PeachParts Mercedes-Benz Forum - View Single Post - Has anyone added the ELR system to a car that did not have it stock....

jay_bob · #8 10-09-2015, 11:36 AM

There are 2 parts to the 87 EDS
EGR/ARF valve control
ELR electronic load regulation

The first part well you know what that is good for, a gummed up intake.
The second part you will probably want for the reasons Max mentioned.

You will need the computer behind the battery. There are probably 2, one is the ABS (further forward on my 124) and the other is the EDS controller.

The pieces you will need for load regulation:
- IP sensor (top of the IP)
- IP actuator (rear end of the IP)
- trimming resistor (the knob marked 1-7)
- reference resistor (on firewall on my 124)
- altitude sensor (also likely on firewall)
- OVP (red tall relay with fuse near battery)
- ring gear sensor (left rear down low on block)
- temperature sensor (middle of the head between 2 of the glow plugs)

Some of these inputs have only to do with EGR/ARF but I don't know specifically. Since you are taking the entire wiring harness might as well get the sensors as well.

- the 2 vacuum transducers and air box sensor are for the EGR/ARF control.
- in the 87 602 I believe they used pressure waste gate and a simple pressure switch that opened a valve for overboost protection like they did in the 87 603. Not like the 90+ where the EDS carried these functions too.

One other thing to consider is that you need to feed the Klima relay with a tach signal. This is derived from the EDS box. If you do not satisfy the Klima the compressor will not start. Yes you can run with it jumped, but you lose the seized compressor protection. I would not want to drive like that and have the compressor fail, shred my belt, and kill my water pump.

I don't know if they published 201 wring diagrams online. I have been looking at the 603 diagrams for my 124 to get my information. I suspect the engine management in the 87 201 is very similar to the 124. If you can't get the 201 diagram I would study the 124 diagram to see how these devices are connected.