300 SDL, what is under the air filter

[OhioSDL]

Pulled off the air filter housing and found it to be sitting on top of a metal box so the air goes through the filter, than the box, than the black rubber intake hose with the crank case vent and than into the turbo. looks similar to a mass air flow sensor/ stupid emissions controll part etc...

what is this box?
What was its intended function?
as all other egr/emmisions controls has ceased to function why should i not remove this and put a re-usable oil,cotton high flow air filter in place of the stock set up?

[Brian Carlton]

I'd sure like to get rid of that box myself. I can't change the bulb on the Euro headlight on the right side because of that damn box. The entire headlight has to be removed in order to change the bulb.

I sure don't see what the function of it is for the SDL.

[psfred]

Should be able to change the headlight bulb with the box in place, I can....

Anyway, the box is the flow meter for the engine controls (idle speed control, air recirc, EGR) found on these engines. It measures the air flow to switch the air recirc on and off, and I guess the EGR as well.

The air recirc valve appears to increase milage a bit on the highway by reducing boost (and hence fuel use) when you don't need it. EGR is another story, most people want to disable it to prevent coked oil in the intake. However, my brother's SDL with 200,000 miles (on synthetic oil since about 80,000) didn't have any buildup when we changed the gasket on the crossover pipe a couple weeks ago, just a thin layer of soot in oil.

You should not put a K&N fliter on it because the paper one works better and is quieter.

Peter

[Brian Carlton]

Originally Posted by psfred

Should be able to change the headlight bulb with the box in place, I can....

Not possible to open the access door on the Depo's because it hits the steel box. The clearance is less than 1/2 inch; not enough to get the access door to release.

[sixto]

Brian,

You should clarify that you can't open the hatch for Euro headlights in a W126.

Sixto
95 S420
87 300SDL

[OhioSDL]

Originally Posted by psfred

Anyway, the box is the flow meter for the engine controls (idle speed control, air recirc, EGR) found on these engines. It measures the air flow to switch the air recirc on and off, and I guess the EGR as well.

The air recirc valve appears to increase milage a bit on the highway by reducing boost (and hence fuel use) when you don't need it. EGR is another story,
You should not put a K&N fliter

Peter

so the box controls the opening and closing of the EGR which is the same as the air recirc valve.

I dont think the opening and recirculation of exhaust gasses has much to do with increasing milage. at steady highway speeds boost pressure drops to about 3-4 psi with or without a workig egr system. touch the throttle and boost goes up.

My point in removing the box is to smooth the flow of air into the turbo intake.
there must be some resistance going through that box.

[Brian Carlton]

Originally Posted by sixto

Brian,

You should clarify that you can't open the hatch for Euro headlights in a W126.

Sixto
95 S420
87 300SDL

The hatch has a tab near the bottom of the headlight. To open the hatch requires that the hatch unclip at the top and rotate on the tab, rearward, about 1 1/2 inches or so. After the hatch opens up to this amount, then the tab at the bottom will release the plastic catch and the hatch can be completely removed from the headlight.

The problem with the right side is that the hatch can only move rearward by 1/2 inch. This is insufficient to clear the plastic catch at the bottom so the door is not removable. This requires removal of the headlight to change the bulb.

Note that this is with the Depo's. Bosch may be different.

[psfred]

Funny that there is enough room in a W124 and not in a W126!

EGR and Air recirc are NOT the same --EGR recycles exhaust gasses into the intake to reduce NOx emissions (and flame temp in the combustion chamber), while the air recirc dumps boost. Separate systems, separate actuators.

The air recirc was partailly for the trap oxidizer to prevent rapid temperature cycling and subsequent thermal damage to the catalyst support, but also to reduce turbo lag -- it vents presurrized air from the intake back around the turbo to the turbo intake. This lowers the boost but keeps the turbo close to full speed. When boost is again required as determined by the control box, the valve is closed.

When mine worked, I got much better milage on the highway at moderate (65 mph or so) speed -- 34-36. After it and the EGR actuators died, I only get 30-31.

Peter

[Hatterasguy]

Isn't that big alumminum box part of the crank case vent system?

I removed the airbox and vacuum actuators beneath it on my 603. Previously removed EGR and replaced with Brian Carltons nice upgrade. Replaced the airbox with a 3" copper pipe from local plumbing store. No obvious performance gain or loss noticed with less restrictive intake air, but I can hear the turbo now. Will moniter fuel economy since the ARV is deactivated too.

[Hatterasguy]

Can anyone post a pic of the arv? I want to disable it but am not 100% sure what it looks like. I think it has the blue/purple vacuum line with a black stripe running threw it. The waste gate is right above it and has a larger black rubber hose coming off it? Or am I wrong?

[sixto]

Originally Posted by psfred

Funny that there is enough room in a W124 and not in a W126!

The interference occurs with Euro headlights in a US spec SDL. IIRC access is possible with US headlights. I don't know if Euro SDLs have the same airflow meter. The airflow meter only serves EGR and ARV. I haven't seen a Euro 603 with EGR. It's possible that Euro 603s don't have ARV either.

Sixto
95 S420
87 300SDL

[psfred]

on the Garret its a vac line to the front of the turbo, just pull and plug. Not sure where on the KKK, but similar.

It's not costing you a thing, and reduces turbo lag -- I'd personally leave it alone if the system holds vacuum.

Peter

[Hatterasguy]

psfred your probably right I should just leave it alone. The egr is blocked that is the most important.