Drive-by-Wire throttle question...

[George M]

A question that is hard to know the answer to unless you have studied it and I haven't. This applies to late model Bimmers with Steptronic transmissions.
Most know that have driven a step that the kickdown switch will supercede the Steptronic manual shift mode. If you floor the car in manual shift mode, depending what gear you are in, the car will downshift as with Sport and Drive modes. Here is the question. Does anybody know if right at the point of depressing the kickdown switch...just before, if the throttle body is wide open? Or...is the throttle butterfly in the electronically controlled throttle body only wide open beyond the kickdown when the pedal is all the way to the floor? The reason I ask is when driving the step in manual mode and getting on it...I many times prefer to be in a taller gear then what kickdown would provide. I wonder if the throttle is wide open just before kickdown or if there is more throttle left after the kick down switch is depressed.
Anybody know?
Thanks,
George

[632 Regal]

I wouldnt know for sure but on the E31 it seems that the throttle opens a bit more after the kickdown is depressed, kind of like the regular throttle cable cars are. How I could tell was when I was holding a lower gear and testing the operation, delay from peddle action and how long it seemed for the throttle bodies to fully open up. Im sure you can get a realistic answer by checking resistance in the peddle end of it.

just a guess...

[winfred]

i am only really just getting into the e46s but most of the ones i get in are not step, some cars have a throttle cable and a eml servo can override your input and others are pure eml so it may depend on the type

[George M]

Thanks guys. I will tell you why I have interest in this. I own an E-46 330Ci with Steptronic. I like the trans and the car. The Step is a tradeoff as most know...whether to purchase an auto versus stick and after seeking a lot of advice, including Bill R etc, I chose the Step which I have no regret. It is a great trans and shifts beautifully. There is an opportunity for improvement however. As I see it, one of the failings of the design is in Manual mode. On occasion, I like to select my own gear. This is particularly desireable for downshifting onto on-ramps etc and staying in a particular gear which is fun. The issue with the Step even in manual mode, is if you floor the accelerator, the car will kickdown into a lower gear if you are cruising in a higher gear in Manual mode. I don't like this feature. I like kickdown in both Sport and Drive modes...where it belongs...but more control is warranted in Manual mode. Now...a thought is...the kickdown switch can be disabled in Manual mode with the Steptronic. The question is, how efficiently can this be performed? I believe it would be quite easy with a discrete switch...simply open the kickdown switch circuit in Manual shift mode. But this isn't the most elegant solution. Best practice would be to wire a relay to the shifter to open the circuit when the shifter is shifted in Manual mode. But this is quite complex. Why? Because Manual and not Sport mode is only enabled when you move the shift lever forward or aft. I could devise a by-pass to the kickdown switch in Sport mode I believe pretty easily by wiring a relay to the lever itself, such that when the lever is pivoted to the left to engage Sport mode, the kickdown is disabled. But...most including me want kickdown in Sport mode...we just don't like it in Manual mode. Wiring the kickdown disabled in Manual mode is much more complex because the only way to initiate Manual mode is with fore/aft movement of the shifter in Sport mode. And so it goes. Since wiring a bypass to the kickdown switch to the Manual feature of the trans is difficult, I may very well have a separate switch to flick when in Manual mode if I want this feature as I can't figure out another way to do it.
Any suggestions are welcome.
George
P.S. Winfred, do you know if the wires to the kickdown switch are accessible on the E-46?...ever been down there poking around the gas pedal? I know that manual cars do not come with the kickdown switch but presume the wiring harness is there.