GM ECM vs MS in E30?

[DaveSmed]

Thanks Dave.

Looks like I might be following in Six_Shooter's footsteps and using a cluster form a GM and a BMW to make a "hybrid" speedometer with the optical speed sensor. Probably easier than reverse-engineering the bimmer's system.

Next on the list is to nab a harness for the under-hood ECM (I have one that can be hacked, but is incomplete), then find/fabricate locations for the rest of the GM sensors.

The knock sensor should be fun to find a spot for :P

What signal does that little yellow box for the optical speed sensor output?

I remember the squarewave working for some later model electronic speedometers from some experimentation with some GM Heads Up Displays.

[ForcedFirebird]

Do you mean working as in you got a signal, or in that the heads up display was working accurately? That would be a plus if I didn't have to dig in the dash (although the odo quit working a few weeks ago haha).


Did you need to modify DRAC to convert the pulses?

[nando]

you don't need any communication from the ECU to get the stock speedometer to work. You can leave the cluster alone, even the tach should work fine.

does the GM ecu require a signal from the speedo sensor to function?

[ForcedFirebird]

you don't need any communication from the ECU to get the stock speedometer to work. You can leave the cluster alone, even the tach should work fine.

does the GM ecu require a signal from the speedo sensor to function?

Thanks for the reply in the CPS thread ;) Just to keep info in one place... yes, I discovered last night after researching that the BMW reluctor wheel is a 60-2. The OBDI GM uses a six nothces, and one referance notch (7x), so it looks like a custom external crank trigger will need to be used.

Well, not sure it the ECM will be fine without vehicle speed data (probably could), but it is definately useful in tuning and datalogging. The $59 code can actually referance boost from vehicle speed and electric wastegate control (Six_Shooter is using it and loves it) and want to go ahead with reading vehicle speed.

I've had a couple more thoughts after going over the eta's wiring diagram and had a few more questions as a result.

1. Nice to see the heated o2 sensor :D even though it won't be long before a wideband is in there, but was curious about how the throttle switch works? GM looks for 0-5v from closed to open throttle.

2. Coolant temp output?

3. Is the idle speed control unit a part of the main ECM? It appears in the diagram that it's seperate from the Motronic.

4. What signal is the timing control looking for? (ie, resistanc/voltage)

Sorry about being lazy and not going out to the car with the multi-meter, but perhaps some of you guys could give me the rundown?

Just dawned on me, this isn't that dis-similar from the MS installs, time to do some more reading :D

Thanks again,
-john

[netcsk]

1. Nice to see the heated o2 sensor :D even though it won't be long before a wideband is in there, but was curious about how the throttle switch works? GM looks for 0-5v from closed to open throttle.

The throttle switch is just that. A switch. There is a closed position, a part throttle position, and a full open position. I don't know the values that come with these, but it is not variable.

2. Coolant temp output?

The engine coolant temp output is resistance. I don't know the range off the top of my head though.

3. Is the idle speed control unit a part of the main ECM? It appears in the diagram that it's seperate from the Motronic.

On the ETA, it is separate. It is the little green or black box next to the motronic.

4. What signal is the timing control looking for? (ie, resistanc/voltage)

No idea.

[Hellabad]

you don't need any communication from the ECU to get the stock speedometer to work. You can leave the cluster alone, even the tach should work fine.

does the GM ecu require a signal from the speedo sensor to function?

This is from memory...

The GM ecu pretty much needs the speed signal because 99.999% were used on auto trannys with lockup converters, so the entire system was designed to exploit the speed input. There are some hacks that eliminate it, but if you can hook it up you will get some benefits with limp mode, warm up, knock sensor sensitivity and a bunch of other features.

Also from memory: the e30 speedo works from a raw signal into the speedo (it is converted in the speedo) while the GM is converted by a "VSS box" that is in the wiring harness, which sends one signal to the speedo and the ecu after converting from the pulses in the tranny.

I think you can use the raw signal from the e30 diff to run the speedo, and parallel the same signal into the VSS box to output to the GM ecu. The GM VSS box also has dip switches or jumpers to compensate for diff gears and tire size. (because the GM signal is befor the diff and the e30 signal is after the diff on the ring gear)

Jay of all trades

VSS is the Vehicle Speed Sensor buffer

[ForcedFirebird]

Thanks Hellabad :D

Yes VSS is vehicle speed sensor, and not sure it's as simple as dip switches, but can go that direction (DRAC).

Any idea on the pulses per mile of the e30?

[ForcedFirebird]

The throttle switch is just that. A switch. There is a closed position, a part throttle position, and a full open position. I don't know the values that come with these, but it is not variable.



The engine coolant temp output is resistance. I don't know the range off the top of my head though.


On the ETA, it is separate. It is the little green or black box next to the motronic.


No idea.

Thanks netcsk. The diagram isn't real clear on the throttle switch, but now that you mention it, looks like a 3 way. GM is a stepper type sensor.

This tells me, I will have to go ahead and fabricate a throttle body adapter to use something from GM. I have a CNC/fabrication shop, so that won't be as difficult as the linkage etc.

Sorry about all the q's, but arming with info will make the transition smoother.

[nando]

Thanks for the reply in the CPS thread ;) Just to keep info in one place... yes, I discovered last night after researching that the BMW reluctor wheel is a 60-2. The OBDI GM uses a six nothces, and one referance notch (7x), so it looks like a custom external crank trigger will need to be used.

Well, not sure it the ECM will be fine without vehicle speed data (probably could), but it is definately useful in tuning and datalogging. The $59 code can actually referance boost from vehicle speed and electric wastegate control (Six_Shooter is using it and loves it) and want to go ahead with reading vehicle speed.

I've had a couple more thoughts after going over the eta's wiring diagram and had a few more questions as a result.

1. Nice to see the heated o2 sensor :D even though it won't be long before a wideband is in there, but was curious about how the throttle switch works? GM looks for 0-5v from closed to open throttle.

2. Coolant temp output?

3. Is the idle speed control unit a part of the main ECM? It appears in the diagram that it's seperate from the Motronic.

4. What signal is the timing control looking for? (ie, resistanc/voltage)

Sorry about being lazy and not going out to the car with the multi-meter, but perhaps some of you guys could give me the rundown?

Just dawned on me, this isn't that dis-similar from the MS installs, time to do some more reading :D

Thanks again,
-john

1.) TPS on the M50 motors is a 0-5v signal. it sounds like the E36 TPS would work fine, and it's fairly simple to adapt it to the M20 throttle body (either with a machined adapter or a modified M20 TPS used as a base). You may have to switch the Vref and return wires if the output is inverted from what the ECU is expecting - the E36 sensor will work in both directions though.

2.) the BMW coolant sensor has a similar resistance range, but you would be best off using the GM sensor (cheap and easily available) as this sensor is extremely important to how the engine runs. They're commonly used on MS installations so you can get it cheap from any MS supplier (such as DIYautotune.com). The output is technically a resistance value VS temperature but the ECU reads this by sending it a Vref signal and measuring the return voltage.

3.) early motronic had a seperate idle computer, but Motronic 1.3 uses a built in controller and a PWM solenoid. I believe the GM ecu uses a stepper motor, which functions quite differently. If you are using an ETA to start with, it's possible you could use the seperate controller but I think you may as well take advantage of the features built into the GM ecu. Also, early cars (with the seperate controller) had 2 wire PWM valves, they don't react quite as fast as the 3 wire versions (although you probably would never notice with a stock eta motor).

4.) not sure what you are asking here, so I'm probably misunderstanding you. Ignition control comes from many different variables and a 3D map; engine RPM, temperature and load are the 3 most important factors for ignition control.

[ForcedFirebird]

1.) TPS on the M50 motors is a 0-5v signal. it sounds like the E36 TPS would work fine, and it's fairly simple to adapt it to the M20 throttle body (either with a machined adapter or a modified M20 TPS used as a base). You may have to switch the Vref and return wires if the output is inverted from what the ECU is expecting - the E36 sensor will work in both directions though.

Are you talking about the throttle switch I see here? I found on MS-converted e30's that using a late model TPS e36 works for it, would need to test one really, but that would eliminate the need for making a TB adapter instead, making up something only to use the stepper GM IAC work.

2.) the BMW coolant sensor has a similar resistance range, but you would be best off using the GM sensor (cheap and easily available) as this sensor is extremely important to how the engine runs. They're commonly used on MS installations so you can get it cheap from any MS supplier (such as DIYautotune.com). The output is technically a resistance value VS temperature but the ECU reads this by sending it a Vref signal and measuring the return voltage.

Yes, understood. It's probably similar to when we swap newer motors in our cars and the temp sensor may work, but will be off from actual temps. It wouls just be a matter of physically putting the sensor somewhere suitable.

3.) early motronic had a seperate idle computer, but Motronic 1.3 uses a built in controller and a PWM solenoid. I believe the GM ecu uses a stepper motor, which functions quite differently. If you are using an ETA to start with, it's possible you could use the seperate controller but I think you may as well take advantage of the features built into the GM ecu. Also, early cars (with the seperate controller) had 2 wire PWM valves, they don't react quite as fast as the 3 wire versions (although you probably would never notice with a stock eta motor).

Ah PWM, FTL :(

4.) not sure what you are asking here, so I'm probably misunderstanding you. Ignition control comes from many different variables and a 3D map; engine RPM, temperature and load are the 3 most important factors for ignition control.

My question I guess is: What signal is the Motronic giving the ignition to tell it to advance/retard the timing? If I could sue the GM to control the spark without going to the waste spark 3coil GM ignition, this can happen a lot sooner.



Just weighing options and wanting to take the simplest route, just to be in control for now. Eventually an entire GM system will be in place, but if I can do a quick "piggyback", that can be built on later.

Thanks again :D

[nando]

Are you talking about the throttle switch I see here? I found on MS-converted e30's that using a late model TPS e36 works for it, would need to test one really, but that would eliminate the need for making a TB adapter instead, making up something only to use the stepper GM IAC work.

yes - although you will still need some sort of adapter, it's very simple and the throttleshaft is the same shape.

Yes, understood. It's probably similar to when we swap newer motors in our cars and the temp sensor may work, but will be off from actual temps. It wouls just be a matter of physically putting the sensor somewhere suitable.

There happens to be a blank spot on the coolant sensor housing that's perfect for adding another sensor. I think the GM sensor is big enough that you may be able to just rethread the original hole as well.

Ah PWM, FTL :(

I don't know if it's just the code, but the 3 wire PWM valves respond much faster on MS than the stepper motors do. But there are some limitations in the hardware mostly that cause this, even though MS2 has direct support for stepper motors..

My question I guess is: What signal is the Motronic giving the ignition to tell it to advance/retard the timing? If I could sue the GM to control the spark without going to the waste spark 3coil GM ignition, this can happen a lot sooner.

it's not sending any signal, it's firing the coil directly. to advance it just fires the coil earlier in the cycle.

Just weighing options and wanting to take the simplest route, just to be in control for now. Eventually an entire GM system will be in place, but if I can do a quick "piggyback", that can be built on later.

Thanks again :D

well if you are going to be using the GM coding wheel and have every other sensor working, hooking up the coils should be really easy. All you would need to do is hook up the spark plug wires differently to get the correct firing order. I think you would hook coil #1 to 1-6, #2 to 3-4, and #3 to 2-5 (not the order that the GM coil packs have on them).

[Hellabad]

Thanks Hellabad :D

Yes VSS is vehicle speed sensor, and not sure it's as simple as dip switches, but can go that direction (DRAC).

There is a jumper kit that you buy from GM. You can learn about it on the 4x4 forums when the guys are adjusting their speedos. I bought one from the dealer for $22, and essentially what you are paying for is the directions in the box.

Any idea on the pulses per mile of the e30?

I used to know, but I am pretty sure it is the same for ALL of the electronic speedo BMWs.


jay

[ForcedFirebird]

After some thought, it might be best to install the GM ECM and start datalogging with it to get a feel for the BMW stock tune. That way I can also get the VSS figured out.

Got some more pics later, got the EEPROMs and chip bypass adapter for the ECM.

Also ordering a DIY wideband kit, and am going to test it on the E30. It's a big bag of parts that you assemble into a WB controller with a digital readout, real-time logging, two programable outputs and free air calibration --- all for less than $100 (sensor not included, but I have a Bosch already :D)

-John

[ForcedFirebird]

OK. I ordered a JAW do it yourself wideband kit for the project.

Total investment, including tuning equipment...

ECM (GM 01227730): $20
DIS (waste spark 3 coil ign) : $150
Wideband with digital readout : $75
Moates.net memcal adapter with 2 EEPROM's: $35 (they have a non - ZIF for $25)
Willems chip burner : $50
ALDL Cable I got free with the burner, you can make one for about $10-15 with an rs232 chip or buy one for $30-60.

Laptop helps, but is only necessary for datalogging.

I have a Bosch sensor, but need the connector from BMW (~$15), but I will keep up to dat on the progress, but be patient. 4 kids, two companies (CNC shop and General Contractor), and four vehicles, my projects take a while...

[nando]

the best laptops for tuning are older IBM thinkpads - you can get a pretty nice one on ebay for around $200. They're fucking tanks too, I had mine slide off the seat and smash into the glovebox while it was datalogging and it kept on ticking (somebody pulled out in front of me).