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  #1  
Old 01-11-2009, 12:54 AM
Ian White's Avatar
machinemanjr
 
Join Date: Jan 2009
Location: Spokane, Washington
Posts: 728
Exclamation 81 300 SD Boost and tranmission questions.

Hello,

I have been apart of benzworld.org for a while and wanted to become a member here.

Our car has 300,xxx miles on it. I cant remember exact. I installed a autometer boost gauge that goes to 30 psi. It is running about 8 psi under full acceleration. I believe factory spec for boost is 12 - 13 psi. I would like to adjust it back up again, even if it doesnt help greatly with a power increase. I have also cleaned the boost signal line that goes to the ALDA. The ALDA has been tampered with, although the previous owner did the tampering haha. The car had the 617 3.0 Diesel. It is a california spec car, The car is drivin at about 150 feet above sea level; so its not as if I live in Denver.

The Transmission feels and shifts strong because I turned up the vacuum supply via the modulator. My question is under full acceleration in drive, the car will sometimes start off in first; especially if accelerating from a dead stop, but sometimes it tries to start in secondgear. After the first shift the car will accelerate and hold the rpm steady at 2000 RPM through the rest of the gears. I think it should rev at least 500-750 more RPM to build more ground speed and thus power. Or am I wrong? If I am right, How do I adjust the shift points up slightly?

Thank you to all you benz-a-holics like me.
Cheers!

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Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)
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  #2  
Old 01-11-2009, 12:55 AM
Ian White's Avatar
machinemanjr
 
Join Date: Jan 2009
Location: Spokane, Washington
Posts: 728
Please feel free to post or PM your replies, as I am not picky just wanting to figure out some little quirks with this great w126.
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Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)
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  #3  
Old 01-11-2009, 01:22 AM
ForcedInduction
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Boost spec is 11-12psi. Adjusting the bowden cable on top of the valvecover will adjust your shifting RPM.
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  #4  
Old 01-11-2009, 03:04 AM
Ian White's Avatar
machinemanjr
 
Join Date: Jan 2009
Location: Spokane, Washington
Posts: 728
any tips on re-adjusting the bowden cable? How much slack or what?

Any help would be mucho helpo

thanks!
__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)
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  #5  
Old 01-11-2009, 04:24 AM
bgkast's Avatar
Rollin' on 16s
 
Join Date: Dec 2005
Location: Vancouver WA
Posts: 6,528
Try a search here for Bowden cable. Lengthening the sheath (tightening the cable) will allow the car to hold gears longer. Which turbo do you have, KKK or Garret (AirReserch)? If you have a garret you can adjust the wastegate like so: http://www.serenitysys.com/MB/Service_Info/Turbo_Tweak/tweaking_the_mercedes_617_turbo_.htm You can also try adding a boost controller. If you have a KKK turbo adjusting the wastegate is much easier, but the boost spec for the KKK is a few psi lower than the garrett.
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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Last edited by bgkast; 01-11-2009 at 04:32 AM.
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  #6  
Old 01-11-2009, 10:39 AM
Banned
 
Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
Quote:
Originally Posted by Ian White View Post
The Transmission feels and shifts strong because I turned up the vacuum supply via the modulator. My question is under full acceleration in drive, the car will sometimes start off in first; especially if accelerating from a dead stop, but sometimes it tries to start in secondgear. After the first shift the car will accelerate and hold the rpm steady at 2000 RPM through the rest of the gears. I think it should rev at least 500-750 more RPM to build more ground speed and thus power. Or am I wrong? If I am right, How do I adjust the shift points up slightly?

Thank you to all you benz-a-holics like me.
Cheers!
Your symptom of a second gear start and very early shift points lead to a conclusion of no functioning Bowden cable. If this cable is not attached to the throttle linkage or if it's broken, the results will be exactly as described.

Take a look under the hood for a bracket near the back of the engine on the right side. Attached to this bracket should be a black cable. The rubber sheath for this cable will be on the engine side of the bracket and at the end of the rubber sheath will be a snap on ball type connector that attaches to the throttle linkage. Either it's not attached properly or the cable is broken.

Report back and/or take some photos of this area and we'll diagnose the issue.
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  #7  
Old 01-11-2009, 09:29 PM
Ian White's Avatar
machinemanjr
 
Join Date: Jan 2009
Location: Spokane, Washington
Posts: 728
trans...

All is well with the bowden being hooked up to the throttle linkage. I think the white plastic adjusting nut with threads is stripped because it seems loose in the internal threads of the black retainer. Any tips on what to do from here on out? Heres some picts.

Thanks!
__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)
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  #8  
Old 01-11-2009, 09:43 PM
bgkast's Avatar
Rollin' on 16s
 
Join Date: Dec 2005
Location: Vancouver WA
Posts: 6,528
The pictures did not show up. If the adjustment threads are stripped it will cause the cable to be loose and the car to shift early.
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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine
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  #9  
Old 01-11-2009, 10:03 PM
Ian White's Avatar
machinemanjr
 
Join Date: Jan 2009
Location: Spokane, Washington
Posts: 728
...

Im having a problem getting my camera to hook up to the computer sorry... But yes the threads are stripped causing it to shift a bit early. I tied it back with some zip ties to see what its like with long gear holds, its impressive! The car is shifting at about 3000 rpm now except the shift from second to third gear which is still low at about 2200. Any Ideas?

Thanks a million!!
__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)
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  #10  
Old 01-12-2009, 12:19 AM
bgkast's Avatar
Rollin' on 16s
 
Join Date: Dec 2005
Location: Vancouver WA
Posts: 6,528
My 2nd to third shift is a bit lower than the rest too. Maybe it is just the nature of the beast.
__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine
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  #11  
Old 01-12-2009, 12:31 AM
Ian White's Avatar
machinemanjr
 
Join Date: Jan 2009
Location: Spokane, Washington
Posts: 728
really, what business are you in? You got that sd for 500? wow, haha really small world. I got my Benz from the original owner who moved from AZ to Vancouver, and I paid 750 for it. It smoked, and rattled and leaked oil like a hog, in fact I got as far as Longview, and had to put 8 qts in it. It ended up being a valve cover gasket. $20 fix and some other mods and here I am. My SD has an asston of miles, last I remember was 303, and some odd. But it gets me about 27 MPG... so I'm happy.

__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)
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