Return of the Blue Flying Saucer - PeachParts Mercedes-Benz Forum

sjh · #1 01-13-2011, 03:19 PM

I have a '90 300D 2.5L Turbo w124. Nice car. I got it about 6 months ago.

I've been following the various suggestions on this board and performed the wastegate swap. In a posting, I think from gsxr, I also saw the removal of the vacuum amplifier, affectionately referred to as the Blue Flying Saucer (BFS).

No matter how tight I made the vacuum system, and even after adjusting the VCV and modulator pressure the shifts were to abrupt and jarring on the car.

Before doing the wastegate swap (and removing all 3 vacuum control units on the passenger side) and before removing the BFS the car has very soft shifts and some flaring.

So I have returned the BFS, adjusted it such the set screw is fully retracted, and the shifts are somewhat smoother.

So what might work well for one reader with one model engine/transmission may not do so well in another vehicle.

The BFS has returned!

vstech · #2 01-13-2011, 06:44 PM

harsh shifts sounds like you had a vacuum leak.

sjh · #3 01-13-2011, 10:05 PM

Quote:

Originally Posted by vstech

harsh shifts sounds like you had a vacuum leak.

I know it does but when I put my vacuum gauge on the line to the transmission it's right at spec. I shut off the engine and the vacuum under the hood and at my HVAC dashpots is held for 20 minutes or so.

It use to flair or is it flare when the vacuum solenoids were present and I think when the prior owner had the trans-modulator replaced the mechanic turned the pressure up very high to stop the flaring.

I believe everything under the hood (VCV, vacuum integrity, etc) is at spec. I have misplaced one of the two green restrictors and hope that have that in place tomorrow. Reinstalling the BFS helped.

I know the Bowden cable only influences the location of the shift points but I still think I should slightly shorten the cable. After that I will try to lower the trans-mod pressure by a half turn at most.

That's as far as I can see at the moment.

Jeremy5848 · #4 01-13-2011, 10:58 PM

Quote:

Originally Posted by Dr_SJH

. . . when the prior owner had the trans-modulator replaced the mechanic turned the pressure up very high to stop the flaring. . .

Boogering by previous owners and their mechanics is the bane of this subsystem. Since this car doesn't have a carburetor, it has a BFS (to add "challenge" to "Pride of Ownership"). Both are packages of compromises held together with spit and baling wire. Like the little girl with the curl, when they work properly they're fine.