ALDA boost disconnect=better performance?! - PeachParts Mercedes-Benz Forum

locry · #1 06-01-2010, 01:51 AM

under what conditions will disconnecting the ALDA boost line produce better performance?

i do not have a boost gauge... i wanted to find out if I had boost or the lack of it so i disconnected the boost line to the ALDA to get a baseline. Lo and behold, the car "seems" to be more responsive below 2.5k rpm... and slightly better above 2.5k rpm with the boost line connected. whuttda?

Aquaticedge · #2 06-01-2010, 01:55 AM

I got better fuel economy with a hole in my boost line. but it was sluggy and I never got over 2KRPM

Jeremy5848 · #3 06-01-2010, 01:58 AM

The only way I can think of is a problem in your vacuum and boost plumbing (mis-connected lines, etc.) such that the ALDA boost line actually has vacuum on it rather than pressure. Then it would help to remove the line.

locry · #4 06-01-2010, 03:19 AM

i'm positive the line to the ALDA is the boost line...

mespe · #5 06-01-2010, 08:16 AM

If somebody adjusted the ALDA incorrectly, removing the boost line might increase performance.

LUVMBDiesels · #6 06-01-2010, 10:12 AM

Is it an OM603?
If so there are two lines going to the ALDA, one is the boost line from the manifold and one is a vacuum line that keeps the ALDA from increasing fuel until the car is warm and the vacuum switch shuts off.

If you just pulled the vacuum line you would see an increase in performance.
If the vacuum line was pulling a strong enough signal to counteract the boost even when the car is warm pulling the lines would show you increased performance.

I would run a line directly from the intake manifold to the ALDA and see what happens.

Or you can do what I did and remove the ALDA and just plug the lines

locry · #7 06-02-2010, 01:31 PM

yes its a 603. AFAIK there is only 1 line that goes to my ALDA, and that line comes from the overboost solenoid, which has a line going directly to the manifold.

... the ALDA, when triggered by enough pressure (boost) just supplies more fuel to the IP correct? so by disconnecting the boost line i'm not allowing the ALDA to supply that extra amount of fuel. If on the other hand vacuum is "somehow" applied to the ALDA... then wouldn't that just be the same as having the boost line to the ALDA disconnected?
why then do i have better performance?

how can an IP be misadjusted? aside from the usual calibration, what else can be manipulated/altered?

scottmcphee · #8 06-02-2010, 02:46 PM

ALDA can fail in interesting ways, that can actually reverse its intended operation!

I've gone through a couple (broken seal on one, broken aneroid on the other). The aneroid one was a stumper - we couldn't understand why the car turned to into dog literally overnight between drive cycles. It seems an aneroid capsule in the ALDA had fatigue crack, vacuum lost, expanded the capsule, which pushed down on the limit plunger on top of the IP. Result equals dog.

The other broken seal failure, more common failure, means ALDA was holding pressure only intermittently, so the aneroids wouldn't compress, kept plunger down, dog. You get the idea.

ALDA is much better now that it is off the car and staying that way.

No ALDA means plunger stays up, nothing can possibly push it down, car goes as it should.

If you're worried about lack of overboost protection, refocus your worrying on something else, really. I've never heard of one case of these cars going into overboost needing to protect itself. You'd be lucky if all the overboost hoses, sensor, solenoid, etc. stayed clean enough to work when they might be really needed anyway.

If you're worried about black smoke, lighten up on the pedal. Ta-da!

locry · #9 06-02-2010, 09:11 PM

hehe, i see. if i remove the ALDA... will any rack MISADJUSTMENTS, if any/possible, be nullified?

LUVMBDiesels · #10 06-02-2010, 09:21 PM

Quote:

Originally Posted by locry

yes its a 603. AFAIK there is only 1 line that goes to my ALDA, and that line comes from the overboost solenoid, which has a line going directly to the manifold.

... the ALDA, when triggered by enough pressure (boost) just supplies more fuel to the IP correct? so by disconnecting the boost line i'm not allowing the ALDA to supply that extra amount of fuel. If on the other hand vacuum is "somehow" applied to the ALDA... then wouldn't that just be the same as having the boost line to the ALDA disconnected?
why then do i have better performance?

how can an IP be misadjusted? aside from the usual calibration, what else can be manipulated/altered?

Om my SDL, there was one line going to the ALDA, but it had a "T" with one line going to the over boost switch and the other line going to the temperature switch and then to vacuum.

The best thing to do with an ALDA is take it off

I plugged the holes. I also removed all the hoses going from the vacuum pump across the front of the engine to the EGR and ALR systems. That made a big difference as well...

locry · #11 06-02-2010, 09:54 PM

all my EGR stuff has been disconnected an plugged.

will try to remove the ALDA this weekend. yeah baby!

winmutt · #12 06-03-2010, 09:45 AM

Quote:

Originally Posted by mespe

If somebody adjusted the ALDA incorrectly, removing the boost line might increase performance.

Impossible, assuming they didnt break it.

locry · #13 06-04-2010, 02:47 AM

Quote:

Originally Posted by winmutt

Impossible, assuming they didnt break it.

that's what i thought too...

to make things clear... the ALDA just lets one access the "remaining" rack travel correct? so is the transition gradual? depending on throttle/boost? or is it basically an on/off deal?

let's go further... is the max rack travel on a non-turbo 603 IP the same as a turbo 603 IP when the ALDA isn't boost activated (eg. boost line disconnected)

i want to know if running without turbo assist is the same as driving a non-turbo.

winmutt · #14 06-04-2010, 08:56 AM

Quote:

Originally Posted by locry

that's what i thought too...

to make things clear... the ALDA just lets one access the "remaining" rack travel correct? so is the transition gradual? depending on throttle/boost? or is it basically an on/off deal?

let's go further... is the max rack travel on a non-turbo 603 IP the same as a turbo 603 IP when the ALDA isn't boost activated (eg. boost line disconnected)

i want to know if running without turbo assist is the same as driving a non-turbo.

It's a fuel cut off switch using boost as its signal to turn on the fuel. It is gradual. Look at the section on the turbo charger in the fsm, they have a cut away diagram of the ALDA.

babymog · #15 06-04-2010, 12:36 PM

It LIMITS rack travel vs rpm. As the RPMs increase with full-throttle so will the fuel via rack advance, but this travel is modified by the ALDA so that there is less fuel if there is less air. It also serves to keep the engine from overfueling at high altitudes (3% loss in atmosphere per 1000' above sea-level) so the NA engine has an aneroid to replace the ALDA.