Modern EFI in the old Benz - Page 4 - Mercedes-Benz Forum
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post #31 of 36 (permalink) Old 05-06-2019, 06:32 AM Thread Starter
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Date registered: Feb 2010
Vehicle: 1972 280SEL daily driver. 904 Dark Blue with cognac interior. euro 4.5 engine
Location: Williamsburg, VA
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I would gladly share my spreadsheet.......except my computer seems to have dumped my megasquirted folder. I think I have a hard copy in my garage but won’t get to that until this weekend.

I can answer any questions you have but basically I’m running a 36-1 wheel on crank pulley with GM LS coil-near-plug in wasted spark. Semi sequential on fuel with 19# injectors from a Ford. Idle air control via a Jeep 4 liter and a Bosch TPS from a Volvo. I can get all the PN for you if you want.

I did find my wire harness details. I did run a shielded twisted pair for the crank position sensor. Some people have issues with noise on their sensors but mine is clean.
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post #32 of 36 (permalink) Old 05-06-2019, 07:17 AM
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Date registered: Apr 2019
Vehicle: 1972 280SEL 4.5L
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If you could get the pn's that would be AMAZING! I've been tinkering with this for the past ~year & 1/2 and am ready to upgrade (especially after reading how well yours is working).
Hope to start on this by June (weather permitting)
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post #33 of 36 (permalink) Old 05-15-2019, 10:24 AM Thread Starter
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Date registered: Feb 2010
Vehicle: 1972 280SEL daily driver. 904 Dark Blue with cognac interior. euro 4.5 engine
Location: Williamsburg, VA
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72W108 I have been unable to find my old parts list, but I will attempt to recreate it one system at a time.

For today, I have the parts for the idle air system. I chose to completely remove the idle screw and the associated thermo valve. If you remove those two items from the intake, you end up with a hole which is open to the coolant passage from the heads and you have two mounting holes where the idle screw were. In an ideal world, you would like to maintain the breathing of the engine the same and have a computer controlled idle. To do that, I fabricated a small (perhaps 2"x2"x1"tall) air box which mounts to the old mounting holes for the idle control valve. Into one side of the box, I ran a hose direct from the throttle body (where the old hose from the idle air and thermo valve attached). Into another side, I welded a metric nut with threads to accept the old breather element with the hose coming from the left hand valve cover. Out the back, the air box ties into the pipe that feeds into the RH and LH bank of the intake (where idle air used to go). On the top of this box, I installed the housing from the idle air valve from a Jeep 4.0 liter engine (part number 53032023AC). I replace the existing Jeep valve with a new stepper motor one (part number AC320) so I could use the stepper motor controls in Megasquirt. I believe the IAC housing is from a 4.0L jeep of the 1996 year range. I purchased a very cheap ebay jeep throttle body, kept the IAC housing and disposed of the throttle body.

So, on cold start, the MS opens the stepper the appropriate amount based on coolant temp. Air bypasses the throttle butterfly via my Jeep housing and air box and is fed to the individual cylinders as original design. The breathing of the LH bank is still as originally designed. As the engine warms up, stepper motor closes and controls idle at the determined speed. I also creep idle speed up a few RPM if coolant temperature rises above 200F.

The hole left by the old thermo valve is now covered by a 1/4" thick steel plate drilled and tapped to accept a GM coolant temperature sensor. I purchased my sensor with the connector from DIY autotune.

By the way, I purchased all my sensors and connectors with bare pins so when I made up my connectors, I was crimping to new pins, not splicing to pigtails.

Attached is a photo which shows what I just described
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post #34 of 36 (permalink) Old 05-15-2019, 10:32 AM Thread Starter
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Date registered: Feb 2010
Vehicle: 1972 280SEL daily driver. 904 Dark Blue with cognac interior. euro 4.5 engine
Location: Williamsburg, VA
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For the throttle position sensor, I removed the old one, cut a bit off the end of the butterfly shaft and fitted a BOSCH 0 280 122 001 (from a 90's volvo 850) onto an adapter plate I made to match the mounting holes for the new sensor. Not MS has a smooth throttle position signal. You just have to make sure you mount the sensor correct so you retain full range of motion on your throttle.

I don't remember where I purchased the mating connector but it is common.
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post #35 of 36 (permalink) Old 05-22-2019, 01:26 PM
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Thank you so much! ready to get working on this once the weather cooperates!
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post #36 of 36 (permalink) Old 05-23-2019, 03:51 AM Thread Starter
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Date registered: Feb 2010
Vehicle: 1972 280SEL daily driver. 904 Dark Blue with cognac interior. euro 4.5 engine
Location: Williamsburg, VA
Posts: 390
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For fuel, I kept the stock D-Jet pump and filter at the tank but the rest is new. I used EV1 19# injectors. I purchased a length of fuel rail billet (DASH-6) from Ross Machine Racing and drilled the bores for the EV1 o-rings. I tapped the ends of the fuel rail with an NPT tap and used simple NPT to barb hose fittings to run my fuel line. I used a generic inexpensive vacuum compensated pressure regulator which is set at 45# with no vacuum. There is a vacuum connection at the rear of the intake lower plenum which I used for the vacuum signal for both the fuel regulator and the MS MAP sensor. The tank return from the regulator is original. I did not keep the fuel damper.

I used to chase fuel leaks on my D-Jet regularly. I have not, knock on wood, had a leak since the conversion to MS. I am only running a 36-1 crank sensor so I am using semisequential injection.

For ignition, I decided to eliminate the distributor. I know you can keep it, but I wanted control of advance and I wanted to eliminate the issues with rotor cap wear and the resistor/non resistor plug/wire issues we all seem to chase. I removed the distributor completely and machined a round blank with an o-ring groove in it the same diameter as the distributor base. I then welded that to a small plate with a hole that lines up with the distributor hold down bolt location.

I added a 36-1 wheel to the crank pulley (you have to grind off and reattach the balance weights if yours has them). I purchased the wheel from a guy on ebay in Belarus. I used a Honeywell 1GT101DC hall effect sensor for the trigger signal. I made a mount for mine which attaches to the front of the engine. It replaces the existing plate which covers the distributor timing gear. I don't have any good pictures here but will take some this weekend and post for you.

For ignition, I chose to use LS2 coils and do coil-near-plug with wasted spark. I purchased a set of used LS2 coils complete with bracket and harness. I reused the harness but made my own bracket. It is probably hard to see in photos, but my fuel rail is held in place by two brackets which bolt to holes in the head for the original injector hold downs. The billet fuel rail has plenty of meat at the bottom to drill through without hitting the bore which carries the fuel. For my coils supports, my bracket also attaches to the fuel rail in two places and I tapped the two "holes" in the valve cover originally used for the plug wire guide. For plug wires, I used MSD wires from a "build your own" kit and purchased MSD 45 degree LS2 connectors for the other end. (I made my own because stock LS2 coil wires are about 3" too short) I am also running plugs for an LS engine. The threads are the same even though the socket size is smaller.
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