Is this what the CDV does?

[azroadie]

My z4 is my first manual car so I can drive it really well without any jerkiness as I don't have prior habits to break. So I didn't think I needed to mod the cdv. But there's one thing that I've noticed and am now wondering if the CDV is the cause.

When I'm at a light or making a turn and decide I need to pull out very quickly from a stop, my car doesn't respond! I simultaneously press on the gas pedal and quickly release the clutch. To my surprise, the car just sits there for about a second before accelerating!?! Keep in mind that the gas pedal is to the floor and my foot is completely off the clutch (I've tested this in safe conditions.) I understand that there won't be much power as the rpms are very low. But the car just sits there! I don't think its the DSC and no lights come on. The first time I noticed this behavior, I thought I was going to get sideswiped by oncoming traffic since my car didn't go when I asked. Very scary!!!

So my question is...is this the CDV taking it's good old time to engage? And is this causing the hesitation before acceleration begins??

I'd really like to get this sorted out. They're redoing all the roads in my neighborhood over the next year so pulling into traffic is a nightmare. So I need the car to go when I want it to!!! It's way too dangerous. Thanks!

 

[Curtis]

It sounds like it could be the CDV, some seem to be worse than others. My 330 used to slip the clutch like crazy if I tried to do a quick getaway but the Alpina wasn't too bad. Needless to say they've both been removed now!

 

[pvr]

If the clutch was slipping, the revs would be very high though which he said they were not though?

 

[ovrkll]

Sounds a bit odd to me :scratchhead: Are the RPM's increasing at all?? If not, then there is something going on with your throttle position sensor.

 

[azroadie]

Sounds a bit odd to me :scratchhead: Are the RPM's increasing at all?? If not, then there is something going on with your throttle position sensor.

That's a good point that I forgot to mention. The RPMs don't increase. I'll have it floored, foot off the clutch, there's a second or so pause, then the car seems to rev normally from zero...just VERY delayed.

So if it was the CDV causing the delay, the rpms should still be increasing right?

 

[AlanL]

Clutch Delay Valve does exactly what it's name implies and nothing else. It simply slows down the engagement of the clutch relative to how fast you dumped the clutch pedal. It has no effect on the throttle whatever so if your engine revs are not doing what your right foot asked your engine to do this is another matter entirely.

The most likely impact of the CDV in the situation you describe would be for the engine to rev wildly waiting for the clutch to engage......

 

[WaZZZZman]

Clutch Delay Valve does exactly what it's name implies and nothing else. It simply slows down the engagement of the clutch relative to how fast you dumped the clutch pedal. It has no effect on the throttle whatever so if your engine revs are not doing what your right foot asked your engine to do this is another matter entirely.

The most likely impact of the CDV in the situation you describe would be for the engine to rev wildly waiting for the clutch to engage......

I agree it is not a clutch issue. Also poor driving practice. "Clutch out-throttle in evenly". No jerking or popping unless you really really like paying for big ticket repairs. Yes Father yes father. I know no fun!!!

 

[flyboyaj]

My car does this too. I always thought it was the DTC doing it's thing and I've learned to overcome it by just being smooth but aggressive with both pedals. I let the RPMs rev a bit then smoothly but without hesitation release the clutch and simultaneously increasing pressure on the gas. When I do it this way I almost always get a little squak of the tires followed by a rocketing sensation. I've been practicing doing it without getting the squak and about 1/3 of the time I'm successful.

 

[Curtis]

Sounds a bit odd to me :scratchhead: Are the RPM's increasing at all?? If not, then there is something going on with your throttle position sensor.

That's a good point that I forgot to mention. The RPMs don't increase. I'll have it floored, foot off the clutch, there's a second or so pause, then the car seems to rev normally from zero...just VERY delayed.

So if it was the CDV causing the delay, the rpms should still be increasing right?

I didn't realise the revs didn't increase. Your in a whole different ballgame then. What happens when you sit stationary and just blip the throttle pedal, does it respond instantly or do you still get this delay?

 

[2dogs]

My car does this too. I always thought it was the DTC doing it's thing and I've learned to overcome it by just being smooth but aggressive with both pedals. I let the RPMs rev a bit then smoothly but without hesitation release the clutch and simultaneously increasing pressure on the gas. When I do it this way I almost always get a little squak of the tires followed by a rocketing sensation. I've been practicing doing it without getting the squak and about 1/3 of the time I'm successful.

Mine the same I just set the revs just before I lift the clutch
I must say I a lot lot better in sport mode (now iv found it!!!!
"not going to go in to that") :shutup:

 

[flyboyaj]

Yep, with Sport mode engaged the gas pedal is way sensitive and I always get major squak and DTC light flashing on takeoff. Hell, I got the DTC light flashing last night around a corner @ 30mph in third gear on dry pavement!!! This baby's got some major low end ponies. Well, that or maybe I stumbled into a little dirt pile in the curve. I'm starting to get to the point where that light annoy's me and I may just turn the DTC off (half way only of course) for everyday drives. Bad news is that I've been averaging around 24 mpg lately... I just can't seem to lay off the gas pedal :evil:

 

[mikedav]

When I'm at a light or making a turn and decide I need to pull out very quickly from a stop, my car doesn't respond! I simultaneously press on the gas pedal and quickly release the clutch. To my surprise, the car just sits there for about a second before accelerating!?!

To me this sounds exactly like you are giving it too much right foot with the DTC on. Perhaps your DTC light is dead? DTC cuts the power when the wheels are spinning, so nothing happens. Then when they regain traction it gives you power again. So if you floor it too much off the line you get that 'wheres-the-power-jaysus-thats-a-big-truck-coming-at-me-on-the-right-oh-my-god-I-am-going-to-die' moment. But then you could argue that wasn't a safe point at which to pull out anyway...

To avoid it turn the DTC off, but then you get a whole new set of challenges and getting sideways will be very easy. Kinda half the fun of a RWD BMW but not what you are looking for me thinks! To get instant grip off the line no matter what revs you give it, you need AWD. Which is boring.

 

[azroadie]

Now if I rev up the engine to a couple thousand RMP, I don't get this effect. In fact, I can easily get wheel spin and get the DSC light to come. It really only happens when I floor it. It very much feels like the DSC is kicking in, I just don't get any lights coming on like normal. Could it be the the DSC is kicking in because I have it floored (and limiting torue), but the light isn't coming on because there is no wheel spin or slipping? I could see this being possible.

I may go to a safe area and so some testing. Good excuse for some burn outs right!!

 

[flyboyaj]

Sounds like problem solved to me

 

[Aebous]

Yay!!!