So have I stumbled on to something here ?

By disconnecting the vac line to the flapper device, and things as they r in my car -- egr disconnect but vac line still attached, there is no way for the car to know anything is amiss and cut boost to the engine ?

Is there a way for the computer to stop the turbo from going full speed ? I do not think so.

The accel is really smooth. No sudden build up of boost.

Thanks for all ur input. This model does not have much writeup.

We could use what we learn on this experiment on other similar setups. MB is know to stick to designs for years.

What do u think of my deductions ?

I think you have a serious case of the placebo effect - have you done any actual measurements of 0-60 times?

I once monitored the vaccum applied to the flapper valve, as I recall it was held in the open (default) position 99% of the time. On throttle tip in the ECU would close the flapper valve for a very brief time period (like < 1 second) and then it would immediately revert back to the fully open position.

I'm assuming this is done to promote faster turbo spool up by effectively reducing the volume of the intake manifold. Smaller volume = faster boost response.

BTW a "sudden build up of boost" will cause the engine to reach full boost more quickly off the line and it should decrease 0-60 times. I'm betting if you actually measured the 0-60 times you would find your car would be slightly SLOWER off the line with the flapper disconnected. Once boost is up I don't think it really does anything,

Tim,

Do you have any data as to what the EGR was commanded to do by the EDS
when the "Flapper Valve" was closed?

I can see the pressure between the "Flapper Valve" and the compressor wheel
building more quickly when the valve is closed,but as soon as the flapper opens
the compressor must fill the larger void in the intake system????

I did monitor the EGR function - I don't recall anything specifically related to the EGR with respect to the flapper valve. It's been quite awhile but I seem to remember the EGR valve was activated in light throttle conditions in the 30-50 MPH range. I could never detect any performance or driveability improvements with my EGR disconnected on my W123 vehicles so I never bothered trying to figure out a way to disable it on my 2.5 turbo.

With regard to your "flapper" observation - you are correct that there would be a pressure drop in the intake manifold (as measured between the turbo and the flapper valve) when the flapper valve opens but remember the turbo would be in a fully spooled-up state when the flapper valve opens so I suspect it would be able to keep the manifold pressurized pretty well.

This is all speculation on my part - maybe I'll do some 0-60 timings and measure the boost ramp-up rate with the flapper connected and disconnected and see if any of these theories hold water.

This is my story, and I am sticking to it!

My believe is this - the EGR is the root cause of engines overheating, rods bending etc.

The soot that comes back to the intake, deposits on the walls. This thickens over time and retains more heat. Hence the over heating problem.

The deposits on the walls r not even, more like stalactites (seen in the roof of some caves). These deposits harden over time. (Next time u remove ur glow plugs, feel at the hardness of the carbon deposit on the plugs.)

Just one small rock, from the stalactites, that falls in the intake can cause damage. It does not have to be the size of the Rock of Gibraltar. Just small enough to cause a slight wedge any where it happens to land. That would be enough to cause the rod to bend, increase in oil consumption, over time.

That is the only credible theory that explains what happens.

IF I find, and buy, a good car with a 350 engine, first order of the day would be to look at the EGR setup.

yeah I know this is an antique thread, but i'm just curious if anyone has worked on this since it was originally posted. At the time, only 1 person had attempted it I believe.

__________________
1996 E300 D
1992 300D
1990 Ford E-350 7.3 Diesel AKA "the Deep Fryer"

I did my '96 E300D by simply inserting a piece of sheet metal (an "un-holey" gasket) in between the EGR valve and the crossover pipe. I also put a solid disk of metal where the flex pipe attaches to the exhaust manifold. Thus the exhaust is doubly blocked. All of the vacuum and electrical stuff was left intact and to external examination the system is untouched. Might even pass inspection in the states that do such things.

The '96 is, of course, less computerized and doesn't care if there is no flow through the EGR valve. I have heard that the computer will set a code if the EGR is missing or if the vacuum is plugged, however, so something has to be there.

Jeremy

__________________

"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