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Old 01-13-2004, 10:39 PM
JHZR2's Avatar
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Join Date: Jan 2002
Location: New Jersey
Posts: 4,233
Will upping boost fix it all?


My 83 300D has 215k, and makes 9psi of boost, max.
I have a loner 83 300D with 225k that is significantly faster than mine. My 300D is by no means a slug, it can merge, keep up with traffic and accelerate well. But, 0-60 and 55-75 definitely feels a lot stronger in the loner 300D.

My car gets 27.5-30 mpg, so it doesnt immediately indicate that anything is wrong. Both cars start easily after sitting in below freezing temps overnight.

So what could it be that makes my car feel a lot slower?

Will upping the boost from my 9 psi to say, 11.5psi make that much of a difference? Thats the one thing that immediately triggers my thoughts, since my turbo is a little weak. If this is the case, and then I can get the full fuel enrichment, etc. it ought to go better.

But then I have to think, maybe my boost is low because Im not getting any ALDA enrichment... There is oil at the alda side of the boost tube... Neither my or the loner car's alda has ever been touched. But, if my ALDA was broken, the car would essentially go like a non-turbo car, making about 85hp or so, right? I definitely feel more acceleration as I hear the turbo spool up, so I assume that fuel enrichment is there, and the ALDA is working at least somewhat. But, I dont know if its working much at all.


How can I check to see that the alda is helping performance much, if at all? would disconnecting it alltogether and then driving it show me? I assume if its more or less the same with the boost line disconnected, then the alda isnt working.

Would injectors that are a bit worn make much of a diference? My first 2 injectors appear to leak a slight bit.

Is it typically time to get the IP calibrated and gone over by a bosch shop at 215k? Maybe that would be it?

It is really kind of annoying that here I thought my car was really great, but now I see just how strong my car ought to be.

So any help or advice would be great. I really would like to get that extra off the line power that my car ought to be making. I just dont want to be disapointed when my boost controller comes, if performance gains are negligible despite extra boost.

Any suggestions would be most appreciated.


Current Diesels:
1981 240D (73K)
1982 300CD (162k)
1991 350SD (113k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)
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Old 01-14-2004, 02:14 AM
Posts: n/a
When I bought my TD, it was a slow, crusty, and a pig on the freeway. It would do 0-60 in 21 seconds (True). Now, with a lot of work, I have got it down to 15.2 seconds 0-60mph WITH a nailing problem.

Here are my suggestions by my order of attack:

Valve adjustment. If you have not done it, do it now.
Timing. Camshaft, injection pump, and full throttle linage stop. VERY big diference.
Filters. They must all be fresh and clean.
Boost. I started with 8PSI stock. I raised it to 13psi max. with a good improvement.
ALDA. Upping it by 1/4 - 1 turn will help ALOT!
EGR. Disconnect it. Take it off the manifolds and see if it's closing completely.
Weight. If you have a lot of junk in your trunk, it will just hold it back. I don't carry my spare tire in my car.
Synthetic oil. It will cut down on friction.
Electric fan. Stock engine fan takes quite a bit of power to turn. It could help with overall peppieness.
A/C. You may not use it in winter, but you never know. Mine does not work so I just remved the belt. (One less belt turning nothing.)

I'm sure there is far more to do. I just have not got to it yet: Intercooler, IP full load stop increase, swap engines with a Dodge 2500 Cummins....
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Old 01-14-2004, 02:30 AM
Registered User
Join Date: Sep 2003
Location: Santa Barbara, CA
Posts: 471
If I might butt in...

About this electric fan thing... have you done it? How big a difference did it make?

We have such underpowered alternators is it really a good idea? It sounds interesting, but I'm worried my new headlights and stereo combined with god-knows-what might be plugged into the cigarette lighter at any given moment (phones, laptops...) and various other electric items might to too much already. Does the fan draw a lot of power?
'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)
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Old 01-14-2004, 03:53 AM
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The fan has a 30A fuse that has not blown in the 5 months I've used the fan.

So far, I have not had any problems with it. I don't have any major power draws except the headlights and the fan. No subwoofers, no laptops, etc. It gave it a noticable increase in throttle response, mostly when downshifting. And I know it takes a good amount of power to turn the mechanical fan going down the highway at 2500rpm+.

I do have an overheating problem. It's fine under 3000rpm/8psi (About 65mph). If I go above that, it will creep to the 100*c line. I suspect it's not fan related as it started to show the signs of a cooling problem before I even thought of the fan. I'm getting a complete radiator/engine flush with new coolant this saturday, we'll see if that solves it.

One side note, get the biggest fan to can fit in there. Anything from a 3.5L V6 or larger should work. DON'T get one of the store fans like the ones at autozone/pep boys/ o'rileys for $70-90. I got mine from a scrapyard '97 Potiac for $12!
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Old 01-14-2004, 10:26 AM
Posts: n/a

One thing that might have been overlooked is
the banjo bolt on the back of the intake manifold.

It runs to the alda and if it is plugged with carbon
the IP will see it as overboost and cut the
fuel to the engine.
Clean it with brake cleaner or the like.
The bolt is located under the aircleaner assembly.

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Old 01-14-2004, 01:53 PM
Registered User
Join Date: Sep 2003
Location: Santa Barbara, CA
Posts: 471
I do have an overheating problem. It's fine under 3000rpm/8psi (About 65mph). If I go above that, it will creep to the 100*c line.
Hmm, I drive significantly faster than that. Tell me what the result of your flush is this weekend :-).

I've always wondered - at highway speeds it seems like there'd be enough air forced through the radiator due to the car's movement that the fan would have little extra effect... Though I know nothing at all about that sort of thing so I'm probably wrong ;-).

What triggers your fan to turn on?
'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)
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Old 01-14-2004, 11:46 PM
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Originally posted by 81Wagon
What triggers your fan to turn on?
It's on full time, I can't trust a thermal switch on somethng so critical as cooling.

The overheating problem is odd. Last week it got to 100*c while going 70mph in 19*f outside air. I know the thrmostat is working. My heater puts out air at 145*f, when the engine temp is up the heater will go down to 80*f.

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