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INTRODUCTION

Both the Rover (Bosch) Mafs (L series & 75/ZT/TD4) are expensive - about £200 + vat and delivery = ~£250. They become unpredictable and temperamental and are easily damaged by moisture & oil contamination. So if your car has done over 30-40k and the performance &/or fuel consumption has worsened, the maf is probably to blame.

But why pay over £250 for another, which may not last more than a year or two when you can fit a Pierburgh one for 1/3rd as much?

Either way, a Digimafam DGM1 IS ESSENTIAL when a Pierburg Maf is fitted to either 25/ZR/45/ZS or a Synergy 2 or DGM2 for the 75/ZT and Freelander TD4. The total cost is therefore, around £160 but it will work better and more reliably than the Bosch maf and save you over £100

The photos show the Bosch (left) & Pierburg (right) MAFs.

Mechanically & dimensionally they are identical so fit the existing housing without any mods being needed.

The sensor is held in using two security screws. These will be either security Torx 6pointed or 5pointed. We now stock the hard to find 5pointed type for £10

(NB. The Bosch unit is supplied as the complete air mass meter - the sensor plus its duct, whereas the Pierburgh maf is just the sensor as shown above. It therefore replaces the Bosch sensor without the duct needing to be removed.)

TESTING. (Mafam already installed)

Interchanging the MAFs produced barely discernible differences. There were no side effects - no jerking or hesitation, no flatspots or misfiring, no uneven acceleration or uneven response to the accelerator pedal. A cold start first thing showed up no problems - it was exactly the same whether idling or driving off as it was with the Bosch Maf.

 I did get the impression that the engine seemed freer revving a higher rpm with the Pierburgh maf fitted.

In view of the cost difference it has been a worthwhile exercise.

Pierburg on left, Bosch (Rover) on right.

Both output about 1v engine stopped and the PB reads about 2v and the Bosch 2.2v engine idling & EGR closed.

WHY CAN'T I LEAVE THE MAF UNPLUGGED?

Some owners have been advised that its okay to just leave the maf unplugged. This is not a good idea for the the following reasons:

a) Not only is there no air flow measurement, but no intake air temp sensing either so the ecu defaults to -5C. This results in over fuelling, especially in warm weather leading to poor fuel consumption and lump running.

b) The lack of air temp sensing means the timing is not optimum as the ecu uses the IAT to adjust the injection timing.

c) The ecu's overrun fuel cut off feature may be disabled, also making fuel consumption worse and engine braking worse.

d) Performance is worse: A higher revs on the L series - the engine won't rev past 4000rpm and on the 75/ZT/TD4 there is a stodgy, choked feel probably due to the overfuelling.

NB FOR 75/ZT/TD4 OWNERS: : DO NOT FIT PIERBURGH MAF 7.22684 09.0 with or without a Synergy 2 as this ONLY for BMW vehicles.

A WORD OF WARNING: Beware the non Bosch mafs and suspiciously cheap Bosch ones - years of feedback from owners who have tried these confirms that you get what you pay for. So its a 100% genuine, unopened Bosch maf or a Pierburgh in my view.

Finally, many thanks for Pierburg subsidiary Motor Service International for emailing me the data sheet.

Both Bosch and Pierburg have provided technical information quickly in response to emails, whereas requests to Rover for data seem to have disappeared into a black hole.....