I remember reading on one of the other threads about removing the ALDA and that you need to remove other boost related components. Is this correct? I might have misread this thread but I want to be clear before I remove it this weekend. Will the internal components of the ALDA just fall out if I unscrew the ALDA casing?
Thanks
A

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1987 300SDL
187,000 miles

You will have to plug the boost tube that ran to the ALDA. If you take out the 4 body screws the lower bellows will come right out, the top one you will have to remove the 10m locknut and unscrew it.

do you have to take it off\gutt the alda for it, "not to work"

or can you just unhook and plug the lines on both ends

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1985 300D - 599,xxxk - blue interior #265 Monark Nozzle, AL129X, 15" Ronals, Gen II Big Brakes hunting
1985 300D - 491,xxxk - in prog-{A-A IC, 3" exhaust, psi\pyro, 28*BTDC, Hella Euros, IP Limiter removal
1985 300TD - 783,xxxk - parts car,used new engine with ALDA cap inplace
1987 Kenworth T-600 8LL 425 CAT Mech. - 6,000,000+k - DEI exhaust wrap, punched through resonators, 1 recent rebuild,

If you plug the lines, it will not allow fuel enrichment.

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Gone to the dark side

- Jeff

Right, just plugging the lines will hurt power. You have to physically remove and/or gut the ALDA.

Do you have to plug the hole left in the top of the IP?

As a newbie myself, I'm reluctant to weigh in on this thread but I've spent hours reading this topic in other threads - you would benfit from more reading also. Do a search for "ALDA Removal". I learned that this depended a lot on what engine you are working with. For my 617 in a 123, I came to the conclusion that it needed to be left in place (perhaps with a slight adjustment). Your last question makes me think you are also doing a 617, right?
Charles

* I must be missing something here. Why would anyone remove an ALDA unit, and leave it off or gut it and try to do without it's function??
* If you need to remove it to reshim it, or to replace it with a new one, then it just takes an open-end wrench (27mm?) to break loose the compression-type nut holding it to the injection pump. It's natural to fear that there's some linkage that extends down into the governor which has to be released some other way. There's not. The ALDA unit just lifts off (well, there's not much room to lift, but it does come off without removing the intake manifold or the inj pump). Of course you'll need to disconnect the vacuum line to it.

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ASE Master Tech
Quality Enterprises
Mercedes Svc. & Restoration
Sheridan, IN
317.769.3536

The ALDA removal is experimental. Putting new nozzles(injector) on the SDL and planning on removing the ALDA. It is a slug off the line. I believe monitoring the boost will be adequate enough to ensure no overboost. I installed a manual control for the turbo on my 99 diesel Suburban. I monitor the boost to ensure I am not applying too much boost during tow. Works like a champ. So I am going to tinker with the boost on the SDL to see if there is any gain in performance.
A

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1987 300SDL
187,000 miles

No.

The ALDA has no direct effect on the boost. Its function is like an aneroid, to decouple the rack position/fuel flow increase from the throttle pedal, or to delay the initial increase/surge of fuel flow when the pedal is pressed quickly until the airflow and boost have incresed and keep them proportional. It also functions as an altitude compensation device.

So, indirectly it does affect boost, by limiting fuel to a proper proportion of fuel-air. It seems in my experience that they tend to err on the lean side as the car ages, but also in my experience with the 602 and 603 it can be adjusted to a point where it runs too rich and puffs a little black on take-off, unless it is completely unable to pressurize/function properly.

The first step in troubleshooting the alda is to ensure that the fitting on the intake manifold just above and rearward of the ALDA is clear by blowing through it, then take the line from that fitting and run it directly to the ALDA, bypassing the switchover valve to see if it helps improve takeoff (indicating a clogged switchover valve or a leak).

If the ALDA does seem to be the problem, it can be adjusted on the car (with some patience), I believe that 1/2 to 1 turn CCW is the standard initial adjustment.

It can be done without removing the intake manifold or plumbing, either removing or adjusting it. However, from some people's experience, it seems that it is faster to remove, adjust, and reinstall the ALDA than to adjust it in place, I've always done it in place and it is a tedious task.

__________________

Gone to the dark side

- Jeff

As the originator of the 603 ALDA removal, I'll respond to your query with the following observations:

1) The function of the ALDA is to limit fuel under low boost conditions when the engine has insufficient air. A typical driver will get fairly heavy smoke if he mashes the pedal below 2200 rpm.

2) The rack controls the amount of fuel. Therefore, a driver who is cognizant of the limitations of the engine below boost levels, can, effectively limit the fuel by judicious use of his right foot. Keeping the go pedal below the 1/2 position below 2200 rpm will ensure that the engine is not overfueled.

3) I've removed the ALDA on both 603's and find that the part throttle performance is improved dramatically. There is no smoke below the onset of boost if the vehicle is driven properly. The fuel economy of the vehicle (27-29) is unchanged by the modification.

The only possible benefit to the ALDA is the benefit of overboost protection should the wastegate fail. But, in reality, most of the manifold sensors are plugged after 20 years and this protection is really not available to most drivers anyway.

* I can't believe that a little part-throttle improvement isn't costing you more somewhere else (by removing the ALDA altogether). Or Mercedes would have just left it off. As someone has already explained, this unit does a lot more than just trim emissions.
* Last year, at the owner's request, I reshimmed an ALDA unit on an OM603 engine in a '90 350SDL. That became the fastest W126 diesel I've ever driven, off the line, mid range, or wide open. 'Course we don't have emissions inspections here in Indiana.
* The waste gate is the first line of defense against an overboost. But in the unlikely event that the waste gate fails, it would be smart to have a back-up. Seems to me that the time spent checking the overboost safety circuit would be time better spent.

__________________
ASE Master Tech
Quality Enterprises
Mercedes Svc. & Restoration
Sheridan, IN
317.769.3536

No, all its for is emissions. Its only reason to exist is to prevent black smoke with low boost.

Black smoke indicates overfueling, which contaminates oil as well as air. The 60x engines' oil change interval is extended from the 61x engines partly because it burns cleaner with the ALDA in place.

__________________

Gone to the dark side

- Jeff