My '87 300D used to make a turbo whistling noise. Then I removed the intake manifold (second time) to replace some fuel line clips and remove the ALDA cap. There is a chance I changed the ALDA setting after I removed it. I reassembled everything and there is no turbo spooling noise (it used to sound like a semi). But power did not seem to be down.

I turned the ALDA 2 turns ccw and then 1/2 ccw more. I don't think the car felt any more powerful any sooner after 2ccw, but I think it could be slower with the extra 1/2 ccw.

Does any of this make sense? I do not see plumes of black smoke, it seems to smoke about as much as it always does.

Brian

Brian,

The ALDA adjust only improves off-idle power. If the car was quick off the line before, turning the ALDA won't help. It's odd that you got no power increase with no change in smoke, though. If it was too rich you would get noticeable smoke, at least off idle. Hmmm. Have you tried timing your car 0-60 on a flat road? The factory spec is 10.9 seconds (at sea level - above 2-3000 feet there is a significant power loss off idle.)

BTW - read my "Free HP" post for something else to check!


Regards,

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

Please tell me if this is correct: Turning ALDA ccw will improve off-line power at best and continuing to turn ccw will increase smoke but at no point should the power (from fueling) decrease (unless the ALDA breaks during adjustment).

Could the change in turbo noise be because something was leaking in air that shouldn't have and after re-installing the manifold everything is sealed again?

I'm going to check this in a few minutes when I get off work.


Thanks,
Brian

P.S. I was not trying to get any performance edge by adjusting the ALDA. I have a cruise surge problem on flat and downhill roads and heard from Marshall Booth that 2 ccw turns solve his cruise control surging problem.

Well, if you over-richen the mixture, you could lose power - but this would normally come with black smoke too. If the ALDA breaks it will drastically reduce power above 2000rpm. I HIGHLY recommend unplugging the ALDA tube and driving the car, just so you know what it feels like to have it disconnected. It's a real eye-opener. Power off idle is identical, but above 1500-2000rpm it's just a DOG.

The lack of whine is a good thing. If you have the KKK turbo (no rubber hose to the wastegate canister, which is under the turbo), it should be silent - at least it is on my car. The Garrett (which has the canister above the alternator, with a rubber hose to it) makes an audible while when I lift off the throttle at low speeds. Normally road noise covers this sound - it's quite faint. I wouldn't worry about it.

Now, there is a cruise control surge fix in the service manual, however it can rob you of power (see my other post). HOWEVER, I bet if you disconnect both the EGR and air recirc valves at the turbo (plug the lines), AND lubricate all 3 or 4 throttle linkages (they carefully pop off), that may fix your surging problem. I am surprised Marshall said the ALDA fix cured a cruise surge - that sounds *very* strange to me. The ALDA adjustment only changes the fuel minimum (off idle), not anything when the engine is revved up. Perhaps he misunderstood your problem...?


Best regards,

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Dave
Boise, ID
Check out my website photos, documents, and movies!

Dave, I only hear a whine for a split second when the car downshifts at low speeds. I will verify tonight. I will also disconnect ALDA to see what that does, never thought of that. I have the Garrett turbo. I do believe Marshall understand the problem correctly, He discovered this when trying to solve some other problem on his car. I lubed the throttle linkages with ATF before asking him.

The whine you describe is exactly what I hear with my Garrett turbo. I believe it is normal for this turbo. If the sound goes away, I wouldn't worry at all. If it got a LOT louder then maybe I'd be concerned.

Last question - do you have the EGR and air recirc valves disconnected or otherwise disabled?

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

On the way home from work, the car seemed to have enough power once it was at speed, but it lacked the familiar feel that it had before I started messing with the ALDA cap. At home I gave the ALDA one more turn ccw and now its starting to feel like its old self. (I must have turned the ALDA clockwise A LOT when I removed the cover.) So now the turbo is whistling more like it used to. I'm not sure that the car is any faster, but it sounds more like a semi, which is like it used to sound. Maybe its the wastegate.

A friend that used to drive semis suggested the car is burning more fuel and therefore higher EGTs and therefore turbo bearing making noise? He said his pyro was one of the most important gauges on his truck.

This might make sense. I think the whisteling noise become more pronounced in December, after I swtiched to synthetic oil. So, perhaps the turbo bearing was coked from infrequently changed dino oil or dino oil too thin (as can be seen as wear on my camshaft lobes) and the synthetic freed up the coking of the turbo and now its making noise?

Unfortunately I don't have a pyro gauge installed, and don't have a spare turbo to test with. With my current setup there is still no smoke and the car sounds nearly like it did before I ever adjusted the ALDA.

Ideas?

Brian

I still would like to know the results of a 0-60 test in your car. I just tested mine (after correcting the ALDA plumbing) and I'm getting a very respectable 11.0-11.5 seconds, repeatably, according to my stopwatch. What does yours do? And what elevation do you live at?

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

Dave,
I can't come up with a 0-60 time today. The elevation is somewhere around 500 ft, but there are no flat nor straight roads in my county. Can possibly do this tomorrow. The flattest stretch of road that has a 4-way stop (or stop light) that I can think of is 90 miles away. Other roads may be flat, but they are limited access. Can't exactly stop on the freeway and then do a 0-60 time

No 0-60 time to report yet. BUT i did make more adjustments to the ALDA. I have noticed that ALDA adjustment affects engine RPM at speed and shift points. Can i attribute this to the rack position sensor?

Before I started all this, at 77 MPH my car would run about 2950-3050 RPM. At various points of turning clockwise the ALDA, it would increase to 3200 and shift often to get there.

By adjusting the ALDA closely back to 2950-3050 RPM (actually its a HAIR highter than it was before), the car is SMOOTHER. With WOT the power is smooth. Before it would be a bit jerky kind of like my control control problem. However, the cruise is still jerky at times. I removed the air recirc hose last night and will see what hapens.

QUESTION; Those '87 300D drivers, what RPM does your engine run at 77 MPH (or 80, whatever) under steady load (flat or uphill)? Please state engine speed and flat/uphill conditions, altitude.

Brian

Wow - that's weird. Anyway, on flat roads it should be ~3000rpm at ~75mph. Under load (i.e., uphill) the torque converter allows some slip and you could see higher RPM at the same MPH (say, 32-3300?). However, that is all relative to gearing & RPM, messing with the ALDA should NOT affect any of that. The shift points (RPM) are changed by the "kickdown" cable that goes to the tranny. The shift feel (soft/firm) is changed by the vacuum signal to the tranny. BTW - when you disconnect the EGR and/or recirc, make sure you plug the hoses or you'll have a big o'l vacuum leak!


HTH,

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

Dave,

Based on your RPM numbers my car has spent most of its life at slightly lower RPM. I did make my car run at 3200 RPM at 75 MPH but since it always ran slower than that, I turned up the ALDA some more. This relates to turbo spooling noise - with lower ALDA setting there is less/NO noise from the turbo. To make my car the way it was 100% I believe I would give the ALDA a bit more ccw. But, its fine just the way it is. I may even turn it back a hair if more people say higher RPM at 75 MPH.

If there is not enough fuel (ALDA too low) then the engine power curve is not right. Therefore I am pushing down the accelerator more to compensate. That in turns affects the RACK LOAD SENSOR. But with the accelerator down more its also affecting the Bowden cable and therefore shifting.

As far as the RPM, maybe it has to do with the torque converter operation.

No vacuum leaks, those line are plugged!

Thanks,
Brian

Ah, good points. BTW, after studying the manuals so more, I'm pretty sure the rack position sensor (3-wire connector near the ALDA & shutoff pod) is only required for the EDS (Electronic Diesel System). I don't think it affects power output (if EGR & recirc are disconnected) or I/P operation. It was used, AFAICT, to tell the air recirc & EGR solenoids when to open & close. If it's not related to the ELR (electronic idle speed control) then the load sensor would be basically useless with the aforementioned items disabled. I haven't experimented yet though. Good luck!

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

Thanks for the comments, I have been able to adjust my ALDA to get rid of 95% of my cruise control surging and the turbo does not make much, if any, noise in approximately 5000 miles of driving over the past two weeks

Brian