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      06-15-2007, 06:15 PM   #1
Wissam
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6MT shifting with AC on

I normally shift around 2700-3000 rpm, but I noticed when the AC is on it becomes hard to shift smoothly at these rpms and I would have to go north of3500 rpm to help smooth the shifts out. Are you guys noticing the same thing? I know the AC puts extra load on the engine, but it should not be this noticeable on an engine this size.
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      06-15-2007, 07:08 PM   #2
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i have noticed that as well...below 3000 rpm the engine drops like a rock and I have to quick shift or blip the gas to keep it from lurching.
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      06-15-2007, 08:33 PM   #3
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I, too, notice that. But I notice it with other cars as well. I believe when the a/c is on, it's using a lot of juice from the surge compressor that's why.
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      06-15-2007, 08:57 PM   #4
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Yes, especially if you "Max" out the A/C. I feel the power lost is more apparent when shifting from 1st to 2nd.
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      06-15-2007, 10:54 PM   #5
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Thanks guys for your feedback...
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      06-15-2007, 11:11 PM   #6
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especially here in the desert where its 120 in the summer, if I need a little more power off the line, I shut off the ac till I reach speed
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      06-16-2007, 12:53 AM   #7
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You know I never thought I would say this, but with this particular car and this particular auto tranny....

This car is better driving and more user friendly and for the most part faster with the Steptronic. It's almost as if this car was built around that tranny.
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      06-16-2007, 06:22 AM   #8
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Quote:
Originally Posted by TRZ06 View Post
You know I never thought I would say this, but with this particular car and this particular auto tranny....

This car is better driving and more user friendly and for the most part faster with the Steptronic. It's almost as if this car was built around that tranny.
I don't notice the a/c on at all with my steptronic. Shifting is consistantly smooth with or without it on. Engine speeds between shifts do not change. In short - one does not notice any difference in engine power/smoothness.

In my old e36 m3 ...oh yeah, you felt it kick in even while at highway speeds...car would slow for a second when you turned it on, needless to say I rarely used the a/c.
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      06-16-2007, 11:53 AM   #9
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Yes, I can tell when the AC is turned on. The revs must drop faster during shifts so this requires more attention to be smooth.
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      06-16-2007, 11:57 AM   #10
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I notice the same thing... I try to keep the AC off as much as possible.
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      06-16-2007, 03:32 PM   #11
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Quote:
Originally Posted by epiphone3 View Post
I notice the same thing... I try to keep the AC off as much as possible.
+1

They need to make a/c run off the electrical system, not the engine.

-Dan
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      06-16-2007, 03:51 PM   #12
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Quote:
Originally Posted by danimal View Post
+1

They need to make a/c run off the electrical system, not the engine.

-Dan
it is much worse ...
in this case the a/c will take the power from the generator that of couse
will take the same power off the engine (becaming harder to spin as you
request more current). Not only, since the generator has a 80%
efficency you will loose ... after this your 'electric' A/c will require a compressor (another electric motor ...).

Attaching the compressor directly to the engine is actually the most
efficent option

fdc
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      06-16-2007, 03:54 PM   #13
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never noticed this....
i guess i usually shift higher than 3500 rpm....
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      06-16-2007, 04:12 PM   #14
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I got the cdv delete. Now it shifts like a hot knife through butter. Even with the AC on
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      06-16-2007, 06:12 PM   #15
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Quote:
Originally Posted by fdc View Post
it is much worse ...
in this case the a/c will take the power from the generator that of couse
will take the same power off the engine (becaming harder to spin as you
request more current). Not only, since the generator has a 80%
efficency you will loose ... after this your 'electric' A/c will require a compressor (another electric motor ...).

Attaching the compressor directly to the engine is actually the most
efficent option

fdc
I'm not an electrical engineer, so I can't really debate you on the details, but I know the a/c on hybrids tends to be electric (since the engine is frequently turned off) and electric power steering is popping up on all types of vehicles, so it's definitely possible. Electric a/c may require a higher voltage electrical system or a larger battery, but those things are likely to appear anyway with the increasing use of electronics in vehicles.

-Dan
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      06-16-2007, 09:12 PM   #16
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Quote:
Originally Posted by bmw0perat0r View Post
I don't notice the a/c on at all with my steptronic. Shifting is consistantly smooth with or without it on. Engine speeds between shifts do not change. In short - one does not notice any difference in engine power/smoothness.

In my old e36 m3 ...oh yeah, you felt it kick in even while at highway speeds...car would slow for a second when you turned it on, needless to say I rarely used the a/c.
Quote:
Originally Posted by TRZ06 View Post
You know I never thought I would say this, but with this particular car and this particular auto tranny....

This car is better driving and more user friendly and for the most part faster with the Steptronic. It's almost as if this car was built around that tranny.
This is the same for AT, you guys don't notice the powerloss because you are already being "shielded" from the torque-converter.

AT usually gives up 10% to 15% of the engine power compared to MT as a result of powerloss in the torque-converter.
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      06-16-2007, 10:57 PM   #17
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i posted this same topic a couple months ago, check it out
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      06-16-2007, 11:15 PM   #18
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Quote:
Originally Posted by danimal View Post
I'm not an electrical engineer, so I can't really debate you on the details, but I know the a/c on hybrids tends to be electric (since the engine is frequently turned off) and electric power steering is popping up on all types of vehicles, so it's definitely possible. Electric a/c may require a higher voltage electrical system or a larger battery, but those things are likely to appear anyway with the increasing use of electronics in vehicles.

-Dan
FDC's right

with AC the way it is now, you have a certain amount of engine power that is required to turn the AC compressor

if you had an electric AC compressor, you'd need electricity, which is made by the alternator, which is spun by the motor. So if you needed electric AC the alternator would draw more energy from the motor

turning mechanical energy into electrical energy is not a %100 efficent process, so if you had an electrical AC compressor your engine would have to work harder than if you had a standard mechanical AC compressor
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      06-17-2007, 12:27 AM   #19
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i just tried to avoid the ac just because i know its going to change the car's performance
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      06-17-2007, 12:31 AM   #20
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Wow, having Step, I've never experienced this, but it sounds like a pain in the ass, any way to fix it for you 6mt guys?
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      06-17-2007, 12:54 AM   #21
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i noticed this with my ac on as well. but i figured since the ac was on it was normal. and sine everyone else is posting about it i guess it is.. i cant shift was smooth..
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      06-17-2007, 01:36 AM   #22
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drive with window down =P
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