I keep running into this discussion and must say I am still confused.

If I understand correctly the IP has three pieces of information to determine the quantity, duration and starting point of the injection.

These are throttle position, engine RPM and boost pressure. Now you could argue that any one of them does not meter but instead restricts with full flow being unrestricted. I do not see how the difference is significant.

If any of those three circuits are not functioning correctly of limiting fuel when they shouldn't it seems to me they should be fixed. The aneroid capsule in the ALDA is designed (if I understand correctly) to increase fuel flow (or decrease less if that is an improvement) as more boost is applied.

If the ALDA is defeated how does the IP know to deliver more fuel with high boost as compared to a near identical situation with low boost? I do not believe I have ever heard a good answer to that question.

So, I know it is done often enough, but I think the ALDA should be adjusted correctly for optimal performance not removed. I'm quite willing to be shown the error of my thoughts though.

There's quite a good MB diagram of an IP showing how the ALDA's plunger and its related linkage restricts rack movement when the plunger is depressed. When the ALDA is removed, the plunger is fully raised because it is sprung that way. In the fully raised position, this linkage will not restrict rack action in any way. So the rack is allowed to move its full range under the influence of other inputs (your foot), unfettered by the ALDA. Pulling the plunger up further, if you could, would not add more fuel.

ALDA on a turbo car does two things: 1) lowers the plunger at lower barometric pressures (e.g. higher altitudes), 2) raises the plunger under boost.

Removing the ALDA on a turbo car means the fuel curve for full boost is available at all times. If you use the curve (with your foot) without having the associated boost, you get a black cloud. If you had more boost earlier (at lower RPM) as VNT promises, you'd get less smoke more usable power. Faster off-the-line.

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Cheers!
Scott McPhee

1987 300D

With the ALDA adjusted correctly, it would allow that fuel anyway, as soon as the vnt makes that boost, correct? It seems like more of an economy control to me, stopping you from wasting fuel when the engine can't use it.

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'82 300SD - Somewhere over 220k - Becoming reliable...

Scott. We're saying the same thing but coming to opposite conclusions. I acknowledge how the ALDA works in the IP.

Please answer me this basic question: How does the IP differentiate between two different scenarios in the car when the RPM and throttle position are the same but the boost in one case is 0.1 atm and the other case 0.8 atm?

If you needed to remove the ALDA because your car was fuel deprived at low RPM then it was not functioning properly or setup properly.

This, is of course, off-topic from VNT.

Correct. Whether you want to call it economy, emission control or in my case wishes to reduce diesel exhaust in the car.

The ALDA should allow appropriate fuel delivery at no boost and maximum boost. Without it there is NO mechanism that the IP has for compensating for varying boost levels.

I also understand how the ALDA works although my familiarity with the Bosch inline pumps is not nearly as thorough as my understanding of the VE pumps. I've seen the same argument/discussion regarding the VE pumps. Both ways of looking at it are true according to Einstein's theory of relativity. I like the scene in the new Star Trek movie where Spock shows Scotty the equation for trans warp beaming and Scotty responds, "Imagine that. It never occurred to me to think of Space as the thing that was moving." I definitely prefer to have the ALDA functional as I prefer to set the accurate fuel map for the various driving situations and not have to constantly monitor the rear view mirror and EGT gauge to know when I'm laying down a smokescreen or melting pistons. It also eases up concern if someone else is driving the car, reduces excessive fuel consumption and the negative effects on the environment.

WRT my VNT installation I would most definitely want the ALDA functional. The vanes are closed proportional to pedal position and so fastest spool time only occurs when the pedal is floored. Without boost present there would be a thick black cloud in that situation. Granted, the turbo would spool very quickly and clear the cloud but that's not my style.

Actually I think I understand the IP and the ALDA but keep asking these questions because none of the advocates of removing the ALDA have answered my one question, "How does the IP differentiate between two different scenarios in the car when the RPM and throttle position are the same but the boost in one case is 0.1 atm and the other case 0.8 atm?"

PS - I'm glad your thread was restored. It's unfortunate that the urge to be clever or perhaps cruel interferes with our various discussions.

Without the ALDA functional, it doesn't. It will deliver the exact same amount of fuel.

Peace on the ALDA. Mine's off only because I replaced it once, then that one died too (aneroid capsule failure)... and figured it wasn't worth the money. If I had a perfectly adjusted one handy, I'd have no qualms about putting it on the car. It wouldn't get in the way.

And you're right, with no ALDA, there goes your input to the IP that differentiates more/less fuel is needed to match boost when all other factors are held constant. The driver becomes the ALDA. A good working turbo and little common sense with driving familiarity quickly tunes you not to darken the skies with soot.

Back to VNT, I think this is a key statement: "The vanes are closed proportional to pedal position and so fastest spool time only occurs when the pedal is floored." i.e. calling up the demand for boost.

Goldmine: http://www.thedodgegarage.com/turbo_vnt.html

__________________
Cheers!
Scott McPhee

1987 300D

Thanks Scott. Just wanted to make sure I understood how it worked.

There have been a number of other posters that were quite adamant that my understanding was flawed. I either wanted to learn that I was wrong and correct it or learn that I was right and be satisfied.

I agree the VNT is very interesting and your link is helpful.

No, you are correct. The posters who claim otherwise are either dealing with cars that are seriously underfueled off idle, and/or they are blissfully ignorant of the black cloud billowing behind their car at low RPM when they mash the pedal. Some pumps are so low on fuel delivery that they don't smoke at all with the ALDA removed, but this does not prove that ALDA removal is a good thing. I've given up trying to argue this point though, most of the pro-removal crowd basically falls back on "I want to control the soot cloud with my foot, not let some mysterious black magic square aluminum box do it for me!". OK, fine, whatever floats your boat.

My hybrid 6mm pump is a great example of this, btw. The ALDA is installed but currently set too rich, and under medium throttle at low RPM (i.e., slowing to make a turn at an intersection then accelerating again) it smokes pretty badly until boost builds. Without VNT, the only way to control this is via the ALDA adjustment. It would be far worse with the ALDA removed! I already have zero shims under it, now I have to pop off the tamper seal & turn down the setscrew. VNT would be a nicer solution of course as the lag would be reduced.

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

Definitely another way to go. You might find the Sprinter VNT a bit small for the 3.0L engine. I believe I have a Sprinter VNT here and it has a very cool stepper motor control with position sensing. The turbos themselves are fairly common and relatively cheap used. I'm not sure how much the rest of the control would cost, tho, and that's not the direction I will personally focus. I'd definitely love to see someone else pick up that particular torch as a standalone electronic control would be a fantastic option.

I don't don't agree that vane angle should be linked solely to rpm. Exhaust flow, which is what produces boost, varies massively for a given rpm based on load and fueling. As I outlined in my initial post, IMO, a much better control is basing vane angle on the demand for power in order to have the fast spooling available when called for but back pressure reduced during low demand situations (idle/cruise).

The turbine inlet flange is smaller than the T3 that was original on mine. The turbine outlet is similar but a little smaller as well.

Here's a photo of the modified manifold. Everyone would be encouraged to resist the urge to tell me that welding on the cast manifold will crack. It has been a daily driver for 3 or 4 years and driven on longer trips (e.g. to Vegas, baby) without any issues whatsoever.



The bolt patterns of the stock turbo and the 2559 are close enough that bolt holes overlap so a single adapter was not really possible. I considered making a double plate w/ tube in the middle but wanted to save the engine real estate and keep the turbo close to the engine.

I'll try to post some more pics when I have a little more time, although I don't have a throttle on my engine.

Thanks Dave.

And thanks, again, for your great pressure-actuated, wastegate mod.

Meh, it might crack eventually, but I wouldn't lose any sleep over it. When welding cast, preheating with a torch helps big-time! What makes cast so tricky is that it expands a lot when heated. As counter-intuitive as it would seem, stainless is a better match, because of its expansion rate. Use some 309 welding rod and it will bond with both materials.

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'82 300SD - Somewhere over 220k - Becoming reliable...

It's really hard to get a decent angle here, but here's a little better picture of the attachment at the turbo which has m6 threaded rod threaded into the stock vane actuator attachment.



Here is a picture of the linkage when the accelerator is floored. Sorry for the crappy pic. Hard to hold the accelerator with one hand and snap the picture with the other. It looks quite similar to the pic with vanes open, but the vanes are pulled to the closed position and boost can is move toward the engine accordingly.


Here's a picture of the intercooler I used. I would reiterate that I would opt for a water/air system if doing over. The intercooler core is thicker than necessary requiring a lot of work to move the radiator and condenser toward the engine. I also lost the electric fan. Routing the intercooler tubing was also quite a challenge. Overall it worked out and does well, but the rewards of an water/air system in this application are very apparent.