I have never really paid any attention to fuel control at full throttle as I have never had a deficiency that related to the electronic control at WOT. I will say that I'm pretty sure what you are seeing is appropriate. The only action I could imagine different would be a lack of control (open loop) at WOT. Many systems will do this, not sure about KE. Open loop at WOT would put EHA current at 0.0ma with any base mixture setting.

If the system is still in closed loop it is natural for it to go negative WOT as the base system is designed to be richer at that set of circumstances, I would presume.

As to adjusting the EHA, all you are doing is changing the size of the fixed leak. It really shouldn't be done without monitoring the differential pressure. The main reason I say that is that if you really have a problem here it is probably due to a variation in differential pressure that isn't current related. In other words at different fuel flow rates the differential pressure would vary with the EHA unplugged. This is not how it is supposed to work but a number of conditions can cause it.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks, Steve, for your answer. I understood most of it (I guess ;-)I believe it works the way it should, too. Maybe the next few hundred miles will show if the mileage and driveability are OK. I may rely too much on measured (or missing) current values, when tha WIS says the full load enrichment should be about +3...+6 mA.

The next step would be a wideband AFR meter, but that costs something like 300 euros. I want to get the basic settings right before I'll add some forced induction to the motor.

tomant

One thing about your WIS data: any correction of such a nature is added to the current situtaion. I've not experienced WOT enrichment but I do know of accereration enrichment. It is based on the rate of change of the airflow pot. It can give 3-5ma of enrichment. That doesn't mean that while watching EHA current one would see a reading of 3-5ma. What it means is that if one were in closed loop at -2 to -3ma (a nice rich basic setting), and one floored it and got a 5ma enrichment the values one read would be +2 to +3 ma a CHANGE of 5ma.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

KE Jet should have full load enrichment but no acceleration enrichment when engine tempereture is above 80 degree C. You are right about the enrichment current being added to the cruise current. I just don't see any full load enrichment in the form of increasing current even though the full load switch seem so work OK. The current typically decreases to -10 mA. That still puzzles me.

tomant

What constitutes a closed loop system?What items are included in the loop,If you can Isolate each, can you find the input for bad or different reading? JNT

I bought a TechEdge wideband lambda meter. The AFR stays at 14.5 at idle and cruise. At WOT acceleration the AFR is around 11.5 - 13 and then gets back to 14.5 at constant speed. So the KE-Jetronic mixture formation seems to be working great.

What would be a good value for AFR for a NA engine and a turbo engine in closed loop operation? The wideband meter has a narrowband output to the ECU and I can program it to give almost any AFR in closed loop. I think I must change the basic CO and/or EHA mixture accordingly. Do the EHA basic setting (the adjustment screw inside the EHA) and the CO setting (idle mixture screw) affect the whole mixture scale from lean (or stoichiometric) to rich mixtures in the same manner or is there some principal difference between these settings?

tomant

Sorry I'm a bit late to this thread...

Are you saying KE Jet above 80 degrees has no acceleration enrichment? So with the EHA unplugged it should accelerate similarly to when plugged in (except for when you go to WOT)?

__________________
190E's:
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black 2nd owner
http://www.maylane.demon.co.uk/190esmall.jpghttp://www.maylane.demon.co.uk/190esmall2.jpg

According to SAE paper nr 820253 "KE-Jetronic - A New Continuously etc." by Wolfgang Maisch that is the case. The acceleration enrichment ends at 80 deg C. The full load enrichment should be 10% between 1500 and 3000 rpm and 5% above 4000 rpm. This may be for early KE-Jet models, maybe later are different? My KE-Jet seems to keep the AFR value at 14,5 until WOT acceleration. After that the AFR varies from 11 to 13 at acceleration and unplugging the EHA doesn't seem to affect these WOT values.

tomant

Hmm, excellent research there. I haven't felt much of a difference with EHA unplugged it has to be said.

__________________
190E's:
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black 2nd owner
http://www.maylane.demon.co.uk/190esmall.jpghttp://www.maylane.demon.co.uk/190esmall2.jpg

bump

__________________
Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red