Backing out the SDLs ALDA 1 1/2 turns made an astounding difference in off-the-line performance. No change in smoke under acceleration or at idle (it's always left a slight haze at idle).

This talk of ALDAcision has me thinking of yanking the wagon's to see what happens...that car has always been an oinker off the line (ALDA backed all the way out).

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IMNSHO... if the car runs better without the ALDA installed, you have other issues... like an IP that needs proper calibration.

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Dave
Boise, ID
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I can say that it runs better without the virgin factory ALDA installed. If I drive it properly, it performs significantly better and without much smoke.

It would be difficult to argue pump calibration considering the 0-60 times that are in the 10 second range (one run at 9.70).

Whether an ALDA that is properly setup can offer the same performance is unknown. I may reinstall the ALDA, adjusted for more fuel, and see if the vehicle can match the performance without the ALDA installed.

The calibration of the ALDA, even when tweaked, might still restrict fuel more than desired. It's certainly not a precision device.

It's not super precise, no, but it does have a purpose. When boost is low, a properly calibrated pump with the ALDA removed should be overfueling, and smoking noticeably off idle and until boost builds. Once boost is present, the smoke would clear up. The ALDA basically limits fuel delivery until there's enough air present to handle the extra fuel.

My theory is that over time (like, 2 decades) the internal springs & whatnot end up moving the overall fuel curve quite a bit leaner. So lean, in fact, that when the ALDA is removed entirely, the extra fuel delivered is basically bringing it back to how it should have been in the first place. I'm not sure if this is true or not but it's what I suspect is going on on these older pumps.

I think a better cure would be to turn up the internal full load screw about 1/4 turn. Maybe some day I'll try pulling the ALDA off my pump and see how it runs... never tried that, as my power delivery is normal (uh, actually above normal as I've got the full-load up 1/2 turn from stock and it actually out-runs my 300E up to 50mph, despite taller 2.65 gears... the early 300E has a 3.07 ratio. The 300E is a bit quicker from 60mph up though. For now. )

Since the rack is the ultimate determination of fuel, the engine won't be overfueled in operation below the point of boost onset, provided that the driver does the fuel modulation. In theory, if the rack is opened not more than 1/2 of its available travel, the engine can't be overfueled. A knowledgeable driver should easily be able to modulate the fuel in similar manner as the ALDA. If full fuel is available at 10 psi (24.7 absolute at sea level), then roughly 60% of this fuel would be applicable without boost (14.7 absolute at sea level). So, with a properly calibrated pump, the engine won't smoke if the pedal travel is limited to 60% of full travel below the onset of boost.

I'd agree with the thought of turning up the full load screw, with the understanding that the IP is running without sufficient fuel at full load, but the 0-60 times don't support this. If a 4000 lb. SDL (with driver and tools) can accelerate 0-60 in 9.7 seconds (G-tech time), the argument to adjust the full load seems without merit. Some of this time benefit surely comes below 2000 rpm when the engine is definitely overfueled slightly and does produce a bit of black smoke.

All this talk and banter over more power out of the hole gets me exited (AND A LITTLE MOIST) but since I clocked my mileage a few weeks back at 33.5 MPG I decided I would be happy with the sluggishness under 25k rpms as I would think more fuel means less mileage?
Ive been using the car for a two hour freeway trip once a week into the az mountains and I seem to be able to keep her going faster then most of the other cars climbing those big hills!
I wonder how messing with the Alda would effect the car at the higher altitudes? It is it smells like charcoal lighter when I go to leave the job site up there~~and clatters a bit more~which REALLY amuses me~!

Cheers

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[B]AlanT
BELEN NM


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IF it plugs in, lights up, makes noise,
I'M ON IT!

Here's my take on this, FWIW:

If you wish to accelerate the vehicle at a certain rate, say whatever the rate would be at 2000 rpm engine speed, the amount of fuel required to do this is fixed. If you provide more fuel, the engine will climb above 2000 rpm and the vehicle will accelerate faster. If you provide less fuel, it won't make 2000 rpm and the vehicle will accelerate slower.

So, if the ALDA is present and restricting fuel based on the original factory setting, you'll need, say 1/2 pedal to achieve 2000 rpm. Now, remove the ALDA. The same amount of fuel is provided at 1/4 pedal and you think that the vehicle has significantly more power. It doesn't. It simply gets more fuel with less movement of the pedal because the IP is not limiting the movement of the rack.

So, provided that you don't overfuel the engine, the fuel economy should be unchanged.

I've got no data to back this up yet, but, I'll have one tank's worth in about a week or so.

Brian,

What you are saying makes sense, but it may be difficult to control in practice. I'm still messing with the ALDA on my new IP, and I have tried to run it "richer" while using less throttle. It's pretty hard to do this by feel. What tends to happen is I don't know that I've been over-fueling until it hits about 2000 rpm and I get a huge puff of black smoke. It almost feels like the excess fuel is building up until the turbo comes on line, then you get the smoke as all the excess fuel burns off all at once. With the ALDA, you have the option of giving it some extra peddle and waiting for the engine speed to catch up without creating a smokescreen. It seems like there are just too many variables to do this by feel (for me anyway). For example, I may be able to pull away from a stop with 1/4 throttle with decent acceleration and little smoke, but if I do the same thing again on a 1% grade it feels completely different and I get a bunch of smoke.

I have noticed the new IP is more sensitive to small ALDA adjustments than the old one, which leads me to believe the IP did lose some capacity as it aged.

I'd like to hear if you can get good performance, decent mileage, and acceptable smoke control without a ALDA.

My milage has gone up since I removed the ALDA.
The severe drop was due to a nasty fuel leak that got out of hand.
The other gap is due to incomplete tank fills.

Each dot is one tank. First is 11/31/05, last is 8/25/06.

Attached Thumbnails

 

I don't think you can generalize between the 603 and the 617. Two completely different engines and different injection pumps as well.

This 603 is nowhere near as sensitive as what you're describing with the 617. If you can only apply 1/4 pedal and the black smoke is the resultant, then, clearly, you're going to need to keep the ALDA in place.

I may remove the ALDA from the 617 and see if I confirm your findings with that engine.

I agree, the 617 is probably much more likely to smoke due to incomplete combustion when it's over-fueled. It would be interesting to see how your 617 acts without a ALDA. It's obvious that mine needs the ALDA to control smoke. If I turn mine up more than about half way it's ridiculous, and I can feel it load up on fuel (almost like a gasser that's flooded). It appears that the "sweet spot" is much narrower with my new IP. With the old one half a turn on the ALDA would hardly be noticeable, on the new one a half turn can make a significant difference in both smoke and power.

I would not run a car without the ALDA installed. And I am one who takes all unnecessary items off the engine - like EGR. Without the ALDA, you cannot drive in high altitudes, say 10000-12000 ft. It would overfuel something awfull. You don't need that much fuel without proper boost. It is just wasting it and mileage should go down. I can see where adjusting the ALDA to be a little more generous with fuel could help acceleration, but taking it off completely is going too far. IMHO

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Not many people drive up Pikes Peak often enough to worry about that.

I live at 5800' altitude and low-boost smoke is not an issue. Since it runs so well without it, MPG has gone up, and smoke is not an issue with my engine, I plan on leaving it off permanently.

Another variable, as mentioned above, is altitude. At 5000', you're only working with 12.2 psi below boost. That's a significant difference in air volume and further pushes you toward the need for the use of the ALDA vs. my sea level tests.

Strange, I can only guess that you have another issue with your IP that is limiting fuel flow. Even my old IP would make unacceptable amounts of smoke if I turned it up all the way. The IP "should" over-fuel the engine without an ALDA installed, especially at 6000 feet.