[Diy_efi] Hot wire/hot film mass flow meters

[Bill Washington]

Gents,
	From my reading on these devices they work well but require some management/ 
periodic maintenance to keep them operating correctly - the wire requires 
periodic, carefully controlled 'over heating' to burn off the crud (including 
oil) which accumulates on it from the air - the air filter doesn't stop 
everything - without this periodic 'cleaning' the accumulated particles form and 
insulating coating on the hot wire/hot film which does not assist with the 
normal operation of the unit.
	I have not, however, had direct contact with them - perhaps someone who has 
played with them may like to comment further....

Regards
Bill
	
> 
> 
> Our Good friends at Bosch have five Mass Flow meters that are
> 0-5 volt. Not exactly linear but very doable with an A/D and
> a look up table
> 
> Starting at approx. ~150 hp and getting up to 450 hp or so.
> 
> I have seen them in print and considered them for a project I was working on.
> 
> I don't know if they have ever been used in an OE installation.
> 
> Hit google with the query  Hot-film air-mass meter, Type HFM 5
> or use the part numbers below.
> 
> Measurement of air-mass throughflow up to 1000 kg/h
> 
> HTH
> 
> Phil
> 
> 
> The following table can be reassembled if you tab it.
> 
> Output voltage UA = f(Qm) of the air-mass meter
> Part number 0 280 217 123 0 280 218 019 0 280 217 531 0 280 218 008 0 280 002
> 421
> Characteristic curve1 2 3 4 5
> Qm/kg/h UA/V UA/V UA/V UA/V UA/V
> 1118 1.4837 1.2390 ? ? ?
> 1110 1.5819 1.3644 1.2695 ? ?
> 1115 1.7898 1.5241 1.4060 1.3395 1.2315
> 1130 2.2739 1.8748 1.7100 1.6251 1.4758
> 1160 2.8868 2.3710 2.1563 2.0109 1.8310
> 1120 3.6255 2.9998 2.7522 2.5564 2.3074
> 1250 4.4727 3.7494 3.5070 3.2655 2.9212
> 1370 4.9406 4.1695 3.9393 3.6717 3.2874
> 1480 ? 4.4578 4.2349 3.9490 3.5461
> 1640 ? ? 4.5669 4.2600 3.8432
> 1850 ? ? ? 4.5727 4.1499
> 1000 ? ? ? ? 4.3312
> 
> 
> 
> 
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