any manual owners find down-shifting not as smooth when using A/C?

Bamaben · 07-11-2011, 01:44 PM

kind of hard to describle, but when the ac is on and I downshift and let out the clutch, it seems to clunk a little or not let out as smoothly..maybe this has to do with the load on the engine and i'm not matching rev's good enough? anyone else know what I'm talking about?

Foxcolt · 07-11-2011, 03:03 PM

Turning on AC does place a small amount of extra load on the main crank pulley (where the AC belt attaches) but it's such a small amount that I would be very surprised if it would affect the way you downshift.

Without AC you would have to be rev matching so perfectly that when you turn on it on that tiny amount of extra stress would cause the RPM's to drop such a small fraction of an amount faster that it would mess up your rev matching....you are either

A: A robot

B: related to Mario Andretti

Kidding aside, try rev matching at a slightly higher rev depending on your speed/gear, if that gets rid of the thunk then you'll know it's the AC.

tres · 07-11-2011, 03:11 PM

i find shifting is a little jerky with the ac on so i just compensate by pressing the the gas pedal down a little more

MusclezMarinara · 07-11-2011, 03:14 PM

its the CDV take it out

achien · 07-11-2011, 03:17 PM

you need to give more throttle and rev the engine up more before you shift...

Quote:

Originally Posted by Bamaben

kind of hard to describle, but when the ac is on and I downshift and let out the clutch, it seems to clunk a little or not let out as smoothly..maybe this has to do with the load on the engine and i'm not matching rev's good enough? anyone else know what I'm talking about?

CJ421 · 07-11-2011, 03:19 PM

Yes there is a small difference when you use AC.

Solution: shift faster

And get rid of the stupid CDV.

Bamaben · 07-11-2011, 03:35 PM

Quote:

Originally Posted by tres

i find shifting is a little jerky with the ac on so i just compensate by pressing the the gas pedal down a little more

I think 'jerky' is a better description of what I'm experiencing..like when I don't exactly rev match well enough (or at all ) at lower speeds and just shift down from 4th to 3rd and let out clutch.. I do really need to get rid of that CDV.. is BAVAUTO the best place to get a hollowed out one?
thanks!

TOPEC · 07-11-2011, 03:35 PM

Quote:

Originally Posted by Foxcolt

Turning on AC does place a small amount of extra load on the main crank pulley (where the AC belt attaches) but it's such a small amount that I would be very surprised if it would affect the way you downshift.

Without AC you would have to be rev matching so perfectly that when you turn on it on that tiny amount of extra stress would cause the RPM's to drop such a small fraction of an amount faster that it would mess up your rev matching....you are either

A: A robot

B: related to Mario Andretti

Kidding aside, try rev matching at a slightly higher rev depending on your speed/gear, if that gets rid of the thunk then you'll know it's the AC.

hes right, with the ac on the load causes the engine to drop rpm a tiny bit faster

ull have to either a: shift faster and let the clutch out faster before the revs drop, or b: rev a bit higher to compensate for the rpm drop

07-11-2011, 01:44 PM	#1
Bamaben Major 183 Rep 1,082 Posts Drives: 07 335i blk/blk/alum 6MT Join Date: Jun 2010 Location: Bimmertown iTrader: (0)	any manual owners find down-shifting not as smooth when using A/C? kind of hard to describle, but when the ac is on and I downshift and let out the clutch, it seems to clunk a little or not let out as smoothly..maybe this has to do with the load on the engine and i'm not matching rev's good enough? anyone else know what I'm talking about? __________________ It takes a big man to cry. It takes an even bigger man to laugh at him-- Jack Handey mods: blackout grill, finishing rods, badges, Blacklines.
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07-11-2011, 03:03 PM	#2
Foxcolt Private First Class 3 Rep 109 Posts Drives: AW E92 Join Date: Apr 2011 Location: VA iTrader: (2)	Turning on AC does place a small amount of extra load on the main crank pulley (where the AC belt attaches) but it's such a small amount that I would be very surprised if it would affect the way you downshift. Without AC you would have to be rev matching so perfectly that when you turn on it on that tiny amount of extra stress would cause the RPM's to drop such a small fraction of an amount faster that it would mess up your rev matching....you are either A: A robot B: related to Mario Andretti Kidding aside, try rev matching at a slightly higher rev depending on your speed/gear, if that gets rid of the thunk then you'll know it's the AC.
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07-11-2011, 03:11 PM	#3
tres Major 34 Rep 1,381 Posts Drives: 2011 bmw 335is 6MT Join Date: Apr 2009 Location: maryland iTrader: (6)	i find shifting is a little jerky with the ac on so i just compensate by pressing the the gas pedal down a little more
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07-11-2011, 03:14 PM	#4
MusclezMarinara Banned 263 Rep 5,018 Posts Drives: VALNCYA Join Date: Jan 2009 Location: Jersey iTrader: (23) Garage List 2011 BMW 1M [9.22] 2009 335i Sedan xdrive [9.34]	its the CDV take it out
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07-11-2011, 03:19 PM	#6
CJ421 Brigadier General 1567 Rep 4,109 Posts Drives: BMW M3 Join Date: Feb 2011 Location: Blue Bell, PA iTrader: (1) Garage List 2024 BMW M3 Sedan [9.50]	Yes there is a small difference when you use AC. Solution: shift faster And get rid of the stupid CDV. __________________ 2024 BMW M3 Sedan Frozen Pure Grey II/Fjord Blue, 6MT Past: 2021 Z4 M40i Frozen Grey II/Black Alcantara \| 2017 F30 340i Mineral Gray/Coral Red, 6MT \| 2011 E92 335i Le Mans Blue/Black, 6MT
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