Lambda tower anti tamper top - PeachParts Mercedes-Benz Forum

#1 01-27-2005, 01:18 PM

Quick question. I want to adjust the idle mixture on my 103. To get by the anti-tamper ball on top of the lambda tower, can I just cut right under it with a dremal cutting bit, or cut to the side and pry it out? Looks to me like I might be able to just leave the tower in place (instead of drilling out the 2 screws that secure it), cut carefully around or beside the anti-tamper ball, pry the ball out, then proceed with the normal procedure. Any reason I shouldn't do this?

Thanks in advance.

Wayne

Duke2.6 · #2 01-27-2005, 01:27 PM

Why do you want to adjust the mixture? Is the duty cycle out of spec?

Duke

#3 01-27-2005, 01:44 PM

Yeh, the duty cycle is just outside of the 10% window between idle and 2500 rpm, just a litte bit out on the rich side. Driveability is great, but gas mileage isn't very good, so I'm looking for anything that may legitamately help my mileage. I just want to get it within the 10% spec and see if I can improve my mileage without hurting the driveability. BTW, car has 187K miles and the idle has never been adjusted. Last emissions test here in Florida (before they stopped doing it here a few years ago) it passed barely, and was on the high side of CO at idle. I think I just need a little tweek. Can I just split the top of the lambda tower and pry out the ball?

Thanks

mctwin2kman · #4 01-27-2005, 03:45 PM

I took a very small drill bit to do mine. Drilled a little hole next to the ball while covering everything else to not get metal shavings anywhere and then used a very small tipped screw driver to pry the ball up. Then again that was because I had stupidly put the ball in instead of giving it time to adjust and all after I replaced my lambda tower. You are supposed to buy a new tower to do this, since they are only like 12-15 bucks!

#5 01-27-2005, 04:39 PM

I'm glad to hear that I'm not the only one that does things like that.

Thanks for the tip, I'll try it tonight.

Wayne

mctwin2kman · #6 01-27-2005, 04:57 PM

Just do it slow so you don't go to far if at all possible!

Duke2.6 · #7 01-27-2005, 05:13 PM

I think there is a misconception of what the basic mechanical mixture adjustment does. It ONLY affects the mechanically derived idle mixture based on air flow plate deflection when the car is in open loop operation during cold start and warmup. Once the O2 sensor gets up to 300C and the engine goes into closed loop operation (typically at around 60C coolant temperature), the O2 sensor and electronics will maintain a stoichimetric mixture at all conditions except WOT as long as the basic mixture adjustment is not so far out of wack that the control system has insufficient authority to maintain stoichiometry.

A slighly "rich" mixture at idle, as indicated by the duty cycle <50%, will aid cold start and warmup driveability, but will not have a signficant impact on fuel economy unless your average trip length is less than a couple of miles.

I measured my duty cycle in the range of 40-45 percent at idle and 50-55 at 2500 revs, no load, and my car has excellent cold start and warm-up characteristics, so I think the duty cycle is just about perfect.

What are your measured duty cycles at idle and 2500? A difference in duty cycle of no more than ten percent is probably considered "ideal", but there is no actual specification as long as the mixture can be maintained at stoic. by the control system during closed loop operation, which would likely be well over 20 percent difference, however if the idle duty cycle is over 50 percent, cold start and warmup may be poor due to leaness.

Another thing to consider is that if you have oxgenated fuel during the winter and non-oxygenated fuel in the summer you will get slightly different duty cycle readings with summer and winter fuel. Say you achieved a 50 percent idle reading on non-oxygenated summer fuel. The duty cycle on winter fuel would increase because the O2 sensor will detect a "lean condition" because of the extra oxygen and will have to run, on average, a little richer to maintain an average low O2 content in the exhaust.

Duke

embeetek · #8 01-27-2005, 10:42 PM

My little input- I'm a mb tech. at a dealer, & we're sometimes able to 'pop' the ball out of the Lambda tower by tapping two hammers on either side if the tower at the same time, being careful to have a rag covering the air intake valve...(ball bearing in intake = not good

.

Before adjusting the Lambda setting, make SURE you know what you're doing & why. This adjustment is very precise & not very forgiving.

#9 01-28-2005, 01:39 PM

My duty cycle is bouncing around 55-60 at 2500 rpm, and 45-50 at idle.

So from what your saying, even if I lean out my idle adustment a little, the only time that will change any thing is during the warm up cycle?

Also this would mean, I guess, that if you run a CO sniffer in your exhaust while tweaking the mixture, and the car is fully warmed up, the feedback system would negate any changes you are making with the adjustment screw (unless you go to extremes), and the CO content would remain unchanged even though you are turning the set screw?

If so, then if a car was truly out of spec (running abnormally rich all of the time, even when fully warmed up) how in the world do you adjust the mixture? Or would this be pointing to a sensor or mechanical failure?

I just want to make sure that I understand the system. I spend a lot of time in bumber-to-bumper traffic, and was hoping that a slight tweek toward the lean side might help me. But if it is only going to make a difference during the warm up cycle, this won't help me much. I have a 35-40 minute drive to work, but the bumber-bumper doesn't start untill after the car is fully warmed up anyway.

I think that you are telling me that I should leave it alone. You're probably right. The car starts cold fine, idles cold fine, transitions into closed loop flawlessly, and has great all round driveability. Exhaust does smell a little rich even when the car is fully warmed up, but I guess that this can't be changed.

Anything else that I should check to see if a can get a little increase in MPG? Plugs, wires, oxy sensor, air filter, fuel filter, etc. all new or young. Car runs great, closed loop system seems to be working, just doesn't seem to get very good mileage.

Thanks,

Wayne

350SL4spd · #10 01-28-2005, 02:15 PM

What kind of mileage are you getting? Just for fun you can check it against what the gov't thinks your mileage should be on you car. There's a thread on that in diesel forum right now.

I also remember a thread a while back on adjusting the EHA on higher milage M103s to pick up some of the general "slack" in a well worn engine. Search for it the archives. Can't remember if that was to correct a lean condition or the other way around...

Good luck...there's only a select few of us obsessed (or stupid) enough to try and match wits w/ this damn injection system MB stuck us with.

-M-

mctwin2kman · #11 01-28-2005, 03:39 PM

Yeah the lambda tower is the base adjustment for idle! Once the gas is pressed and the AFM plate moves down more then the EHA takes over! The EHA also is what makes the Duty Cycle change. For better fuel exonomy you can turn the EHA screw 1/8-1/4 turn Counter Clockwise and then it will lean the whole mixture out as far as I can tell. This would of course also make for a slightly leaner condition at WOT as well from what I understand on how the EHA works. As for Emmissions testing, since that is done at idle in most cases then the Lambda stightly lean would be good as well to correct that. Since if you notice the mixture will en-richen or lean based on the Lambda tower setting. Remember this is the base point for mixture so it will slightly affect the mixture throughout the whole range since the EHA can only do so much.

Edit: If you really want better economy and all then I would go with an EFI setup on there. This gives you much better control and you can setup the Fuel maps however you would like. There was a guy on 190revolution.net forums that was selling the kits complete and with instructions for around $1000 and he even had base maps for the M102 and M103 depending on what you order programmed in. He has a few kits left I believe. Also he has done many of these kits and put a lot of time in them, he is in Europe somewhere and has a shop that deals with EFI and MB and BMW!

Duke2.6 · #12 01-28-2005, 03:58 PM

Quote:

Originally Posted by PaulReynolds

My duty cycle is bouncing around 55-60 at 2500 rpm, and 45-50 at idle.

So from what your saying, even if I lean out my idle adustment a little, the only time that will change any thing is during the warm up cycle?

YES

Also this would mean, I guess, that if you run a CO sniffer in your exhaust while tweaking the mixture, and the car is fully warmed up, the feedback system would negate any changes you are making with the adjustment screw (unless you go to extremes), and the CO content would remain unchanged even though you are turning the set screw?

YES, AS LONG AS YOU DON'T MAKE SUCH A LARGE CHANGE IN THE BASIC MIXTURE ADJUSTMENT THAT THE LAMDA SYSTEM HAS INSUFFICIENT CONTROL AUTHORITY TO CORRECT IT BACK TO STOICIOMETRIC.

If so, then if a car was truly out of spec (running abnormally rich all of the time, even when fully warmed up) how in the world do you adjust the mixture? Or would this be pointing to a sensor or mechanical failure?

YOU WOULD HAVE TO LOOK FOR A PROBLEM IN THE LAMDA SYSTEM, BUT YOUR DUTY CYCLE READINGS TELL ME IT'S FUNCTIONING PROPERLY.

I just want to make sure that I understand the system. I spend a lot of time in bumber-to-bumper traffic, and was hoping that a slight tweek toward the lean side might help me. But if it is only going to make a difference during the warm up cycle, this won't help me much. I have a 35-40 minute drive to work, but the bumber-bumper doesn't start untill after the car is fully warmed up anyway.

AS LONG AS THE LAMDA SYSTEM IS OPERATING CORRECTLY, AND IT SOUNDS LIKE IT IS, THERE WILL BE NO EFFECT.

I think that you are telling me that I should leave it alone. You're probably right. The car starts cold fine, idles cold fine, transitions into closed loop flawlessly, and has great all round driveability. Exhaust does smell a little rich even when the car is fully warmed up, but I guess that this can't be changed.

CORRECT

Anything else that I should check to see if a can get a little increase in MPG? Plugs, wires, oxy sensor, air filter, fuel filter, etc. all new or young. Car runs great, closed loop system seems to be working, just doesn't seem to get very good mileage.

Thanks,

Wayne

What is your fuel mileage? The ONLY way to get a real measurement of fuel mileage is to record miles and gallons at every fill up for at least a half dozen tanks to get a reasonable average and average out measurement errors and differences in driving conditions from tank to tank.

I recall that the EPA mileage ratings for the my five speed 190E 2.6 are 18 and 26. I think the autos are a little lower, especially on the highway since they don't have the benefit of an overdrive top gear. I've seen as low as high teens in heavy traffic and a best just a bit over 30 in freeway cruising at about 65 MPH over 17 years of ownership. Typical mileage in a mix of freeway and surface street driving is low twenties and mid to high twenties on long highway trips.

Your duty cycle looks A-okay to me! If you read all the various driveability problems that M103s can experience - cold start, cold and hot idle, stalling, etc. some of which are very difficult to diagnose and correct, be happy that you have a M103 that runs just about perfect. I know I am.

Duke

Duke2.6 · #13 01-28-2005, 04:09 PM

Quote:

Originally Posted by mctwin2kman

Yeah the lambda tower is the base adjustment for idle! Once the gas is pressed and the AFM plate moves down more then the EHA takes over! The EHA also is what makes the Duty Cycle change. For better fuel exonomy you can turn the EHA screw 1/8-1/4 turn Counter Clockwise and then it will lean the whole mixture out as far as I can tell. This would of course also make for a slightly leaner condition at WOT as well from what I understand on how the EHA works. As for Emmissions testing, since that is done at idle in most cases then the Lambda stightly lean would be good as well to correct that. Since if you notice the mixture will en-richen or lean based on the Lambda tower setting. Remember this is the base point for mixture so it will slightly affect the mixture throughout the whole range since the EHA can only do so much.

Edit: If you really want better economy and all then I would go with an EFI setup on there. This gives you much better control and you can setup the Fuel maps however you would like. There was a guy on 190revolution.net forums that was selling the kits complete and with instructions for around $1000 and he even had base maps for the M102 and M103 depending on what you order programmed in. He has a few kits left I believe. Also he has done many of these kits and put a lot of time in them, he is in Europe somewhere and has a shop that deals with EFI and MB and BMW!

You do not understand how the KE-system operates.

The lamda system will correct the mixture back to stoiciometric no matter where the initial mechanical adjustment, unless the adjustment is so far off that the lamda's control authority is exceeded. This occurs under normal operating conditions (except WOT) when the engine is warm, including idle. The idle mixture adjustment has no meaningful effect on the WOT mixture, which is automatically richened. The lamda system is ignored during WOT operation, which is signaled by the TPS.

The amount of correction in the rich or lean condition is expressed by the duty cycle. A 50 percent duty cycle means the initial adjustment is right at stoic. If less, it means the initial adjustment is a bit rich and the lamda spends a bit more time leaning than richening and vice versa if the duty cycle is above 50 percent.

Suggest you reread my previous posts in this thread.

Duke

mctwin2kman · #14 01-28-2005, 07:17 PM

Quote:

Originally Posted by Duke2.6

You do not understand how the KE-system operates.

The lamda system will correct the mixture back to stoiciometric no matter where the initial mechanical adjustment, unless the adjustment is so far off that the lamda's control authority is exceeded. This occurs under normal operating conditions (except WOT) when the engine is warm, including idle. The idle mixture adjustment has no meaningful effect on the WOT mixture, which is automatically richened. The lamda system is ignored during WOT operation, which is signaled by the TPS.

The amount of correction in the rich or lean condition is expressed by the duty cycle. A 50 percent duty cycle means the initial adjustment is right at stoic. If less, it means the initial adjustment is a bit rich and the lamda spends a bit more time leaning than richening and vice versa if the duty cycle is above 50 percent.

Suggest you reread my previous posts in this thread.

Duke

Uhm the lamda tower is a mechanical only adjustment so apparantly you do not understand it. The EHA is the only electrical thing on a KE-II or KE-III based mechanical Injection system. It is the only thing on the engine that has to do with fuel besides the pump that is electronic. It adjusts the pressure between the lower and upper chambers of the fuel distributor. The Lamda tower is purely a mechanical starting point or baseline portion. The EHA uses input from the water temp sensor and the Ignition Controller to go to the ECU to change pressure thus richening and leaning the mixture. If you are going to comment then learn how to read and electrical diagram of the KE system! Sorry but that is just wrong!

Edit: I have an EE degree and know how to read electrical wiring diagrams, especially the ones on the MB Maint CD! I have studied it well so I do not need to pay someone like you how to do something that I can do myself. Sorry but maybe we are confused on teminology here. Lamda mechanical EHA electric. Hence the meaning of EHA, elctronic hydrolic actuator!

Duke2.6 · #15 01-28-2005, 08:46 PM

Well, I have ME degrees with specialized training in IC engines (MS from the U. of Wisconsin Engine Research Center where I performed emissions related research). The KE system is electromechanical and requires some knowledge of both electronic and mechanical systems in addition to a general understanding of chemistry, control systems, emissions, and emission control technology.

All I can suggest is that you reread my posts in this thread and try to absorb what I have said.

The air flow plate adjustment is an initial setting. From there the lamda system will maintain stoichiometry unless the initial adjustment is so far off that the lamda system has insufficient control authority to correct the mixture back to stoichiometric.

Small changes in the initial setting will affect duty cycle - the relative amount of time that the lamda system spends richening or leaning, but will not have any effect on overall operation of the engine, including emissions, as long as it is somewhere within a reasonable ballpark - say a duty cycle of no less than 30 percent to no more than 70 percent at the two test points of idle and 2500 revs, no load.

Maintaining stoichiometry is the primary strategy of modern emission control systems. The exhaust gas constiuency from a stoichimetric mixture is required to achieve maximum efficiency from three-way catalysts, which both oxidze HC and CO and reduce NOx. I use the term "reduce" in the chemistry context, which means to disassociate an oxide into its consituent molecular components.

Duke

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