my theory on all these tranmission issues

[Kirby]

I was thinking about the electronic throttle controls on our cars. There is going to be some inherent lag in the system just because of what has to happen:
1. Accelerator pedal sensor changes position when pedal moves (hardware)
2. New sensor position is processed by computer (software)
3. Resulting commands cause changes in engine management settings (hardware and software)

This process will introduce some transport delay from the initial hardware input to the resulting engine/transmission output. I don't what the spec is for this but I could see it in the range of a 125 ms to 250 ms response time as being acceptable.

Imagine the blank stare you would get from a service advisor if you started talking about this.......

Hehe - Right on. In addition to the processor and electromechanical delays you mention, part of the process you describe is known in the control world as a PID (Proportional Integral Derivative) Control loop. It's the math behind part of the process you described and controls how quickly the output (throttle) responds based on the input (pedal). If the loop is too aggressive, the output overshoots the target speed, surges, etc. If it is too conservative, there is a noticeable lag in the response. Another good example of a PID loop is your cruise control.

I can just imagine the SA's expression if I went in and told them the throttle PID loop is tuned poorly!

 

[bmwrocks]

Thanks Kirby for explaining the feedback control loop. I would bet BMW engineers monkeyed around with the feedback loop and this is the best they could do given the cost limits and sensors they have available.

BTW driving this morning I tested the "lag" some more and it is really not an issue at all. The throttle response is virtually instantaneous after the car is warmed up. It does seem to lag a little bit more when ICE cold but I bet this can be attributed to the feedback loop when fed with cold engine parameters.

 

[wallace]

Slip Problem

I have that problem in the morning with my car. 2004 330ci. I am having problems with my dealership helping me. Have the general manager calling me tomarrow. I bought a bmw with yugo service. They are trying to say it is normal!!!! I don't want this car. This many problems at 3000 miles, what is going to happen at 50 when my warranty is up. I have had other cosmetic problems, also. Does anyone have any suggestions on what I can do.

 

[wallace]

From above, I have the problem where you back up and the car will sit for awhile before you can go, when you put it into drive.

 

[bmwrocks]

My car doesn't have the problem (THANG GOD), but I have read on this forum that BMW recognizes this as a problem, so I don't know what your dealership is thinking.

Read this thread:
http://www.bmwboard.com/forum/showthread.php?s=&threadid=2959

Can you list your other problems?

 

[wallace]

Other small problems: seems like left speaker is always blown. they said they replaced it. Lip around window seal fell down, lights in trunk don't always come on, and can't get the clock to come on the radio anymore, yes I have read the mannual.

Talked to the GM today, ordering a new transmission. After 3000 miles. I have been a BMW freak all my life. I still stop in a parking lot and look at older beemers. Now that I can afford one, my car is a piece of s*&(. I have 1999 4runner with 120,000 miles that has been in the shop less.

I should of bought a used M3, they seem to put more care into those cars. Is the flat 3 series the red headed step child?

 

[MyHarley]

I was questioning my decision in purchasing a 2003 versus a 2004.........but in hindsight, it was the best decision.........my only problems have been in components of the car that BMW does not make.......so I guess some of us should count our blessings......

Wallace, Kirby and everyone else with the tranny problem, what does BMWNA say when they call you on the survey......obviously you have gotten several survey calls by now??

 

[Kirby]

The survey questions that I was asked only addressed the dealer's level of service and my satisfaction with the dealer. None of the questions ask about satisfaction with BMW quality. I point out at the end that I am very satisfied with the dealer, it's the BMW product quality I am unhappy with.