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TZ_280SEL 06-05-2016 03:17 PM

Modern EFI in the old Benz
Let me start by saying I think the D-JET system is great and was ahead of its time......but mine is 44 years old and has about 450k miles on it. I was struggling with very inconsistent running.....great when cold outside, poor when hot outside...horrible when it rained...but never the same two days in a row.

I decided to take the plunge and do a megasquirt conversion. I completed it this weekend (except for tuning) and am glad to say, it runs better with the default tune in it than it did on D-JET.

I decided to do the whole thing...I went with the Megasquirt MS3X DIY kit, installed a 36-1 wheel on the crank pulley, went with Chevy LS2 coils in wasted spark mode, used EV-6 19.3# injectors running semi-sequential, installed billet fuel rail from Ross, TPS from Bosch, and an IAC valve from an older jeep. Car started on the first try and idled like a champ.

Not cheap. I think when it is all done I will have spent about $1,243.03 to do the conversion, but it was my christmas/birthday present to myself. Probably way cheaper than sorting out my DJET.

If anyone is interested in more details, let me know.

TZ_280SEL 06-05-2016 04:23 PM

3 Attachment(s)
A few photos of the install

Mike D 06-05-2016 05:31 PM

3 Attachment(s)
My M115 build.

GM 2.5L TBI, MSII-E, 36-1 trigger wheel, IGN-4 coil from DIYAutotune wasted spark mode, standard GM temp sensors.

Initial install, all the wiring has been cleaned up and properly re-routed.

Attachment 1900073

Attachment 1900081

Attachment 1900089

Made the wires up before I finish mounted the coil. Not happy with the way they came out so I'm going to make a new set and get a cleaner, stock look

Scoot 06-05-2016 07:26 PM

Has anyone done this on an M180 engine?

Mike D 06-05-2016 07:57 PM

Scoot, I started engineering one for the M130 (same manifold I believe). I got stuck trying to match TBI's to supply both sides equally. Matching air flow characteristics to the torque requirements of the M130/M180 put a real crimp in the project. The closest I came was some single BBL TBI'S from an early Toyota.

Tried to source a manifold for the original injected system and went into cardiac arrest at the prices people were asking.

The guy bought 2 new Zeniths and the project got dropped.

A custom manifold would be the easiest and best solution.

alabbasi 06-06-2016 08:35 AM


Originally Posted by TZ_280SEL (Post 14473985)
Not cheap. I think when it is all done I will have spent about $1,243.03 to do the conversion, but it was my christmas/birthday present to myself. Probably way cheaper than sorting out my DJET.

Well done, you could probably sell your D-Jet suff and make most of that money back. I suspect that you're going to get much better fuel mileage with this setup.

Grubeguy 06-06-2016 02:13 PM

Fuel mileage alone would be an interesting reason to keep up with this thread. Keep the updates coming!

TZ_280SEL 06-08-2016 07:38 AM

Quick update. I finally got to spend about 10 minutes last night doing some basic tuning. The car now idles at a rock solid 900 RPM with an AFR of 15.0 (I'm using an Innovate wide band sensor). Was able to do some quick tuning at the higher loads/RPM and took the car out. It definitely has a very throaty note now when you accelerate and feels much stronger. Also smells better when idling.:smile

I must say that incorporating the Jeep 4.0 IAC valve was the best decision I made. I was able to build a small air box under it so I bring air from the throttle body to the idle valve and I return it to the engine using stock lines to the intake. I was also able to incorporate the crankcase vent to the air box so it works just like stock. The stepper motor allows you to dial in the idle EXACTLY where you want it.

On another note, I also pulled the entire dash to replace the non functioning heater blower. When I put it all back together, I took some time to seal the air ducts for the A/C system as they appeared to have some leaks. Well, it now blows as much on low as it used to blow on the highest blower setting. On high, it will actually blow your hair. I should have done this years ago.

I hope to get it tuned up over the next few weeks and then check mileage. I used to get about 14 in town and 17 on HWY.

Mike D 06-08-2016 07:59 AM

I'm interested in whether you see any mileage improvement using the ignition control. I MSII'ed my M117 (fuel only) and didn't really see much, if any, increase in MPG's. Power and drive-ability yes, mileage no.

Not really a good comparison on mine because the K-jet system I had was pretty trashed.

alabbasi 06-10-2016 12:14 PM

I just bought a W109 3.5 that I would really like to try this on. I'd be interested in seeing running results. Is this the same car with the Euro 4.5 engine?

TZ_280SEL 06-10-2016 01:08 PM

Yes. This is on the euro 4.5. I have a detailed spreadsheet with every part I purchased. I can also take some photos and sketch how I did my crank sensor mount, idle valve, and coil mounts.

alabbasi 06-10-2016 01:33 PM

I have to wonder how well this car runs compared to a US 280SEL 4.5. HP wise, it should be getting close to 6.3 territory.

TZ_280SEL 06-10-2016 08:15 PM

According to what I've learned, this engine was 225hp from the factory thanks to higher compression and different cams. People claim to add power to these engines with better fuel/ignition control. That with my cold air intake may put it at 235-240hp and a bit over 275ft-lb so that's enough for this chassis. She definitely saw an improvement going from the us spec to the euro. Now that I've driven it with mega squirt for a week, it DEFINITELY has a large improvement over d-jet.

TZ_280SEL 06-14-2016 06:25 AM

Quick question for all you gear heads. I removed the old distributor and installed the LS2 coils for ignition. I replaced the long resistor plug wires with short (about 16") wires by MSD which I added the special 45 degree LS boots to. Because I went from resistor to non resistor wires, I felt obligated to change plugs too.

So, because I put on LS2 coils and new wires, I decided to go ahead and install plugs for a chevy LS2 engine. They are same depth from the seat to the electrode tip. They are smaller socket size. But they are gapped at .050

I am now running the .050 gap. I figured match the plug to the ignition system, not the motor. Agree or no?

During testing, I had a plug laying on the valve cover. Boy do those coils/plugs throw a spark.

On another note, slowly tuning the car a little every day. I pretty much have it idling at AFR15.0 and very responsive. She seems to have a very throaty growl under heavy throttle now....almost like secondaries on a carb opening up.

Mike D 06-14-2016 06:44 AM

Plugs are plugs. If they fit, have the proper heat range and electrode extension then you're good to go.

Nothing wrong with opening up the gap to take advantage of the hotter spark available using the coils.

I'd be cautious running 15.0 AFR. Because you are running a hotter spark on an older engine you might run into some heat dispersion problems using the old technology pistons you have.

The older engines liked to run "fat" to achieve a smooth idle. I think you might want to bump the 700-1200 RPM areas into the 14.1- 14.6 AFR range.

Pay attention to your advance curve. A hotter spark will slightly delay the actual ignition point and also prolong the actual event. Probably such a slight difference it may not make any difference but it is something to be aware of.

TZ_280SEL 06-14-2016 09:02 AM

Right now, at about 850 rpm idle and 15.0 AFR, idle oscillates about 25 rpm every 2 sec or so...almost imperceptible. I've yet to really tune idle, it just like to run that way. Doesn't change much with AC on or off. So far, I'm loving that aspect.

It is currently real lean on lift throttle and a bit too fat on heavy acceleration (think 17.0 and 12.0) but we are getting better every day. Baby steps. Log on trip to/from tune at night....repeat.

Mike D 06-14-2016 10:58 AM

Throttle lift will always show lean. Nature of the beast. Hard for the O2 gauge to keep up with the rapid change.

The slight "blip" you are getting at idle is the result of a too lean condition. Fatten it up a bit. Maybe try 14.8 AFR. Once you get the idle set, LOCK that cell! Having a stable idle is a keystone in the tuning process.

I usually tune by Stoich, then go back and adjust my AFR.

I warn you. Tuning gets to be addicting!

I've been adjusting my M110 for three or four years now and there's always that "little bit more" I think it could have.:laugh

TZ_280SEL 06-22-2016 10:30 AM

Time for a quick update now that I can get back into my Benzworld account.

Filled up the tank for the first time since the conversion. Only averaged 13.0 mpg. I know, that sounds not so good, but consider; No trip was over 6 miles, there was a LOT of sitting and idling in the driveway as I waited for the car to warm up so I could do some tuning, The car still does not have a 100% tune, the majority of trips involved a lot of full throttle accelerations (both for tuning/data logging AND because it is a whole lot of fun now). All in all, it is about where it was prior to converting, but it has no place to go but up.

Car now idles at a rock solid 795 rpm (ok, it hunts +/- 5 rpm) when warm. I have the engine VE map pretty solid now so my AFR is pretty solid.

I'm taking time off of tuning VE to tweak the timing a little. I have no advance map so I'm trying to sneak up on a good curve. Keep in mind this is a 8.8:1 euro, not a 8:1 USA engine so results may vary.

I currently have cranking advance at 7 BTDC. Idle is at 10-12 BTDC. Full throttle above 3000 rpm is 26-30 BTDC and cruise at 3000 rpm+ is about 40 BTDC. Right now, I think I may have timing coming in a bit too fast as there is a very slight ping at the 1500-2000 rpm and heavy accel so I'm backing that area off a little.


alabbasi 06-23-2016 04:19 PM

No suggestions, just looking forward to the next tank of fuel once backed off the timing.

Baybear 06-23-2016 04:26 PM

Perhaps the octane gas you are using makes a difference?

MBGraham 06-24-2016 02:41 PM


Originally Posted by TZ_280SEL (Post 14504234)
Now that I've driven it with mega squirt for a week, it DEFINITELY has a large improvement over d-jet.

Interesting project. Have followed some others that have done similar thing. I would like to do same, but need a different car to experiment on!

Big advantage you have, is the wideband AFR. Do you have sensors on both sides, or just after mixing?

I installed a, AEM Uego on my 350SL 4.5 - It makes all the difference to be able to set idle and load AFR at will. Currently have idle at about 13.8 and cruise (mid load range) at about 14.5. Djets would run a lot better if more owners & shops had a good way to set mixture. Most are shooting in the dark.

With good key djet parts like MPS, ECU, Trigger pts, distributor plus Pertronix to overcome any distributor wear, it is amazing how well a 44 year old djet runs.

Keep posting - enjoy seeing how you progress.

TZ_280SEL 06-24-2016 03:29 PM

On the 280SELs there is no crossover pipe. Also, the right side has a tri-y so no easy place for a sensor. So I am running single sensor on driver's side bank

MBGraham 06-24-2016 07:29 PM


Originally Posted by TZ_280SEL (Post 14573298)
On the 280SELs there is no crossover pipe. Also, the right side has a tri-y so no easy place for a sensor. So I am running single sensor on driver's side bank

OK. I have mine on driver side pipe, but it is back of crossover just before first muffler/resonator? Hopefully get some mixing.

TZ_280SEL 06-28-2016 06:14 PM

Quick update. 13.7mpg on last tank all in town, so I'm back where I was prior to the conversion. I discovered the lock nut on the fuel pressure regulator I installed had backed off and fuel pressure was up to 50psi from the 43 I had set it at so I was running a bit rich. That does mess up a good bit of my tuning but I'm getting quicker at it. Hope to see better on the next tank but who knows. Can't wait to get her out on the highway.

Good news is that even with 50psi fuel pressure, no fuel leaks. I have so much more confidence in my billet fuel rails with o-ring seals to the injectors instead of clamps. I have eliminated 10 fuel lines under the hood (one to each injector, one to cold start injector, one to the damper) so that is 20 fewer potential leak points from failed clamps. Love it.

I think the next step is to start adjusting the Air-Fuel ratio settings to get everything running a bit closer to stochiometric. My leanest setting right now is 14.7 on high rpm lift throttle while a lot of my table is in the low to mid 12AFR. I should be able to get another MPG or two from it.

alabbasi 06-28-2016 07:10 PM

Yep, d-jetronic runs super high fuel pressure. If you went with mustang injectors, you might want to go with mustang fuel pressure regulator and fuel pump.

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