Why reloocate MAF of R170? - Mercedes Benz SLK Forum

Performance MODS for the R170 Tuning and Performance modifications for your SLK

 
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#1 Old 01-01-2014
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Why reloocate MAF of R170?

Evidently the factory relocated the MAF on later cars.

Does everyone agree it is a good thing to do on the early cars for slightly smoother acceleration?

Does anyone have anything to add to this explanation I read by Raindog a few years ago?

"I believe that it is rather turbulence than resonance that causes "bumpy" acceleration. Any bend or change in pipe diameter and/or shape will create some turbulence in the flow and the flowmeter (MAF ) can be "fooled" to give a wrong measurement and since the turbulence is not stable the reading may be going up and down even if the air flow is actually constant. I suppose that this could even cause your jerking.

To avoid such errors, it is good engineering practice to install flow-meters with a certain length of so-called "straight run" piping both up- and downstream. The requirements of straight run varies between different flow-meters but around 5-7 pipe diameters upstream and a little less downstream seems common. So if the air pipe is 3" in inner diameter, there should preferably be no bends or other flow disturbances 15-20" upstream and 10-15" downstream - difficult to adhere to in an engine bay! I guess the basic philosophy is: little is better than nothing and do the best you can. As I recall, there is a perforated plate in front of the MAF in our cars - this may assist in reducing turbulence over the MAF."


Thanks for any new comments on this!
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#2 Old 01-01-2014
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Not sure about the rest but I'd think that a perforated plate would ADD significant turbulence, possibly to ensure no stagnant areas and no resonant standing waves at certain flow rates.

The MAF on my 230 and 320 both had a fine wire screen at one end. I suspect that with the tube mounted vertically the screen is as much about stopping things falling in as anything else.
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#3 Old 01-01-2014
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Yes, a screen or perf. plate would act as an air damper, I suppose.
So, might we assume the relocation from bottom of tube to top of tube has no actual benefit?
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#4 Old 01-02-2014
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I'd say about the only benefit would be that foreign objects either get near the sensor diode or they don't. Measurement differences would be next to undetectable as they would be hidden in system noise anyway.

The circuitry in the MAF is actually pretty crude I think, of necessity because of the environment.
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