I am curious to know if there is an alternative MAF sensor for the OM603 on a 87 300D. I have read elsewhere the flapper type sensor is very restrictive. It would certainly make sense to install a vane type sensor as this is a common upgrade on other diesel and gas engines. I have eliminated the air box and installed a K&N air filter directly to the MAF sensor. The noise is noticeable but certainly not extreme. I will take any benefit from making the intake or exhaust more free flowing as they are generally a relatively cheap way of increasing power and economy without sacrificing durability.

The MAF on this car is used only for managing the EGR valve and air recirculation valve. If you have these two disconnected - as most diesels seem to - then you can likely just remove it. The only remaining function of the engine computer is idle speed, and it doesn't use the MAF input for that purpose.

- JimY

Jim is correct. You should have already disabled the EGR and ARV, and then the MAF is useless. I've been meaning to rip the flap out of mine, or something, to see if there's any power difference - but I doubt it. I'm more interested in removing the catalyst from the exhaust to see if there is any power gains from that. I already have the boost turned up to 15psi and the ALDA tweaked. Photos of my cars & engine mods are here, btw:

http://www.meimann.com/images/mercedes/

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

I removed my MAF this past weekend and stuck a cone filter on the intake tube going to the turbo. I can't say that the engine has more power but throttle response seems to have improved. Also, I can hear the turbo whistle from about 1400 to 2100 rpm. It sounds cool.

__________________
2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
-------------------------------------
'92 300D 2.5 Turbodiesel - sold
'83 300D Turbodiesel - 4 speed manual/2.88 diff - sold
'87 300D Turbodiesel - sold
'82 300D Turbodiesel - sold

I was wondering if throttle response would improve with the MAF gutted, or jammed open. I might try that this weekend. Now just think what it would do with the exhaust opened up too!

OK, I just finished modifying my MAF assembly. It was easier than I thought. Remove the MAF and put it on a workbench so you can see what you're doing. Hold the flapper inside wide open. Then use an awl on the top of the housing and gently hammer a couple of dimples in the top, which deform the housing a tiny bit, and jam the flapper wide open. Of course this permanently kills it, but so what, and I have a working spare in case I'd ever need to re-install it. I also removed the little "stopper" at the entry port which should help airflow a tad. I left the temp sensor sticking down but I was sorely tempted to break that off! I won't get a chance to drive the car until Friday, I'll report back with the results then. The flapper has quite a bit of resistance, I'm thinking it may let the engine rev easier, i.e. improved low-end throttle response. We shall see...

One last thing. The Euro models don't have the MAF. They have a nice sweeping pipe elbow with integrated brackets instead. Looks like a nice, clean way to ditch the MAF and shorter "S" pipe on USA models. Special order from Germany, and it's ~$50. Probably less restrictive than the MAF but I doubt there's any power to be gained from it. Just thought I'd let y'all know it's available. I can post a photo if anyone cares...

Dave -

Looking at the times on your posts, it appears eight hours were required to modify the MAF. Does that qualify as a "quick" repair up in Idaho?

My 603 runs well enough, think I'll forget about the MAF and go have a cold beer...

- JimY

Dave:

0-60 times before and after?

LOL! No, it didn't take *quite* that long. I could do it again on another car in under 30 minutes, as long as I don't drop a bolt into the sound panel & have to waste time finding it! I'll see if the car runs any different before deciding if I'd recommend doing this or not.

Speedy, I'm not expecting any full-throttle power gains, so no improvement in 0-60 times. I'm hoping for quicker response at part throttle, which is really subjective and hard to measure.

On a side note, I *am* getting hard data for my brake upgrade project - doing a bunch of 60-0, 70-0, and 80-0 tests with my AP-22 computer and will compare the results with the bigger brake setup. I will do some 0-60 (and 0-70, or 0-80?) testing when I turn up the full-load fuel setting inside the IP though!

Drove the car today. No big difference. I think there's a slight improvement in throttle response off idle, but it might just be the inevitable Placebo Effect. There are definitely no negative side effects, though. Not even any more turbo noise. Anyone else want to modfiy their MAF to see how it affects your engine? Note - ONLY do this on 86/87 turbos! The 90-up models have much more computer controls and it WILL affect how the car runs, and probably screw something up. It's safe on 86/87 models though (or probably anything prior to 1990).

It appears as if the most restrictive part of the intake is actually the point where the aircleaner box mates with the fender. This squeezes the intake throat down to a couple of inches and forces a sharp 90 degree angle. I can see why the late model 2.5 turbos have the intake louvers on the fender. I may try to remove the MAF altogether, since I just hate the idea of killing a perfectly good unit. I wonder if these would work with VW or BMW gassers with AFC-type injection.

Alright, I went and removed the MAF altogether. I placed a 7.5" section of 3" electrical conduit. The result: No change, not even a little sugar pill for my effort--damn. But I am now 6 lbs lighter--that's one heavy unit.

I think I need to adjust my ALDA a bit more to improve the off idle throttle response, and my tranny hangs up and won't shift if I try to give it a full throttle run through the gears. Anyone know what causes this full throttle hangup?

OK, I give up. What does MAF and ARV stand for?

P E H