VW compared to BMW MAFs - The Unofficial BMW M5 Messageboard (m5board.com)

wiggis · 6th November 2006, 22:39

For no particular reason other than age, I took the BMW MAFs out of my car (108,000 miles) and replaced them with a pair of VW MAFs from the group buy.

After about 300 miles, I've swapped back to the BMW units ....... why you ask?

With the VW MAFs :

1) I found that the engine didn't seem to rev up as freely

2) I found that the exhaust would 'pop pop pop' when the engine throttle was blipped at idle

3) I spotted more soot coming out of the exhaust pipes than before

4) The average fuel economy dropped from 19.2 mpg to 17.2 mpg

I have a suspicion that the little round hole in the bottom of the VW MAFs which is not present in the BMW version allows a slightly higher air flow across the sensor than the BMW MAFs do for the same rate of laminar flow of air through the housing. I think this then tricks the DME to put more fuel into the engine than is strictly necessary.

In some circumstances, I believe this may result in a slight power increase, but in my case, I just didn't like what it appeared to be doing to the engine - especially the 'pop pop pop' noises on the over run, and the general fear that too much fuel was being thrown into the engine (which might dilute the oil, wash the cylinders, lead to carbon build up, etc etc).

I've got the BMW MAFs back in the car, and normal service is resumed - popping is gone, engine revs more freely, etc.

Of course, I have no proof because as far as I am aware, no one has measured the electrical response of the VW and BMW MAFs in the same operating conditions - so all of this is my opinion based on observation. YMMV - but I would urge caution.

Laidback · 6th November 2006, 23:17

Interesting observations anyone had the same experience?

Nabio · 6th November 2006, 23:24

I just installed some VW MAFs earlier this week. I'll keep a close eye on the performance of my engine, including sounds. I'll post back here later on today after my midterm--going out for a drive so what better time to take a look.

edit: One thing, has anyone considered calling up Bosch and inquiring as to the difference between the two MAFs? I know the VW one is manufactured in Mexico as opposed to the BMW ones in Germany but besides that I don't know.

Beamer_usa · 7th November 2006, 00:30

Wiggis & Nabio: Post your results here:

POLL: VW MAFS? YEA! or NEA!

M5MJ · 7th November 2006, 01:09

I bought a set a couple weeks ago, but haven't installed them yet. Interested to hear if anyone else has experienced similar issues to those listed above. It seemed like lots of people running VW mafs had excellent results in the VF maf poll thread.

aaronmiles · 7th November 2006, 03:12

interesting regarding the extra hole on the VW ones. I have a set and a BMW set sitting here.. I might take a look and see what I can find.

aaronmiles · 11th November 2006, 12:55

I measured the voltage coming out of a VW one compared to the BMW one and they are so close I would say they are the same... At idle the BMW one shows 1.27v and the VW one is 1.26v. Their diagnostic voltage is 1.01 and 1.00 respectively which is pretty good.

DavidS did a few tests on them and may comment further....

wilmus · 12th November 2006, 22:40

I had at the time about 110K miles on my 2000 M5. I never had the MAF's replaced. Nothing seemed to be wrong with them but all the talk about replacing them with the cheaper VW units had me excited to try them.

I bought them locally from a VW dealer using the part numbers posted on this site. I went home and installed them after getting the screws out using a hack saw to cut a groove in the top of each screw.

I drove the car and the longer I drove it, the worse it got. Never before did it run this bad. So I picked one and replaced the original back in. It helped. Not till i replaced them both with the originals did it run good again.

So after thinking about it, i tried to replace one side. Mix and match them. Trying to figure out if i only had a problem with one of the new ones. It only took me 2 mintues to replace each one so it turned out to be a dailey thing of trying them out and replacing the old ones.

Finally I threw the new ones in the trash. I couldn't return them because I took them out of their original MAF units.

Now it's back to normal. (shrugs)

Blockdoc · 12th November 2006, 23:08

My take so far...
I have onlyt 35K on my beast, but after all the talk, and in the endless quest to keep her running as well as possible...I ordered a pair of MAFs from Performance Cafe and swapped them out about 100 miles ago. (My instrument cluster MAF test read 136 preexchange, so my originals were probably fine anyway). Just wanted to see if I noted a difference.

So far, I have had no problems...but have also noted no difference for the better. New testing yields essentially the same numbers. Interestingly, many have noticed roughness initially after install purportedly due to ECM recalibration, I have not.

Given the lack of difference, I will probably reinstall the OEM parts until they crap out. But based on my current experience, I will put the VW ones back in when needed.

Brian

BKH · 12th November 2006, 23:46

Yes, the experience with the VW MAFS seems to be all over the map. I installed a pair of them with no hiccups whatsoever and verified on the dyno that they worked great. That said, I'll still probably go back to OE MAFS in 25K miles or so, or whenever these start acting up and I decide to junk them. Before the group buy I bought a pair of OE MAFS with housing, the deep discount price being about $450+/pair, I can no longer remember exactly. Anyone get a better price recently?

gbogh3 · 13th November 2006, 00:05

Quote:

Originally Posted by BKH

Yes, the experience with the VW MAFS seems to be all over the map. I installed a pair of them with no hiccups whatsoever and verified on the dyno that they worked great. That said, I'll still probably go back to OE MAFS in 25K miles or so, or whenever these start acting up and I decide to junk them. Before the group buy I bought a pair of OE MAFS with housing, the deep discount price being about $450+/pair, I can no longer remember exactly. Anyone get a better price recently?

That is a great price! I called two $tealers, one at $360 per MAF and the other $470!
I have a pair, brand new, I might sell them, but it would be $600 for the pair.