Boost Gauge - Page 2 - PeachParts Mercedes-Benz Forum

dieselmania · #16 12-25-2005, 10:32 AM

"A 1987 300D turbo should be doing a 0-60 time in the 10.5 second range."

That would be nice. Where do I start? I always keep my filters changed, more often than recomended. My injectors are new this year, the trap is long gone. This car doesn't get much use, only about 5K per year. (It's my wife's car.)
I am the one who works on it, washes it and refuels it. Every time I drive it I give it a brief Italian tuneup. Can the filters get restricted from sitting a long time?

Brian Carlton · #17 12-25-2005, 01:48 PM

Quote:

Originally Posted by dieselmania

"A 1987 300D turbo should be doing a 0-60 time in the 10.5 second range."

That would be nice. Where do I start? I always keep my filters changed, more often than recomended. My injectors are new this year, the trap is long gone. This car doesn't get much use, only about 5K per year. (It's my wife's car.)
I am the one who works on it, washes it and refuels it. Every time I drive it I give it a brief Italian tuneup. Can the filters get restricted from sitting a long time?

We start with post #6 in this thread.

There is a line from the manifold to the overboost protection switch on the firewall. There is another line from this switch to the ALDA on the injection pump. Disconnect these lines and thoroughly clean them. Usually the line from the manifold gets plugged and/or the overboost valve itself gets plugged.

You can then take it for a drive and see if it improves. If not, it's time to pickup a boost gauge. When you have it, post again and we'll show you how to hook it up to find the issue.

whunter · #18 12-25-2005, 07:20 PM

Quote:

Originally Posted by tangofox007

Cleaning the pressure line from the intake manifold to the switchover valve has been known to cure "sluggishness." Along with adjusting the ALDA.

dieselmania · #19 12-26-2005, 04:25 PM

Brian,
ok I checked the lines in question, they were clean and open. I also removed the barb from the intake to verify it is open. Plus I checked the switchover valve, it is open when off and closed with 12V applied.
I am kind of wondering how a clogged line could cause improper boost anyway, since according to the manual the switchover valve only admits air to the ALDA during an overboost situation. So even with the line removed, it seems that boost would be unaffected.
Plus, as you stated, I can feel the boost really kick in at 2400, like it should. I think my problem is in the lower RPM range, as when the boost kicks in at 2400 it really takes off like a rocket. So two things come to mind, wastegate and ALDA. I had the turbo out last year and it was clean. Do you think it would be wise to try the ALDA adjustment? I can't very well verify IP and cam timing at home, if you think that should come first I can take it somewhere.

P.S. I do have a book on Mercedes Benz written by James Taylor (not the musician, I don't think) and it shows 15.5 seconds in the spec section. This seems to indicate it would take a non-factory setting to achieve 10.5, like maybe the ALDA?

Thanks for yours and the others help, I love this car, I love this forum.......................Brian in AZ

dieselmania · #20 12-26-2005, 04:28 PM

Oh I forgot to mention I am heading out right now to see if I can locate at least a pressure gauge for a temp hookup.
Plus a 24MM wrench

Brian Carlton · #21 12-26-2005, 04:35 PM

Quote:

Originally Posted by dieselmania

Brian,
ok I checked the lines in question, they were clean and open. I also removed the barb from the intake to verify it is open. Plus I checked the switchover valve, it is open when off and closed with 12V applied.
I am kind of wondering how a clogged line could cause improper boost anyway, since according to the manual the switchover valve only admits air to the ALDA during an overboost situation. So even with the line removed, it seems that boost would be unaffected.

OK, that's excellent. Those lines must be open to get fuel enrichment. The ALDA receives pressurized air from the manifold under all conditions. The more pressure that it sees, the more it advances the rack, and the more fuel is provided to the engine. Without the line attached, all the boost in the world won't give you any more fuel. Without fuel, the boost does nothing. In fact, you can't even get full boost if the ALDA doesn't provide fuel to allow more exhaust flow.

Quote:

Originally Posted by dieselmania

Plus, as you stated, I can feel the boost really kick in at 2400, like it should. I think my problem is in the lower RPM range, as when the boost kicks in at 2400 it really takes off like a rocket. So two things come to mind, wastegate and ALDA. I had the turbo out last year and it was clean. Do you think it would be wise to try the ALDA adjustment? I can't very well verify IP and cam timing at home, if you think that should come first I can take it somewhere.

You can certainy try an ALDA adjustment. If the vehicle performs poorly at low rpm's, turning the adjustment screw counterclockwise will provide more fuel throughout the RPM range. If you go too far, you'll see the evidence of black smoke. Then, simply turn it clockwise by 1/4 turn. You can attempt this without verifying cam or injection timing. If the engine was reasonably well cared for, the timing won't be too far off the spec. How many miles on the engine?

Quote:

Originally Posted by dieselmania

P.S. I do have a book on Mercedes Benz written by James Taylor (not the musician, I don't think) and it shows 15.5 seconds in the spec section. This seems to indicate it would take a non-factory setting to achieve 10.5, like maybe the ALDA?

If you have a 1987 300D with the OM 603 engine, the spec is very close to 10.5 seconds. If you have a 1985 300D with the OM617 engine, the spec is close to 14 seconds. One of our members has an intercooler on the OM603 and he has achieved 8 seconds with a wagon!

AFAIK, there is no turbocharged diesel powered 300D with five or six cylinders that has a factory spec of 15.5 seconds. If I am mistaken, others will correct me.

dieselmania · #22 12-26-2005, 05:39 PM

The engine has 140K, well cared for. I removed the line from the intake before I read your post to see if it would make a difference, I could not even get up to 60. I didn't realize the pressure to the ALDA regulated fuel, now it makes more sense to try the ALDA adj. I assume this will not risk engine damage, as the boost will still be limited to 1.1 bar?

The specs in the back of my book came from a test published in Autocar and in Motor, May 1990. I don't know how they got such slow times.

Thanks again, I'll try the ALDA later this week.

Brian Carlton · #23 12-26-2005, 05:49 PM

Quote:

Originally Posted by dieselmania

The engine has 140K, well cared for. I removed the line from the intake before I read your post to see if it would make a difference, I could not even get up to 60. I didn't realize the pressure to the ALDA regulated fuel, now it makes more sense to try the ALDA adj. I assume this will not risk engine damage, as the boost will still be limited to 1.1 bar?

Well, it might make 60, but, it'll take awhile.

So, you definitely have boost.........the question is whether it's to spec or not. You need a boost gauge to confirm this.

You won't run the risk of any engine damage by adjusting the ALDA. The only risk is reduced fuel economy and some black smoke if you go too far with the adjustment.

BTW, let me know how far you adjust it. I need to do the same exact mod to the '87. It's a dog at low speed.

dieselmania · #24 12-28-2005, 01:25 PM

ok Brian I got my gauge. I am assuming I will tee into the line off the manifold with 1/4" line. Where is a good place to come thru the firewall?

Thanks.......Brian

Brian Carlton · #25 12-28-2005, 10:28 PM

Quote:

Originally Posted by dieselmania

ok Brian I got my gauge. I am assuming I will tee into the line off the manifold with 1/4" line. Where is a good place to come thru the firewall?

Thanks.......Brian

Don't even bother trying to route it through the firewall. You just want to take it for a spin one time. Just route the hose over the cowl and in the driver's side window. Leave the window open about 1/4" for the hose. Works just fine for a test.

Now, if you want to permanently mount the gauge, that's a another project.

dieselmania · #26 12-28-2005, 11:07 PM

Yes I got a nice gauge and I want to mount it permanently. I see a rubber seal where other lines enter, it looks like there's some unused ports in it. It's up high, right behind the instrument cluster. I might try there, probably need to remove the instruments.

Brian Carlton · #27 12-28-2005, 11:11 PM

Quote:

Originally Posted by dieselmania

Yes I got a nice gauge and I want to mount it permanently. I see a rubber seal where other lines enter, it looks like there's some unused ports in it. It's up high, right behind the instrument cluster. I might try there, probably need to remove the instruments.

Yes, that would be a good place. The cluster just pushes out from behind, or you can get the fancy hooks to pull it out.

dieselmania · #28 01-01-2006, 06:58 PM

OK lots of stuff today. First, I installed the boost gauge. Here are the readings: 3-4 PSI @2000 RPM; 7-9 PSI at 2500 RPM; and boost maxes out at 11 PSI around 3000 RPM. It never goes over 11 PSI.

I also removed the ALDA and adjusted it CCW one turn. It seemed a bit peppier at initial throttle, but not by much. My 0 - 60 times showed very little if any improvement, it still takes about 16 seconds. I verified that the tranny was starting off in 1st and I also verified that the throttle linkage was moving all the way to the stop at WOT.

After reading some posts about wastegate adjustments I am thinking either my (Garret) wastegate needs adjusting or maybe it is stuck partway open. One thing I noticed is that the rod and the wastegate linkage both appear to be frozen. Shouldn't I be able to get even a little movement out of the linkage?

Thanks in advance for the help.

Brian

Hit Man X · #29 01-01-2006, 07:30 PM

Hrm, I though 603 boost was a tad higher at WOT...

When I adjusted my ALDA on the SDL it took MANY turns to get maxed out, then backed off one half. I'd say a good five to do so CCW to max. It's just a bit too much currently as it blows when I first hit the pedal off a stop light. The smoke goes away pretty quickly as the RPMs get into the 2400-2800rpm range.

That linkage is VERY stiff on the Garrett setup. I was not able to move it by hand on the extra turbocharger I have sitting in my garage.

Brian Carlton · #30 01-01-2006, 07:38 PM

Quote:

Originally Posted by dieselmania

OK lots of stuff today. First, I installed the boost gauge. Here are the readings: 3-4 PSI @2000 RPM; 7-9 PSI at 2500 RPM; and boost maxes out at 11 PSI around 3000 RPM. It never goes over 11 PSI.

I also removed the ALDA and adjusted it CCW one turn. It seemed a bit peppier at initial throttle, but not by much. My 0 - 60 times showed very little if any improvement, it still takes about 16 seconds. I verified that the tranny was starting off in 1st and I also verified that the throttle linkage was moving all the way to the stop at WOT.

After reading some posts about wastegate adjustments I am thinking either my (Garret) wastegate needs adjusting or maybe it is stuck partway open. One thing I noticed is that the rod and the wastegate linkage both appear to be frozen. Shouldn't I be able to get even a little movement out of the linkage?

Thanks in advance for the help.

Brian

11 psi at 3K is fine. The spec, IIRC, allows 13 psi, or so, but that's not the major source of the problem. You can adjust the wastegate to get 13 psi and you might get some additional power, but, something remains seriously amiss with 16 second 0-60 times.

The wastegate linkage has a very strong spring and you probably can't move it by hand. If it's going to move, it likely will require about 40 lbs. to do it.

As Eric mentioned, the ALDA could probably use some additional tweaking, but that is not the source of the problem.

Please advise where you measured the boost? Did you T into the line to the ALDA or did you T in somewhere else?