300E m103 turbo build
Thread Starter
Newbie
Joined: Jan 2025
Posts: 5
Likes: 2
300ce
300E m103 turbo build
Hello
I have bit longer thread, started around 2018 when i got that car. It was meant winterbeater but kinda went out of hands.
When i got it, rear brakes didnt work, was kinda rustbucket, lifters making noise and so on.
Engine is 3.0 m103 without cat and 722.3, year is 86.
First i did minimum work, made brakes work, changed oil to 5w50 (engine really liked that) filters etc. Also wheels.
Also got some winter action.
Some winter fun.
Changed wheels, those are under my c124 at the moment.
Next i decided to paint car myself, i think for first time i got it ok. Color is Mercedes Champagne Metallic – DB473.
Next it went kinda out of hands. First i welded underside of car, restored rear axle fully. Also engine got overhaul, new head gasket, new chain, guides etc, restored head (had one made for my turbo coupe but used here instead), new fuel and brake lines.
After i got engine back together i did efi conversion (actually did it before i pulled engine appart)
Easyecu 3+
Fuel rail + 3.5bar fpr
36-1 trigger
new injectors (first i got it running with 330cc, but i have for turbo 630cc injectors)
wiring loom
i kept distributor for oldscool.
also all sensors, wb, tps, iat, coolant, egt.
Next was turbo manifold, first i had one big schwitzer turbo, but later i replaced that with internally wategated scania hx52.
I tryed to make twin scroll and as short as possible runners, to get best spool and maybe loose top end.
Thats with current turbo.
Video from first startup.
Next is to make intercooler piping and put interior back in, havent set deadline, doing it when i have sparetime from family and home.
I have bit longer thread, started around 2018 when i got that car. It was meant winterbeater but kinda went out of hands.
When i got it, rear brakes didnt work, was kinda rustbucket, lifters making noise and so on.
Engine is 3.0 m103 without cat and 722.3, year is 86.
First i did minimum work, made brakes work, changed oil to 5w50 (engine really liked that) filters etc. Also wheels.
Also got some winter action.
Some winter fun.
Changed wheels, those are under my c124 at the moment.
Next i decided to paint car myself, i think for first time i got it ok. Color is Mercedes Champagne Metallic – DB473.
Next it went kinda out of hands. First i welded underside of car, restored rear axle fully. Also engine got overhaul, new head gasket, new chain, guides etc, restored head (had one made for my turbo coupe but used here instead), new fuel and brake lines.
After i got engine back together i did efi conversion (actually did it before i pulled engine appart)
Easyecu 3+
Fuel rail + 3.5bar fpr
36-1 trigger
new injectors (first i got it running with 330cc, but i have for turbo 630cc injectors)
wiring loom
i kept distributor for oldscool.
also all sensors, wb, tps, iat, coolant, egt.
Next was turbo manifold, first i had one big schwitzer turbo, but later i replaced that with internally wategated scania hx52.
I tryed to make twin scroll and as short as possible runners, to get best spool and maybe loose top end.
Thats with current turbo.
Video from first startup.
Next is to make intercooler piping and put interior back in, havent set deadline, doing it when i have sparetime from family and home.
Newbie
Joined: Nov 2023
Posts: 4
Likes: 1
From: CO
1990 Polar White 300E M103 2012 Black Sapphire 750Li 2011 Carbon Scharwz 550i M Sport Carneol CLS55
Gorgeous build. I see that you’re running EasyEcu3 I was wondering how you wired it. Iam currently using the same ECU and I can’t seem to get power to it. How were you able to wire the ECU.
Newbie
Joined: Nov 2023
Posts: 4
Likes: 1
From: CO
1990 Polar White 300E M103 2012 Black Sapphire 750Li 2011 Carbon Scharwz 550i M Sport Carneol CLS55
Thread Starter
Newbie
Joined: Jan 2025
Posts: 5
Likes: 2
300ce
Didint u get any manual? Ask k-jet killers EN version of easyecu 3.
Also on ottomotive.pl page is polish version of manual - pinout is readable (u can find latest versions of software and firmware too) . Also u can use google translate for that pdf.
For triggering main relay i took signal from OE ecu plug - cant remember pin.
For wiring i used same logic as megasquirt - seperate fusebox and relays for efi, just disregarded ecu plug side and did grounds as easyecu needs.
I have easyecu 3 and for timing 36-2 trigger (replaces harmonic damper) and new bracket for sensor. May not be best to loose damper but havent got any issues - also turbobantit used same system.
For updates - unfortunately i havent got time to finish it, standing as is. For side guest i have one w124 with m102, running on speeduino, saab 9-5 aero rail and injectors, vag short cop's, ecu is speeduino - plan was to get mot and use as winterbeater, but discovered rear swaybar mounts are rusted, have to weld those on my driveway and then its a go.
Newbie
Joined: Nov 2023
Posts: 4
Likes: 1
From: CO
1990 Polar White 300E M103 2012 Black Sapphire 750Li 2011 Carbon Scharwz 550i M Sport Carneol CLS55
Thanks.
Didint u get any manual? Ask k-jet killers EN version of easyecu 3.
Also on ottomotive.pl page is polish version of manual - pinout is readable (u can find latest versions of software and firmware too) . Also u can use google translate for that pdf.
For triggering main relay i took signal from OE ecu plug - cant remember pin.
For wiring i used same logic as megasquirt - seperate fusebox and relays for efi, just disregarded ecu plug side and did grounds as easyecu needs.
I have easyecu 3 and for timing 36-2 trigger (replaces harmonic damper) and new bracket for sensor. May not be best to loose damper but havent got any issues - also turbobantit used same system.
For updates - unfortunately i havent got time to finish it, standing as is. For side guest i have one w124 with m102, running on speeduino, saab 9-5 aero rail and injectors, vag short cop's, ecu is speeduino - plan was to get mot and use as winterbeater, but discovered rear swaybar mounts are rusted, have to weld those on my driveway and then its a go.
Didint u get any manual? Ask k-jet killers EN version of easyecu 3.
Also on ottomotive.pl page is polish version of manual - pinout is readable (u can find latest versions of software and firmware too) . Also u can use google translate for that pdf.
For triggering main relay i took signal from OE ecu plug - cant remember pin.
For wiring i used same logic as megasquirt - seperate fusebox and relays for efi, just disregarded ecu plug side and did grounds as easyecu needs.
I have easyecu 3 and for timing 36-2 trigger (replaces harmonic damper) and new bracket for sensor. May not be best to loose damper but havent got any issues - also turbobantit used same system.
For updates - unfortunately i havent got time to finish it, standing as is. For side guest i have one w124 with m102, running on speeduino, saab 9-5 aero rail and injectors, vag short cop's, ecu is speeduino - plan was to get mot and use as winterbeater, but discovered rear swaybar mounts are rusted, have to weld those on my driveway and then its a go.
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Thread Starter
Newbie
Joined: Jan 2025
Posts: 5
Likes: 2
300ce
very nice thanks for the reply. I’ve been struggling to power the ECU from the OVP relay I used 3 different wires from the relay thinking it was the one to power the original computer. I finally used the right wire from the OVP which was the green and red wire. Come to find out one of the two fuses isn’t getting power so iam just gonna get a PDM for all the EFI bits. Also K jet killers haven’t been much help with my problems as they just tell me to wire 12v to the ECU like really I didn’t know that lol. Eventually I want to get to a point with this chassis where I can have two running ones at the same time like you lol
Edit: dont forget 3amp fuse between ecu and power.
Last edited by Pelle300CE; Oct 13, 2025 at 08:21 AM.
