Inadvertently left the upper resonance flap disconnected after the last intake R&R. The car seemed a bit peppier down low. Anyway, noticed it disconnected so I pulled the crossover and re-connecetd it. Hmm?

Car seemed to be a bit more lethargic at low rpms. SO I pulled the crossover again and plugged the vacuum line to the upper flap.

While it might be a bit louder at idle ( this 97 has no sound panels and is much louder than either the 95 or 97 I had with them) , the car seems to have gained a smidge of low rpm TQ, still accellerates as well ( if not better) and is logging slightly better combined mpg than before ( 29.5 V 31 mpg), in similar weather.

Not trying to re-engineer anything, as I'm no engineer, but I'm leaving it disconnected and continue to wonder why it seems ( and logs beter mpg) better without it.???

FYI!

I believe that your airflaps are not working correct, at low rpm the flap closing to form the upper crossover in two tubes makes for better low rpm torque - like sucking coke from a straw.

High airflow pays off on high rpm - where both the flaps open up.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Well, unless someone before me crossed the vacuum lines, they work MUCH better now, disconnected! At least the upper one in the crossover tube.

I did clean and test them when I had the intake hot tanked.

Have you defeated EGR and cleaned the intake manifold and associated plumbing of all of the black gunk? Made sure the flaps aren't so crudded up they're not working correctly? Checked the electric-vacuum valves, etc.?

This is a link to another thread in this forum showing how dirty the intake on my '96 E300 was after only 249,000 miles.

1996 W210/M606 Intake Cleaning and Glowplug Removal

Here's a graph from the Mercedes 1995 "Introduction into service" manual showing the torque curve of the OM606NA engine as a function of RPM and flap opening. I don't want to jump in and claim "there's something wrong with your car." You are there and I'm not and you know what's going on. All I can do is show what the factory says it's supposed to do.

Jeremy

Attached Thumbnails

 

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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

I cant say for other cars, but when I drive mine it moves off slow then the engine literally streams the car ahead in a constant electric pull (I can relate it to about 1500 rpm) - the gear shifts are seamless too.

You only see the rpm needle move slightly on gearchange but the engine pull is constant. I think that the resonance flaps are doing their thing at that time. If you are feeling that the engine is a permanent dogs breakfast then you should check the flaps for sticking - the electricky bit can also go bad in a way that it does not vent vacuum when required.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

See above post: I took the time to remove, clean, and check the flaps before reinstalling them. They work with a MightyVac. How that switch actuates them, I simply dont have the time to play with. HOWEVER, the upper flap remains inoperative. Seems better that way. Maybe that swtich is bad.

EGR has been 90% defeated. Intake is clean, well it was 30K ago. ( was surprised how dirty it got in 30K, so I defeated the EGR).

Next time the intake comes off, maybe I'll reconnect.

The chart is nice but without scale of limited info. Also, I have option D going on. A is aways open, B opens at rpm.

Questions:

1. Which is the A flap? The upper or lower?
2. Is the default position (no vac) open or closed?

Thanks! These flaps have been the bane of my existence - am getting the P0120 code back again.

__________________
Charlie

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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)