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  #1  
Old 03-17-2013, 08:59 AM
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Question M120 V12 Engine management questions

Hi all,

I've been thinking about theoretical engine swaps using the m120 v12, but would like to simplify the wiring side of things. Can anyone help with a few questions please?


1. Does the engine use a separate management system for each bank of cylinders or are they controlled by a single ecu?

2. How similar is the m120 to the m104 in regards to the management system?

3. Would it be possible to run the m120 as 2 6cyl engines by using dual m104 management systems?

4. On the early w140 600sel with a 4 speed auto, does the gearbox talk to the ecu? Will the engine run with the autobox removed?

Thanks.

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  #2  
Old 03-17-2013, 12:08 PM
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From what I've seen, there are two computers, throttle bodies from the M104 with each running one bank as the M120 is just two M104 engines put together. I'm not sure if the two talk to each other.

The 4 speed trans will be hydraulic shift so the only info will be output shaft speed ( speedo ) , there might be a input for gear selector position ( neutral , drive ) . The 97 up electronic shift 5 speed talks to the engine computers.

Someone ( in England I think ) was building a kit car / Lotus 7 type with the M120.
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Old 03-17-2013, 06:29 PM
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Quote:
Originally Posted by 97 SL320 View Post
From what I've seen, there are two computers, throttle bodies from the M104 with each running one bank as the M120 is just two M104 engines put together. I'm not sure if the two talk to each other.

The 4 speed trans will be hydraulic shift so the only info will be output shaft speed ( speedo ) , there might be a input for gear selector position ( neutral , drive ) . The 97 up electronic shift 5 speed talks to the engine computers.

Someone ( in England I think ) was building a kit car / Lotus 7 type with the M120.
Thanks, I'll see if I can find anything on the kit car project.

My reasoning for wanting it to run with the m104 systems, is for ease of transplanting the engine into other cars. I can wire up an m104 loom and ecu, but I dont want to try and play with the m120 loom.
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  #4  
Old 03-17-2013, 07:07 PM
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In addition to the 2 LH modules , there are 2 DI to run the ignition and there is an EA module to run the two throttles with varying degrees of communication between them. That EA will be your undoing (aside from the M120 being a turd) as 1 is traditional EA with mechanical limp mode and the other is a slave only.
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  #5  
Old 03-17-2013, 08:07 PM
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Quote:
Originally Posted by duxthe1 View Post
In addition to the 2 LH modules , there are 2 DI to run the ignition and there is an EA module to run the two throttles with varying degrees of communication between them. That EA will be your undoing (aside from the M120 being a turd) as 1 is traditional EA with mechanical limp mode and the other is a slave only.
Thanks.

I was thinking of using the complete m104 setup for each side, fit the m104 throttles to the inlet manifold, and use the m104's wasted spark setup for the ignition.

I'm assuming that the m120 crank and cam position sensors take their readings at the same points of rotation as an m104 would?

I had the idea of shoehorning the m120 into a w124 e320, use the existing m104 components to run one bank of the engine, then use a second m104 loom, ecu, ect to run the other bank.

But it couldn't be that easy of course, or could it?
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  #6  
Old 03-17-2013, 09:51 PM
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It's going to be lots easier to use the complete M120 harness and computers. There are only a few wires that make their way to the outside world.
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  #7  
Old 03-18-2013, 01:46 AM
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It were to swap in a 12 (I wouldn't) I would still run it with the 6 Cyl management but double the ignition and fuel injector outputs and set it up as wasted spark and semi-sequential injection.
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  #8  
Old 03-18-2013, 09:15 AM
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This is an interesting idea. I think you might be able to do what you are saying. The early engines really did run as pretty much two different engines. If I remember correctly there are two crank sensors and cam sensors etc. Main thing would be if the firing order is correct and remember that the intake is swapped from ignition on the banks. So passenger intake and drivers ignition is an engine. Vice versa for the other side.
I think you could just tie in another ecu to the rest of the car pretty easy though. If you had ASR this would be really difficult to keep both actuators working right. Throttle linkage is going to be a real pain if the factory v12 stuff does not work. Have fun fitting it in the engine bay.
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Old 03-25-2013, 05:56 PM
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Quote:
Originally Posted by whipplem104 View Post
This is an interesting idea. I think you might be able to do what you are saying. The early engines really did run as pretty much two different engines. If I remember correctly there are two crank sensors and cam sensors etc. Main thing would be if the firing order is correct and remember that the intake is swapped from ignition on the banks. So passenger intake and drivers ignition is an engine. Vice versa for the other side.
I think you could just tie in another ecu to the rest of the car pretty easy though. If you had ASR this would be really difficult to keep both actuators working right. Throttle linkage is going to be a real pain if the factory v12 stuff does not work. Have fun fitting it in the engine bay.
Thanks, most people I've asked about it just say it wont work, but cant give a reason why not. Besides, I like a chalenge!

It does look possible on paper, looking at some pics I found your correct about there being 2 cam and crank sensors. The only strange thing is that both cam sensors are on the right side of the engine, sharing one camshaft. Not quite sure on the reasons for that?

The engines do share the same firing order luckily enough, so no problems there. Most of the w124's here dont have asr, only the realy late ones sometimes have it so that wont be a problem either.

I thought about having the throttle cable go to the right side throttle then a second cable from there over to the other throttle. A bit of adjustment should get them working together I hope.

I think the problems would be the positions of the cam and crank sensors giving the wrong readings to the m104 ecus, but there must be a way round that...
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  #10  
Old 03-25-2013, 07:00 PM
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Cam sensors are usually there just to sync up the injectors ( this helps idle quality ).

It really doesn't matter what cam the sensors are on, just that they are on the cam side of the timing chain reduction and are synced so they pick up that cylinder X is on the firing stroke. ( or exhaust stroke if the software is looking there.
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  #11  
Old 03-26-2013, 06:24 PM
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Quote:
Originally Posted by 97 SL320 View Post
Cam sensors are usually there just to sync up the injectors ( this helps idle quality ).

It really doesn't matter what cam the sensors are on, just that they are on the cam side of the timing chain reduction and are synced so they pick up that cylinder X is on the firing stroke. ( or exhaust stroke if the software is looking there.
I suppose if the m120 pickup point is different to the m104, I could rig up the m104 cam sensor to read a pickup mounted where the m120's rotor arm should be? I'd be using the m104 wasted spark setup anyway, so the rotor arms wont be needed.

Sounds a bit crude but it might work.
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  #12  
Old 03-26-2013, 07:06 PM
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The cam phase will be the same to the ignition point. It has to be. It just determines top dead compression vs overlap. Actually it would run fine without it but the cam advance would not actuate probably. It is mostly just for emissions on the firing of the injectors. Prevents intake wetting. It will spark and fire injectors based on the crank signal. So one would work off the one sensor and the other off the other. Main thing is to cross over the air mass sensor wiring to the correct bank.
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  #13  
Old 06-11-2013, 01:20 PM
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Originally Posted by 97 SL320 View Post
It's going to be lots easier to use the complete M120 harness and computers. There are only a few wires that make their way to the outside world.
Where was this information for the past few years when I was looking!?
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  #14  
Old 07-24-2013, 11:22 PM
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See this thread for all your questions and some of your answers.

2 ECUs one for each side. If you use a pre 96 4 speed trans and engine things will be easier.

If you use the earlier non COP system things get easier for megasquirt and similar systems.

For me I wanted that 5th gear and I wanted COP.
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  #15  
Old 07-29-2013, 01:28 PM
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Originally Posted by Roncallo View Post
See this thread for all your questions and some of your answers.

2 ECUs one for each side. If you use a pre 96 4 speed trans and engine things will be easier.

If you use the earlier non COP system things get easier for megasquirt and similar systems.

For me I wanted that 5th gear and I wanted COP.

Sorry, Ron - but which thread are you referring to?

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