Optimizing D-Jetronic, Brainstorming.... Options

[pbanders]

Here are my thoughts on a systematic approach to optimizing D-Jetronic for a specific stock or near-stock engine - just putting this down and looking for comments:

1. First step - make sure the engine has no other faults. Mechanicals perfect, all systems present and working. correct part numbers, timing/dwell set to spec, valves adjusted to spec, fuel pressure to spec. etc., etc.....
2. Set the MPS using a dyno
   • Set the basic mixture (inner screw) - goal here is fuel economy and low emissions with reasonable performance (suggested AFM targets?)
   • Set the transition vacuum to full load (outer screw) - goal here is to eliminate flat spots
   • Set the full load mixture (full-load stop screw) - goal here is to set for maximum performance at WOT
3. Get car fully warmed-up and set idle mixture to spec CO - goal here is to reduce emissions and fuel consumption, and to minimize idle droop with electrical loading (the leaner the better).
4. Set idle speed with bleed screw to 1000 rpm
5. Let sit overnight
6. Insert 300 ohm potentiometer into the CHT circuit (make cables long enough to adjust from the cockpit
7. Start car and drive for 15 to 30 minutes, with frequent stops - you're looking for:
   • Proper aux air regulator operation (at least 5 minutes of idle higher than 1500 rpm after starting)
   • Idle stability without drooping, oscillations, or stalling
   • No popping on overrun
   • Minimum idle droop when electrical loads are on (lights, heater, blower)
8. If the conditions above are noted, increase the pot setting slowly until the best compromise performance is achieved.
9. Remove pot from circuit, read value - fabricate 1/4W ballast resistor to insert in CHT circuit of same value.

Comments?

If the intake system has been significantly modified (e.g. different cam, big valves, etc.), then to do the dyno procedure correctly, an assessment of the VE changes would need to be made, and the ECU daughter-card SC circuit would need mods - but this is beyond a reasonable approach for most people.

[r_towle]

So, from what I see there, if I want the motor to be a tad richer over the entire heat range, I have to start at 500 ohms.

Anything less seems to only affect the warm up time period, which may only last a few minutes.

Now, back to the MPS.

What is a simple and effective way to set up the MPS on a bench, like it was done at the factory, BUT...big BUT...with normal tools, normal guages...I will consider normal a hand vacuum pump.

I would love to find a way to do this without buying the two (one time use) tools to set up the car.
Without an O2 sensor, and without the special meter (cant remember the name)
These two tools seem to be one time use only..once the car is set, its set...no need to futz with it iny more, at least the FI settings..they are not dynamic, so no need to watch them with a meter/guage...who cares.

Rich

[pbanders]

So, from what I see there, if I want the motor to be a tad richer over the entire heat range, I have to start at 500 ohms.

You can try it, but again, the issue is you'll never have a stable mixture when warmed-up.

Anything less seems to only affect the warm up time period, which may only last a few minutes.

It only affects warm-up if it's 200 ohms or so. Warm up lasts a lot longer than a few minutes, even in warm areas (I live in Phoenix) it takes a minimum of 10 minutes in the summer and up to 20 minutes from what I've seen.

Now, back to the MPS.

What is a simple and effective way to set up the MPS on a bench, like it was done at the factory, BUT...big BUT...with normal tools, normal guages...I will consider normal a hand vacuum pump.

There is no simple way to properly set up the MPS using "normal" (i.e. found in nearly every garage) tools ang guages. See my web pages for details. The only way I've found that you can accurately set an MPS to factory spec is to have a setup that simulates the FI system running at a set engine speed, and to measure the injection pulse duration over a full range of load conditions. This requires a specialized D-Jetronic tester or a homebuilt setup that simulates the contact trigger points operation at a set engine speed. You also need a reference characteristic for the MPS you're calibrating to. I've gone and done this for the 043, 037, and 049 MPS's.

My web page describes a procedure using a Wavetek LCR meter, but I do not consider this to be an accurate procedure. It's OK for getting an MPS to a workable state, but has too much variation to be a calibration method.