ROVER MG MAF PROBLEMS.

I have come to the conclusion that many diesel owners (& I'm one of them, & not just MG-Rovers owners) are paying for expensive tuning boxes or remaps when in fact the MAF sensor is to blame for a loss of performance and driveability. The Mass Air Flow sensor is located in the inlet duct near the airfilter and its signal is used by the ecu to modify the amount of fuel injected in proportion to the air flow. You can read more about how the maf sensor affects the performance here, suffice to say that it is crucial in obtaining full performance from your diesel.

My first Rover 45, a 2000 model, was just awful below 2000rpm, with most of the accelerator travel doing nothing until about 2000rpm when torque improved a bit, and then there was a sudden surge around 2200-2400 as the turbo came in strongly. In a word it was 'gutless'.

This made driving in town very tiresome as lots of revs are needed to pull away quickly then the turbo cut in abruptly. Similarly, on hilly country roads, if my speed dropped much below 50 I'd have to change down. Only above 60 when full boost is available did it really perform like it should and at motorway speeds the performance was quite respectable. The rest of the time it was so bad that I had a £500 Superchip remap done last year & this gave a big improvement in driveability below 2000 as well as a noticeable if slightly disappointing increase in max torque & power.

I didn't realise then, that the poor performance and somewhat disappointing improvement after the remap was due to the MAF sensor.

"I wish I'd known about the Maf sensor then - I'm confident I could have saved myself the cost of that remap"

In fact the the maf sensor signal fades over a period of several thousands of miles and at first the drop in performance goes un-noticed. Then gradually you begin to feel that you'd like a bit more power. Maybe the car seems to struggles up hills it once sailed up, or seems sluggish when overtaking. As nothing else is wrong, and even a trip to the dealers shows up nothing amiss, you would never guess that the Maf sensor would be responsible for that gradual loss of performance.

So after a rechip or remap or even a new Maf sensor, and considerably poorer, your car is now little better than MG Rover actually intended!

If your maf is faulty, you'll never ever get the most from that tuning box or remap. more details

1) I contacted Van Aken last year with a view to buying one of their SmartBoxes. The response I got was along the lines of - 'we can't give any bhp or torque figures because every Rover seems to respond differently. So we will only fit it ourselves, we won't supply it for diy fitting.'

2)When I had my 45TDiL Superchip remapped, their agent's technician 'palmed' me off with the chart from a petrol turbo (peak torque at 4000rpm - not on any diesel I've seen mate!!) and claimed there was a hole in the exhaust. I later suspected that they too had not been able to achieve Superchips' quoted bhp and torque figures.

3) Another Superchips' customer has just had a similar experience. It took a Digimafam to release the true performance of his Superchipped 45. (see feedback below..

"If you feel your 25/45/Zr/Zs is under performing read my Maf questions page next" more details

My first Rover diesel, a non-intercooled & mechanically injected 420D showed a similar lack of response below 2000rpm so I was beginning to think it was simply due to the spec of turbo fitted & a characteristic of the engine. But adjustments to the VE pump as described in my 'Tuning the Non-Intercooled booklet', can produce substantial gains in power and torque from below 1500rpm even on this engine and without masses of black smoke.

I just needed to find a way of increasing the fuelling without having to resort to expensive remaps or tuning boxes....

I decided the MAF was a good candidate for tests. I unplugged its connector & drove off, noticing there that there was quite a lot more torque from 1200 - 2000, then the turbo cut in a bit sooner, but didn't achieve the same boost pressure, being about 4psi down and max revs were limited to about 3800-4000.

My conclusions were that the default values used by the ecu in the absence of a MAF signal had increased fuelling below 2000, but limited it above this. I then constructed an amplifier that boosts the MAF signal by a variable amount, thus fooling the ecu into injecting more fuel. The chart shows the dramatic effect.

Without a Digimafam there is only half as much boost available and the build up from 1250rpm is slow, then there's that 'all or nothing' effect from 2100 to 2500rpm. The torque curve closely follows the boost pressure so you can see why they are gutless with a weak maf signal.

Compare that to when a Digimafam is fitted - twice the boost at 1500, and more than double at 1750 and 2000rpm.

Only over 3000rpm does the Digimafam stop giving an improvement - that's 81mph in 5th.

I couldn't believe the difference! There was a dramatic improvement in response from just over 1000rpm & little sign of any smoke except once when deliberately using full throttle below 1500rpm up a steep hill!

The car was a joy to drive -even around town - just needing a whiff of throttle & far fewer gear changes. No more revving up and slipping the clutch for quick getaways! I drove 2000 miles in 2weeks on all types of roads & traffic conditions & fuel consumption was no more than 2 mpg worse and is typically 50mpg per tankful over a 1000 mile week.

The throttle response was also very progressive: very responsive & gradual up to about 50% of travel, then after this its like a second turbo cutting in. Not suddenly, but impressively nonetheless.

The testing was done using OBD Logger in 4^th gear from 30-80. (1500-4000rpm) logging just rpm, Map & Maf sensor data. Also, no OBD logging software is totally accurate since the update rate is only about 2-3 readings per second & times are shown to the nearest second but they are useful as a comparison when testing. The speeds were calculated from the rpm - 4^th gear is 20.5mph/1000rpm.

I eventually have got round to fitting one to my 113ps 45. This goes well below 2000 compared to the previous 45 so I was not expecting much, if any improvement.

Wrong! With 40k on the odometer, there is no doubting the improvement in low down torque, extra smoothness, reduced noise and very very good throttle response. I've noticed over the last week that around town, I can remain in a higher gear, and the extra fuel has resulted in, for the first time, a feint sign of soot on the bumper, just above the tail pipe. Yet fuel consumption has remained unchanged at 50mpg average per tankful.

I must admit that the performance of my Rover is superb - the L series can certainly deliver smooth, torquey, fuss free performance. It is free revving, eager, very responsive, pulls strongly from just over 1000rpm - even in 5th and really gets going from 1750rpm. It's too easy to run into the rev limiter and it isn't that loud even when revved. 1/2 boost is available from under 1500 and 10psi from 1600rpm, with the new max of 20psi occurring at 2300rpm.

Top gear acceleration is so good, its hard not to use it. I think my cruise control has been a licence saver!

I recently measured the 50-70 in 5th time with a stopwatch on my nearby 'test track'. It was 6.86 and 40-60 in 4th was 5.05. This compares with my 75CDT 116ps was recorded - 50 - 70 in 9 - 9.3 as standard and 7.4 - 7.6secs with my TU3 tuning box (prototype) connected on the same stretch of road.

50-70 in 5th in around 7secs is quicker than 90% of cars - petrol or diesel and extremely exhilarating, not to mention making overtaking much safer..

It really is most impressive for such an old design. I can't help feeling that MGR failed to exploit this engine's potential and so missed out on much positive press coverage. Pity we'll never see a common rail or variable geometry turbo version.

I recently obtained a Sykes Pickavant ACR4 fault code reader / diagnostic tool and their latest Rover pod (v4).

I experimented by disconnecting various sensors and got the following codes: 0237 - map sensor low - because I unplugged it; 1218 - egr fault - I had unplugged that too; and 1402 - needle lift sensor - I had unplugged that as well. Thus proving that the ecu logs fault codes when sensors malfunction and the ACR4 can read and clear them.

Don't take my word on the difference a Digimafam will make, read what other owners have said.

Hi Ron,
I have just fitted the Pierburg sensor and DigiMafam I received this morning.WOW, preceeded by several profanities,it is magical,it has transformed a tractor into a sports car.Simple to fit,excellent instructions,quick delivery and it does the job what more could I ask?I dread to think how much it would have cost if a Diesel specialist had been involved,they wanted £240 just to supply a Bosch MAF and £70 just for a diagnostics.I am extremely chuffed with my purchase and I must say your Website is a God send.

Thank you for the delivery of the mafam. I can't believe the difference in the car. I was considering selling my car as the heart stopping delay in pulling off (especially at roundabouts) was beginning to get me down. This is the best amount of money that I could have paid out on my car.

Just to let you know, I've had the mafam box fitted to my car for nearly a month now and it is running superb! I've also followed your guide on increasing the boost and also purchased the ITG air filter and the combination of all these components has transformed the way the car drives. I can pull off from a complete stop with nearly no revs at all now which is a total relief, especially for those times when I pull out of junctions and cars are coming a little faster than I first thought. I can rely on my car to just go when I throttle it rather than waiting for the surge of the turbo to kick in before it pulls! I've also noticed an increase in maximum revs. Where as before it would rev out at about 4400rpm(but a decrease in pull from about 4000rpm). It now revs surprisingly to about 4900rpm and the power increases all through the rev range. Thank god I managed to stumble across your site and reference the tuning guide you have wrote otherwise I'd still be driving around oblivious to the fact that my car was not performing to it's best. Many thanks for the info on your site and the mafam you supplied!

"I've followed your mafam developments for a while and it was your web-pages that helped me identify a faulty MAF in January. I replaced it with the Pierburg and it was much better. With the mafam now now installed it makes my 2000 45 TDi go like my old 420 GSDi. I'm particularly impressed with the low revs performance as well as the improved acceleration at higher speeds without changing gear. Constructions is also good with the potted components and I don't know how you got it to me so quickly!"

"Hi mate, just wanted to say thanks! The mafam has worked a treat!! The car is totally different- i didn't realise how bad it had got.
I am doing the permanent fit this weekend. Any more tuning tips? Its a 25TD 101ps. Cheers mate you're a genius!!"

"Hi Ron, I fitted the mafam this morning, Just come back from a test drive, wow!! What a change in performance! Pulls like a train below
2000rpm! Totally transformed the car from lazy performance to "how it should be" for a 2ltr car! I set the control to around 60%and it seems
fine so will leave it there,.."

If it wasn’t for your website I would have probably sold the car and brought a 130 Golf or Skoda and put a big dent in my bank account. But now I have saved myself a fortune and the thing is flying for what it is, 60-100mph has never been so easy. It is now a pleasure to drive and all the frustration I had with it has now gone.

"First impressions are very good its certainly making a difference. I've never had a good maf so hard to judge but its a hell of a lot better low down (I would say its slightly better than a disconnected maf) and it pulls really well up to 3500 rpm, (500rpm higher than unplugged maf). Just been out for a spin and the mafam is working great, its like driving with a new engine, pulling really well from 1750rpm in any gear, its like my old 220di used to be & maybe even a little better than I remember."

"I have been using the mafam for a couple of days and the results are pretty good. The sudden power delivery at 2000 rpm is smoothed out and the car is much better under 2k. I have pulled out and floored it a couple of times at low rpm and the car has responded, instead of giving me a heart stopping delay!"

" anyway, back home now and I eventually got round to fitting the mafam last week (its my wife's car) and we've both been using the car for the past few days with it fitted. The results are far more impressive than I was expecting. The car feels so much more responsive and the increased torque can be felt at almost any rev range. before the car was gutless below 2000rpm and then a slight increase in power could be felt over 2250rpm. There's far more power now way below 2000rpm and pulling out on roundabouts is much easier. I've turned the adjustment screw to about 65% and the car pulls like a steam train with no obvious black smoke. Should I reduce or increase this setting ?

THE DIGIMAFAM

By using digital technology the Digimafam improves upon the original analogue mafam to maximise performance. The 8 settings offer different curves to alter the fuelling at both ends of the rev range by different amounts and this is of particular benefit to those who are intending to tune their engines with for example, sdi injectors.

The original (old) Pierburgh maf sensor (£68) is also compatible with the Digimafam.

If you are intending to fit sdi injectors then the combination of the old Pierburgh maf and Digimafam works well and helps control the overfuelling at low rpm that occurs when sdi injectors are fitted to the 25/45/Zr/Zs engine.

The sdi injectors have a lower opening pressure and therefore on the later engines with a higher pressure injection pump, open sooner and close later. Therefore more fuel is injected and the pump also has an easier time, making it more reliable. However too much fuel can be injected at low rpm (before the turbo is up to speed) with the standard maf.

Fitting a Pierburgh maf reduces the fuelling, and this is normally not what you want, but in this case, we do want it, but only at low rpm. So the maf signal needs to be reduced at low rpm and then restored back to, or even slightly above normal as the revs increase. The only way to achieve this is with a Digimafam DGM1 combined with the 'old' Pierburgh maf.

The settings are selected by the dip switches shown in the photo above, with the on/off switch just to the right of the red switch block. Access to the switches does not require any tools as the end cover just slides off. The led shows that the cable is connected correctly and the programming pins are to the right of the led.The unit measures just 90x65x19/28mm and is supplied with velcro and cable ties.

A heavy duty cable is fitted, with oem maf connectors (male & female as shown below) for most vehicles.

The instructions explains what each map does and the label on the front shows how to set the dip switches for each of the 8 maps but there is no harm in experimenting with the settings. You must restart the engine after moving the switches or the new setting will not come into effect.

On pre 2002 25/45/Zr/Zs vehicles it can release a fair bit more power and torque even with a good Bosch maf, but on later cars, if the maf is working properly, then the results are limited unless you have done other mods such as raising the boost pressure and/or fitting sdi injectors.

On later cars (post 03/04 Facelifts), if you disconnect the maf and there is no or very little improvement below 2500rpm, the DGM1 will not have much effect. If there is an improvement at higher rpm (usually there's a loss of power above 3000rpm when then maf is disconnected) then the DGM1 will help, but is best fitted along with the old Pierburgh maf. (£68 for my online shop)

NB MAF 30DAY MONEY BACK GUANATEE ONLY APPLIES IF ITS RETURNED UNOPENED.. This is standard practice for car spares* and the Distance Selling Regulations only apply to items NOT WANTED or WRONGLY ORDERED and hence sent back unopened.

Please note, we do NOT support the Mafam or Digimafam when used with mafs other than the standard Bosch one, or the Pierburgh maf we supply.

If you wish to use a mafam with other non standard, aftermarket, Bosch alternative or used parts, and the results are not acceptable do not blame the mafam. Failure is very rare so the problem will most probably be down to the actual maf you have fitted.

I am happy to test the mafam or maf supplied by us, but there is a £10 charge for this to cover time, postage and packing. This will not be levied if a fault is found.