The M103 CIS-E performance ECU module thread
 

I recently cured a recurrent high idle problem on Benzer 1 by replacing his ECU with the only other one I had quick access to, the one from Benzer 2. But this left B2 without an ECU so, when I had the first opportunity, I nabbed another one for B1 so I could give B2's ECU back. We'll get to that "new" ECU in a second. I actually installed B2's ECU while I was playing with B1 at the dragstrip and found that B1's ECU was a bit quicker! I'm not going to post the numbers because they are skewered by other factors such as me taking weight out of the car and the D/A numbers steadily improving for the rest of the day. Suffice it to say that the fact that my quickest run of the day was with B1's ECU despite being in the worst D/A of the day and with the most weight of the day (I had no wheelspin all day so that is not a factor) is enough proof for me to conclude that B1's original ECU was the quicker of the two ECUs. B1's ECU number is 008 545 16 32 and B2's ECU number is 004 545 38 32. I would have thought that the older, earlier ECU would have had the edge but I'm sure there are other factors at play here. Heck, it could even be the fact that B2 is suffering from some other issues right now and as a result his ECU is adapted to a bunk set of parameters and there wasn't enough time for that ECU to adapt to B1's much better running engine before I ran the 1/4 mile with it. (I guess I should have run that ECU on the street for a week before I tried it at the track.) Still, this got me wanting to try more ECUs which brings us back to the "replacement" ECU. I deliberately picked up the earliest version of a M103 CIS-E ECU I could find reasoning (and hoping) that since the smog standards weren't as stringent in 86 as they were in 88 and 89 , maybe the older ECU might be a little more generous with the fuel when in the "Let's party" mode. So I ended up with an ECU bearing part number 002 545 97 32. I installed it Sunday. This thing rocks! Both part throttle and full throttle response is markedly improved! If I am unable to get a much needed throttle actuator for B3 in time for our next track day, I'll take B1 instead and quantify my findings. If I don't take B1 to the next track day, I'll take him to the one after that to provide the proof of my results.

I'm creating this thread because I want to get others thinking and experimenting and posting their own results. Please, we need to try to provide proof of some sort like dyno numbers or dragstrip timeslips. I just wanted to get the ball rolling so to speak since you all don't need to wait for me. This is too good to wait! Be aware though that there are plenty of other factors here at play when we switch these ECUs and I don't expect or promise that everyone will see a gain in throttle response and/or power. All I'm trying to do is get you all to experiment a little and post your results so we can get an idea of which ECU seems to be the best for the most applications. Then the ECU that performs the best can be the one you run and the other one(s) can become a spare(s). It's always good to have a spare or two!

Other CIS-E guys and gals are encouraged to participate too! (Early M104s, M102s, M116s, M117s, etc.)

Remember, on the M103s (and probably others) 90 and later CIS-Es are different in several ways from the 89 and earlier ones so I don't think switching ECUs between those and the 89 and earlier ones is a good idea. In fact, I think it's a bad idea and, at best, probably won't work and, at worst, might even fry something. Keep the 86-89s in one group and the 90 and later CIS-Es in the other group.
Regards, Eric

Eric, dont forget that the EZL of Different part numbers also has Different timing maps, and thus changing the EZL with another can produce other results as well.

but again i tell u and before u jump abt looking and switchin ECUs, just splice the harness of the Rear main CTS that feeds both the EZL and ECU, fit varaible resistors, and mess abt with them and ull see similar results. if not better. ill try and post few pics of how my car was set up.

Yes, I'm aware of the fact that we have another potential gain in trying different EZL units as well. I'm hoping someone will investigate this further and start an EZL thread similar to this thread because it will take me too long to get around to it!

Yes, we of course love the CTS mod but I think the ideal would be to fool only the EZL side as fooling the CIS-E side has detrimental effects on fuel economy unless used for short full throttle blasts only. The CTS mod does definitely have it's place though. Remember what I said about how it's good to learn all the different ways to break the rules?

What I've been after forever with both B1 and B2 is to improve part throttle response so I don't have to go full throttle all the time which also puts fuel economy in the toilet. This ECU swap has given me that. I might even remove the "For Sale" tags on B1 and B2 in my sig!
Regards, Eric

didnt mean it that way, i know ur always looking for new ways to tune those CiS cars.

I think ull be seeing lower MPGs with that last ecu. Older w124s are known for lack of econo.
The EZL thread wont come easy since those units are expensive and even rare these days.

I'm also always looking for new ways to tune M-119 cars.

M103 EZLs are easy to get here because M103s are really showing up in large numbers at the U-Pull-It type yards.

I don't think fuel economy will suffer because I'm not having to bury my foot in the throttle all the time now like I was before so I think it's gonna average out. I think the poorer fuel economy of the older ones was at least partially due to the fact that the pre-90 3.0s had 3.07 gears in back and the 90 and later ones had 2.87s. (wagons, 4-matics, and 2.6s are different.) My two M103s both only averaged 20MPG at their best in mixed driving which is no better than what my 400E gets! I can't imagine it getting much worse. Fuel economy will be another variable that we will all be posting on this thread.
Regards, Eric

Euro spec M103, M104 w124 never came with a rear longer than 3.07. i have never ever seen a W124 I6 here with that rear end. i have seen M104s with 3.69 ASD diff fitted to the early 3.0 M104. while the 320 M104 usually has 3.46 or something.

Wow, some 3.2 M104 W124s even went to a 2.65 for a while here. Be that as it may, I still think that the fact that I'm not having to bury my foot in the throttle all the time now like I was before is gonna average out the fuel economy.
Regards, Eric

Eric400e,

The reason the 400e's get better mileage is the 2.24 rear-end ratio. The 300e's are a bit tizzy with 3.65?


Michael

Yes, thanks. I am very aware of that and in fact, all of my M119 buddies are trying to get me to put 2.65s or 2.82s in which I refuse to do for economy reasons.

Pre-90 3.0 300Es got 3.07s, except TEs which got 3.27s, the same gear that the 2.6 W124s got. After 89, everything went taller a notch, cars that had been 3.27s went to 3.07s, and 3.07s went to 2.87s. In 93, when everything went M104 HFM, things went taller still as mentioned in my previous post.

I had to go back to the U.P.I. today and I discovered that the car I pulled the magical ECU from is a non-Calif car! Maybe this is the reason I noticed a difference with only this ECU. Up until now, all I've had access to are Calif ECUs. We do know that in many cases Cali cars are slower than the other state's cars, that's been proven time and time again since the 70s. So I don't know at this point if it's because it's an early ECU or if it's because it's a non-Cali ECU but we are gonna find out at the track how much we have gained. When you ask? It depends on the weather. I'm still trying to beat my best E/T with Benzer 3 and cool weather gives me my best chance at doing that so cool weather days are reserved for Benzer 3. When an impending track day looks like it's gonna be a warm/hot day, Benzer 1 gets to go which means the ECU test will be done at that time.
Regards, Eric

Finally had a chance to take Benzer 1 to the track again this past week-end and with NO OTHER CHANGES from the previous time I had Benzer 1 at the track, except for the substitution of that ECU bearing part number 002 545 97 32 and the removal of the resonator and muffler, Benser 1 went a full second quicker in the quarter mile in much worse conditions than what we had the last time we were there! We are talking an uncorrected 15.95 @ 87.27 (15.487 @ 89.939 MPH corrected) where last time we couldn't do better than a 16.95! Mind boggling! We repeatedly spanked a Bimmer 525i in the process too! (Well, actually, slaughtered the Bimmer.) I honestly think that I was more thrilled to get that 15.95 out of Benzer 1 than I was when I got that 14.348 out of Benzer 3!

I told you all that there is more in these old M103s than you think! You just have to give them some love and do some experimenting! I violated the one-change-at-a-time rule by doing the muffler and resonator delete too before this track day so we don't know for sure just how much of the gain came from the exhaust mods and how much of it came from the ECU change but, given the huge full second gain on a poorer condition day, it wouldn't be unreasonable to conclude that the gain was a result of a little of both. Surely, the exhaust alone can't be credited with this full second gain, at least SOME of it HAS to be a result of the ECU swap. So the rest of you CIS-E folks need to do some experimenting too cause there are definitely some performance gains to be found if one is willing to do a little digging.

Oh, and BTW, Benzer 1 isn't for sale anymore! You guys should have grabbed him when you had the chance! I am way too pleased with the performance of Benzer 1 now to let him go!

I will post or at least link some timeslips and videos too once my friends get them up for me.
Regards, Eric

I should try this on my 3.4 amg see what it does.
It was planned to be done last month but neither I or Jay had the time, so next vacation for sure!

Sorry I never did follow through on this but I may have figured that since I am always updating my drag racing thread most all of you already saw the videos anyways. But I still should have followed through here too because I said I would. So here are some videos from that day: #3 Mercedez Benz 300e w124 Vs. e34 BMW 525ti - YouTube #4 Mercedez Benz 300e w124 Vs. e34 BMW 525ti - YouTube

I can't for the life of me remember where the three 15.9x timeslips from that day are. (Or ANY of the timeslips from that day for that matter.) I thought I linked the 15.95 one here to this site somewhere. (The 15.924 E/T referenced in my sig is from a later date on a different track with a quicker shifting "T-bar" modded transmission..... too many variables that don't apply to the experiments we were conducting in this thread.) For now we will have to make due with the witness of a unbiased Volvo guy on the second video attesting to our 16 flat on that particular run, which isn't too far removed from our best of day 15.95!
Regards, Eric