N52 Swap Discussion

[hoveringuy]

Here's my wiring question: Pin 2 of the X6001 is the "Start signal" that comes from the car access module.

The S54 swaps have a similar pin and the explanation is as follows "6. Starting signal [ wire this to pin 18 on X20 it signals dme that engine is cranking]"

This makes absolutely no sense to me as the motor know it's starting from crank sensor signaling rotation.

Is this only related to "convenience start" or is it actually required?

[nando]

nando : The C101 gives us vehicle speed to the Motronic on pin 14. Motronic uses that to change at least idle speed when the vehicle is stopped. The MSV70 accepts a signal (on pin 17 of the X60001) from the dynamic stability control which is called "signal processed wheel speed, rear right." It seems curious that this wouldn't be done over CAN on the modern computer, but if it IS given its own wire, I expect that means the DME will understand the e30's signal?

My example MS43 wiring I've been referring to doesn't use that signal, but you reference it here:

https://www.r3vlimited.com/board/for...p-speed-signal

Just checking that the same holds true for the MSV70... it sounds like the DSC is just "faking" the vss pulses.

Yeah, surprisingly it comes from a wheel speed sensor, not CAN. It's actually very simple - I just change the number of pulses per mile (the "K" factor) from whatever the E90 is to 9 for the E30 diff sensor, then adjust for tire diameter. Fortunately it's an unsigned DWORD so there's plenty of room to adjust it.

You of course need to run the signal from the cluster (that gets processed through a little chip on the speedometer PCB), which goes to the C101 anyway - and not directly from the diff sensor, which is just a reed switch and presumably quite noisy. If somebody wanted to ditch the E30 cluster, you can salvage that chip and make your own signal processor for it, the function of it is pretty dang simple. This is what I was doing with my E46 M3 cluster that I finished but haven't got around to making it all plug in.

MS43 does use VSS as does basically every DME since at least MS41 - it's used for things like VANOS actuation and a ton of other things on MSV70. But, most people with those older DMEs left it disconnected (rather than just dealing with it properly), and worked around the issues of it being missing by changing the VANOS maps, etc. so it wouldn't run in limp mode.

[hubcapboy]

Ok. Here's an attempt. This should incorporate:

-EKP under the hood and driving the fuel pump through the C101
-All connections to the C101. No check engine light is provided, but I'm extending that to the glove box for later use. Service reset will be a momentary switch at the firewall, oil pressure is taken from the harness, oil levels are taken from the e30 switch via an abandoned secondary O2 sensor circuit.
-Econometer signal from Steve's former Seattle Circuit early model taking a signal from an injector
-OBD2 plug using ISO 9141-2 K-line.
-Accelerator pedal that I forgot to draw traces for but trust me they all go to X60001
-A spare PT-Can plug in the glove compartment for later use.
-An American Autowire 11V threshold charge light trigger
-An added circuit for the 2nd coolant temp signal for a double temp sender (one for gauge, one for DME)

Fortunately I've never been asked to design a PCB. This is messy laid out flat... it's not as bad as it looks.

n52_E30 HARNESS.pdf

[hubcapboy]

nando : The C101 gives us vehicle speed to the Motronic on pin 14. Motronic uses that to change at least idle speed when the vehicle is stopped. The MSV70 accepts a signal (on pin 17 of the X60001) from the dynamic stability control which is called "signal processed wheel speed, rear right." It seems curious that this wouldn't be done over CAN on the modern computer, but if it IS given its own wire, I expect that means the DME will understand the e30's signal?

My example MS43 wiring I've been referring to doesn't use that signal, but you reference it here:

https://www.r3vlimited.com/board/forum/e30-technical-forums/24v-engine-swaps/m54-s54/382375-mss54-s54-swap-speed-signal

Just checking that the same holds true for the MSV70... it sounds like the DSC is just "faking" the vss pulses.

[hoveringuy]

458lbs with everything except oil and exhaust.. Includes A/C, engine mounts, wiring, the shifter, G6-17 transmission.

M20+G260 is about 497lbs.