Max Boost on 82-85 300D Turbo

[Jeff Warren]

What is the max boost from the factory on a 300D Turbo 82-85? At what RPM
is this reached? Can it safely be turned up a few lbs (I would not do it,
just wondering how close they are from peaking out the engine)?

Thanks,
Jeff Warren

[Dan Woodward]

This group seems to always contain only messages asking for help on some
technical problem--with few answers ever given which the whole group can
read. Does no one ever get any help from this newsgroup. A bunch of
unanswered messages just makes it sound like MB's are always broken down and
every dealer and shop always charges way to much.
Please, if anyone is reading these and has the answer (or a possible) PLEASE
post to the entire group, not just to the individual.

We want to learn too.

Dan

87 300E 156K with a cruise control which allways works, but feels like it
is constantly varying by small amounts. (about 1 second apart). I have
already done the "Star" resolder of the amp board, but have not yet checked
the linkage under the air cleaner, for slack.
Any help appreciated.

[Vikash Ravi Goel]

"Jeff Warren" geti...@NOSPAMearthlink.net wrote:

I don't remember the max boost off the top of my head, but I think the <gak>
Haynes manual lists it, so I'll check for you.

I don't understand this topic fully, but as I understand it, increasing boost
pressure with a diesel engine doesn't directly result in more power.
Turbocharging diesels is different from turbocharging gasoline engines.

Because there isn't a stoichiometric air/fuel ratio, you basically pump in as
much fuel as you can without getting the engine to smoke due to too rich a
mixture. Adding boost raises this limit, but that's all.

So, after you change the air intake system (by increasing the boost), you'd
need to modify the fuel delivery system. I have no idea if anyone's tried this
with a 300D, or how it would be done.

I'm basing the above on what I read once in a book called Maximum Boost (by
Hugh McInnes, I think). I remember one part where it said that if you take a
stock naturally aspirated diesel engine and bolt on a turbo, you'll see
approximately no change.

--
Vikash Ravi Goel
goelv...@aol.com

[Tiger]

Resoldering of the amp board does not means it is fixed because components
may fail or is failing in your case. You can buy a remanufactured unit with
one year warranty from Beckmann Technologies. They only reuse the circuit
board and change everything else. Fraction cost of new unit.

[Jeff Warren]

You were right... I was wondering of increasing boost pressure would
generate more power. I have a turbo on a V6 Buick and you can modify the
boost by 2-3 lbs and it make quite a bit of performance difference, and add
more fuel and change the boost from about 13 lbs to about 19 lbs and it is
no comparison. Thanks for the info!

Jeff warren

"Vikash Ravi Goel" <goelv...@aol.com> wrote in message
news:20000628085110...@ng-md1.aol.com...

[T.G. Lambach]

The specification is about 10 psi at 4,000 rpm, under load. The turbo's
wastegate, a spring loaded valve, controls the maximum boost pressure. The
engine also has a fuel cut off safety switch to prevent its runaway
destruction above 16 psi boost.

Unlike a gas engine, one cannot harm a diesel engine by running it too lean.
The more air the better but its power comes from the fuel, not the air. The
more air there is to support combustion the more fuel can be efficiently
burned. So M-B uses a clever idea for some added fuel to enhance the turbo's
boost. The boost pressure is transmitted, via the banjo fitting and
switchover valve, to the aneroid compensator. The AC's job is to adjust the
fuel volume to the manifold pressure and so prevent over fueling (smoke).

Some owners have adjusted their engine's wastegate to achieve the 10 psi
boost which is fine but then have gone on to "adjust" the aneroid compensator
to ensure the engine didn't run "too lean". Running a diesel "too lean" is an
impossibility, all they accomplished, IMHO, was to screw up their aneroid
compensator's bench set factory setting. The AC is a series of metal bellows
that expand and contract in reaction to ambient pressure. This minute
expansion and contraction is transmitted via some levers inside the injection
pump to the fuel rack which regulates the engine's fueling. Don't mess with
the aneroid compensator, you'll never get it back to spec and may damage its
bellows.

These small 3.0 L (about 184 cu in) engines produce about 120 HP or 40 HP/ L
and were designed for durability and smoothness (relative to their '80s
contemporaries). Their combustion smoothness comes from their prechamber
design, which IMHO hobbles their performance. The latest M-B CDI diesels
produce about 60 HP / L, power equal to gas engines of similar size. So the
best we can do with our old oil burners is to keep them adjusted to
specification, for that's their optimal output level.

Jeff Warren wrote:

> What is the max boost from the factory on a 300D Turbo 82-85? At what RPM
> is this reached? Can it safely be turned up a few lbs (I would not do it,
> just wondering how close they are from peaking out the engine)?
>

> Thanks,
> Jeff Warren

[wambam]

That was great, T.G.! One question, have you ever heard of a 240 D being
'turned up' ? My mechanic did this, I assume by doing something to the round
deal on the top of the injection pump. It was peppier then but got terrible
mileage, somewhere around 20 mpg. It also smoked alot at lights. I had him
change it back and it gets a little bit better mileage than before, but not
at 27 where it was before. And it still smokes at lights. I guess he didn't
get it back where it's supposed to be. Anything I can do myself? My SD
smokes a little at lights also but it gets great mileage and purrs like a
kitten.

Bill

T.G. Lambach <tlam...@home.com> wrote in message
news:395A4FA1...@home.com...

[T.G. Lambach]

I don't know the term "turned up" but your mechanic changed the setting of the
240's aneroid compensator so it now overfuels the engine, thus the smoke.
Suggest you undo his handiwork, but in small stages since you don't know how
much it was changed from its factory setting. I suggest you turn the aneroid
compensator's screw IN, not more than one quarter turn at a time, drive the car
for a while and adjust it again, and again - until you are satisfied with the
engine's performance, economy and smoke.

These engines will always make a bit of smoke but excessive smoke is the result
of too much fuel (for the engine's capacity to efficiently burn it). I'd leave
the SD as is.

[Frank J. Bertrand]

I measured the boost from the turbo on my 84 300d and at idle 500-700
rpm it was about 1 psi and gradually increased to 8 psi at 3500 rpm,
then peaked and dropped back to 7.5 at 3800 rpm. There was never any
vacuum in the manifold. I thought that as strange, for that means the
turbo is working all the time and the pistons don't naturally aspirate.
Is that a valid observation? Not any black smoke out the tailpipe
either. I'm satisfied.