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#1
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OM603 - Why does ALDA adjustment affect shifting so much?
the shutoff valve on my '87TD went bad and i replaced it. the ALDA came off in the process so i adjusted it 1.5 turns CCW. off the line acceleration was greatly improved and shifting was smoother too. the only issue was mileage went down drastically. i removed the ALDA again yesterday and set it back to the original spot. now i can't stand the way the car shifts, it is hard into second and worse into third. the car needs the diff carrier mounts replaced also, and this makes for a nice 'clunk' into third gear, depending on the throttle position when it shifts the 'clunk' is more or less pronounced.
so what exactly is going on? if the ALDA is controlling mixture, why does the richer mixture so drastically affect the shifting of the transmission? also, is it normal for mileage to take a nosedive when the ALDA is adjusted 1.5 turns CCW?
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________________ punkinfair |
#2
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The only way "ALDA adjustment" can affect shifting is by affecting the vacuum to the transmission. Since "ALDA adjustment" does not normally affect vacuum, it probably means that there is a check valve or other component that is damaged or leaking.
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"Buster" in the '95 Our all-Diesel family 1996 E300D (W210) . .338,000 miles Wife's car 2005 E320 CDI . . 113,000 miles My car Santa Rosa population 176,762 (2022) Total. . . . . . . . . . . . 627,762 "Oh lord won't you buy me a Mercedes Benz." -- Janis Joplin, October 1, 1970 |
#3
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Quote:
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"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy" Current Monika '74 450 SL BrownHilda '79 280SL FoxyCleopatra '99 Chevy Suburban Scarlett 2014 Jeep Cherokee Krystal 2004 Volvo S60 Gone '74 Jeep CJ5 '97 Jeep ZJ Laredo Rudolf ‘86 300SDL Bruno '81 300SD Fritzi '84 BMW '92 Subaru '96 Impala SS '71 Buick GS conv '67 GTO conv '63 Corvair conv '57 Nomad |
#4
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Quote:
i did a bit of searching on this forum and others have commented on shifting improvements after adjusting the ALDA.
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________________ punkinfair |
#5
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The ALDA changes the throttle : power ratio. In other words, with the alda 1.5ccw you're using less throttle to accelerate the same so the transmission shifts more softly. With the alda back, youre using more throttle to accelerate so the tranny shifts harder.
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#6
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that makes sense. i'm still not sure i understand the mileage drop. the car is driven mostly by my wife and she drives gently, but still the mileage went way down, maybe about 30%, with the ALDA 1.5 turns CCW.
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________________ punkinfair |
#7
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You're pressing the throttle like youre used to which consumes more fuel to accelerate faster.
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#8
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i guess it could be that simple.
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________________ punkinfair |
#9
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When you play with ALDA and are getting more power for less pedal, adjust the Bowden cable going to the tranny and it will get engine and tranny talking the same language again. IIRC, Bowden sets the RPM shift points.
You can also adjust the blue UFO pod a little bit, there is a screw on its underside, this will affect tranny shift firmness. And so will any other vac mods you do in the area.
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Cheers! Scott McPhee 1987 300D |
#10
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It is this simple: whenever you see black smoke blowing out the back, that's unburned fuel. Your mileage is going down the tubes the more/often you see black.
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Cheers! Scott McPhee 1987 300D |
#11
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Anything that affects engine performance can affect transmission performance. Even a fresh fuel filter can improve transmission performance.
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#12
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there was no black smoke at all with the ALDA 1.5 CCW, that's the odd thing and part of why i was so surprised to see the mileage dive. i suppose i might have been able to make it smoke with a very heavy foot but there was no smoke with normal driving.
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________________ punkinfair |
#13
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If you are showing a measurable change in fuel mileage from ALDA adjustment, something else is at play. I'll spare you the speech about the inaccuracy of single-tank MPG comparisons as it seems that you're aware enough to know.
As the ALDA only increases off-boost fuel (actually limits it, the adjustment increased it) and that fuel flow even tripled wouldn't be enough of your total fuel useage to drop your average mileage 30%, seems unlikely. There must be something else at play, I'd go with the 1-1/2 turn CCW adjustment or wherever you have good performance with just perceptable smoke at take-off, and leave it there for a while to see if there's something else affecting your mileage. My right foot seems to be my biggest problem, only solution seems to be Cruise-Control. Which BTW is another point; on the highway you pretty much always have boost, so the ALDA won't affect the power or mileage there either.
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Gone to the dark side - Jeff |
#14
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Quote:
i will do some work on the car over the weekend (in between olympic hockey games) and see what i can see.
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________________ punkinfair |
#15
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Canada rocks, sent those Russians packing!
C'mon Germany!
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Cheers! Scott McPhee 1987 300D |
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