ALDA, fuel delivery, air fuel ratio, and boost. - Page 3 - PeachParts Mercedes-Benz Forum

Brian Carlton · #31 05-29-2009, 01:24 AM

Quote:

Originally Posted by scottmcphee

Sorry to be pest, but any tips on testing an ALDA out of the car?

You'll need one of the high end Mityvacs that develops pressure. If you use vacuum, you'll destroy the unit.

Apply pressure to the port and ensure that the piston underneath is moving. The movement isn't all that much..........maybe .150" or so.........as the pressure is increased from 0 to 12 psi.

winmutt · #32 05-29-2009, 02:05 AM

Quote:

Originally Posted by scottmcphee

Sorry to be pest, but any tips on testing an ALDA out of the car?

Now that is something I would love to discuss. I am of the opinion that they stiffen with age changing the boost curve drastically. It would be nice to know the original specs.

scottmcphee · #33 05-29-2009, 10:58 AM

With light pressure blowing into the nipple, I can feel movement with my finger - and wiggling that thing with my finger there is a point where air escapes out the threaded port. Is that supposed to happen, or is something ruptured in there? (I have not cracked open the 4 screws yet, I the adjuster nut still has a sealed can on it).

winmutt · #34 05-29-2009, 11:00 AM

Well you don't wiggle it, it moves up and down.

Brian Carlton · #35 05-29-2009, 11:17 AM

Quote:

Originally Posted by scottmcphee

and wiggling that thing with my finger

.............some things are better left alone..............before they get broken.

oldsinner111 · #36 05-29-2009, 12:06 PM

Can't resist.I used mine last night.
I have been happy for months now with my ALDA in the garage.
My next thrill will be a mild propane boost,with a switch on the shifter.

scottmcphee · #37 05-29-2009, 12:52 PM

Quote:

Originally Posted by Brian Carlton

.............some things are better left alone..............before they get broken.

Brian, nobody can confirm this is broken! Blowing with mouth pressure is not going to blow any kind of diaphram. Wiggling the plunger gently with my finger is not going to rupture or break it..

C'mon all you guys with ALDA's sitting on the shelf... pull one down:

shake it mildly, any kind of rattle?

blow into it with your lungs, does the plunger pad move outward from the device or suck up into it? how far?

how much resistance is felt on the plunger pad?

does air ever release from the threaded opening when you're doing this?

thanks

Bajaman · #38 05-29-2009, 03:15 PM

Sounds broken, shouldn't be any air getting past a diaphragm.

winmutt · #39 05-29-2009, 03:45 PM

Quote:

Originally Posted by oldsinner111

Can't resist.I used mine last night.
I have been happy for months now with my ALDA in the garage.
My next thrill will be a mild propane boost,with a switch on the shifter.

Just turn the delivery valves holders and keep the propane on the bbq.

scottmcphee · #40 05-29-2009, 06:17 PM

Quote:

Originally Posted by Bajaman

Sounds broken, shouldn't be any air getting past a diaphragm.

Kinda what I'm thinking, but did you try yours?

scottmcphee · #41 05-30-2009, 10:29 AM

I figured out the ALDA. ... other posts, forums, saw the tear down. Did my own.
BTW you need air impact to get those screws out.

But once I saw inside and found a seal that was basically shot.. everything makes sense.

If you blow in the nipple and the pressure pad moves downward (out of the hole), or does not move at all, your ALDA seal is shot. It should move into the ALDA.

If air escapes from the actuator area as you're blowing into the nipple, your seal is shot.

If it rattles when shaken lightly, your seal is shot.

When your seal is shot, the ALDA performs no effect or perhaps even the opposite effect of what it's supposed to be doing. ALDA *requires* a good seal to work because it needs an atmospheric pressure reference maintained inside the case.

Factory spec is when you apply pressure into the nipple, this compresses the capsules inside using relative pressure, allowing the pressure pad in the actuator hole to rise up into the ALDA. This allows the plunger on the top of the IP to rise up (you know, like it is when you pop the ALDA off completely). And you get "enrichment", or "no restriction", whichever suits you.

Tweaking the screw on the top very much, or shimming up with lots of washer when the problem is shot seal simply covers up that problem - you may as well remove the ALDA completely in those cases. In both these cases, your overboost "protection" may not be functional with an overcranked CCW screw or over-shimmed ALDA with a shot seal. Even if you blow out your vac lines, clean the vac switchover valve, have a good cleaned 1.2 bar switch on the manifold... you're fooling yourself about that protection.

Bottom line for me is, either you have a healthy ALDA and use it. Or lose it completely, and all the circuitry about overboost. Which has been done in my car.

scottmcphee · #42 05-30-2009, 10:20 PM

Pulled and tested another ALDA and it was better, seal intact. No rattle, does the right thing under pressure... so I put it on my daily driver. Yup! The ALDA is back on, shimmed up one washer's worth. There's a reason why I shimmed instead of popping the cap to adjust the screw. I believe the cap is there to keep things hermetically sealed so atmosphere is held inside the ALDA. You create a leak there, it's as bad as having a bad seal.

If you choose to screw instead of shim, I suggest you dope the area with some kind of sealer when you're done.

I was unscientific about how much washer to shim it up. The car it came off had 2 copper washers. One was thinner than the other. My daily driver (where the bad ALDA came off) had what looked like one copper washer sitting there.. it was kinda stuck to the IP so I couldn't get a tool in to pry it up and check. So, I took the thicker washer off the 2nd car's ALDA stack, and put it on my car. I didn't caliper it just stuck it on. Then put that ALDA on my car and connected manifold pressure to it again.

Wow, this fixed the smokey idle and no black cloud under hard accel from a stop. But there is no detrimental performance either - it's just as fast as it was with no ALDA. At the top end too! She scoots!! I adjusted the bowden cable while I was in the area and set shifts to about 3000 RPM.

Now I am totally pleased with the driveability and good manners this car now has... power like it should and shifts like it should. It's been a year and a half since my ownership.. The PO would have asked another couple thousand if it ran like this when I bought it.

I'm still going to install the manual boost controller I've got coming. I will also re-hookup and *drive test* the overboost protection circuitry (electrical and vac) to make sure that is working. I bought a buzzer today and will hook that up to the 1.2 bar switch in parallel. I'll test this by grounding the pin on the 1.2 bar switch while driving hard under turbo boost and see if ALDA does its job and eases off fuel. Then I'll test again with MBC set at around 20 psi and just drive to see that the 1.2 bar switch works itself... while watching the boost gauge. When that's done, I'll dial the MBC back to 12 psi and leave it there.

badgator · #43 05-31-2009, 01:49 PM

Interesting read !!!

Keep on posting.

scottmcphee · #44 06-01-2009, 10:02 AM

The simplest way to test that the shimmed height of the ALDA is right, and not too high, is just unplug the manifold pressure going to it and go for spin. There must be a noticeable difference, less power, while on boost. It should starve the engine of the diesel that it wants. The top end power should go down.

There will still be boost registering on your gauge. Maybe not quite as much, and coming on as soon, but the turbo will be trying. Your car will be getting more air than is necessary. This is not harmful in diesels, it does not represent "too lean" and does not burn too hot.

The MB shop manual says the ALDA should still be delivering the amount of fuel that a normally aspirated engine would get. But who can tell exactly what that is? You'll only be able to feel it is more sluggish than your turbo aught to be.

The unplug test represents the "best case" that overboost control can achieve, because this is exactly what it would be doing in overboost conditions detected (if that circuit it working right).

After adjusting your ALDA up and you notice substantial power gains, like most of us do.... If you then disconnect the ALDA pressure line, and have no noticable difference in performance (it stays strong under boost) your ALDA is over adjusted. Too shimmed up or too cranked CCW. Or the ALDA could just be shot (stuck in position).