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Thread: Aftermarket MAF’s vs Bosch

  1. #1
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    Aftermarket MAF’s vs Bosch

    I have a 3.5” maf. It was an original 800 Bosch maf that just crapped the bed. I replaced it with a junkyard 740 maf to hold me over (random off brand). If I buy a new maf, should I go for any new maf or spring for the Bosch 800? What say you? Have you seen much difference in Bosch vs eBay/off brand (of any size)? Old vs new?

  2. #2
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    Never use anything less than an OEM MAF.

  3. #3
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    Id def go with Bosch considering they run about $150ish.

  4. #4
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    We have discussed that in length on the German 8 series forum and someone chimed in who works for Bosch where the original ones for the E31 850 among others are made, here his comment in German and below a quick translation:

    Ich arbeite für das Bosch-Werk in ....... und wir bauen die LMM, über die hier gesprochen wird fuer den M70. Vom Typ her sind es Hitzdraht-LMM, bei denen ein Platindraht oder ein platinbeschichteter Golddraht durch den Luftstrom gekühlt und über den Widerstand ein elektrisches Signal aufgebaut wird. Genau dieser Draht ist zu 90% die Ursache für einen Defekt. Es gibt einen Bosch-Standort . Hier werden die zurückgesandten Austausch-LMM aufgearbeitet, d.h. es werden neue Drähte eingezogen. Die nicht zu reparierenden 10% werden entsorgt.

    Ihr glaubt gar nicht, was unsere Qualitätsabteilung für einen Schrott aus aller Welt bekommt, wo auch LMM drauf steht. Manchmal ist sogar das Bosch-Zeichen oder unsere Werk-Nummer aufgeprägt. Teilweise sind die Teile sogar ganz gut gemacht. Hier ist dann nur die Abgleichkurve grundverschieden (bei uns wird jeder einzelne LMM mit einer festgelegten Luftkennlinie beaufschlagt und abgeglichen, somit sind sie gegeneinander austauschbar) und der Motor läuft sogar irgendwie (allerdings mit Einschränkungen wie Mehrverbrauch, schlechter Motorlauf usw.). Es gibt aber auch Teile, die ganz billig mit einem Kupferdraht aufgebaut wurden. Die sind teilweise den Materialpreis nicht wert. Also Obacht vor den "absoluten Sonderangeboten". Was billig ist, ist nicht immer gut.


    I work for the Bosch plant in ....... and we build the MAFs, which is spoken here for the M70. In terms of type, it is hot-wire MAF in which a platinum wire or a platinum-coated gold wire is cooled by the air flow and an electrical signal is generated via the resistor. This wire is 90% the cause of a defect. There is a Bosch location where these are repaired. The returned replacement MAFs are processed, for example new wires are installed. The 10% that can not be repaired are disposed of.
    You do not even believe what our quality department gets for scrap metal from all over the world, where MAF is synonymous. Sometimes even the Bosch mark or our factory number is imprinted. Partly the parts are even quite well done. Here then only the adjustment curve is fundamentally different (in our case each MAF is charged with a defined air characteristic and adjusted, so they are interchangeable) and the engine even runs somehow (but with restrictions such as excess consumption, poor engine operation, etc.). But there are also parts that were built very cheap with a copper wire. Some of them are not worth the material price. So watch out for the "absolute special offers". What is cheap is not always good.
    Shogun tricks and tips for the E32 series are HERE!

  5. #5
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    That’s what I’m leaning towards. Rather than junkyard an 800 I’ll probably buy new. A lot of the wrx guys replace them proactively @ 100k, despite no code. Are MAF’s a wear item on obd-1 cars? I’ve never threw a code on any vehicles and just periodically cleaned with CRC. What’s optimal?

  6. #6
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    On my E32 750 from 11/1988 and 175000 km still the original MAFs are properly working.
    By far the most common MAF failure is caused by accumulation of dirt, oil mist or fine dust even though the sensor is protected by the air filter. On some sensors like the one on my M70, the hot wire is momentarily heated to about 1,000 degrees when the ignition is turned off to burn it clean. Performance aftermarket air filters that use oil to trap fine dust particles are a prime source of MAF contamination because people tend to put too much oil on the filter.
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    For an HFM or MAF, I’d buy new or used original, not aftermarket.

  8. #8
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    you can buy a cheap MAF.. and long as its from a vendor that has a good rep, its an OE Bosch and its on sale...

    Autohaus had a sale not too long ago where the HFM 803 MAF was only 120$.. factory bosch came
    98 Estoril ///M3 4/6
    S54 swap CSL

  9. #9
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    I bit the bullet and bought a new Bosch 800 from Amazon for $140. I’m still curious on comments

  10. #10
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    I bought a new Bosch 800 on Amazon. $140 shipped. I also grabbed the air box Venturi from a 740. Now my intake goes from just behind the headlight (4”) to kamotors shielded filter to 3.5” Venturi to 3.5”Maf to stock tb. May not make more power but I now know that I will have a good Maf reading and it sounds great!

  11. #11
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    I threw the new maf on and the car runs great but I had the Maf code 29 flash near redline (trm). They suggested trying different clocking positions. My car seems very sensitive to clocking. 9 o clock and 12 o clock won’t allow the car to rev over 5k rpm. No codes though so I’m stumped. I didn’t realize clocking had such an effect. My intake has no bends before or after the Maf
    Last edited by Rugbyfan; 12-22-2017 at 12:02 PM. Reason: Spelling

  12. #12
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    what kind of filter?
    98 Estoril ///M3 4/6
    S54 swap CSL

  13. #13
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    I copied this from a MAF online shop info: A MAF Can Be Damaged by the Following

    -Running an intake without a filter: The MAF canot send an accurate signal through bugs and dirt, so put that filter back on. It’s not restricting flow as badly as you may think
    -Spraying injector or brake cleaner directly onto the air filter or MAF sensing wire: There’s a specific mass air flow sensor cleaning spray, don’t confuse it with other cleaners
    -Touching the MAF’s sensing element: The oils and acids on your skin will contaminate the sensor
    -Never cleaning your intake’s filter: This will eventually make the filter element break down, causing, oiled gauze, bugs and whatever else that’s caught into it to crash into the MAF’s sensing element
    -Not tightening the battery’s terminal connections after installing an intake: Every time the battery’s cables make adequate contact with the terminals, damaging voltage spikes can be created, potentially frying your mass air flow sensor
    -Driving through puddles or torrential downpours with a low-slung cold air intake installed and not using a hydroshield on its filter
    -Over-oiling an air filter while cleaning: You only need to discolor the filter with oil for it to work correctly, so if you’re going through a bottle of oil each time you clean your filter, you’re using way too much
    Shogun tricks and tips for the E32 series are HERE!

  14. #14
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    Air filter brand is unknown as it came with the KAMotors intake, the filter isn’t the issue as a recent blackstone analysis showed adequate filtration and I never used to get the random Maf code 29. I’m back to full 7k rpm redline and the car runs great so I guess it’s an annoyance I’ll live with. I do plan on a custom tune at TRM in a month or two so perhaps there’s more to follow.

  15. #15
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    There have been some issues (many in fact) in the past with some of the OBD1 tunes for the 800 MAF. It seems that no one ever bothered to get the MAF scalar correct. My RK Tunes tune did this repeatedly (my rev limit in 1st and 2nd was 7,800). Every time I crossed the 7,000rpm threshold, the CEL would come on. Never did any damage, just a pain in the ass/disconcerting to see the CEL come on when you're beating the piss out of your motor.

  16. #16
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    Just for info: the one for my 02/98 M3 would be Hot-film air mass meter 4-POL 13621703275, 13621703275 Hot-film air mass meter 4-POL From: 06/01/1994 To: - , Part 13621703275 was found on the following vehicles:
    •3' E36   (05/1994 — 08/2000) M52 EURO and S52 US engines
    •5' E39   (02/1995 — 08/2000) M52 engines
    •7' E38   (03/1995 — 07/2001) M52 engines
    VDO Siemens MAF Air Flow Meter BMW 5WK9600Z 13621703275

    alternatively BS-13621403123 Bosch - Mass Air Flow Sensor; European Version; 3.5 Inch Diameter
    but that is as per realoem only for the S50 EURO engine http://www.realoem.com/bmw/enUS/part...123&series=E36
    Shogun tricks and tips for the E32 series are HERE!

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