Mafs And Mafam: Faqs

[Rover_ron]

Maf sensor - the actual sensor. When fitted in its duct it is often referred to as the air mass meter. If you buy a Rover one from a dealer you get the air mass meter - i.e. the sensor prefitted in its duct. If you buy a Pierburgh maf, you get only the sensor and have to swap it over.

Which models suffer from maf sensor deterioration affecting the performance?

All 5pin maf sensors fitted to post 99 L series i.e. the 25/45//Zr/Zs
All R75, ZT and Mk2 Freelander Td4s (same BMW engine).

The 4 pin maf fitted to the '95-99 Sd, sdi and early (L series) Freelanders is only used for egr control so they are not affected. Any minor improvment by disconnecting the sensor is due to the egr valve being disabled.

Which mafam do I need?

Lseries cars need a MF1 or MF1p
BMW engined cars need a MF75 or MF75p

The following faqs apply to the L series and BMW engined cars.

What's differerent on the 'p models?
These can be used with both the Rover (Bosch) sensor and the cheaper Pierburgh maf sensor which does not have an intake air temp sensor. So the 'p models come with one.

How can I tell if my maf sensor has deteriorated?
Simply unplug it (with the ignition off). If there is an improvment below 2500rpm a mafam is needed.

Why can't I just leave the maf sensor disconnected
On the L series, you lose performance over 3500rpm, usually the engine isn't willing to rev beyond 4000rpm.
On the BMW engine, overfuelling occurs partly due to the lack of the air temp sensor, overrun fuel cutoff ceases as does egr control and the injection timing can be affected. My CDT generally feels choked and stodgy with it unplugged and mpg suffers badly.

Can I fit just a Pierburgh maf?
You can, but you won't be very happy with the lack of low down torque! A mafam is a must to match the Pierburgh maf to the ecu.

Do I need to inform my insurance company if I fit a Mafam?
The Mafam is not a tuning box, its intended to restore performance lost by gradual maf sensor degradation. Any improvement over and above this is a bonus and mainly at lower rpm. In other words, the power band is widened rather than boosted. However its up to you to decide, though I personally would not like to try and explain to them what a mafam is or does!!

Ron

[gammaphile]

Hi Ron,
I have a 98 220SDI, i would like to try the MAF disconnection as i think the car is very sluggish below 2500. Question is where the hell is it! :-)
I do not have a manual yet.

Cheers

PAul

[Rover_ron]

Originally Posted by gammaphile

Hi Ron,
I have a 98 220SDI, i would like to try the MAF disconnection as i think the car is very sluggish below 2500. Question is where the hell is it! :-)
I do not have a manual yet.

Cheers

PAul

You will not see much of a difference as the maf sensor on the sdis doesn't affect the fuelling. Its only used to control the egr valve so any effect you feel will be due to this staying closed.

The sensor is located in the intake duct from the air filter housing.

Ron

[gammaphile]

Thx Ron
Yep it made no difference :-) guess i will just have to wait till i get the decat fitted. Also do you recommend ITG filters?? i read a thread about the chap who makes the decat's and something about him selling green filters on ebay??

Paul

[Rover_ron]

Originally Posted by gammaphile

Thx Ron
Yep it made no difference :-) guess i will just have to wait till i get the decat fitted. Also do you recommend ITG filters?? i read a thread about the chap who makes the decat's and something about him selling green filters on ebay??

Paul

I have used ITG filter and the part no for all the L series is ITG- WB290 from
http://motorsportworld.co.uk

I don't think there will be much to separate the various makes, though I recommend a preoiled one (ITG, Green,BMC) on the 25/45Zr/Zs in case you over oil it and the excess contaminates the maf sensor.

Ron

[Rover_ron]

I can now suply these for £50 inc vat + £3.50 p&p. Eurocarparts price is £52.69 + postage.

Postage is free if you buy one with a mafam or Synergy.

The maf will fit the 75/Zt/Freelander Td4 and the 25/45ZR/Zs L series.

It MUST be used with a mafam: MF75p for the BMW engine, MF1p for the L series.

So the total cost for a mafam and maf is £107.50 inc postage & vat

The PB maf seems to be more reliable than the Bosch one and defintiely more relaibe than the Chinese copies being sold on ebay.

Please see this thread:

http://forums.mg-rover.org/showthread.php?t=156195

Ron

[SteveChilds]

Originally Posted by Rover_ron

Can I fit just a Pierburgh maf?
You can, but you won't be very happy with the lack of low down torque! A mafam is a must to match the Pierburgh maf to the ecu.

Arrg! Wish I had known that before I fitted it! I changed the MAF at my Dad's in Spain and drove back with it fitted. (I had removed the TU3 box following the problems I had with the Diesel leak, but it will be going back on now)

Was wondering why it was struggling to pull the trailer & his 400!

eek. Driving it since I dropped the trailer off, I'm amazed it could pull anything at all, its only slightly quicker with no trailer and no 400! That's probably around 1.25 tonnes less to pull.

[Dr Dave]

Stick to what you know best Steve and I'll do the cars!

[richyg]

Hi, sorry but could someone clarify something for me. I've got a '98 sdi and am curious as to the role of the MAF. I think mine's goosed, disconnected it and got aminor improvement. If i understand correctly the MAF in the 98 sdi is only used to control exhaust gas recirculation and a common mod is to blank this off. Is disconnecting the MAF acheiving a similar effect, or does disconnecting the MAF on 98 sdi do anything else?

If iw as to get a new MAF would a standard 4-pin Pierburg be ok? or would i require the MAFAM mod too? Just consccious of 'modding' and insurance ramifications!

Could someone clarify in idiot speak so i can understand the role of the MAF on a 98 sdi?

thanks!

Rich

[Rover_ron]

Originally Posted by richyg

Hi, sorry but could someone clarify something for me. I've got a '98 sdi and am curious as to the role of the MAF. I think mine's goosed, disconnected it and got aminor improvement. If i understand correctly the MAF in the 98 sdi is only used to control exhaust gas recirculation and a common mod is to blank this off. Is disconnecting the MAF acheiving a similar effect, or does disconnecting the MAF on 98 sdi do anything else?

If iw as to get a new MAF would a standard 4-pin Pierburg be ok? or would i require the MAFAM mod too? Just consccious of 'modding' and insurance ramifications!

Could someone clarify in idiot speak so i can understand the role of the MAF on a 98 sdi?

thanks!

Rich

The maf on the pre '99 L series does only control the egr valve so when you disconnect it, the only reason you feel any improvement, which is usually small, is because the egr valve remains closed.
You can prove this by reconnecting it and instead disconnecting the small vacuum tube (3mm dia) from the egr actuator. The same small improvement will be felt. This is my preferred way to disable the egr valve.

It's therfore not necessary to replace the maf. If it fails and the engine warning light comes on, you can unplug it.

Ron

[vivienz]

My Rover was recently written off in an accident and it had a MAFAM unit fitted. The insurance company have asked about it and I tried to give a brief description of what it was designed to do, or at least my understanding of it. So far the company are dragging their feet on a settlement and I am getting concerned that they might use the MAFAM box as an excuse not to settle.

As my description to the insurance company may not have been particulaly good, and I know you say on your web site that you wouldn't want to be the one to try and explain about the unit but any assistance to placate the insurance company would be much appreciated. The only point I did try to stress was that the unit wasn't designed to boost power.

[Rover_ron]

Originally Posted by vivienz

My Rover was recently written off in an accident and it had a MAFAM unit fitted. The insurance company have asked about it and I tried to give a brief description of what it was designed to do, or at least my understanding of it. So far the company are dragging their feet on a settlement and I am getting concerned that they might use the MAFAM box as an excuse not to settle.

As my description to the insurance company may not have been particulaly good, and I know you say on your web site that you wouldn't want to be the one to try and explain about the unit but any assistance to placate the insurance company would be much appreciated. The only point I did try to stress was that the unit wasn't designed to boost power.

Have they told you why they are dragging their feet?
If they try to claim the mafam was a mod and use it as an excuse, please let me know and I will email you a letter explaining what the mafam does.

Ron

[linkovitch]

My 420 SLDi Turbo's (1999) maf is (according to Haynes) connected to the EGR and the fuel pump. Does the MAF really have nothing to do with the fuel pump ?

[Rover_ron]

Originally Posted by linkovitch

My 420 SLDi Turbo's (1999) maf is (according to Haynes) connected to the EGR and the fuel pump. Does the MAF really have nothing to do with the fuel pump ?

No it is only used by the ecu to regulate exhaust gas recirculation on the sdis.
Hence changing it is a waste of time.

On the later models, it is used to control the fuelling as well mainly below 2500rpm.

Ron

[SDI_Tim]

On an SDI etc, could a really contaminated MAF cause the EGR to operate under loads when it would affect performance/mpg, i.e. when you want power, by vastly under-reporting the air flow, or is there a load/throttle position calculation considered by the ECU when deciding whether to employ EGR or not which would prevent this?

Does anyone know?

[Rover_ron]

Originally Posted by SDI_Tim

On an SDI etc, could a really contaminated MAF cause the EGR to operate under loads when it would affect performance/mpg, i.e. when you want power, by vastly under-reporting the air flow, or is there a load/throttle position calculation considered by the ECU when deciding whether to employ EGR or not which would prevent this?

Does anyone know?

Since some owners report an improvement in performance when the egr valve is disconnected or the maf is disconnected, I believe it is possible for a faulty one to adversely affect the performance & mpg.

This can be explained by the egr valve being open too far or too early, or not being closed soon enough.
It has no direct effect on the ecu's fuelling in as much as the mass of air flowing is not used to alter the fuel quaitiy injected. (like it does on the 25/45)

But if its open when it shouldn't be, it will let boost pressure bypass the intake manifold. This is the most likley explanation why disabling it improves the low down throttle response.

If it is open too far, hesitation is possible for the same reason.

Ron

[SDI_Tim]

Originally Posted by Rover_ron

Since some owners report an improvement in performance when the egr valve is disconnected or the maf is disconnected, I believe it is possible for a faulty one to adversely affect the performance & mpg.

This can be explained by the egr valve being open too far or too early, or not being closed soon enough.
It has no direct effect on the ecu's fuelling in as much as the mass of air flowing is not used to alter the fuel quaitiy injected. (like it does on the 25/45)

But if its open when it shouldn't be, it will let boost pressure bypass the intake manifold. This is the most likley explanation why disabling it improves the low down throttle response.

If it is open too far, hesitation is possible for the same reason.

Ron

Thanks Ron

[1260 pete]

Where abouts is the maf on the rover 75 please as i would like to test mine out.

[Rover_ron]

Originally Posted by 1260 pete

Where abouts is the maf on the rover 75 please as i would like to test mine out.

There's a photo on my 75 Home page

http://45zs.info/75Zt/R75home.htm

You need to remove the air filter cover to get to it.

Ron

[1260 pete]

Cheers Ron