Valved Exhaust wired to M button?

[Thumbie]

Is it possible? Is it practical? Is it a waste of effort?

Seems pretty nice to just press one steering wheel button.

To make it work, there'd have to be some type of signal from the computer that is controlled when in m-sport mode. One that you could tap into to control a switch of some sort. Does that exist? The rest would be just like normal.

Why? just wondering if it's possible.

[Shirazkhan]

Possible yes.Waste of time and energy,my opinion.

[MineralWhiteF80]

The potential problem you could run into is interfering with the M button's primary function of switching driving modes.

The M button's standard operation does not function as a normal switch per se. Instead, depressing the M button triggers the SZL module (clock spring, steering angle sensor thing behind the steering wheel) that a change is necessary, and the SZL module sends an "on/off packet" through the car's CAN network to the DME (car's ECU) to change the driving mode.

I know the actual M button is a simple switch that completes a basic circuit to the SZL to signal a change request, so it may be possible to splice into the actual switch wiring.
What I don't know is what happens if you add a simple power or ground circuit into the factory M button circuit between the physical steering wheel button and the pins on the SZL, and what it could do to the SZL->DME CAN bus communication.

You also have the issue of running new wires and 'bridging the gap' between a rotating steering wheel and fixed steering column.

[Thumbie]

Hmmm ok. Just was something I was thinking about the other day.

I wonder if there's something out of the steering column and on the ECU that you could tap into...but MineralWhite's comments about adding voltage is basically telling me to stop thinking about this. I have heard these cars are very sensitive to the slightest change in voltage. Moving on then. Appreciate the insight.

Another idea: I installed coilovers and coded out EDC. Maybe using the now-unused EDC button would be better.

Overall this idea came from minimizing buttons to press.

[Shirazkhan]

Now thats an idea.And just get another button 3d printed and rename it.Would be unique,but then again why?1day when u want to put everything back to stock,will be easy if u keep it original.

[GinTonic]

If you have homelink, you can just program the signal to that. No reason to complicate it.

[Brandoch]

Originally Posted by GinTonic

If you have homelink, you can just program the signal to that. No reason to complicate it.

Cool idea!

[tighfitzgerald]

Originally Posted by Thumbie

Is it possible? Is it practical? Is it a waste of effort?

Seems pretty nice to just press one steering wheel button.

To make it work, there'd have to be some type of signal from the computer that is controlled when in m-sport mode. One that you could tap into to control a switch of some sort. Does that exist? The rest would be just like normal.

Why? just wondering if it's possible.

A very cool idea. I'm going to start working on this immediately. I'll be in touch.

[Ajolives]

Originally Posted by GinTonic

If you have homelink, you can just program the signal to that. No reason to complicate it.

Same here, I also had EDC and was gonna reuse the button or add one near the seat warmers. The garage door opener button takes about 30 seconds to set up, no wires or coding.

[nycplumber]

Originally Posted by GinTonic

If you have homelink, you can just program the signal to that. No reason to complicate it.

how is that done?

[Thumbie]

I wish I had homelink, I saw elsewhere people have done that.

I think EDC button is the move.

This guy set up his cutouts to a spare button next to the auto start/stop, also a clean option. Or the rear sunshade I guess but same button bank, depending on your M3.


Overall, some good options besides using whatever aftermarket button comes with the exhaust. Or a tacky key fob. Wait, is the key fob how you program to homelink??

[Redd]

This is what I did. I think it looks quite OE+. I wanted a button which I could see if it was enabled or not. You can buy the button off AliExpress.

https://a.aliexpress.com/_onjorcy

[Thumbie]

I like that button. I saw you post that in another thread.

[chocstraw]

There's room for it on the steering wheel and you could easily disassemble the button and use it as a traditional gating switch, which likely would't interfere with function, but all steering wheel data gets sent through the clock spring, which is a long ribbon cable that allows it to function throughout the rotation of the wheel, you'd have to route and hide a bunch of extra cable length so it doesn't break. if you check my thread, I used a dummy button under the CD slot, where the auto start stop button is / power rear sunshade / heated seats on older model years.

[Thumbie]

Yes I did see your thread and really like what you did. I believe what you did may be the cleanest option.

[Green-Eggs]

The M button emits a message on the PT-CAN bus. My friend may know what it is, but I don't. Getting a sniffer on the PT-CAN bus is easy to wire in and there are DIY's out there for that. You can sniff the PT-CAN for the message, then trigger a 5V output which would then control your valved exhaust. It's actually pretty easy, but you have to be very tech and electronics savvy to do it.

[Green-Eggs]

I asked...here's what I got.

M Button is part of the steering wheel buttons group on the PT-CAN bus.

Function: M-Button pressed
PT-CAN Address: 0x1D6
Start location: bit-14
Size (in bits): 1

Hook up a can bus sniffer to the PT-CAN bus, and you can see this bit toggle when you press/release the M-Button. What you do with it...is up to you.

[Thumbie]

Damn ok there we go!! Thanks, boss.