[BarryJI]

Yeah, I feel they have minimized the effect of a/c on power output in the 228i but I still won't use it if I want all to drive feeling I've got everything the car has under my right foot.

[raisingAnarchy]

Originally Posted by aerostar

No I mean if I rev'd to 3k RPM, shifted to 2nd or whatever next gear, the RPM would drop like a rock and I'd have to clutch in clutch out as fast as I could to make it on time.

You don't experience that now? My E90 does that now, not sure if it's AS fast as your WRX would drop, but it's fast enough that I keep my foot on the throttle a bit to help slow the RPM drop.

The compressors on BMWs are still belt driven correct?

[3.0L]

Originally Posted by aerostar

No I mean if I rev'd to 3k RPM, shifted to 2nd or whatever next gear, the RPM would drop like a rock and I'd have to clutch in clutch out as fast as I could to make it on time.

This suggests another little advantage of having the 8-speed automatic.

[2msport]

TBH running the fan system with the AC OFF still robs noticeable power. Logically running anything including the NAV screen, speakers, headlights will take power from the engine. Small or large but it adds up. It may be true that modern cars disconnect the AC compressor during WOT, however it's quite apparent to me you still don't get the same power as with it all off. Let alone the process takes a second to disconnect, so your acceleration won't have the same initial kick. IMO with every car I've driven.

[BMW335iOn18s]

All manual transmission cars will experience the above...it was noticeable on my VW and it's noticeable on my M235i. I actually always keep the AC on because I prefer how the car drives.

[xantdieselx]

As mentioned earlier A/C compressor disengages under WOT. Also in Auto mode A/C is cycled on/off which means you are using your A/C in the winter too when climate control is set to auto. Because of the cycling on/off you are less likely to see any differences in power delivery when it is hot and you have the A/C on.

[jtzako]

Using electronics such as nav etc may have an impact, but it is likely extremely small and not noticable on a modern car. If you had extra electronics that use a significant amount of power (amps etc) them maybe it could be noticeable by a very accurate dyno, but probably not by someone just driving the car. This is due to the Alternator always being driven regardless of load, the base level of power reduction will be there and the changes due to increased electricity demand are minor.

The A/C on the other hand, is not always engaged so it could be felt by the driver. On the 228i it doesnt seem to be much of a problem. I actually noticed the A/C more on my Camaro SS w/ 400 HP more than I do on the 228i for some reason.

[Advanced]

my experience/history (all with MT):

- 2004 Acura RSX Type-S ~ with A/C on the car felt like it lost 100hp, clutch/shift felt terrible!
- 2008 BMW 128i ~ car felt great, even with A/C on the power loss was not too noticeable
- 2011 Subaru STI ~ this car was love/hate for me, but with A/C on the power was not too noticeable
- 2013 VW Golf R ~ this car was amazing! very little effect with A/C on
- 2015 BMW M235i ~ cannot comment, still another 2-3 weeks before delivery

from what i gather, it appears that as the cars get newer it seems the issue with A/C drawing power becomes less apparent. regardless of how big or small the effect, the power loss was there in all vehicles i've driven. i think it also has to do with how much hp/tq the vehicle has (hopefully the M235i will be amazing with A/C on or off)

[BimmerMat135]

Good to know they might have fix this issue with the M235i. I'm doing anything to avoid turning the a/c on in the 1m the gear shift are terrible with it on.