Hello Denrac,

'EGR valve and wastegate are 2 separate items : wastegate is located on the turbo and is not easily seen from the top of the engine. On your car (1991), you have 3 vacuum transducers (round thing with 3 hoses and a double electrical connector) : one goes the EGR valve, another to the intake flap and the third should lead you to the wastegate vacuum control. From that control, a rod goes into the turbo housing to operate the waste valve. If you look attentively, you'll see the control rod moving backward when the intake flap closes.'

I have checked under the bonnet - now I could see only 2 vac transducers. One was beneath the air filter, the other above air filter, opposite side. Both of which had rubber hoses to either EGR valve or the flap. I could not locate the third transducer. Where is it supposed to be?

About the wastegate - looking closely I could see a rather thick rod going to the turbo housing itself from somewhere beneath the engine. Is this it? When revving up the rod did not move. How is the rod operated? I probably need to get under the car to find out.

The rod near the turbo is very likely part of the wastegate mechanism. It won't move when you rev the engine because almost no boost is created in park/neutral, you have to put the car under load. Even then it won't open until you start getting near the boost limit, which is 10-12psi in this case. Bottom line, you will never see the rod move under any conditions unless the car is being tested on a chassis dyno, or you hook up a video camera to monitor it while driving...! ;)

Hi

Is your car an american or a european version ? (I've once had a ROVER 2000 TC. The shop manual listed «english» and «american» names for different parts : an american «hood» was an english «bonnet» :) )

Didn't find any sketch or photo for a 1991 602 W124, but from other models, I would guess that the EGR and flap transducers should be located somewhere above the air filter and the wastegate one more at the bottom. Is your flap vacuum controler connected via a switchover valve to the wastegate transducer ? If so, you car is configured as a 1992.

At idle, although you don't have lot of turbo boost, the wastegate should be closed. On a 3 transducers configuration, the flap transducer is not energized and the flap is opened ; the wastegate transducer is energized and the wastegate valve is closed. As the speed is slowly increased to 2000 rpm, voltage rises at the flap transducer and falls at the wastegate transducer : the flap is closing and the wastegate is opening. You can see the wastegate rod moving from the vacuumed position to the unvacuumed position (we are looking at part load conditions).

On a 2 transducers configuration, the flap/wastegate transducer is energized at idle and vacuum goes to a pair of switchover valves. At idle, the wastegate switchover valve is opened and the flap one is closed (wastegate closed - flap opened). At 1000 rpm, the wastegate switchover is closed and the flap one is opened (wastegate opened - flap closed or closing).

Jassper

I think that you are looking at the oil return tube. The wastegate - vacuum control rod is less than 1/4" thick and runs horizontaly, parallel to to engine.

Whoa, youre lucky i came across this thread, ive been working on this in my '91 602 for months (thanks to gsxr and Denrac's tips).
the latest is that my fuel injection computer needs replaced. big $, but ive tried everything else.

- gsxr

this is true, but in my research, ive found that replacing the wastegate on the T-025 and TB-025 is not possible. not %100 sure. if someone has done it, please let me know.
Ive considered the possibility of replacing my US EDS computer (since mine is shot anyway) with a european one, so im gunna see about that.

The turbo wastegate is directly on the underside of the turbo, you wont be able to see it unless you take off the bottom cover and get under there.

- Jassper

The MAF sensor is right on top of the air filter housing box. it says "bosch" on it i believe and it has a big electric plug going into it.

- jassper

if youre going to test 0-60 times, you have to punch the throttle to the floor every time, thats the only way you can be certain that the throttle is the same. dont worry, i do it all the time.

- jassper

i havent changed my fuel filter in alot longer than that! (i wont mention how long, for fear of being held in contempt by the members of this board) if there is no reason to believe that the fuel youve been using is bad, then i think youre ok.
im just assuming that engine temp for the 0-60 test was in Celsius, not F. if its in F, then the EGR would have been disabled anyway, since the computer lets the engine warm up before it opens up the EGR at all.

i hope for the sake of us both that you find a simple solution to this problem.

I believe it was OldSouth who replaced his computerized/vacuum wastegate on a 603 with the older mechanical type. But, if that't correct, his 603 turbo may be different than your 602. I'd look him up and ask a question or two...

:)

yeah, hes got a TB-03

i think it was tony stewart who said you couldnt do that on the 602. apparently he talked to a garrett distributor. thats all in a thread somewhere...

Hi

Here's a photo of a T-25 Garrett turbo fitted on a Volvo 940SE (gaz). I don't know what are the differences between a T-25, a T-025 and a TB-025 (all listed in the W124 shop CD), but on that particular T-25, you can see that the wastegate is pressure actuated (see the control unit at the bottom of the picture - the other control unit on the side, near the top is a Compressor Bypass Valve [CBV] and as far as I know is used only on a gaz engine).

The W124 shop CD shows vacuum diagrams where you don't see any vacuum line going to the turbo on car equipped with a Garrett T-025 or TB-025 (e.g. 602.961 W201 1987 USA model).

So, maybe finding a pressure actuated wastegate control for a T-25 is possible ?

Photo from http://brickboard.com/FAQ/700-900/EngineTurboIdentification.htm

what i was told is that there are T-025's with pressure actuated wastegates, but you cant just replace the wastegate. you would have to replace the entire turbo.

oldsouth just replaced the wastegate on his T-03

Potomac German has a turbo from a 1987 190D-T that should probably work perfectly, but they don't list a price. Hmmm. Next cheapest was $400 for a used one (ouch). :p

Would it be possible just to replace the actuator ?

The wastegate by itself is just a valve : instead of an actuator where a spring keeps it opened and vacuum closes it, you want an actuator where a spring keeps it closed and pressure opens it.

Don't forget : if you don't already have a separate overload protection in the ALDA plumbing (like a 1992 W124), you'll have to retrofit one.

i have disabled
 

the wastegate on my '90 603 motor. my indie blocked that vac hose and insterted a plate in the bolted connection.

the car seems quite powerful. you are saying that it should inhibit performance? but his test results show it improved it, right?

so which is it? faster or slower?

tom w

Depends on the engine controls. I forget if the 1990-91 OM603.970 (3.5L) has a computer-controlled wastegate or not. If not, there will be no power loss and you can easily disable the EGR.

:o

BUMP.



I'm looking into disabling my EGR and switch to a pressure-operated wastegate. Does anyone have a S/N for the garret T3's found on the 92 300d's? M&M Distributers carries the required parts, I just dont have the S/N of mine handy.

Something like this is what you need: http://cgi.ebay.com/ebaymotors/Garrett-T3-Wastegate-Actuator-with-Brackets_W0QQitemZ230078656773QQihZ013QQcategoryZ33742QQcmdZViewItem

BTW, if you replace your actuator with a pressure one, I want to buy your vacuum one if you will sell it.