I've been carefully monitoring the amount of smoke I get in the rear view mirror under full throttle, and it is very very little. It's most like particulate matter than gray smoke. I installed a boost controller and locked it in at 13.5 psi like "Speedy" and have already turned the ALDA counterclockwise 1.5 turns. Is it conceivable that I could need another half turn counter clockwise? I'm going by the fact that I dont get the gray smoke at full throttle above 3000 RPM. The car runs great but I'd like to get the mixture right for performance and fuel economy reasons. Thanks

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

On my car, two turns counter clockwise was as far as the ALDA would go. Currently it is at as 1.5 turns ccw and my mileage hasn't suffered much. Still averaging about 26mpg.

You are doing it right. Adjust for faint smoke visible in the rearview at full throtle under load at 3000+rpms in full sunlight. One of my SDs has the ALDA all the way out and I wish I could go a little more, the other is 3/4 turn out from stock and I might turn it back in 1/16th to lighten up the smoke this weekend.

P.S. How can I include a picture in a post without making it an attachment? I've tried putting one in the signature line and using the IMG function (it just seemed to insert a link) Thanks.

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Bob D.
Parrish, FL
1 SDL, 1 D, 1 TD, 1 Mog

The problem with adjusting for more fuel is that, using your methods, you have NO way of knowing if you are actually damaging your engines. The only way to know for sure is to install a pyrometer. Several styles are available from various manufacturers, VDO, Autometer, Isspro, etc. The VDO's are very nice and "teutonic" enough to not look out of place in a MB. A pyro measures exhaust gas temperature (egt). Most turbo diesels have a safe maximum of 1250* measured pre-turbo. Some are able to withstand 1400*. The result of engine operation with excessive EGT is MELTED PISTONS. This is NOT an exaggeration, I have seen this in pulling vehicles and pickup that have been tweaked and pushed a little too hard. It is a very expensive lesson to learn. There are two locations to install the EGT probe, pre or post turbo. Post turbo installs are generally easier however the EGT readings are @ 200* cooler as the turbo soaks up some of the heat during operation and the readings are not as responsive. EGT guage/probe packages cost $90-$150 and are easy to install. "Smoke" is not a reliable way to judge fueling. Tweaking a diesel without one is playing with fire, you will "burn" something sooner or later. I am not advocating not tweaking these engines, by all means, get all you can out of them, but at least be prudent enough not to melt anything unintentionally. Good Luck! RT

I've noticed alot of the high performance rice burners using exhaust gas temperature gauges. You can also find them in single engine piston driven airplanes. You use it to determine how "lean" to set the mixture once you get to cruising speed/altitude. Lean the mixture out until you see a temp rise and then richen it slightly.

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Jim

I wish I could claim the smoke method as mine, but I am relating work done by others far more experienced than me. The method has been checked with an EGT and on an injection pump test stand and found to be very safe. Exhaust temperature is lower on either side of proper adjustment. If you adjust the alda out too much and start getting heavy black smoke the exhaust gas temperature drops because there is too much fuel for the given quantity of air. If you're too far in on the alda and have no smoke you have too little fuel for the amount of air and the egt drops. Mercedes carefully engineer these engines to be very reliable. They included many systems to increase reliability like the waste gate and over boost protection switch and piston cooling nozzles. I am not advocating forcing your engine beyond what MB intended only restoring the performance they designed into it. Checking your boost sensing line. Adjusting your wastgate to factory specifications and adjusting the alda for optimum efficiency will not harm your engine. If you lock down your wastegate and bypass the overboost switch you can and probably will run into problems without an EGT gauge. I would never advocate abusing an engine like that but it would be a very interesting test ;-)

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Bob D.
Parrish, FL
1 SDL, 1 D, 1 TD, 1 Mog

I beg to differ but: A diesel is not like a gas engine. When you lean out a gasser it runs hotter, and richer is cooler. With a diesel it is the exact opposite, the more fuel you add the hotter it will run, especially if you are lugging it up a hill/mountain or pushing it hard on the highway into very stiff headwinds. At no time can you add enough fuel to your diesel to "cool it down from lack of air" You cannot test for high EGTs on a injection pump test stand, they only test pumps.... A dynamometer would be a better choice.... You can better believe that the MB engineers thought this through, and that is EXACTLY why there was a tamper-proof ALDA adjustment! You have chosen to modify/adjust the system quite possibly way beyond what they ever intended. The least you should do is monitor the EGT's You are also talking about almost 20 year old diesel technology. I have seen melted pistons from some of the most advanced modern computer controlled diesels, simply because somebody pushed too hard. I find it hard to believe that you think 20 year old technology, no matter how good it was, will keep you safe particularly since you have tampered with the safeguards in the process. RT

R.
I consider any day I learn something new to be a successful day and I try to do so every day. After only 22 years working on diesels there is still much I have to learn. I didn't feel my sentence regarding EGT and test stands was so ambiguous as to cause confusion. This is why I inserted the and between the two examples. I have personally done work with EGTs on both gas and diesel engines and at full throttle and full load either too much or too little fuel will result in inefficient combustion and therefore a drop in EGT. I must point out that the word throttle is somewhat misleading in the case of most diesels but I use it here for the sake of simplicity. I try to share some hard won knowledge with others in the hope that they will reciprocate. The ALDA adjustment I and others offer is an approximation, but a very good one if done carefully. I mentioned the test stand only because after setting one by the smoke method I have had it checked and found to be within specs according to Bosch. The Tamper cap is there to satisfy EPA requirements. In the early 80s MB started delivering 617.95 engines with slightly lean ALDAs in order to lower combustion temperatures and reduce the formations of NOx compounds. If you don't feel comfortable adjusting your engine to operate as originally designed Then you should not do so. With the over boost switch and waste gate operating as designed there is nothing you can do with the ALDA screw even approach melting a piston. Now carbon deposit formation and wasted fuel are other matters. One final caveat MB does not specify any method of adjusting the ALDA other than on a test stand and it has been reported that some ALDAs will fail when adjusted.

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Bob D.
Parrish, FL
1 SDL, 1 D, 1 TD, 1 Mog

I found an Alda in the junkyard but the problem is, it is already adjusted. On most that tweak the Alda, is it 2 full turns ccw? If so, can I just turn it half a turn cw as I don't want it out fully. Most suggest 1 1/2 turns ccw and that is what I want to try. Thanks in advance.

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96 Legacy LSi wagon
92 Mitsu Expo
95 525iT
1983 300TD clackclackclack sold
1972 Toyota Corolla wagon TE28 sold
1991 Galant VR4 pshhhhh non-op
1989 Montero RS pop's ride

There is no set number of turns. When you car is at operating temperature find a safe stretch of road preferably with an uphill grade and do a full throttle run with one eye in the rearview. In full sunlight at full throttle full load at 3000+ rpm you should see faint dark smoke. If the smoke is heavy turn in 1/4 turn(clockwise) less fuel, if no smoke turn out 1/4 turn counterclockwise) and re test. It might take a while to find the perfect setting down to 1/16 of a turn, but you can do it over several days. Don't be influenced by "smoke" at night viewed in trailing headlights. Also check your boost sensing line to make sure it is clear.

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Bob D.
Parrish, FL
1 SDL, 1 D, 1 TD, 1 Mog

Hi Guys-
I've recently installed a boost control on my 85 300D. Previous to doing that I adjusted the ALDA. I could not believe the difference it made in low end performance. The problem is this. By degrees I have made adjustments counter clockwise till there is no further room to turn. I still get no smoke under hard acceleration. That is how I have it adjusted now. I understand that you are suppose to adjust counter clockwise until it smokes under hard acceleration and than adjust clockwise until the smoke is faintly visible. The problem is, I can't get it to smoke and it's turned all the way out. What should I do?
Thanks.

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Ed
1985 300D w/ 196,000 miles

Thanks Bob. I'll try those suggestions out when I install it this weekend.

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96 Legacy LSi wagon
92 Mitsu Expo
95 525iT
1983 300TD clackclackclack sold
1972 Toyota Corolla wagon TE28 sold
1991 Galant VR4 pshhhhh non-op
1989 Montero RS pop's ride