jsal

Clutch performance was significantly improved. I was finding it very difficult timing my clutch/gas in order to have smooth shifts - especially under heavy acceleration. The CDV screws that up, becuase it adds a slippage or delay when engaging the clutch. Also, under very slow movements, like parking, it is smoother. Now, when you let the clutch out to engage, you have control over the engagement point. It took a little bit to re-learn my timing, but now I get smooth shifts.

I do a lot of my own stuff also, but I was unsure of this task and bleeding the clutch, so I took it to a independent BMW mechanic. It was a fairly easy job. The hardest part was getting access to the brake/clutch fluid, which we did not need to do (only if you get air in the system and need to bleed it).

You need to remove the chassis cover which has about 15 screws. It was easy on a lift but would be difficult otherwise. We clamped the clutch hose so as not to leak/lose fluid. Then it is just a matter of replacing the valve.

My guy did not lose any fluid so we did not need to bleed the system. The whole job takes less than an hour as long as you don't have to bleed the system.

jsal

Yes, I guess the CDV could be the important unknown. I have no idea if my car has one, whether or not an unmodified 545i with one would behave similarly or not, and the modified CDV 545i cars throw yet another wrinkle in...

I can say with certainty however after numerous "tests" that during normal leisurely driving either the throttle or the clutch is somehow easier to operate on my car. It's as if when DSC/DTC are enabled, the computer is retarding the throttle application or softening it, which might be a self-preservation measure for general longevity.

I notice it most during leisurely standing starts and 1st to 2nd shifts.
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You can checkout / contact in order to find out if your car has the CDV:

http://www.zeckhausen.com/CDV.htm

rollee

UUronL i know exactly what you mean. i too found the car to be more 'juicy' when DSC is off.
seems like the power transfer is m ore instantaneous and torque increased.

i had DSC switch off since day 1 after i noticed the effect, and have forgotten this factor. thanks for bringing it up again.

clived

Those of you who say you're turning DTC off. When you press the DSC button once (on my car at least) you ENABLE dynamic traction control (dynamic being the important word here - you're enabling the "dynamic" bit - allowing a little slip, rasther than the standard mode of trying to eliminate slip) and RESTRICT DSC. I find this a great mode for pushing on, without losing the safety net altogether. Are you guys saying you're holding the buttong down to turn it all off completely? If so, have you even tried the "middle" mode?

rollee

i press and hold. all off.
no alphabet soup assist whatsoever.