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Looking for characteristic curve for MAF 0280217114

3624 Views 9 Replies 3 Participants Last post by  dandywarhol
Trying to find the characteristic curve for the 0280217114 MAF used in the SLK230.
This is the Volts output for a specific kg/hr throughput.

I've got the bosch HFM2 and HFM5 spec sheets (attached) but cant get it nailed with the same PN#
It looks like a HFM5, but I cant match the dimensions exactly.
I can find a HFM2 as a 0280217120 and the dimensions all check out, but its not a 0280217114.

Anyone who's been down this road before - advice/help appreciated.


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My other thought, is to stick voltmeter and test on run, not on idle, to avoid bypass open, and at the same time, check the live data and ecu's maf read. If the range of low and high value and 1-2 values in middle volts is according to that graph, then they match.
Would be good to get the chart. I noted that this is only Pages 55=57 of some larger Bosch document. There might be others on pages 0-55...?

Not sure what you mean about "test on run, not on idle, to avoid bypass open". Surely everything goes through the MAF for your fuel algorithms.
I cant recall - is g/sec air shown up on the OBDII live data? I don't have a logger.
sounds about right....
using 478.8kg/hr = 133g/s

if you use the old 150hp/100cfm rule
133g/s at STP (25C+101kPa) gives you 236cfm = that'd gives you 160bhp or 120kW.
That's in range.
Some run these 230's upto 170kW 220bhp without either reporting or knowing if the MAF is reading incorrectly at the requisite 183g/s (660kg/hr).

I guess they're still working ok but someone may have reported a problem elsewhere....??
Okay - work around - waiting to be confirmed

It would be good to do the multi meter thing to confirm the following.....

1. I confirmed the terminal on one end (the rounded socket end) is terminal 5 and is the "spare" temperature resistor (RTD). The centre pin I also confirmed as the Earth post.
Then I confirmed it matched the 2.20kOhm output with the spec sheet and the temperature at the time of 22.7C. I formulated a plot for 10-50degC and worked out a reverse engineering formula (solution) that - given a kOhm output I can work out a degC.

2. I had a bit of think. I figured the HFM-5's* "may" all use the same element, and the element is simply influenced (as a very rough assumption) by the velocity through the throat/venturi.
So I analysed the kg/hr, worked out m3/s and then divided by the throat m2 to get m/s throat velocity. I then read off the Volts at 100, 300 and 48kg/hr for each of the 5 curves. Then I plotted velocity versus Volts output and voila....a reasonable fit.

I've attached my rough calc sheet - for anyone interested.

Measuring our throat at 60mm ID, I'm thinking we are closest to Curve 1, however it tails out at <400kg/hr and so I think that's why it has the 130mm length - to afford some more flow straightening.

Anyway - I'm going to move on and work with this until a better curve pops up. I'll hook up my spare to 14V battery and a pitot tube flow bench setup and see what comes out.

*(note - ours is called a HFM5-4.7 by and I've emailed them for a chart)


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and a direct replacement?
You are obviously happy dandy.
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