Throttle or clutch?

[11135i]

Just picked up a used 135i but I'm a bit baffled by the clutch setup on this car. It seems like I can't seem to shift smoothly in this car. The throttle seems to hang for a bit too long whenever I disengage the clutch. Is it just me? Or is this the symptoms of a wonky clutch?

[akak1997]

it's the clutch delay valve, all stick shift BMW has it. search for CDV mod or CDV Delete.

[Tom K.]

I haven't noticed the "throttle" hanging symptoms you described since trading my '97 Z3 - and I've owned 4 MT BMWs since, all with the CDV intact.

Sounds to me that there may be an issue with the engine management electronics, rather than the clutch.

(Also, I assume that you are completely releasing the throttle prior to disengaging the clutch and that your floor mat is not getting in the way of either gas or clutch pedals.)

Tom

[Vorsprung_CJB]

Never noticed a problem that seemed like the CDV, but I found after getting a clutchstop my shifting was much smoother, no more hunting for the engagement point so I could match revs perfectly.

[11135i]

I guess the engagement point is just really really muddled, it just seems incredibly "mushy" trying to find the engagement point.

The throttle also doesn't seem nearly sensitive enough as when I release the gas, there seems to be a split second where it'll hang and I'll see my RPM surge when I've already engaged the clutch. Previous car was also a DBW but that one actually felt like there was a wire and would respond instantly to my gas inputs and releases.

Seems like two separate issues that are muddling my experiences right now.

[hondaluvr1985]

My 2011 does the same thing. RPMs hang for a second or two before dropping. My '09 did not do this do I am a bit concerned. Anyone have an idea?

The CDV is the root of your shifting ailment...night and day trust me...and the 1000s of others- get rid of it!!!!

[That Guy's Alter Ego]

I swapped the CDV to Zeckhausen Racing on my 2005 Z4 3.0i and thought, yeah, that made a bit of a difference in feel and smoothness. But when I swapped the CDV to Zeckhausen in my 135i the difference was night and day. Much much bigger improvement than I imagined it would be. I can actually feel the pressure plate now. I can modulate engagement.

I'm not affiliated with Zeckhausen in any way, but my experiance has been positive.

[RPM90]

Originally Posted by 11135i

I guess the engagement point is just really really muddled, it just seems incredibly "mushy" trying to find the engagement point.

The throttle also doesn't seem nearly sensitive enough as when I release the gas, there seems to be a split second where it'll hang and I'll see my RPM surge when I've already engaged the clutch. Previous car was also a DBW but that one actually felt like there was a wire and would respond instantly to my gas inputs and releases.

Seems like two separate issues that are muddling my experiences right now.

The engagement point is a bit different in BMW manuals, but it's not really muddled. It's always in the same place, you just need to find it and commit it to memory.
Get a clutch stop, it really helps with making the friction point feel as if it's closer to the clutch stop point. Stock position has at least 1" of dead space.
A CDV mod might help a bit, but it only regulates the rate at which the clutch fluid moves and doesn't affect the actual engagement point
It can speed up the time it takes for the clutch to engage once you release the pedal. That may help you during a shift if you get on the throttle quicker than when the clutch actually grabs.

BMW manuals are a bit "odd" per se. It takes a bit to get used to the clutch travel, and especially the engagement point of the actual clutch itself, as translated through the pedal.
There is a good bit of dead space/travel in the clutch coming off the floor.
In an empty lot, try finding the actual engagement/friction point of the clutch. It'll give you an idea of how to then time your throttle inputs.

In my last 2 BMW's I never experienced any "hanging" of the throttle.
If you push the clutch pedal all the way in, which disengages the clutch, and you've let go of the throttle, engine rpm should start to fall fairly quickly. If the engine rpm hangs there for more than a 1, 2 count then one of two things could be happening.

1, you might be pushing in the clutch pedal before you release the throttle.
If so, then the rpms will rev up a bit as you're still on the throttle when the clutch disengages. That indicates you are not releasing the throttle early enough.

2, if you are releasing the throttle and then push the clutch in and the revs are hanging there, that could indicate an actual mechanical problem.
When I've encountered this in my cars or other cars, it's usually related to an intake leak somewhere. It can indicate a lean a/f condition where unmetered air is getting into the intake.

In the above post, you say that after shifting gears and releasing the clutch pedal there is an engine rpm surge.
This too can be a shift timing issue where you may be getting on the throttle too quickly before the clutch is fully engaged.
If that is the case, then you are going to wear out your clutch as that symptom is indicative of clutch slip.

You can't stab at the clutch too quickly, shift, and hit the gas like you can in say a Honda manual trans where the clutch travel is very short and the friction point is nearly right off the floor or stop.
In a BMW you have to be deliberate, but you can be fast too, just get a feel for the timing of all of it.

If you are sure you're not mistiming the shifts, then maybe your clutch is actually slipping.
Once the clutch pedal is fully out, the clutch is engaged. You should freely be able to apply throttle and the car should move forward with no hesitation or slippage or rpm surge.
If the clutch is engaged and you're getting a rise in rpm without equal forward movement, then it could be a clutch problem.

It's possible that 2 problems are happening at the same time, an intake leak and a slipping clutch. But, it's more likely you need to adjust your shifting technique.
Slow down, and get a feel for how the clutch engagement point and the DBW throttle respond. Once you get it it'll become second nature and you'll love the car even more.

[daMau]

I also vote for a clutch stop and CDV delete. Just finished both of these on my 135i and I agree with those who say the difference is night and day. I have no idea how anyone can accept the CDV in a car that is otherwise engineered so beautifully.

[MZWIE]

CDV and DBW throttle make for a very bad combo.

[11135i]

Wow, thanks for all the responses and feedback. I think I might end up going the CDV replacement route, is there any place that has the Zeckhausen CDV besides their actual store? It seems I want a consistent and precise engagement point and the stock CDV seems to be pointing to one of my current woes.

Thanks again for everything.

[GaryS]

Originally Posted by 11135i

The throttle seems to hang for a bit too long whenever I disengage the clutch.

That is not the CDV that you're describing. It is the heavy flywheel. Just get used to it, because it's too expensive to change until you need a new clutch.

...adding: Several vendors sell a modified CDV. Here's one: http://www.burgertuning.com/bmscdv.html

[JimD]

I would drive it awhile before modifying it. You did not mention your experience with a manual transmission but I wonder about those who find the BMW difficult. I've been driving for nearly 40 years now and most of my cars have been manuals. My 128i vert is as easy to drive as any car I have driven (including a 911 Carerra). I switch back and forth almost daily between my bimmer and my manual transmission SUV. They have different feel and clutch placement and the SUV is a 5 speed. I think it might be harder if both were cars - the SUV feels different from every perspective. But I drive them both smoothly (most of the time). People riding with me have commented they did not realize the vehicle was not an automatic. I also carry on normal conversation while shifting, it is just pretty automatic at this point.

Shifting is mostly a timing thing. I don't really stop moving the clutch. It is just in and back out with the gear selector moved at the appropriate time. CDV probably helps your shifting be smooth once you get used to it but it's main purpose seems to be prolonging the life of the drivetrain when you get more energetic with it.

I think the hardest thing is to get going on a fairly steep hill without having to over rev the engine and come back down. I ususally do the over reving routine on my SUV because I don't want to kill it. The hill hold on the bimmer helps as does the relatively torquey 6 cylinder. I almost always can start without feeling the need to over rev in the bimmer. It is an easy and fun manual to drive. Pedals are also much better positioned for heel and toe.

Jim

[Vectors2final]

I liked the hill hold assist on my WRX, it was pretty awesome. I've never had a problem with hills, but it's awesome to know you have it at your disposal.

[11135i]

Used to own an Integra GS-R and I'm hopping over from a Mazdaspeed3, got about 7 years experience with maybe close to 100,000 experience, both largely stock. I supposed I don't have much experience compared to others here but I'm finding myself to be really disliking this clutch. I just can't "find" its proper engagement point as my previous car's clutch was either fully engaged or not at all. My last car wasn't easy to drive smoothly but this one I feel like I'm almost learning stick all over again as I'm probably too paranoid for my own good sometimes.

The hill assist feature is a interesting little animal as I've never really had too much trouble with rolling back and I can catch cars usually quite well without over-revving as my house's driveway is close to a 45 degree angle so I've got quite a bit of practice of shifting my feet from brake to clutch+gas. No shortcuts here ^^.

[Dackelone]

Originally Posted by akak1997

it's the clutch delay valve, all stick shift BMW has it. search for CDV mod or CDV Delete.

+1. It is the CDV. Do the delete and you will be SOOOOO happy you did so.

Here is how... (just incase you don't know how to search!)

http://www.1addicts.com/forums/showt...cdv+delete+diy



Dackel

[11135i]

Originally Posted by Dackelone

+1. It is the CDV. Do the delete and you will be SOOOOO happy you did so.

Here is how... (just incase you don't know how to search!)

http://www.1addicts.com/forums/showt...cdv+delete+diy



Dackel

I was reading through that thread and I was wondering about your experiences as well, namely, I didn't understand what troubles you were going through when you punched through a spare CDV. It was something about the pins, but I didn't fully understand it as it has something to do with the pathways of the newly modified CDV?

[GaryS]

Originally Posted by Dackelone

+1. It is the CDV. Do the delete and you will be SOOOOO happy you did so.

He will be happier because the clutch engagement point will feel more precise, but the throttle will still "seem to hang" when he disengages the clutch. That hanging is caused by inertia of the heavy luxury flywheel that BMW puts in these cars. Lots of people in the E90 forum have solved this problem by installing lightweight performance flywheels. But they are expensive and can be noisy.

[GO135i007]

Definitely CDV. GEt rid of it and your issues will disappear.

[RPM90]

Originally Posted by JimD

I would drive it awhile before modifying it. You did not mention your experience with a manual transmission but I wonder about those who find the BMW difficult. I've been driving for nearly 40 years now and most of my cars have been manuals. My 128i vert is as easy to drive as any car I have driven (including a 911 Carerra). I switch back and forth almost daily between my bimmer and my manual transmission SUV. They have different feel and clutch placement and the SUV is a 5 speed. I think it might be harder if both were cars - the SUV feels different from every perspective. But I drive them both smoothly (most of the time). People riding with me have commented they did not realize the vehicle was not an automatic. I also carry on normal conversation while shifting, it is just pretty automatic at this point.

Shifting is mostly a timing thing. I don't really stop moving the clutch. It is just in and back out with the gear selector moved at the appropriate time. CDV probably helps your shifting be smooth once you get used to it but it's main purpose seems to be prolonging the life of the drivetrain when you get more energetic with it.

I think the hardest thing is to get going on a fairly steep hill without having to over rev the engine and come back down. I ususally do the over reving routine on my SUV because I don't want to kill it. The hill hold on the bimmer helps as does the relatively torquey 6 cylinder. I almost always can start without feeling the need to over rev in the bimmer. It is an easy and fun manual to drive. Pedals are also much better positioned for heel and toe.

Jim

Timing is key.

The other major point about the CDV is that it is specifically designed to SMOOTH out shifting, not to make it choppy.
But, it's make to do this when driving "normally", not so much in a very spirited manner.

Most manuals have these in them, and their intent is to smooth the shift.
So, I find it odd how many people point to it as the reason for their lack of proper shift technique.
Don't mean to offend, but being able to shift and operate a manual trans is much more important than blaming a CDV as to why shifts aren't smooth.

[RPM90]

Originally Posted by 11135i

Used to own an Integra GS-R and I'm hopping over from a Mazdaspeed3, got about 7 years experience with maybe close to 100,000 experience, both largely stock. I supposed I don't have much experience compared to others here but I'm finding myself to be really disliking this clutch. I just can't "find" its proper engagement point as my previous car's clutch was either fully engaged or not at all. My last car wasn't easy to drive smoothly but this one I feel like I'm almost learning stick all over again as I'm probably too paranoid for my own good sometimes.

The hill assist feature is a interesting little animal as I've never really had too much trouble with rolling back and I can catch cars usually quite well without over-revving as my house's driveway is close to a 45 degree angle so I've got quite a bit of practice of shifting my feet from brake to clutch+gas. No shortcuts here ^^.

If it's that bad, it's possible there is something wrong.
As I said before, the engagement point is not variable, it's always there in the same spot. The only difference is how one engages and times everything.

It sounds like you have the required experience to find the BMW's sweet spots. Have you had someone with experience with BMW MT's take your car for a test drive? That might help.

[11135i]

I feel it's varying as though it's not catching when I want it to. Guess a CDV mod is in order!