Electrical issues with manual conversion

[Slavvy 0]

Hey all. I'm new and I figured I'd get right to the point and ask about some nitty gritty technical stuff I have an '87 635Csi that I'm looking to manualise. I'm pretty familiar with old bimmers but I've never manualised an m30-powered car and before I launch into something stupid I wanted to make sure I have my facts straight. The trans and everything else is coming out of an '83 735i (a shame but it's too rusty and crap to continue rescuing). Both cars are motronic, neither has cruise control.

Two things concern me: firstly, what happens to the e24 if I just yank out the auto trans computer and everything associated? Will the warning lights go haywire, will the engine run at all? My assumption is it won't even notice but I really don't know. Google isn't very conclusive on this stuff. Related to this, how do I go about switching from the large, rubber-boot covered TPS on the auto engine to the simple little switch that the manual has? ie how do I wire up the manual TPS and will the e24's engine computer accept it at all? Finally, would there be any other electrical issues I'm not anticipating?

I'm sorry if this has been asked before or if I'm not being specific enough lol

[jochen 4]

Get the BMW electrical manuals for the donor car and the recipient car.

Compare wiring diagrams side by side.

That's the only way to stop fishing about in the dark

[BM WORLD 1286]

pretty straight forward on the old stuff.

make sure the donar gearbox and flywheel have the sensor trigger pionts as per the side left side of your auto box or the car wont run.

as far as the wiring goes you can remove the auto switchable wiring loom if you want (they unplug and have a couple of plug that just plug back together so it will start) . or just bypass the switch with a jumper wire etc.

call me if you are not to sure

021433600

[User Name 19]

Brent is you man - and i have the Conversion papers on how to remove the starter reley for the auto so the car starts PM if you need it

[Slavvy 0]

The starter relay and flywheel sensors don't worry me all that much, as I said my main concern is throttle position sensor, located on the throttlebody. Every manual car I've seen (not that many admittedly) has a small plastic thingy a few cm across, including my e23. Every old (pre e34/32) automatic I've seen has the big rubber booted sensor the size of a tennis ball, including my e24. I just want to know what I need to do to switch from the auto one to the manual one.

Edited for pictures:

Manual sensor

Auto sensor

Edited September 9, 2009 by Slavvy

[BM WORLD 1286]

The starter relay and flywheel sensors don't worry me all that much, as I said my main concern is throttle position sensor, located on the throttlebody. Every manual car I've seen (not that many admittedly) has a small plastic thingy a few cm across, including my e23. Every old (pre e34/32) automatic I've seen has the big rubber booted sensor the size of a tennis ball, including my e24. I just want to know what I need to do to switch from the auto one to the manual one.

Edited for pictures:

Manual sensor

Auto sensor

doesn't matter that you have the auto one .

it has 2 functions one function is to tell the ecu if you are full thottle or idle (both manual and auto switches have that part)

the other part is a varriable resistor to tell the auto ecu box where your foot is on the gas pedal so it can work out when to change gear etc .

so that part will just go no where important when you convert it to a manual.

[Slavvy 0]

doesn't matter that you have the auto one .

it has 2 functions one function is to tell the ecu if you are full thottle or idle (both manual and auto switches have that part)

the other part is a varriable resistor to tell the auto ecu box where your foot is on the gas pedal so it can work out when to change gear etc .

so that part will just go no where important when you convert it to a manual.

Brilliant, thank you! I assume that if i just transfer the manual sensor and connect the appropriate wires on the harness to the plug that goes with it it'd work fine? Now that I know what it does exactly I'll be able to figure it out. Thanks again.

[Vman 0]

How did you get on with this?

I also have a 635csi I'm looking to convert to manual. I'm looking to use a M535i as the donor however.