PDA

View Full Version : Life without MAF - 1000 miles later


tonewheeldude
9th May 2013, 01:13
Some time ago my MAF started acting up on my 2004 CDTi 131 (after driving through severe motorway spray) its was ok after a day or two but as soon as there is moisture in the air it would act up again. Anyway I ordered a new one, but have not got around to getting the security bit to remove the old unit so left the MAF unplugged.

Anyway that was 8 days ago..and now, 1000 miles later the car runs superbly, its fast, responsive and economical (50.3 mpg) and I am beginning to question why I even want to fit a new MAF now. Is it possible the tuning boxes on the market actually just bypass the maff as required to give more power?

What are the reasons to fit the new maff? I read on forums:

1) the fuel economy will be bad....False
2) Poor performance above 2000rpm...False
3) Engine will take ages to warm up with poor econmy when cold....false
4) engine will misfire...false

marinabrian
9th May 2013, 03:06
Treat yourself to one of these (http://www.ebay.co.uk/itm/BOSCH-MAF-0928400520-MHK101130-LAND-ROVER-Freelander-2-0-Td4-LN-MG-ZT-Rover-75-/130860509540?_trksid=p5197.m1992&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3 D1%26asc%3D14%26meid%3D7499980072974781598%26pid%3 D100015%26prg%3D1006%26rk%3D2%26sd%3D221224286703% 26) before your ECM settles into bad habits.

You also don't need any special tools to fit it, unlike the incorrect MAF you've already bought ;)
If the corrugated intake trunking has been cut away from the front of the engine, reinstate it now.......

Tuning boxes do not replace MAF's, their purpose can be twofold.
1. To attenuate the signal from the HP rail sensor, this causes the injector pulsewidth to be artificially extended, thus injecting more fuel.
2. Amplification of the MAF output signal, contrary to popular belief Bosch MAF sensors rarely if ever fail with a lower than expected output.

In fact the exact opposite is normally the case, and amplification of the signal compounds the MAF error.
Brian :D

tonewheeldude
9th May 2013, 08:01
Thanks for the reply. So what is likely to happen if the ECU doesn't get its maf fix? Are you sure its not the car equivelent to an Appendix? ;)

mh007
9th May 2013, 09:28
It's a strange one this.
I have a few customers driving around with disconnected MAF's (their choice) with nothing but good results.
They've covered many thousands of miles without issue & passed emmisions tests at MOT time with flying colours.
I can see where Marinabrian is coming from though but it does make you question the MAF's purpose on this particular engine !

Mike Noc
9th May 2013, 10:33
With a diesel engine the MAF is used for smoke limitation and good economy when you are pushing the engine.

If you have a very light right foot and drive economically anyway then there's no reason why your fuel consumption should increase if you unplug the MAF.

Don't forget though that without the MAF the ECU reverts to preset values, so the engine may not perform as well at high altitudes.

I think it's better to have the correct MAF fitted and working correctly so the engine can perform well in all conditions, but each to their own. :D

Frank Incensed
9th May 2013, 13:15
It's a strange one this.
I have a few customers driving around with disconnected MAF's (their choice) with nothing but good results.
They've covered many thousands of miles without issue & passed emmisions tests at MOT time with flying colours.
I can see where Marinabrian is coming from though but it does make you question the MAF's purpose on this particular engine !

As I've previously posted, unplugging my MAF resulted in an increase in fuel consumption of about 30%.:eek:
Not bothering to replace it wasn't a viable option. With the thirst my car normally has, I'd have been better off using a V8.
Look out for a diesel fuel consumption challenge thread I'm going to start tonight.

ceedy
9th May 2013, 14:06
Here here!! ..;) since the synergy came off and the IPK supposedly reading more accurately .. my Auto gives 34-35 mpg for general running around ( mostly 4th gear) ..:(

C.

tonewheeldude
9th May 2013, 21:59
I would like to say I have a light foot...but it would not be true. I enjoy driving ALOT and work the car well through the gears. I work in the next town and take the country route as its more fun. I try and stick to the speed limits on the motorways, but often have to nurse a damaged conscience! I am not a fast lane hogger I change lanes all the time.. its more enjoyable to do it properly and move across the motorways to overtake.

For me to average 50.3mpg over 1000 miles is simply amazing and I have never achieved this before with any other vehicle I have owned.

So if I fit a MAF, should I expect to get MORE MPG??

Frank Incensed
9th May 2013, 22:10
Seems like you're an ideal candidate for my challenge. But you might not have accumulated evidence over a sufficient mileage. DON'T reset your trip computer.

http://www.the75andztclub.co.uk/forum/showthread.php?t=146266

Have a read.

E_T_V
9th May 2013, 22:31
For me to average 50.3mpg over 1000 miles is simply amazing and I have never achieved this before with any other vehicle I have owned.

So if I fit a MAF, should I expect to get MORE MPG??

Have you worked out he milage using fill-up data or just the car display. Is the accuracy of this altered when the MAF is unplugged?

Bosch MAF failure on the other diesel engines (L series) in the rover range almost always presents itself as failing with a low signal. No idea on the BMW units though but I'd assume they are the same.

BigRuss
9th May 2013, 23:49
Bosch MAF failure on the other diesel engines (L series) in the rover range almost always presents itself as failing with a low signal. No idea on the BMW units though but I'd assume they are the same.

The Bosch MAF as fitted to the M47 in the 75 almost always fails with a signal that is too high.

Russ

tonewheeldude
10th May 2013, 07:56
Seems like you're an ideal candidate for my challenge. But you might not have accumulated evidence over a sufficient mileage. DON'T reset your trip computer.

http://www.the75andztclub.co.uk/forum/showthread.php?t=146266

Have a read.

I had aquick look, but I have to drive to Wales today (another 300 mile round trip), I will have a propper read when I get back

Have you worked out he milage using fill-up data or just the car display. Is the accuracy of this altered when the MAF is unplugged?



10 days ago I disconected the MAF to fit a new one...but didn't have the security tool so left it disconnected. 9 days ago, the fuel light came on so I reset the trip counter on the forecourt when I filled up (Esso) and worked out from my receipts and the trip counter at the point the fuel light came on again

The journeys consisted of a mixture of dual carriageways (A14, A11) , some motorways (M1 and M5 but not long hauls) and lots of A and B roads (across the cotswolds and around North Norfolk). These have mostly been work related trips.

After the next couple of weeks my mileage should drop down to an average again - but its a good time to test as I have so much mixed driving to do just now.

hogweed
10th May 2013, 10:46
You also don't need any special tools to fit it

HAH! No no no. You need:

1. Seven hands
2. All of the hands must be ½ human size, with 9 double-jointed fingers
3. X-Ray vision

Strictly speaking, all the above are required to relocate the air filter cover, not the actual MAF replacement.

Give up and buy a Mondeo now.

I’ve seen so many of these threads about the MAF – as always, all I can do is relate my experience. My car’s performance was dead flat; I discovered the MAF was disconnected (when I bought it); I fitted a new sensor (BigRuss assures me it’s the wrong one, overfuelling by 4% I think, but it seems to do the job); the car runs MUCH better with it than without.

tonewheeldude
10th May 2013, 12:29
HAH! No no no. You need:


Give up and buy a Mondeo now.



Man they are so snoozeworthy, cheap seats, cheap plastic dash and the thinnest steel for the panels Ford could possibly manage. As a consequence park next to a mum with a kid at Waitrose and you have to call mend-a-bend. On the plus side they do have a MASSIVE load area if your into that kind of thing- big enough for a King Size bed and room to take your boots off too without getting mud on your lady friend.

I don't know whats going on with these results though. How can one person get only 30mpg out of their diesel and I am getting 50.3 mpg without the MAF fitted?

I will fit a new one and run that for 1000 miles and compare results. If the economy and performance goes down I will just leave it disconnected all the time.

hogweed
10th May 2013, 12:35
How can one person get only 30mpg?

Wasn't his an auto?

wuzerk
10th May 2013, 13:24
I don't know whats going on with these results though. How can one person get only 30mpg out of their diesel and I am getting 50.3 mpg without the MAF fitted?

.

simple really, it depends entirely on the type of journeys that you make.
My diesel auto will read just above 50 mpg on motorways but, used solely for 1 1/2 mile trips in London it will read 27MPG. The secret is the 'average speed' as shown on the dash readout. For 27mpg my average speed is 17mph.

jonathan63
10th May 2013, 19:09
I have run my CDTi for about 5000 miles without a MAF and it seems fine. It vibrates at tickover but it did that when i bought it 12,000 miles ago.
Every now and then i plug the MAF back in and run for a mile or so. It seems to stop the ECU reverting to limp mode.
Works for me.
MPG last week= 48.2 (brim to brim(dash said 43)) 100 miles running round and 330 easy drive to suffolk.
Easy drive home and the dash says 47.8, so i expect thats just north of 50.

tonewheeldude
10th May 2013, 19:37
I have run my CDTi for about 5000 miles without a MAF and it seems fine. It vibrates at tickover but it did that when i bought it 12,000 miles ago.
Every now and then i plug the MAF back in and run for a mile or so. It seems to stop the ECU reverting to limp mode.
Works for me.
MPG last week= 48.2 (brim to brim(dash said 43)) 100 miles running round and 330 easy drive to suffolk.
Easy drive home and the dash says 47.8, so i expect thats just north of 50.

Now this is interesting thank you for posting, both you and I are running without MAF and we are around 50mpg. I will connect the MAF and run another chunk of miles and see what the difference is - not just yet though...I am loving the high MPG!

Frank Incensed
11th May 2013, 08:15
simple really, it depends entirely on the type of journeys that you make.
My diesel auto will read just above 50 mpg on motorways but, used solely for 1 1/2 mile trips in London it will read 27MPG. The secret is the 'average speed' as shown on the dash readout. For 27mpg my average speed is 17mph.

:wot:

But, it doesn't explain why I can regularly achieve only 35 to 37 mpg over long distances (up to 350 miles) at relatively constant, legal speeds, when others say they can get get over 50% more mpg on runs which should in theory be less economical. :shrug:
(OK - 2 things. It also doesn't explain why the OP is getting good mpg by unplugging his MAF, which is totally opposite to the 20 mpg experience I got when I did it).

hogweed
11th May 2013, 08:28
But, it doesn't explain why I can regularly achieve only 35 to 37 mpg over long distances (up to 350 miles) at relatively constant, legal speeds, when others say they can get get over 50% more mpg on runs which should in theory be less economical.

I thought that was about right for an auto box? You simply won't get the same mpg as a manual. And the other thing… this will come as a terrible shock to you I know, but people exaggerate ;)

Mine (manual) does 41-43mpg, driven very calmly on normal rural roads, very little use of the turbo.

dotsie
11th May 2013, 09:32
I thought that was about right for an auto box? You simply won't get the same mpg as a manual. And the other thing… this will come as a terrible shock to you I know, but people exaggerate ;)

Mine (manual) does 41-43mpg, driven very calmly on normal rural roads, very little use of the turbo.

No exaggeration but mine does 48mpg..heavy foot,unions and country roads to work.Took it to Edinburgh and got 55mpg hitting 80/90 miles ph. Mapped to 150.
SWMBO has a lighter foot and crowns, hers returns 51 mpg on country roads commute. 131 map. Both cars are manual.

MrDoodles
11th May 2013, 09:42
But just think how it would run with a new Bosch MAF and a 160 re-map! ;)

dotsie
11th May 2013, 09:50
If the corrugated intake trunking has been cut away from the front of the engine, reinstate it now.......

Why Brian? On hers its cut away(before we bought it) Intrigued..

Frank Incensed
11th May 2013, 09:51
No exaggeration but mine does 48mpg..heavy foot,unions and country roads to work.Took it to Edinburgh and got 55mpg hitting 80/90 miles ph. Mapped to 150.
SWMBO has a lighter foot and crowns, hers returns 51 mpg on country roads commute. 131 map. Both cars are manual.

Not so sure about your car, because it's not got a standard map, but I'll take advice on this from an ECU expert.

http://www.the75andztclub.co.uk/forum/showthread.php?t=146266

Mrs dotsie's car sounds ideal for my challenge. Are you willing and do you have the required evidence?

dotsie
11th May 2013, 09:58
Not so sure about your car, because it's not got a standard map, but I'll take advice on this from an ECU expert.

http://www.the75andztclub.co.uk/forum/showthread.php?t=146266

Mrs dotsie's car sounds ideal for my challenge. Are you willing and do you have the required evidence?

Mine is a Viezu map. SWMBO's car doesn't have the required evidence i'm afraid. I only check consumption brim to brim and don't keep records. Hers has done 136k, mine 107k. I will be doing 1000 miles in mine next bank holiday weekend..that will be interesting :)

marinabrian
11th May 2013, 10:01
If the corrugated intake trunking has been cut away from the front of the engine, reinstate it now.......

Why Brian? On hers its cut away(before we bought it) Intrigued..

Because this effectively bypasses the water shedder under the bonnet slam panel.
The purpose of this is to prevent water spray being atomised through the air cleaner, and as a result deposits build up on the platinum hot wire sensor within the MAF leading to failure.
Call me cynical, this particular "performance mod" was recommended by a person who has vested interests in selling replacement MAF sensors :getmecoat:
Brian :D

dotsie
11th May 2013, 10:06
Because this effectively bypasses the water shedder under the bonnet slam panel.
The purpose of this is to prevent water spray being atomised through the air cleaner, and as a result deposits build up on the platinum hot wire sensor within the MAF leading to failure.
Call me cynical, this particular "performance mod" was recommended by a person who has vested interests in selling replacement MAF sensors :getmecoat:
Brian :D

thanks for the quick reply and explanation Brian..off to Sean's now to get the part :)

tonewheeldude
11th May 2013, 18:09
I thought that was about right for an auto box? You simply won't get the same mpg as a manual. And the other thing… this will come as a terrible shock to you I know, but people exaggerate ;)

Mine (manual) does 41-43mpg, driven very calmly on normal rural roads, very little use of the turbo.

I guarantee I am not exaggerating.

The figures were based purely on setting the trip meter to zero on a fill up just as the fuel light came on. after just under 1000 miles the light came on again and then using my receipts (which I have to keep for work) I calculated the mileage using an online calculator (rather than trusting my own math!) It came out at 50.3 mpg.

Wether you believe it or not is of no consequence to me as I am simply trying to work out wether the car is better with the MAF or without. But if your reading this and are in the same boat as me I would appreciate your input

tonewheeldude
11th May 2013, 18:12
By the way my tourer does not have a fuel computer (its a club), but is an XPOWER 131

Mike Noc
11th May 2013, 18:18
Tone the only accurate way to check fuel consumption is a brim to brim check: Fill the car up and zero the trip meter. Run the tank down then fill up again and check the miles done against the amount of fuel used.

Try that with the MAF disconnected, and then again with the correct MAF in good working condition connected.

Only then can you determine whether you are better off with the MAF connected or not.

hogweed
11th May 2013, 18:24
Only then can you determine whether you are better off with the MAF connected or not.

And then you’ll want to stick it on a dyno to see how your power output compares… you can't tell by the seat of your 4rse.

MrDoodles
11th May 2013, 18:26
Trust me, if MGR could have saved £100 a car by not fitting one, they would have!

Frank Incensed
11th May 2013, 18:38
And then you’ll want to stick it on a dyno to see how your power output compares… you can't tell by the seat of your 4rse.

A certain high tech dyno, capable of of handling 4x4's with up to 1000 bhp, "proved" that my car had marginally less bhp than an acquaintance's Ford Fusion 1.4 TDi. I think because it was a 75, the dyno man thought it ought to have 75 bhp. :shrug:
Strange, but the Rover is still capable of out-performing hers. I suppose it's because she's slow at changing gear (thank goodness - I love to watch her:D).

tonewheeldude
11th May 2013, 21:06
Tone the only accurate way to check fuel consumption is a brim to brim check: Fill the car up and zero the trip meter. Run the tank down then fill up again and check the miles done against the amount of fuel used..

Thats exactly what I did, except there were fill ups in between. But I did not calculate until the tank was empty. The more miles you do the more acurate the result should be.

The mileage covered just about every kind of driving. Motorways, Dual Carriageways, A roads, b roads and even unclassified by-roads! Flat and hilly terrains, town and country.

When I fit the MAF I will try the same thing and compare results.

marinabrian
11th May 2013, 21:46
Thats exactly what I did, except there were fill ups in between. But I did not calculate until the tank was empty. The more miles you do the more acurate the result should be.

The mileage covered just about every kind of driving. Motorways, Dual Carriageways, A roads, b roads and even unclassified by-roads! Flat and hilly terrains, town and country.

When I fit the MAF I will try the same thing and compare results.

A proper Bosch MAF, or the insert you have now :shrug:, the results will be skewed if it's the latter ;)
Brian :D

wuzerk
12th May 2013, 09:39
I thought that was about right for an auto box? You simply won't get the same mpg as a manual. And the other thing… this will come as a terrible shock to you I know, but people exaggerate ;)

Mine (manual) does 41-43mpg, driven very calmly on normal rural roads, very little use of the turbo.

The usual 'exaggeration' is due to the fact that anyone with a Synergy is getting an optimistic readout as it is a feature of the system. If you zero the
MPG readout when you hit a motorway then you should see at least 48MPG
on an automatic until you leave it. IMO that is a reliable indication that your car is performing satisfactorily. If you see less than 40MPG then your engine is not running as it should do or, you have low tyre pressures, binding brakes, a very heavy right foot,or you drive with the windows open all the time!

dotsie
12th May 2013, 09:50
Have to say that a 4 wheel alignment made a big difference to my consumption. I was told that both front and back wheels were toeing (pointing inwards).Can see how that would be a drag...

Rev Jules
14th May 2013, 10:06
I have a Synergy 2 fitted with the MAF turned off, I drove to Wolverhampton over the weekend for a Nano meet, I did most of the journey doing between 70/80 mph, both there and back the IPK was showing on average of between 57/62 MPG, I have a Diesel, good or bad????.
And what is this on here about restoring the bellows on the air intake because of a certain person recommending taking them of with the inference it was finacially motivated, I thought taking the bellows out would give more air into the engine. without any restrictions.

Julien ( Bluebird)

Trevor1975
14th May 2013, 11:28
Its too early for me to tell my MPG, just bought my 75 cdt and put £20 in her. Next week is payday and I plan to fill up every payday too, so in 5 weeks I'll have my first official MPG :cool:

Meantime I've heard a few other interesting stories such as using 5W30 synthetic oil, increasing mpg... by 3-4 mpg better???

Its always good to have decent tyres with the correct PSI inflation. If you inflate your tyres with an optimistic gage and the weight of the car on the tyre, it could be quite soft compared to the right PSI on an unloaded tyre. Also injector performance is crucial. A good atomised spray will burn more efficiently than a clogged up injector spraying out droplets. I ran some injector cleaner through mine and gave it a good thrashing (3000-4000 rpm in 3rd / 4th a few times... it seems to have made it run better.

There are so many factors that affect MPG... weather, traffic, tyres, tracking (as above), oil, injector condition, boost pressure etc etc..

I'll do all I can, within reason / budget to get the best MPG and see what I can achieve this coming month, with a 'brim to brim' test at the same diesel pump :D

tdi90
14th May 2013, 12:33
Both of my MAF's have died with too higher output. Loadsa black smoke when under hard throttle but not alot of power. Synergy MAF compensator hasn't helped, so my MAF is disconnected until I can afford a new one.

I was given a spare MAF when I brought the car, both were iffy eBay jobbies, but for about 18 months I've been swapping em around and cleaning them with brake cleaner which has worked upto now lol.

RE the corrugated bit of the air intake; surely the air filter will stop any water getting to the sensor? Some performance air filters must be oil'd so are they a problem as well? (next on my shopping list)

I chopped my corrugated intake off and added a home made air 'scoop'. While sounding abit gash, it has helped bring the intake temperature RIGHT down when on the move.

hogweed
14th May 2013, 12:53
I wonder about cold air intake on diesels… it’s a big thing with people trying to get extra power out of petrol engines, and debate over how best to do it raged when I moved in BMW M3 circles. General consensus was that cold air is denser, so you get more molecules in your combustion chamber, so a bigger bang on cold nights…

But my Rover gives me 1mpg better in the summer than it does in the winter, which I wonder about. Yes, I know the engine will warm up quicker, the oil is thinner etc… but I’m wondering if the effects of air temperature on combustion work differently with diesels too…

Trevor1975
14th May 2013, 18:50
I wonder about cold air intake on diesels… it’s a big thing with people trying to get extra power out of petrol engines, and debate over how best to do it raged when I moved in BMW M3 circles. General consensus was that cold air is denser, so you get more molecules in your combustion chamber, so a bigger bang on cold nights…

But my Rover gives me 1mpg better in the summer than it does in the winter, which I wonder about. Yes, I know the engine will warm up quicker, the oil is thinner etc… but I’m wondering if the effects of air temperature on combustion work differently with diesels too…

Good point! N/A petrol engines love cool air. Turbocharged cars have intercoolers because the process of compressing the intake heats the intake air. Plus the turbo boost is used as required, So a few degrees difference on the inlet side or small change in air pressure due to inlet pipe temperature will probably have negligible impact on the performance of a turbo diesel.

Having a bigger air scoop may help reduce the suction side of the turbo, meaning less losses in terms of driving the turbo around. This might help a bit.

Like Tesco, Every little (bit) helps :D

tonewheeldude
14th May 2013, 19:25
Having a bigger air scoop may help reduce the suction side of the turbo,

Would this be appropriate?

http://www.ramjetsspeedshop.com/R5239.html

tonewheeldude
20th May 2013, 21:31
Just completed 2000 miles without the MAF sensor still with no ill effects - no missfires, no poor economy, no lacking of power, no ecu slipping into 'get you home mode' etc etc. the car is still very fast, very smooth and unbelievably economical. Service is due next week.

As far as I can tell the only possible downside may be emmisions when it comes to MOT (although there is no smoke even when going up hill with a full load)- maybe thats what the MAF was all about? ...To make sure there was not a surplus of fuel which could be burned off wastefully...I realy don't know. The MOT is not up for 10 months, wether I will leave the MAF disconnected until then remains to be seen.

Trevor1975
23rd May 2013, 17:27
Well my 99 CDT 116 was flat below 2,000 rpm. I managed to get my MAF plug off tonight and just a quick run up the drive and back in 1st / reverse and its totally transformed! cant wait to go for a proper spin to see what happens!

Billy1mate
23rd May 2013, 18:12
Give up and buy a Mondeo.

No chance! Injectors, HP pump, DMF oh & turbo failure, plus the fact it is mundane.

wuzerk
23rd May 2013, 19:40
Well my 99 CDT 116 was flat below 2,000 rpm. I managed to get my MAF plug off tonight and just a quick run up the drive and back in 1st / reverse and its totally transformed! cant wait to go for a proper spin to see what happens!

Well. as I am sure you know, that proves that your MAF is not working properly. You can run for as long as you like with it disconnected until you decide what you wish to do.(which is what this
discussion is all about).

75driver
24th May 2013, 00:12
Well. as I am sure you know, that proves that your MAF is not working properly. You can run for as long as you like with it disconnected until you decide what you wish to do.(which is what this
discussion is all about).

Makes you wonder though.....
If cars run fine (even better) without it... Why fit it in the 1st place?

paul d
24th May 2013, 04:54
Found out about a month ago my MAF was shot so disconected it. MPG went up by about 4 to 40ish, mainly around town/local stuff.

Got a brand new Bosch one, not a cheapy, fitted it & the MPG has gone DOWN to just over 30 doing the same sort of trips. How can this be.! Don't get it.! Nothing else has changed.

Thinking of disconecting it again for a few days to see what happens.

Regards

Paul

hogweed
24th May 2013, 08:19
How can this be.! Don't get it.! Nothing else has changed.

Are you measuring the amount of diesel actually consumed over a set mileage? Don’t rely on the computer, especially after you've changed something…

Mine was very flat running without a MAF and, being so down on power, may well have been more economical – who knows? But it totally came to life when I fitted a new one.

paul d
24th May 2013, 08:41
Are you measuring the amount of diesel actually consumed over a set mileage? Don’t rely on the computer, especially after you've changed something…

Mine was very flat running without a MAF and, being so down on power, may well have been more economical – who knows? But it totally came to life when I fitted a new one.

Yes i calculate it myself brim to brim & to be honest i haven't noticed any difference in the performance from MAF disconected to new MAF fitted

Regards

Paul

hogweed
24th May 2013, 08:56
Yes i calculate it myself brim to brim & to be honest i haven't noticed any difference in the performance from MAF disconected to new MAF fitted

Regards

Paul

Weird how it seems to differ so much between cars. For what it's worth, if you exclude the few people who reckon to get 150mpg at a constant speed of 110mph, in reverse, most seem to average around 42 - I do.

paul d
24th May 2013, 09:58
Weird how it seems to differ so much between cars. For what it's worth, if you exclude the few people who reckon to get 150mpg at a constant speed of 110mph, in reverse, most seem to average around 42 - I do.

Lol

Just goes to show, i've had 118mph in reverse:D 125 if the wifes not in it.!:D:getmecoat:

Going to leave MAF in 'till next fill up, see what the MPG is then. If its not around 40 then i'll disconect the MAF for the next one & compare then

Regards

Paul

tonewheeldude
25th May 2013, 17:09
The last tanks of fuel was down in MPG and calculated out at 41.97 (http://www.mpg-calculator.co.uk/), although this was to be expected as it has been almost entirely city driving trips plus a drive from Northampton -> Stanstead -> London N7 - > Soho - > Northampton.

It actually cost much more as I forgot to pay the congestion charge and by the time I remembered the date range was gone :/

I have decided not to fit a new MAF. Last week I went with a friend to pick up a Monde ST220 from Telford and back to Northampton. He had only a slight edge and could not get away from me pulling away from r/bouts etc. He probably has a much higher top speed - but who cares about top speed? All the fun happens between 30 and 70ish.

tonewheeldude
17th November 2013, 08:41
Just thought I would let you know - its been six months now without the MAF sensor being connected. The car is still running well, still good economy.

Mike Noc
17th November 2013, 19:28
If you are very light on the loud pedal then there's no reason why you can't get good mpg with the MAF disconnected.

On light loads there is plenty of excess air available, it's only when you start using the performance that the MAF comes into it's own and prevents overfueling.

Billy1mate
17th November 2013, 20:11
With a diesel engine the MAF is used for smoke limitation and good economy when you are pushing the engine.

If you have a very light right foot and drive economically anyway then there's no reason why your fuel consumption should increase if you unplug the MAF.

Don't forget though that without the MAF the ECU reverts to preset values, so the engine may not perform as well at high altitudes.

I think it's better to have the correct MAF fitted and working correctly so the engine can perform well in all conditions, but each to their own. :D

Loads of soot & 39mpg for me, occasionally 40mpg, think my MAF is knackered.:shrug:

Mike Noc
17th November 2013, 21:37
Try driving with it disconnected.

When my first MAF went the car became decidedly sluggish - like it needed a decoke.

When the non genuine replacement went the only symptom was stalling at idle.

DMGRS
17th November 2013, 22:28
I've been running the non-genuine items I'm selling as an experiment, and it's pointed out that my MAF is actually very much knackered.
Expensive experiment - I was happily in denial! Gained 4MPG, lost my black smoke and haven't lost any power that I've noticed. Fail. :getmecoat:

I ran my old 75 with no MAF, however I do prefer the feel of our cars with one connected. You can certainly feel the difference. :)

Stevie-Blunder
17th November 2013, 23:08
My MAF went in July, I ran it without a replacement till a fortnight ago. I fitted a genuine Bosch replacement as recommended, I'm very seriously considering disconnecting it, my mpg is worse and feels down in power. When I ran it without I did over 4000 miles and it went brilliant, averaging late 40's mpg from brim to brim, now it's doing mid 40's. In fact tomorrow it will be disconnected, with the mileage I do, the extra 3 to 4 mpg will help for Christmas.

DMGRS
17th November 2013, 23:09
It's not unknown for the genuine items to be faulty too - was it a properly priced (£150+) item, and not the sensor element alone? There have been a few 'copies' floating around.

You'll still have a warranty if it was only a few months ago. :)

Stevie-Blunder
17th November 2013, 23:24
A very good friend gave it to me, genuine Bosch with the right numbers, all boxed. He'd bought it for his 75 but sold the car before he had chance to fit it. Been in his garage a few years but kept very well.

tonewheeldude
3rd February 2014, 19:31
If you are very light on the loud pedal then there's no reason why you can't get good mpg with the MAF disconnected.

On light loads there is plenty of excess air available, it's only when you start using the performance that the MAF comes into it's own and prevents overfueling.

I am not light footed and enjoy "driving". A couple of days a week I have to drive over to the warehouse from Northampton to MK and go on the backroads because its more fun! Also I spend alot of time on the motorways and use all three lanes constantly. Not only that I tow stuff around the country...heavy stuff...just last week i towed a box trailer with a Hammond B3 and two leslie speakers in it and another in the car (its a tourer). I dont drive too far outside of the law, but do enjoy making the most of the right side...if you get my drift. So plenty of gear changes and good use of the racing line ;)

But I may have found a possible answer to the MAF question:

I brought 4 tyres last June...the front ones have worn out already :) Its my fault because I drive the car they way I like it. The CDT has so much torque available and its easy to spin the front wheels, even accelerating hard out of a corner in second gear. So maybe the fuel restriction is actually to restrict the power where the engine develops maximum torque (I am guessing around 1700 to 1800 rpm.)

If that is the case, then I am loving the disconnected MAF. Economy is great, power is great, you just have to be carefull not to give it too much power coming hard off of a roundabout onto a dual carriageway otherwise you lose a little speed. I am going to try a different compound tyre next.

I brought a new MAF 11 months ago...I cant even remember where it is, but who cares. No way will I ever be refitting it. The car is WAY too much fun without it.

tonewheeldude
9th May 2014, 08:01
So I thought you might like an update. I just completed 14,200 miles with the MAF disconnected on my CDTi tourer. Last week it went in for the MOT. I left the MAF disconnected. It passed the emmisions without raising an eyebrow.

and repeat what I posted at 2000 miles. "still with no ill effects - no missfires, no poor economy, no lacking of power, no ecu slipping into 'get you home mode' etc etc. the car is still very fast, very smooth and unbelievably economical. "

wuzerk
9th May 2014, 09:26
Those results cannot be ignored, 14000 odd miles is a very thorough test period.

hogweed
9th May 2014, 09:28
Funny how it’s so different between cars though, isn’t it… mine was a total dog with the MAF disconnected; when I put a new one in, it transformed it.

And yes, mine has had a T4 session, with absolutely no faults etc shown, so the presence of the MAF wouldn't seem to be compensating for something else which is faulty etc.

Jakg
9th May 2014, 10:35
But my Rover gives me 1mpg better in the summer than it does in the winter, which I wonder about. Yes, I know the engine will warm up quicker, the oil is thinner etc… but I’m wondering if the effects of air temperature on combustion work differently with diesels too…
I haven't read any other posts, so sorry if this has been covered before - but winter diesel contains anti-waxing agents etc so it's not got as much go-power (technical term) as summer diesel.

Also in the winter you'll have your headlights / heater on etc which use more fuel.

hogweed
9th May 2014, 10:38
winter diesel contains anti-waxing agents etc so it's not got as much go-power (technical term) as summer diesel.

I had no idea - that's the sort of fact that I find really interesting :D

Mr (Z) T
9th May 2014, 11:32
Tonewheeldude I see your car is a 2004 model.
Is your CDTI a facelift model with sensor on intercooler hose?

jonathan63
9th May 2014, 11:39
So I thought you might like an update. I just completed 14,200 miles with the MAF disconnected on my CDTi tourer. Last week it went in for the MOT. I left the MAF disconnected. It passed the emmisions without raising an eyebrow.

and repeat what I posted at 2000 miles. "still with no ill effects - no missfires, no poor economy, no lacking of power, no ecu slipping into 'get you home mode' etc etc. the car is still very fast, very smooth and unbelievably economical. "

Much the same here. Mine is a Mk1 CDTi and now at 201k miles. I unplugged the MAF well over 12 months ago. It must have done near on 20,000 miles without it now and no ill effects that I can see. My average mpg is c47 and best 56.

okenora
10th May 2014, 08:16
The figures were based purely on setting the trip meter to zero on a fill up just as the fuel light came on. after just under 1000 miles the light came on again

You may not be exaggerating but your measurement method has flaws. The light triggers at different levels on our cars so using that as a marker is inaccurate. You say you did 1000 miles, so you had fill ups in between? This again adds to inaccuracy.

If the 1000 miles was a single fill then there is something else amiss as that would equate to near 70mpg, not possible in normal driving on our cars.

The only near accurate way to calculate mpg is brim to brim. Fill it, drive so at least half a tank is gone then re-fill, preferably at the same pump. Then you can pretty accurately calculate your mpg over the travelled distance.

I class mine as economical getting 44mpg average (over a years driving)with IPK showing 47.8 and average speed about 30mph.

tonewheeldude
10th June 2014, 02:59
Tonewheeldude I see your car is a 2004 model.
Is your CDTI a facelift model with sensor on intercooler hose?

Sorry for not replying sooner. Its not a facelift.

I am actually putting it up for sale next week as I have found the worlds only Rover 800 Diesel Coupe!! I have realy enjoyed driving this 75 and the Xpower 135 has made for a fun and lively drive. But I have missed my 800 badly.
https://farm4.staticflickr.com/3775/8769922528_39beab1b1a_c.jpg (https://flic.kr/p/emY9qQ)ROVER75_2 (https://flic.kr/p/emY9qQ) by T_W_D (https://www.flickr.com/people//), on Flickr

https://farm4.staticflickr.com/3672/8769922916_8661d05f00_c.jpg (https://flic.kr/p/emY9xw)My Rover 75 Tourer, 2.0l Diesel Tourer (https://flic.kr/p/emY9xw) by T_W_D (https://www.flickr.com/people//), on Flickr

johnnyb44
10th June 2014, 07:52
This has been one of the most interesting threads that I've read in a long time. Its been a big help.
Many thanks.
..

Johnny

XANADU
10th June 2014, 09:32
This has been one of the most interesting threads that I've read in a long time. Its been a big help.
Many thanks.
..

Johnny
Can I just add my tuppence worth. I've never really had time to sit and post threads on this site due to a hectic lifestyle, however I'm currently having to sit down after a minor op on my foot.

I have found this site most helpful over the years and my ZT is now completely transformed thanks to advice from articles I have read over the past 4 years. Regarding MAF'S I have had all the same issues as others when I first got mine as the car although had one owner from new had not been maintained.

When I first got it the car was sluggish and a bit smoky on hard acceleration, I changed the Maf for a cheap one which was a waste of money. I then did some reading on the internet about cleaning. I found an article from a Bosch representative who was clear that the Maf had no reason to go out of spec unless it was dirty. I then tried cleaning it and it made a difference but was not 100%. I then read some more where people had resorted to putting them in the dishwasher, I thought what the hell. Well I can only go on my experience and the car has no hesitation from a stand still, revs all the way to past 4000, its an auto as well no black smoke anymore, MPG around London 28-30.

For 4 years now I have had the splash shield removed, I also have a large 2" hole cut on the underside of the bellows with 4 smaller ones to get more air into the air box. The filter is a pipercross, these filters have to have a covering of oil. EGR bypass fitted. The car is quick of the mark, no sluggish behaviour at scary junctions, stick it in sport and the car revs all the way with no black smoke trail at all, even at night looking in the rear mirror nothing in the reflection of others headlights.

I know others will say things about the splash guard, bellows and dishwasher and they could well be right but I can only go on my experience and what works for me. I have driven in North Wales and along the M4 in the most horrendous downpours where the rain was at 90 deg and spray and all that but the car never missed a beat. Once a year I chuck the Maf and Pipercross in the dishwasher, let them dry a out for a day, oil the filter and chuck them both back in.

All I would say is if you are thinking of buying a new Maf chuck the old one in the dishwasher first, you have nothing to loose.

jonathan63
10th June 2014, 09:44
XANADU,

Do you put it in the dishwasher on its own or with the dishes and other stuff?

Cheers

Jonathan

XANADU
10th June 2014, 09:58
XANADU,

Do you put it in the dishwasher on its own or with the dishes and other stuff?

Cheers

Jonathan
Not sure if your being sarcastic or not, but its done while the wife is out with the Pipercross. Use a 5in1 dishwasher tablet.

sc008y
10th June 2014, 10:23
Is a large 2" hole larger than a small 2" hole? :shrug:

Sorry, I'm being facetious ;)

Interesting thread and lots of useful information to take forward. Luckily since mine is a 99 CDT I don't have any of these new fangled mpg readouts to confuse me, I simply record mileage and fill-up volume and use good'ol mathematics to calculate my mpg. ;)

With an average of 48-49mpg, good acceleration and no other problems, I've no reason to do anything at all with my MAF, but as mentioned, it's defo worth noting all this stuff.

XANADU
10th June 2014, 10:30
Jonathan, you also stated back in May you have vibration on tick over. I had this and it took me 18 months to find the cause, I changed the bottom engine mount using original and the Red replacement one. I checked pulleys, injectors you name it. In the end it turned out to be the large rubber engine mount on the drivers side had split horizontally but it could only be noticed when the weight of the engine was off it. Changed that and no vibration.

tonewheeldude
12th June 2014, 22:05
Interesting about the dish washer :)

I would still like to know exactly what the MAF is supposed to do. Lots of knowledgeable people with authoritative opinions but still no hard evidence.

Its an MG Rover vermiform appendix!

BigRuss
12th June 2014, 22:37
It's been done a few times, apparently the cheap and nasty dishwasher tablets are the one to go for as they're high in phosphates ;)

No I haven't tried it myself don't have a dishwasher :D

Russ

HarryM1BYT
12th June 2014, 22:43
Interesting about the dish washer :)

I would still like to know exactly what the MAF is supposed to do. Lots of knowledgeable people with authoritative opinions but still no hard evidence.

Its an MG Rover vermiform appendix!

In the MAF is an extremely fine wire. A current is passed through the wire, which heats it up, whereas the air going past it cools the wire down. The faster the flow, the more it is cooled, lower lower its resistance. This feeds into the ECU, as an air flow measurement.

Air varies in density, on temperature, so the ECU also has a temperature sensor in the pipe from the intercooler (MKII).

Knowing how much air is flowing into the engine and its temperature, the engine ECU can adjust the opening period of the injectors, so as not to put too much fuel in.

Lacking the MAF input, the ECU has to make a guess at the amount of air going in, by referring to a table of what it ought to be, based on the rpm. Which is where things can go wrong, because engines are not all identical and parts suffer wear. So we get some saying their cars work normally, some produce smoke, some suffer poor performance, some poor mpg.

Robson Rover Repair
12th June 2014, 22:46
Or you could have a mafless remap like myself! Car drives fully from normal revs like its got a working maf to full rev range.

Just shy of 40k miles later and nothing wrong with how the car drives bar an improved dose of mpg and a saving of a maf replacement which payed for the map!

johnnyb44
14th June 2014, 21:20
Hi.
Im into new territory here but I've just recently had the 160 remap and was advised that my maf was out of spec. I've been running the car with the maf disconnected and the results have all been positive. The car flys along now like a scolded cat !!!and revs so freely, as before it felt quite bogged down. Its so much smoother and flexible it has become a very refined drive all round. There is no smoke thrown out the back either .With the maf disconnected i thought there would of been some drawbacks but i can't find anything. The fuel consumption this week has averaged a shade under 45 mpg which for an auto is not bad at all. It fact i usually average around 43 mpg so early indications suggest its better. After reading this thread with interest it begs the question what's the point of even having a maf fitted to these cars? Will it have any long term detrimental affect if i leave it unplugged ?
If not im leaving my car just the way it is ...Maf less. .
Many thanks.

.
johnny

Robson Rover Repair
17th June 2014, 23:29
The 160 map is designed around a car with a functioning maf, you will be getting peak power only between 2000 and 4000 rpm without you maf plugged in or if you have a failed maf, unlike a car that either has a correct maf within working spec or has had a mafless remap, which will allow to car to not only rev through the range correctly, but give you peak torque from a much lower section of the rev range.