MB CDI Mass Air Flow sensor
There was a time when VW asked 280 euro for a MAF... As Mercedes only asked 90 euro, quite a few people switched over to the Mercedes CDI MAF. VW has now lowered its price to something like 90 euro. So there is no real need to buy a CDI MAF anymore to fix your VW. The page is still here. If my MAF ever breaks down, I may still use the CDI MAF I have or I will fix it with a MAF booster circuit.
In the Mercedes 200 and 220 CDI a Pierburg Mass Air Flow Sensor (MAF) is used that mechanically fits perfectly in the housing of a VW Bosch MAF. The electrical connection is the same (no other connector is needed). There's been quite some discussion already on this sensor on the webpages of www.tdiclub.com. Some people report perfect results, other have doubts. One of the tdiclub members, LeeM, provided a CDI sensor so that I could do some measurements. Thanks LeeM!
The measurements were done in two ways:
On the bench, which is the most accurate as conditions can be held the same. 0..200 kg/hour
On the road, used for higher air flow numbers that could not be achieved on the bench. > 200 kg/hour
In the picture below you'll see the workbench measurement setup. Some home build electronics and original VW parts like the airfilter to make the measurement as accurate as possible (real airflow). Note the small fan motor on the bottom: as I needed a huge airflow I pushed the motor over the limit by supplying the poor thing with 80V, while the rating was only 28V. The poor thing lasted quite some time, but eventually blew at 100 kg/hour and needed to be replaced by a powerful 12V motor which could push the airflow up to almost 200 kg/hour. Large enough to get the PWM regulator hot.