Although I appreciate that it seems simple enough. I know that it is not. I am not speaking in hypotheticals at all. You definitely need both rear wheel speed sensors and they have to have the right tooth count and the correct calculations to get to the driveshaft speed being correct. Exactly correct. I sell tcm packages to about 3-4 people a year that have systems developed by other companies trying to do this exact thing. I think Roncallo's system works because he did it exactly the same as the factory.

And as I said nothing about what you described is cheap or easy. Even if he buys a donor car for 1000.00 to pull this stuff from it is tone rings and custom parts to get this all working and then hours and hours and hours of time stripping the wiring down. Rewiring and installing all this stuff in the car. You could just go get a part time job at Burger King and buy a really nice aftermarket ecu for around 1500-2500.00 and pay someone to install it and tune it in less time and money. Just a simple fact.
And when your DAS key takes a dump and your car wont start and they are discontinued you are SOL.

And S320s came with 722.5 from the beginning or near the beginning to 1996. So quite a few available in the U.S.

I missed that part about the single wheel speed sensor. I believe you will need both wheel speed sensors for the transmission to work, but I cant say for sure, Iv'e only had it with either non or both connected and I ASSUMED that was required.

Actually using the MB electronics is not that difficult, if and only if you start with a running donor car and install it exactly like the donor.

The Pros and cons of using the factory installation vs aftermarket to me really boil down to can you except the configuration from the factory or not. If you want to change your gear ratio. You have to go aftermarket.

If you want a system that was developed with thousands of hours of R&D and hardened to a point that a company could sell to hundreds of thousands of people with the confidence that they could warranty each and every one of those cars and have a product acceptable to the to the public against all competition, then you have to go OE. And that is why I choose to go OE. But it is also why I have to live with my 2.65 rear end ratio and will not use a frequency modulator to fool the system which in my opinion would bastardize the system. Just put a Mega-squirt box next to an ME box and you will get the picture.

I ran into two issues when I built my car using the OE system and one was the gear ratio difference between the 107 and the 129 and the other was how DAS worked. They were issues because I didn't know about them at the time. And at that time a lot of people didn't know about them. But I think, to most people on this forum that's now old news. The physical wiring of the system into the car is not an issue. Just use the MB harnesses and put your boxes where they will reach.

In the near future I will probably be marketing tone rings and sensor mounts for cars with bolt on axles like mine. I'm also considering outboard ones like on the 129's. Not sure if either of those will help the OP as they will be for a 560 type 107.

Iv'e used the OE ME system in the past and am currently working on a new project that will use the ME system as well.

__________________
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John Roncallo

My point is how many man hours in your project and swaping the differential to fit, mounting the tone rings etc, wiring. Then you have the cost of those parts and the adapter braekets and tone rings themselves.
I know those hours add up.
Since I work on these cars for a living I know how long it takes to do the simple remove the wiring harnessess from the car. Much less install them in a car they did not come in.
My hats off to you on your project.
I have a really simple project with the om648 with the factory ECU, EIS, and keys and my standalone tcu running the transmission and CAN bus. Just wiring that up took me a couple of days. And honestly I threw it in there just to get it running and it needs to be redone.

Not to derail your conversation but it really seems like a lot of these issues come from using the 5 speed transmission. It does look like that communicates with the drivetrain more than I thought. However if I put a 722.3 in it the issues don't seem to be there. I should just have to worry about the engine side of things. That would indicate to me that I can pull the harness, ECU, and a few of the security related modules off a w124 without ASR.

Also the parts car idea or going straight to megasquirt is less about cost and more about time and space. With megasquirt you need to build a harness and have no baseline tune. With a parts car you have a torn apart car in your driveway. On their own not huge issues but I'm also going to be doing the actual swap in that time too.

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Current:
'74 450SLC
'89 190E
'95 E420

Previous:
'94 E320
'87 300E
'73 350SL
'75 450SL
'95 C36
'99 C43 55 swap

Two things.
1st is that building a harness or having a professional do it for you is not that big of a deal. If you gave them a factory one then around 500.00 dollars probably. Probably a bit less than one from the factory.
And not that expensive unless you want an Mil spec harness. Even then not to bad.
Building a tune to run and drive again not that bad. And again there are lots of people that have run these engines on aftermarket ecus that have solid basic tunes out there. I included. But really it is pretty straight forward. Once wired up and power on it would take about an hour to have the car up and running and driving. THen a couple of hours on the dyno tuning to have something that works pretty well. Figure a day of tune time.
So all in if you dropped it off somewhere to have it wired up and tuned and bought the ecu probably around 5,000-7000. If you did some your self or all your self, considerably less time to install than factory and around 2500.00. Then if you wanted it to be tuned then that time and money.

2nd as far as reliability of the systems and hardware for the aftermarket computers.
One Megasquirt is not the end all be all. I do not get using them at all. Other than people who like to tinker. You can buy a Bosh Mortorsports ECU that is pretty much the same piece of hardware as the factory Me 2.8 ECU or the like for under 3k. There are many examples of ECUs out there that are OE quality for not a ton of money.
The standalone TCU I sell is actually used by OEs as well.

As far as ecus go I can get a used MS3 for less than a grand. I did FSAE in college and built the harness and did tuning for that car. If I want it to look nice and be tucked with new connectors, which I will eventually do, that is its own project. I'll want to get up into the dash and hook up a display and have the ability to tune the car. I will also need to make the original dash display rpm, temps, and speed too so I'll need some way to convert outputs too. I agree its not that complicated but if I'm going to go to an aftermarket system I only want to make that investment once so I'll spend some time on it. With that an hour on the dyno is not a good tune. That's it running "fat 'n' happy" and it is big investment to do standalone correctly.

If it is at all possible to use a oem ecu with some trans I can at least get the car moving and have a M104 baseline.

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Current:
'74 450SLC
'89 190E
'95 E420

Previous:
'94 E320
'87 300E
'73 350SL
'75 450SL
'95 C36
'99 C43 55 swap

With modern ecus in the aftermarket you have adaptations. Set your target AFR and drive. It really is that easy.
My car has a 10 year old ecu with adaptive VE and is nothing near as nice as the stuff on the market now and really just driving it and letting the VE tables fill in takes a few days of daily commuiting to get 99% of it dialed in.
So a pretty basic map with a proper timing table and a few pulls on the dyno gets you right where you want to be. And with a W/B O2 sensor you can pretty much hit any AFR you want in no time.

That's only tuning the afr and some enrichment. It doesn't do anything for timing, vvt engagement, cold start, hot start, or any compensations for weather and altitude. I mean at the end of the day there is a reason oems spend all the time they do to make a car run well. Then you also have to consider how its going to interact with the rest of the car and what outputs it has for the dash etc.

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Current:
'74 450SLC
'89 190E
'95 E420

Previous:
'94 E320
'87 300E
'73 350SL
'75 450SL
'95 C36
'99 C43 55 swap

You are way over estimating the difficulty here. I know what it takes to do this. I have done quite a few. It just is not that hard or time consuming.
If you know what to do.
But it is ultimately up to you. I have a lot of experience with both paths. Regardless of the transmission you choose or if you went with a manual. I would not even begin to do factory computers for an m104. These are really easy engines to setup and run. Do some homework and you can find any thing you want as far as setup on them. Including on this forum.
I would be happy to share any details myself.
For example Cam the cam advances right off idle and then drops back around 4200rpm. Intake resonance flap moves right after that at I think 4700 rpm. I or do a search can provide you with the exact numbers from the factory.
Timing is really straight forward. These engines run at a max of around 15 degrees advance at WOT. Scale back for knock. Which is a common setup on most ecus today.
You could tune to knock as well in most.
Put a 60-2 tooth flywheel on from an ME engine or most systems will accomodate the 3 tooth setup on the engine already.
Things like cold start enrichment are generally pretty standard. As air and fuel are pretty standard.
If you have never done this stuff or have very little, Yes it takes some time.
My car after sitting for months or a year, with what I consider an archaic system, starts on a dime no matter what the weather with 1000cc injectors.
I think that there is enough info here for which ever path you want to go.
Keep us updated. And check out the 190erev forum for m104 ms tunes. Tons of them over there. I would imagine on the MS forums as well.

If you look at each piece as a little task I agree its not bad. There are a lot of little tasks however and remember I need to make my dash work when I go to megasquirt. Plenty of tuning and wiring to do.

I just don't see how that can possibly be less work than putting a stock ecu in that just needs some pins jumped. Like I've been saying please tell me how I'm wrong with that so I don't waste my time on that if it actually is worse for a temporary solution to get the car running. I do see how a 722.6 would be nightmare on a stock ECU in the wrong car.

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Current:
'74 450SLC
'89 190E
'95 E420

Previous:
'94 E320
'87 300E
'73 350SL
'75 450SL
'95 C36
'99 C43 55 swap

Making the dash work. You mean adding a tach signal to the factory tach. Or if you are using the 3 tooth trigger doing nothing.

I forgot you were doing this in a 450. You might need another tach from a 6 cylinder car if you are using a 3 tooth trigger. Since the v8 uses 4. Regardless you are going to have to do this for any thing you put in the car. Factory or not.
CLt temp, oil pressure, are all going too be drop in if the sensors are even different scales just swap them from your v8.

In fact things actually get harder as cars got more complex and CAN buses took over. You have no TACH output, coolant output etc. from the ecus and the engines did not have redundant sensors on them. One for each function. ECU and cluster.
SPeed is no longer output as a real value. It is all on CAN. This is all pretty easy to overcome technically but adds cost and time. And know how.

If I run a megasquirt with the 60 tooth flywheel I will use the outputs from the ecu for the tach. I probably won't bother with the speedo until I have a 722.6 in the car and I can deal with it then.

If I put a stock ECU in all I will worry about is temp, oil pressure, and a wide band O2. The goal with that set up is to be able to drive the car. It would not need to be perfect because at least as far as I can tell its basically drop in once I pull the parts from a junkyard car as long as its non asr and doesn't have an immobilizer. If I really want I could always stick a w124 dash in it too if I wanted speed and the tach to work with that setup.

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Current:
'74 450SLC
'89 190E
'95 E420

Previous:
'94 E320
'87 300E
'73 350SL
'75 450SL
'95 C36
'99 C43 55 swap

As someone who works on them for a living as well, neither would I. First step is *****can the OE module. Second step is figure out what standalone would meet my goals. FWIW, I run a 103 with 18 PSI boost and pass my state emissions testing with my personally handbuilt, self tuned MS2, that has 30K mi on it.

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff