alda turned up all the way vs alda taken off - PeachParts Mercedes-Benz Forum

TurboSDL · #1 06-18-2009, 10:01 PM

my alda is turned up all the way... will i get anymore throttle response if i take it off?

Simpler=Better · #2 06-18-2009, 10:10 PM

Maybe, but you will lose overboost protection.

If you get any smoke(even a little) pre-boost with the alda maxed out, you have already gotten all the accelerator response possible (Without going VNT)

MTUpower · #3 06-19-2009, 08:36 AM

I see no reason to remove it, although others are happy with it gone.

winmutt · #4 06-19-2009, 06:41 PM

Quote:

Originally Posted by Simpler=Better

If you get any smoke(even a little) pre-boost with the alda maxed out, you have already gotten all the accelerator response possible (Without going VNT)

That is not entirely true, you are assuming that the fuel curve limited by the alda is ideal. I would love some way to measure the fuel curve.

Goatman · #5 06-21-2009, 10:57 AM

Measure EGT's.

winmutt · #6 06-22-2009, 12:06 PM

Quote:

Originally Posted by Goatman

Measure EGT's.

That is only an indication of combustion, not how much fuel you are flowing or what your lambda is. I would love to replace the EGT with something electronic to get as clean as possible with as much power as possible. Certainly a VNT helps but... There is some guessing that could be done I suppose with a rack position sensor.

Goatman · #7 06-24-2009, 05:51 PM

Doesn't matter. EGT's are all you need to be concerned with.

winmutt · #8 06-24-2009, 08:08 PM

Quote:

Originally Posted by Goatman

Doesn't matter. EGT's are all you need to be concerned with.

In regards to what? My original tangent was measuring fuel quantity for the basis of burning cleaner, that I do not believe the ALDA unit to be very suitable for the job by todays standards.

TurboSDL · #9 06-26-2009, 07:51 PM

when i take it off do i just need to plug the banjo lines going to the alda?

Goatman · #10 06-27-2009, 02:11 PM

Quote:

Originally Posted by winmutt

In regards to what? My original tangent was measuring fuel quantity for the basis of burning cleaner, that I do not believe the ALDA unit to be very suitable for the job by todays standards.

Measure you EGT's.... That's how you tell how rich or lean you are. Only measure of fuel burnt that I know of...

winmutt · #11 06-27-2009, 08:12 PM

How would a measure of heat or pressure indicate fuel burnt?

Simpler=Better · #12 06-27-2009, 09:16 PM

Quote:

Originally Posted by winmutt

Certainly a VNT helps but... There is some guessing that could be done I suppose with a rack position sensor.

Why? My GT2056V setup builds enough pressure to match fuel as long as I'm sane when pressing the accelerator; and it's good enough for me

As for matching fuel curves, and how much fuel has been burnt I understand what you're getting at. The ALDA (theoretically) increases fuel by 1 unit per 1psi supplied to it, gradually limiting fuel flow until you reach max boost. Throughout this change in pressure, the AFR is supposedly always ideal.

IIRC, idle speed is affected by the ALDA also-when installed, the idle lowers or 'bogs' down. This leads one to believe that it will also limit top end fuel delivery.

As for temps, my highway cruising temps are lower(50*F) with my vanes cranked down(12psi boost/14psi exhaust) than when opened (3psi boost/4psi exhaust) I believe that this tells me my burn is more complete with the vanes closed, despise the compressed intake air being hotter than when relaxed.

Currently the smoke test is the only cheap way to measure your air-fuel ratio(Which I fail horribly at all speeds-at least 1 injector needs replacing)

Goatman · #13 06-28-2009, 07:19 AM

Quote:

Originally Posted by winmutt

How would a measure of heat or pressure indicate fuel burnt?

You're a big boy, I'm sure you already know the answer, or can find out... If that measuring stick is good enough for everyone else, its fine for you.

TurboSDL · #14 06-28-2009, 10:37 AM

OK SO WHEN YOU REMOVE THE ALDA THERE IS A SHAFT COMING OUT THAT THE ALDA WAS COVERING. WHEN THE RPMS INCREASE THE SHAFT TENDS TO GO DOWN SOME WHICH IS PRALLY LIMITING FUEL. WHAT IF YOU COULD CLAMP THE SHAFT INTO THE PERMANANT UP POSITION? JUST A THOUGHT, MAYBE THERE WOULD BE AN INCREASE IN FUEL THRU MORE OF THE POWERBAND?

OM616 · #15 06-28-2009, 12:44 PM

Quote:

Originally Posted by TurboSDL

OK SO WHEN YOU REMOVE THE ALDA THERE IS A SHAFT COMING OUT THAT THE ALDA WAS COVERING. WHEN THE RPMS INCREASE THE SHAFT TENDS TO GO DOWN SOME WHICH IS PRALLY LIMITING FUEL. WHAT IF YOU COULD CLAMP THE SHAFT INTO THE PERMANANT UP POSITION? JUST A THOUGHT, MAYBE THERE WOULD BE AN INCREASE IN FUEL THRU MORE OF THE POWERBAND?

Torque control fights with the throttle spring to control the fueling curve. The ALDA influences the effective strength of the throttle spring, thus being able to increase of decrease fuel dependent on boost levels.

Holding the ALDA shaft at a constant location, (do not lock it in place), with it adjustable via set screw in line with the shaft, (that is how I have my 616) would allow you to adjust the throttle / rack travel ratio, and would keep the throttle response consistent. It would be like having an external full load adjustment as if the ALDA shaft was raised or lowered the effective throttle output (rack travel) will be increased or decreased.

The reason the ALDA shaft is moving on its own is because of the full load limiter restraining the rack from moving past a point. The throttle spring, at low flyweight strength, will try to move the rack past its limit setting. With the rack limited, the fulcrum needs to move in order to keep the internals from mechanically dead heading. This change in fulcrum location is evident by the movement of the ALDA shaft you describe.

At the end of the ALDA shaft is some linkage which controls the throttle fulcrum position. The throttle arm has a curved vertical slot which allows the throttle arm fulcrum point to change. Changing the fulcrum location changes the throttle to rack travel ratio.

For a VERY simple example of what the ALDA dose, (removing any governor influence from the scenario and assuming percentages), if the throttle was to be held at 50%, and the ALDA shaft was fully extended, the rack position would be 50%. If the ALDA shaft was to be pushed down half way, the rack position would be 30%. And with the ADLA shaft fully depressed the pack position would be 10%.

That is one reason why the cars are gutless without boost. As the boost comes up, the ALDA diaphragms compress, allowing the shaft to come up, which changes the throttle arm fulcrum location, which changes the throttle to rack travel ratio, and in the case of boost, adds fuel. In the case of a loss of boost, the ALDA will decrease fuel (as if the driver let off the throttle).

With the ALDA turned up or removed, the throttle will feel more responsive as the rack is moving a grater distance for a given throttle movement. The driver can mimic the ALDA by being easy on the throttle until the boost is present. With a VNT turbo, boost can generally be created at or just off idle which would allow the driver of a car with the ALDA removed to drive normally for the most part with very little smoke and increased bottom end torque due to the boost on the bottom end.