I've seen the acronym "ALDA" bandied about here and on the
mbz.org mailing lists hundreds of times, but no one ever
defines it or explaims what it is. I've been driving diesel
Mercedes for over six years now, and have owned four of them,
and I still have no clue what this mysterious widget is or does.
I admit my ignorance and throw myself on the mercy of this 'ere
fine forum. Please, I beg of you: WTF is an ALDA?
"'The meek shall inherit the earth?' Not on *my* watch!"
-- G. Gordon Liddy
ALDA = Atmosphaerische Ladedruckanpassung
A tmosphaerische LaDedruckAnpassung
Roughly translated = atmospheric charging pressure adaption
I've also seen it being referred to as
_Barometric Pressure-Charge Air Pressure Compensation _
It is a device attached to the injection pump that increases fuel delivery
when turbo boost is generated from the turbo to make more power. If
additional fuel is not added, additional power is not realized. It works by
allowing two aneroid capsules to compress (collapse) under pressure allowing
a spring loaded rod from the injection pump to extend, adding additional
These are sometimes adjusted to add additional fuel and thus create more
power, however sometimes adjusting them will cause permanent damage. They
are optimized from the factory with a good balance of fuel economy and power
therefore I recommend not altering it. They should have a plastic seal with
a metal band around the adjusting screw on top that is a seal applied when
the pump is on a test bench, and it is on there to discourage adjustment.
If yours has been removed then it has probably been adjusted previously. If
your car is running properly then the power under full boost is not changed
much if any at all.
Ditto, especially about NOT messing about with the ALDA for it can be
broken and is NOT readily available as a repair part.
If you want to see the effect it has just test drive the car with the
plastic lint to the back of the intake manifold disconnected (Pocket the
hollow bolt and don't mind the hissing sound - its harmless).
Incidently the ALDA is at the top rear of the injection pump: square
with a circle that hold the brass spheres.
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