i always thought 603s were all mechanical, so why do i have an ECU? and there's this AFM type thing under the airfilter... what does it compute and why, and what does it do mechanically? lessen fuel output, if yes, then how does it do this? i don't see any servos/solenoids on the IP.

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

The ECU controls the idle speed and the two vacuum valves which regulate the EGR and the boost. The air flow meter in the airbox is an input the ECU uses in controlling the later two functions.

Other that idle speed none of this is really necessary. You can block off the vacuum source to the two vacuum valves located under the air cleaner and the car will run better.

- JimY

On the 87's, the EDS only controls the idle speed and the EGR. The boost is controlled by the pressure actuated wastegate. The EDS uses the AFM signal to decide when to open the EGR. On the 87 there are no ill effects to blocking off the vacuum line to the EGR.

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Dale

http://i52.photobucket.com/albums/g1...MG_2277sig.jpg

1990 300D 2.5 Turbo -155k
2000 E430 - 103k
2014 Jeep Grand Cherokee Ecodiesel 4x4 - 11k
2014 VW Passat TDI SE - 7k Bro's Diesel
2006 E320 CDI - 128k Pop's Benz

Pre-glow - A moment of silence in honor of Rudolph Diesel

Do not block the vacuum line that goes to the turbo (just under the EGR). That would be bad.

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-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon

thanks for the reps guys! that cleared up a few things! just have to block off the EGR now.

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

Only for idle.

Rest is emissions.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I just removed the AFM from my grey 300SDL and plumbed in a tubing section from an '84 SD air filter snorkel to replace it. I noticed correspondingly huge increase in blowby.

This has the same effect as plucking that breather hose away from the turbo compressor snorkel and venting it to the outside air. When I do so, there is no change in said emissions.

Why is this?

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

On an 87 EDS controls idle, EGR and ARV. EDS does not need a MAF signal to control idle. If you disabled EGR, disable ARV as well.

Sixto
93 300SD 3.0 - comatose