[Sea2Ski]

I had no idea how much power the AC took to run, until I got this car with a manual transmision. (First MT car I ever had.) Driving with the AC on and driving with it off is like driving two different cars to me. Not a major issue, just something I have to keep in mind.

[johnjohn]

Originally Posted by urbanite

Damn. I knew I should have bought an AT. It sounds so much better.

So which is better overall ... MT or AT ???

When I got my 335, I sort of went the luxury route instead of ordering one with a sport package and manual.

It's wonderful, it's awesome, the Step is the best AT I've ever driven, by far. Still, guess what I'll do next time? Sport and manual all the way.

Seems like some people who have a 6MT want an AT and vice versa. Just goes to show we're never perfectly happy.

[danimal]

I think a/c units use more power since they got rid of freon (the are "CFC-free" now).

[montreal_bimmer]

a/c compressor takes some juice from the engine.... its normal

[oldaccount]

Originally Posted by homerunball

I meant it was balanced for no AC load.

I'm sure you are a fine driver with no shift issues when the AC is off. I have to change my shifting behavior when the AC is on in any car.

i know man, i was just playin around

[nineth]

Originally Posted by Walked U

I got the cdv delete. Now it shifts like a hot knife through butter. Even with the AC on

Had you noticed this before you deleted the cdv? You probably didn't have this issue even w/ the cdv. May be this only affects the 325/328?

Driving with the a/c on and with a/c off is like driving two different cars for me. The dealer technician told me that this is normal as the compressor is kept running when shifting. Only when the accelerator pedal is depressed or car in idle, additional fuel is injected to maintain the target rpm based on throttle position, etc., i.e., if you suddenly turn the a/c on while driving at a particular speed, you will see a drop on your mpg gauge (fuel economy), but no drop in your car speed / engine rpm. However, while shifting, the compressor does cause the rpm to drop like a rock, esp. in the lower rpm range (< 3500 rpm). This rate of drop when the throttle is closed is something not controlled to compensate for a/c.

If the above is not the intended behaviour by design, I think diagnosing and fixing this is something difficult to get done in the US, where dealerships have limited expertise with manual trans cars (if the DME itself does not record any relevant faults and it does not in my case). Only someone intimately familiar with BMW engineering might be able to tell.

[2008E90TT]

I've noticed the same on my 335i. I figured it was due to either the turbos causing backpressure on the pistons or that the car had a really light flywheel.

It is difficult to get a smooth shift without revving it really high or slamming it into gear. Neither of which I want to do when the car is cold.

[SS e93]

o man i thought it was just me. I kept thinking...how the hell did I F*ck up my clutch.

[texas2009]

I've noticed a lot of driving performances differances. I live in Texas, but flew to Ohio to pick up the car. It was cold cold cold there in march (i saw touchdown Jesus before he toasted, my dealer took me by there!) Drove back the whole time thinking I just didn't 'know' the car yet. Nah, it was changing, for sure. Since the 100 degree weather has set in, it has definitly mellowed a bit. That's a good thing, don't get me wrong. I appreciate the car knowing it needs to chill... even though I just installed the jb3.
I had a 4 hour trip today that 'required' me to give it a little, um, nudge. Let's just say I wasn't even trying and it was still pushing me back in my seat at the same point my old g35 would have cut off. (I can't believe people still try to compare these cars.)
So that being said, if it EVER cools off here in Houston, good.
Altitude, temprature, all that. They make a difference. Running the AC especially. Funny when you want power, the AC robs it, but when my wife used to drive a Honda CRV (NOT another word, I got her in an FX35) it didn't matter a bit on the AC since there wasn't any power to give. ...though it did turn out to be enough power to flip the whole thing in 35mph traffic in downtown houston rush hour traffic... hmm
Did I ever tell you about the time I drove a diesel engined Ford van into the colorado mountains and counldn't go faster than 10mph? No? Mayby next time.

[Kolyan2k]

shifting with ac sucks and there is about 25% power loss and drop in mpg, i drive without ac most of the time. << been like this in all my cars with manual

[caradd]

No doubt the throttle response is slower with the AC on. Whenever I rev-match to downshift I have to hold the gas pedal longer to get the rpm's up.

Probably a tune and DCI would help that.

[cimbali]

i need to rev match most of my upshifts to get smooth shifts with the AC on...no big deal.

[preDoc 328]

Wow looks like everyone is experiencing this. I just drive with windows down. On a day hot enough to require A/C, I don't really want to rev the engine that hard, especially when it's cold. Yea, I know that the modern engine can probably handle it, but I plan on keeping this car for a long time.

Side question: Is everyone also experiencing the occasion reluctance of the MT gearbox to slot into 1st?

[MusclezMarinara]

i the max button, wish we had AC seats

[VanM3Lover]

Also, it sounds like a truck just starting to get moving.

[jetrep]

Originally Posted by tgb335i

Actually, the drag the alternator puts on an engine does not vary by power output. It produces electricity based on how fast it is turned, but does not have a clutch to engage/disengage like the A/C compressor and doesn't have hydraulic drag like a power steering unit. The downside to using up too much power on accessories is the alternator may not be able to keep the battery charged.

An electric A/C unit would allow for cooling without the HP loss of a belt-driven unit. However, the power demands for it would be a bit high for a regular 12-volt system presently available in non-hybrid vehicles.

Please do not post false information. The load placed on the engine by the alternator depends on the load placed on the electrical system. Check out an alternator next time you are at the auto parts store. It will spin freely. Wire a headlight up to it and see how much more difficult it is to spin.

An electric A/C unit would not eliminate HP lose....It would transfer the power generation to the alternator (which would have to be upsized accordingly).

An electric A/C unit would allow the computer systems to have more control over climate control...RPM could be varied and would not be tied to engine rpm (or OFF). I am not a pump expert but I suspect it would also allow designers to improve efficiency of the pump as they could design it to operate in a much narrower rpm range.

[2008E90TT]

Originally Posted by jetrep

Please do not post false information. The load placed on the engine by the alternator depends on the load placed on the electrical system. Check out an alternator next time you are at the auto parts store. It will spin freely. Wire a headlight up to it and see how much more difficult it is to spin.

Word. Someone get that guy a Genecon to play with.

[2008E90TT]

I am finding that I have to blip the throttle between shifts as well. Otherwise, I keep getting asked if I know how to drive a manual.

[nineth]

Originally Posted by cimbali

i need to rev match most of my upshifts to get smooth shifts with the AC on...no big deal.

This is unbelievable!! Rev matching for upshifting is acceptable to you?? This is big deal.

[nineth]

Originally Posted by 2008E90TT

I am finding that I have to blip the throttle between shifts as well. Otherwise, I keep getting asked if I know how to drive a manual.

This is obviously not the right way to work around the issue. You have three options: (1) drive with a/c off when not on the highway, or (2) shift at about >= 3.7k rpm, though not the best for fuel economy, and does not feel perfect for regular driving (any MT car, by design, is not expected to have specific drawbacks when shifting at 2.7k-3k rpm that is a good sweetspot for shifting in terms of a trade-off between fuel economy and reasonable acceleration), or (3) shift much faster when the a/c is on, but this will mess up your muscle memory, and your shifting will be too fast for "a/c off" conditions and cause fwd jerks; this will also be problematic when the temperature outside falls down and the a/c compressor is turned off (automatically) unknown to you. I use option (1) and option (2) only when it's too hot.

Many have stated that they see this issue on other manual trans cars they have driven, but the real issue here is the amount of affect this has in the case of e90s (not sure what all models are affected). Also, this has nothing to do with the car being cold vs warmed up. Shifting with a/c off on my car is perfect (except for the inconsistencies caused due to the CDV which one can adapt to after a long time).

[BayMoWe335]

I've noticed my AC dips a little power when I turn the headlights on.

[konradsa]

Really weird everybody has such issues. Compared to the cars I previously owned, I barely notice any difference in my car (328i auto) with A/C on or off, even on a hot 100F day. I was already wondering whether BMW has done something to make the A/C less noticeable, e.g., make the gas paddle more response with A/C on.

It seems that this effect is much more pronounced with MT.