a little less response, but this seems different.

As I say once I've had it on for a little while, I find that I need more gas to move off etc, it really feels like I am towing or something. Once I put the A/C off, car feels back to normal.

I'm wondering if this is considered normal, or if perhaps it is an indication of a worn pump/compressor or something.

I'm trying not to look for problems, but this has been on my mind for the past couple of weeks.

As usual all comments are appreciated...

Mmm-Five · 30th June 2004, 12:30

I don't notice any difference in power whether I have it on or off! All I notice is that the tickover rises 100rpm!

Also the AC switches off under full throttle anyway to maximise power.

Just need to get mine re-charged/serviced now!

Tomk · 30th June 2004, 14:39

i notice when when mine is on and i think most e34 drivers do...cant say it kills the power but it is noticeable in terms of responsiveness

IvanDias · 30th June 2004, 15:15

I read once that the A/C in a Rolls Royce was equivalent power to 47 fridges.

Given the cubic space in a car versus the relatively quick time it takes to really kick in, I can believe the figure; a E34 is much bigger than a fridge, and cools much quicker than the average Zanussi.

So, I suspect quite a chunk goes missing, hence most owners saying that it is noticeable when on, for blunting normal driving. My Dads little Ford Focus Driving School car really suffers!!

I am blessed with many empty pipes that once contained a very naughty gas that escaped long ago to fly free over the Antarctic.

Therefore I upgraded to the very latest airflow technology, which allows cooling of each seat of the car independently using advanced atmospheric flow control panels made from a special Silicon based, Calcium and Sodium Carbonate amalgam!!

Ivan

plisken · 30th June 2004, 18:15

Quote:

Originally Posted by IvanDias

Therefore I upgraded to the very latest airflow technology, which allows cooling of each seat of the car independently using advanced atmospheric flow control panels made from a special Silicon based, Calcium and Sodium Carbonate amalgam!!
Ivan

I had similar technology when I was based in Zxybor, however, now that I am back on earth indefinately, I have to make do with what ever advancements the current human race can muster.

I do notice the revs rise and fall by about 100rpm, and I'm also interested to learn that it cuts off under full throttle.

What concerns me is that after it has been on a while, part throttle response is very poor, for example when pulling away from a set of traffic lights, driving normally in first and second gear, it actually feels like am towing. now this is definately not the case when it has only been on for 10 minutes or so.

I'm going to have it charged/checked during my next service anyway, I was just curious as to what you guys thought.

I'm my opinion though, it is by far not the best A/C I have ever expierenced, it does stop the windows misting up on a rainy day though, without having the fan speed too high...

IvanDias · 30th June 2004, 19:30

[quote=plisken...after it has been on a while, part throttle response is very poor, for example when pulling away from a set of traffic lights, driving normally in first and second gear, it actually feels like am towing...[/QUOTE]

That`s exactly how Ive found air-con to act on all four various cars I`ve driven that have it.

Ivan.

kevinpayneuk · 30th June 2004, 20:37

With the aircon on, I find it very difficult to drive smoothly at part throttle with the revs changing.

Other than that I don't notice any reduction in power when over 4k rpm.

plisken · 30th June 2004, 23:20

Quote:

Originally Posted by kevinpayneuk

With the aircon on, I find it very difficult to drive smoothly at part throttle with the revs changing.

Other than that I don't notice any reduction in power when over 4k rpm.

I would agree that when driving through traffic, part throttle, it is a bit "jumpy" when the compressor kicks in and out. (I think that is the correct term for what is happening).

I do have to say though that it does require a little more throttle to pull away etc, but this is only apparent after it has been on for 45 minutes or so.

Steve Mac · 1st July 2004, 23:41

Quote:

Originally Posted by Mmm-Five

I don't notice any difference in power whether I have it on or off! All I notice is that the tickover rises 100rpm!

If memory serves it gives yours an extra 4bhp

No wonder you dont notice

I dont notice a difference after a while just a slight loss all the time but she still kicks like an aggravated mule having its b**ls squeezed when asked

M5touring reg · 3rd July 2004, 23:30

as Mmmm-Five@ says
=""Also the AC switches off under full throttle anyway to maximise power"" -
personally I hv never noticed any difference in power-delivery with the AC working, perhaps your DME is not doing what it is supposed to ??