The other is a mixing pipe throttle plate. Wire it open after converting to a boost actuator.

Sixto
87 300D

Bob, if I recall correctly you were one of the ones getting pressure off the manifold ports. There was a bit of talk about distance to the turbo, etc. Has this worked okay for you? I really don't wanna pull the turbo and tap it if I can help it.

If you disable EGR you can fabricate a boost pressure signal source as/into a cover plate.

Sixto
87 300D

Firstly when referring to left and right it is always as though you are sitting in the vehicle. What I am assuming you are referring to is the restrictor plate valve that the computer uses to check that its system is connected... you will no longer need this. check your vacuum line routing but as I remember there is a vacuum suplly at the front center of engine that is routed to the right hand side of the vehicle which provides vacuum supply to all of the vacuum solenoids etc... this can be capped... what you are doing is making a simple manifold actuating wastegate and completely bypassing the computer and its solenoids mounted in the right hand fender well... that said I cant remember if the EGR is disabled as part of this... Sixto... maybe you can chime in on this.

Chris

if you dont mind me chiming in ...
I did a 92 and took the supply off of the existing port on the intake... bottom line on distance... it is a fine point at best... that is to say manifold pressure is manifold pressure regardless of where you take it it will actuate the wastegate just the same... in my experience that is.

The list that I compiled is here referencing back the original thread ... all thanks to gsxr

http://www.peachparts.com/shopforum/showthread.php?p=2792861#post2792861

Yes, I ran it from the manifold, added a T-fitting and ran the hose. I posted some pictures. http://www.peachparts.com/shopforum/showpost.php?p=2445453&postcount=180

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92 300D 2.5L OM602 OBK #59

Good to know - thanks for the feedback... helps to confirm that it will work as desired

Chris

Bob,

Yeah, that tee looked the easiest by far so I was going with your plan

I've got one of these jobs going on this week. Pretty straight forward.

It is interesting to note that the existing wastegate is inoperative. It will not hold vacuum much less close off like it is supposed to. With it inoperative the boost pressure never gets above 7 psi. With the wastegate locked in the closed position 14 psi is too easy.

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Jim

I just got my new part today. The one question I have before cutting up and threading is - does the lever that the shaft connects to operate in reverse now that it's pressure instead of vacuum? In other words, in the original photos where the shaft is extended it's forcing the lever down or to the left depending on your perspective.. pushing it out I suppose you could say. Will it be pulling it in now when installed? or does the wg actuate the control level in the same way just with pressure instead? Hope that makes sense...

The new actuator rod will start extending beginning around 14 psi. This will "open" the wastegate, dumping the pressure. It is my understanding on the old system that vacuum keeps the actuator retracted.

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Jim

Correct. With the shaft retracted the wastegate is closed.

The vacuum actuator (original) keeps the valve closed (under vacuum) to supply boost. The pressure driven actuator (new unit) is closed by default (always supplies boost) except when it receives positive pressure.

The difference between the two is that if the original unit failed the wastegate defaults to being opened while after the swap if the unit fails the wastegate is always closed.

While Dave's original post advises to cut the shaft and add some more threads (Harbor Freight has the dye at a low cost) it has been discussed that it may not be necessary.

The new unit is installed in exactly the same manner as the original one.

You'll also want to clean out tour over pressure switch that goes from the intake manifold to the ALDA.

Yes Don and engatwork you are correct. With this modification boost is always on until it gets to approx 14 or where you adjust it and then it dumps.

sjh, I believe there is no overpressure switch on 92/93 models. Listed in job 09-0050

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92 300D 2.5L OM602 OBK #59

The old vacuum wastegate is extended by default (zero boost) and requires vacuum to pull in (max boost).

The new pressure wastegate is the opposite; it is retracted by default (full boost) and will extend under pressure to open the wastegate (zero boost).

If the new pressure wastegate cannot be adjusted such that it is holding the flap/lever FULLY CLOSED with no pressure applied, you must either cut the shaft, or find some other method to get the wastegate fully shut. Otherwise you'll never build full boost.

Speaking of which, my nephew's 1993 2.5T 5-speed had this conversion done a few years ago by the PO, and apparently the PO got the wrong wastegate... it would top out at 7psi. Clamping off the wastegate hose bumped it to ~15psi. We'll need to add a manual external boost controller to increase it to 15psi, which is easier than swapping the wastegate again....

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