softop2011
New Member
- Posts
- 22
here we go gave your suggestion a try --just went round the block --- disabled the egr took the pipe off -and plugged the maf back in---:ballchain: "stuff this" egr back in maff out :car: ...:crazy_driver:
Range Rover P38 Sluggish / no power
- Thread starter donkrr
- Start date
This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
Datatek
Well-Known Member
- Posts
- 45,023
- Location
- Near Poitiers SW France
EGR will be doing nowt anyway. With the MAF out it will be running on the default fuel map, not much different to the non EGR engine. Try it with the EGR disconnected when you have fitted your new MAF. Hope your new MAF is not a cheapo or it may give you more trouble
- Posts
- 58,170
- Location
- Preston Lancs.
Very little if anything to do with fuel on the turbo diesel. Only there to control the EGR. The fuel map for various engine temps and speeds is in the ECM ECU. Only thing the MAF does is regulate via the EGR valve the amount of air introduced at various engine temps and speeds to limit emissions. The none EGR engine has a IAT sensor in the manifold after the turbo, fuel volume required at any particular RPM is calculated from manifold air temp, manifold pressure and fuel temp. It is a totally pointless excercise to have an air temp reading taken before the turbo which is the only thing the MAF could do. By the time the air arrives in the manifold it with be warmer and less dense so the fuel needed would be less. But the fuel needed according to the colder MAF reading would be injected.
The airflow through the MAF is needed by the ECU so it knows how much to open or close the EGR valve in various conditions. In certain circumstances 50% of the inlet air could be exhaust gas, which if the MAF or EGR modulator was not working correctly, causing the EGR to be open too much would give a serious lack of power, in particular at lower engine revs with the engine cold.
Last edited:
6704nathan
New Member
- Posts
- 339
- Location
- burbage nr marlborough
i guess we will have to agree to diagree!
my biggest concern and iam sure others would agree £60 for a maf guessing its not genuine or oem just hope its not an ebay cheapo more trouble than there worth!!
my biggest concern and iam sure others would agree £60 for a maf guessing its not genuine or oem just hope its not an ebay cheapo more trouble than there worth!!
Davie F
Active Member
- Posts
- 380
- Location
- North East Scotland
All I know is that when my Omega got the MAF done it transformed the motor, I just got a new EGR on the Alfa, but for a little bit of smoke on start up and an engine managment light did not notice much difference in performance, I blanked the EGR on a Pajero I used to have and that did improve the performance a little bit. I was under the impression that the MAF was part of the engine managment system.
Davie
Davie
- Posts
- 58,170
- Location
- Preston Lancs.
Would be interesting to find out just what flow rate the MAF is telling the ECU there is. Obviously it is duff from the above.
- Posts
- 58,170
- Location
- Preston Lancs.
Ok Nathan no problem.
According to Rimmers the MAF is no longer available so i would guess it's not an high fail component on the diesel. Only choice is one from a Beemer.
Last edited:
- Posts
- 58,170
- Location
- Preston Lancs.
It is, on a turbo diesel it mainly controls the EGR. You won't see one on a none EGR engine.
Datatek
Well-Known Member
- Posts
- 45,023
- Location
- Near Poitiers SW France
EGR and MAF were introduced at the same time to reduce emissions, that does not mean the MAF mainly controls the EGR, the EDC contriols the EGR and the fueling based among other things on the air volume indicated by the MAF. You really need to read up on these systems. This is like the discussion we had over the centre diff and the VCU.
- Posts
- 58,170
- Location
- Preston Lancs.
EGR and MAF were introduced at the same time to reduce emissions, that does not mean the MAF mainly controls the EGR, the EDC contriols the EGR and the fueling based among other things on the air volume indicated by the MAF. You really need to read up on these systems. This is like the discussion we had over the centre diff and the VCU.
But it does Keith that's what it is there for. How would the ECU know when to open the EGR valve and by how much if it was not getting flow readings back from the MAF. If the MAF takes air temp readings they would be bloody useless for fuelling when on turbo because the air would change state by the time it has been through the turbo into the manifold. Fuelling for inlet air entering at say -5 degrees when it maybe at 50 degrees as it enters the engine is no good. It would be sticking too much fuel in and making the emissions worse. As there is no manifold IAT sensor on the EGR engine, standard air temp mapping must be included in the ECU according to engine temp. That is the only way the engine can run so well with the MAF disconnected. I don't know quite what the duff MAF when connected is suppressing. But with it disconnected the engine seems to run normally but without EGR and of course possibly more emissions.
Last edited:
Davlyn
Active Member
- Posts
- 243
- Location
- Bodmin, Cornwall
Softop2011 have you fitted that MAF yet?? I've been trawling round trying to find a genuine replacement part and at £168.00 is going to be an expensive experiment!!
Its a Pierburg 2246084
Dave
Its a Pierburg 2246084
Dave
softop2011
New Member
- Posts
- 22
Hi Dave - looked all over for one of these - oem unit £175 via bearmach - the 2218400 pierburg unit - no one can definitely say if the maf is naf ( excuse the pun) - with a fortune already spent on this car over the last month or so i'm risking £58 instead of £175 - although lots of views for and against oem or copies just crossing my fingers - fed up of throwing cash at it ... trouble is since i pulled the plug on the maf unit its flying ... if i plug the new one in when it shows up and it doesn't work - will probably go for the razor blades... or maybe have a range rover burning party - will let you know the outcome as sooooone as i plug it in .
- Posts
- 58,170
- Location
- Preston Lancs.
It more than likely will be the MAF. There is a second hand one from a 325 Beemer on ebay for £35.00 if you consider that less of a risk.
6704nathan
New Member
- Posts
- 339
- Location
- burbage nr marlborough
said it before and will say it again yours is defo a faulty air flow meter, think i said that in the first couple of pages of this thread!
reason why i say go for genuine or oem is if you fit a cheap copy you get just that a cheap copy if it cures the fault then its more a case of how long it works for. if it does not which is not unusual you then spend an age trying to find a fault which you should have allready cured or buying the genuine one anyway!
this is all advice from experience i never fit non genuine air flow meters really is not worth the hassle.
all air flow meters are a common fail strangely from my experience bosch dont seem to last as long as pierburgh.
but each to there own!!!!!
reason why i say go for genuine or oem is if you fit a cheap copy you get just that a cheap copy if it cures the fault then its more a case of how long it works for. if it does not which is not unusual you then spend an age trying to find a fault which you should have allready cured or buying the genuine one anyway!
this is all advice from experience i never fit non genuine air flow meters really is not worth the hassle.
all air flow meters are a common fail strangely from my experience bosch dont seem to last as long as pierburgh.
but each to there own!!!!!
- Posts
- 58,170
- Location
- Preston Lancs.
EGR and MAF were introduced at the same time to reduce emissions, that does not mean the MAF mainly controls the EGR, the EDC contriols the EGR and the fueling based among other things on the air volume indicated by the MAF. You really need to read up on these systems. This is like the discussion we had over the centre diff and the VCU.
Yeah i know Keith, but still can't get my head round how MAF can give a finer control all the way through the rev band. At low rpm maybe before turbo comes in and EGR is working. But can't see how it does it when ECU can only see temp of air coming in through MAF and does not know temp of air in manifold which is critical and will be different.
Datatek
Well-Known Member
- Posts
- 45,023
- Location
- Near Poitiers SW France
Yeah i know Keith, but still can't get my head round how MAF can give a finer control all the way through the rev band. At low rpm maybe before turbo comes in and EGR is working. But can't see how it does it when ECU can only see temp of air coming in through MAF and does not know temp of air in manifold which is critical and will be different.
The critical thing is the volume of air being drawn in whether it is helped by the turbo or not, I agree it would be even better if the manifold air temperature were monitored. The thing is that on earlier systems, if you floored the throttle, the rate of increase of fuelling depended largely on revs and a fixed fuel map so it was a little hit and miss especially as things started to wear, with the MAF the EDC knows exactly the amount of air being drawn in so can more closely control the fueling as the revs rise. The EGR is a bit of a red herring, yes it is used to reduce (allegedly) emissions under certain conditions as part of the overall fuelling strategy, but even with the EGR disabled, emissions are still reduced with the MAF due to finer control of the fuelling. The next development was common rail which gave even tighter control and direct injection leading to fuel conversion efficiencies of close to 80% on large (18,000 litre) engines.
- Posts
- 58,170
- Location
- Preston Lancs.
The critical thing is the volume of air being drawn in whether it is helped by the turbo or not, I agree it would be even better if the manifold air temperature were monitored. The thing is that on earlier systems, if you floored the throttle, the rate of increase of fuelling depended largely on revs and a fixed fuel map so it was a little hit and miss especially as things started to wear, with the MAF the EDC knows exactly the amount of air being drawn in so can more closely control the fueling as the revs rise. The EGR is a bit of a red herring, yes it is used to reduce (allegedly) emissions under certain conditions as part of the overall fuelling strategy, but even with the EGR disabled, emissions are still reduced with the MAF due to finer control of the fuelling. The next development was common rail which gave even tighter control and direct injection leading to fuel conversion efficiencies of close to 80% on large (18,000 litre) engines.
All that on board, but none EGR engines had a IAT sensor in the manifold. And because of this must have monitored fuel quantity better on turbo at least. Manifold air inlet temp is critical to fuelling. The system needs to know the density of the air which varies with temperature to inject the correct amount of fuel. It also needs to know the temp of the fuel, because this again varies in density depending on temp. Unless they have done some serious extrapolative mapping for all engine and air temps which is derived from the MAF temp sensing. Can't see how the MAF can fine control the engine on turbo. Main benifit of common rail is the injection pressure, which is much higher than conventional injection can deliver. Better atomisation is the key with that system. All diesels long ago used diirect injection (directly into cylinder), the swirl port or pre combustion chamber alla the M51 was introduced to reduce diesel knock.
Last edited:
Datatek
Well-Known Member
- Posts
- 45,023
- Location
- Near Poitiers SW France
The IAT gave temperature but not air volume which was measured on a test engine for the maps (Ricardo Engineering), fuel temperature is monitored in the FIP.
Direct injection didn't work on high revving engines, Ford had the first practical DI road engine in the Transit, no power, lots of smoke but very economical. Most marine leisure diesels (Volvo et al) used to be DI low revving units, sadly mostly replaced by indirect injection and these days electronic common rail. The good old DI would start on the handle with no battery in an emergency, great in a sailing boat when the battery has gone flat and you are in the path of a bloody super tanker in the channel.
jamesblake
Active Member
- Posts
- 419
- Location
- South East London - Croydon
The more I read this the more I realise that they should break more often!!!
softop2011
New Member
- Posts
- 22
hope this maf unit works when in get it - or where will this go ... from here for sale nearly good p38 nice to look at but has issues goes like a train if you unplug a few things....
