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  #1  
Old 04-11-2009, 05:14 PM
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Correct Duty Cycle Procedures for CIS-E

Quote:
3) Detach the purge line at the electric switchover valve and seal. On my car, this valve is mounted on the inner wall of the left fender, adjacent to the ABS controller. The subject line is black tubing with white stripes.
Is there a picture of this purge line? I am a little confused over it.

Is it necessary to remove this prior to adjusting the mixture for My 1988 300TE. I want to make sure I am setting the mixture correctly because I am having some trouble getting a correct reading.

This is the step that I WAS taking for my 1988 300TE (California)
1. Ignition on, engine off
2. Go to diagnostic box, press and hold button for 4 seconds to read error codes (none)...then press and hold for 7 seconds. Red light should be solid now.
3. Start car
4. Put negative end of DMM into Pin 3 of X11 connector
5. Adjust CCW = lean, CW = Rich.
6. Adjust until reading oscillates around 50%.

Are my steps correct? As you can see I did not do this purge valve thing...

Much appreciated,
Robert

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Old 04-12-2009, 12:03 PM
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Nobody knows?
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  #3  
Old 04-12-2009, 12:54 PM
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The issue is to avoid the varying effects of differing volumes of purge. In reality unless its real hot out there is usually no purge at idle and the various personal opinions of where to set lambda have more effect than purge. I only disconnect purge when faced with a problem.
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Old 04-12-2009, 02:31 PM
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Originally Posted by stevebfl View Post
The issue is to avoid the varying effects of differing volumes of purge. In reality unless its real hot out there is usually no purge at idle and the various personal opinions of where to set lambda have more effect than purge. I only disconnect purge when faced with a problem.
Other than that, are the rest of my steps correct?
My 260E is right on the verge of passing the smog only failed the HC by 20...so I think if I can get the mixture dead on and get an oil change she will pass. That's why I want to make sure I am doing it 100% correct.
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Old 04-12-2009, 02:51 PM
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Your question means you aren't fully understanding what is happening. There is no better mixture. Whether you set control at 50% or 40% the car runs exactly the same, unless it ever runs beyond control.

Setting to 50% mean the car can correct equally for deviation of mixture both lean or rich. Try it. Set it to 50% watch the control needle goes rich lean rich lean etc etc. Now richen it to 40%, watch it, needle goes rich lean rich lean etc etc. The actual mixture has not changed as the system compensated for the wrong correction. As long as it is in control (rich lean rich lean) the mixture is the same.

The exception and the reason I prefer 40% is that all dynamic mixture is based on the settings not control. This means that when cold (before control) the car is set richer, sudden accel is based on settings as the system doesn't react that fast. But for constant state it make no difference what you set it too till you run out of range at either 0% or 100%. Any setting that allows control is in effect the same.
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Old 04-12-2009, 03:14 PM
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Quote:
Originally Posted by stevebfl View Post
Your question means you aren't fully understanding what is happening. There is no better mixture. Whether you set control at 50% or 40% the car runs exactly the same, unless it ever runs beyond control.

Setting to 50% mean the car can correct equally for deviation of mixture both lean or rich. Try it. Set it to 50% watch the control needle goes rich lean rich lean etc etc. Now richen it to 40%, watch it, needle goes rich lean rich lean etc etc. The actual mixture has not changed as the system compensated for the wrong correction. As long as it is in control (rich lean rich lean) the mixture is the same.

The exception and the reason I prefer 40% is that all dynamic mixture is based on the settings not control. This means that when cold (before control) the car is set richer, sudden accel is based on settings as the system doesn't react that fast. But for constant state it make no difference what you set it too till you run out of range at either 0% or 100%. Any setting that allows control is in effect the same.
Okay....Then why does a difference of lets say 40% or 60% make a large difference in the smoothness of the idle? The engine just "sounds" happier when set to a certain mixture setting.

Thanks
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Old 04-12-2009, 03:32 PM
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It is possible that you are effected by the immediate gratification and don't see that in moments it is all the same again. It is conceivable that it is broken, but since the duty cycle only reacts if it is functioning that is hard to conceive.
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  #8  
Old 04-12-2009, 09:02 PM
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Hi Steve,
I am Ps2cho's father and I have been working with him on both of the cars..
Lets talk about the 260E that we are trying to get thru Smog.
It ran like crap as it had been sitting for a long time, so we started with correct non resister plugs as the originals were wrong and gapped at about 1/2"!
It seemed to run much better although it was very sluggish off the line. It failed the CA smog test as a gross polluter as it had before we got it.
HC was 3 times failure limit and NO was over 2100PPM too.

We put on new plug leads, all new idle hoses, swapped the EHA and EHA seals as they were weeping, reset the throttle plate as it was binding, and checked the fuel pressure and it was spot on.
We set the Duty cycle but were a little confused over a couple of issues... Namely that with Ignition On Engine Off the Meter reads 69.3%, not 70%. The engine was running well at 50%, at idle and 2500rpm about 50% too, but ran even better at about 35% and the 2500rpm reading was very close. As it sounded so sweet we thought we would try again.

The car is transformed... I drove it hard to the smog station to heat the cat and see how it went. Idles smooth and has real punch of the line, in fact it even broke traction for a sec on a dry road in a straight line on the 2/3 upchange!

We went to the Smog station and it failed again but only just.
The HC was exactly on the limit at 15mph at 85ppm but it failed at 25 mph with 135ppm when the max is 110ppm.




I guess we are confused by the Duty cycle issue and need some expert input on how to set it correctly and if indeed a simple adjustment would allow it to pass smog?
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Old 04-12-2009, 10:10 PM
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I'm guessing that the cat is probably original and about dead. If so it is testament to how good they build them.

The issue with duty cycle requires an understanding of fuel control. You must accept the concept that if the car has control, you don't! It is not an arbitrary control. The system is designed to keep precise mixture control in steady state. Off hand I'd rather not speculate on what you are seeing, but if you are right the system is not working properly. The cars mixture is the same as long as it has control. Control is observed when the duty cycle swings rich to lean, etc, etc. When you are at 50% and richen it some, the duty cycle responds by moving to 40% and then resumes control swinging back and forth about 40%. It will keep doing this untill you bottom out the adjustment at 0% or the other way at 100%.

Modern cars were made so those who might not understand this concept have no ability to screw it up. The ability for the lambda correction to stay centered is handled automatically through adaptation. run equivalent to 40% for long enough and either closed throttle or loaded adaptation is borrowed from to recenter. It does this up to its limits at which time it sets an adaptation code.
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  #10  
Old 04-13-2009, 08:13 AM
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Steve

Your responses and explanation of how the CIS-E functions is much appreciated.

Too many ( not neccesarily the opening poster ) try to fiddle with the CIS-E settings to achieve performance improvements.

I bought my 1988 300CE M103-12V new in May of 1988.
Always had it maintained to factory specifications.

In 1997 I was fortunate to purchase a NOS TurboTechnics early 1990's twin turbo kit from Hughes of Beaconsfield, a Mercedes main dealer in the UK who commissioned the kits for installation on new delivery 124 cars.

The kit included a piggy back controller to enrich under boost.
This altered signals and settings to the CIS-E.
It was in my mind a disaster.

We removed the piggyback control, brought the CIS-E back to factory spec and settings.
Most importantly replaced all the brittle vacuum lines and smoke tested for leaks.

The enrichment was accomplished by a stand alone control that fires two additional injectors.

In essence two systems a completely stock CIS-E and a enrichment under boost using a MAP input.

All this to say that last week was the first time since the TT install to renew the registration and undergo the state ( Delaware ) emissions testing.
Not as stringent as CA and done with a tailpipe sniffer at idle only.
Results: HC PPM= 39 ( 220 limit ) CO% = 0 ( 1.2 limit )

If the CIS-E is set to factory spec it will function properly and pass emissions.

Ed A.

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