Dropped the car off at the dealers this morning, got to speak to the "Master Technician" himself so I could explain the problems, asked him to remove the DPF and throw it away!!.

He is suggesting the car should have a new ECU fitted to resolve the issues. I don't care what they change just as long as they rectify the problems.

It does seem as though your fuel consumption is much lower than could be expected, I agree. The technician may have a point about changing the ecu. It may do the trick. I don't know for sure as I have never had any tech experience with SEAT, but it's my guess you may be running completely different software in the ecu anyway compared to Skoda units. This is sometimes the case to allow for differing weights and aerodynamics, different gearing etc of different models and makes of car with the same engine units. So making comparisons between your car and a Skoda my not be very relevant. But I can certainly see something somewhere is probably not right with your mpg. Again do please keep posting on this as the more information going online about it the better for everyone.

You're not a part time pimp are you?

Slappers are the cheapest to run......

Hi Xman,

How ya doin?

Yeah...I'd heard Ford Slappers were cheaper to run tee hee...

Hello,

Hopefully you're right. I must admit, the journey home last night and the two today have shown (according to the computer) unusually high mpg, especially given the low temps and other conditions. Compared to similar journeys before, the mpg seems a lot better. Maybe it's on the way up!! You never know. The last couple of tanks during the really cold weather have shown 50mpg rather than the 52mpg achieved just before. Whilst lower, it might be this is less low than might be expected. I guess only time will tell :-)

Thanks,

Mike

To be honest your not far off a decent mpg. Add on about 8 mpg for summer diesel and warmer temps along with a bit more 'loosening up' your going to be near 60 mpg.

I get a little over 60 mpg in this cold weather driving normally without trying to be frugal. Just under 70 mpg in warmer weather is the norm. Mine will probably just about beat a standard CR for mpg as its been designed for frugality in mind, not just the engine but the whole package. If you look at the numbers I only really get 8 mpg more than you at the moment

If I had a CR 1.6 then 60 mpg would be acceptable to me unless it was a Greenline version. I would expect then to get the same as I do now at least..

If you had never actually read the ridiculous mpg EU generated 'test condition' figures, would 60 mpg be so bad ? The main issue is unrealistic test figures. I dont think new diesels will ever be more efficient than diesels of old. We just arent allowed to pump out any noxious gas we like anymore. Nox reduction in euro IV and V vehicles actually harms mpg........all that lovely oxygen rich air is turned in to not so oxygen rich air to reduce Nox via the EGR system.........its not going to do anything for improving the efficiency of the burn having less oxygen.

Pootling around at low rpm just like everyone used to in older diesels without a turbo just doesnt work for these engines. I did a little experiment. Pootling along using low rpm knocked a fair bit of my mpg. I then tried a run without ever using 5th on my 116 mile commute......the mpg was 2 mpg better than when I used 5th. Thats on 60 mpg A roads. Fifth gear is pointless for me unless I am doing over 60...its a bit like the old fashioned 'overdrive' button.

I can talk rubbish for hours so I best stop there :yes:

Raisbeck, I think I can beat you on rubbish anyday!

Glad to see Estate Man's post of yesterday - as agrees with my own experience. For running in I've taken the view that I shouldn't labour the engine, so always keep above 1500 rpm - changing gears more often like I was told to. This means ignoring the gear change indicator, but as far as I can tell if you are below 1500 rpm the mpg is significantly worse. To start with fuel consumption has been low 50s, but below zero and new engine...yesterday was warmer, about 5C, and went on cross country trip of about 50 miles - computer showed 62mpg on the way out and 65mpg for the return trip. Normal driving, 10 mins jam on way out, 50-60mph mostly, overtaking when I felt like it, and not much time in 5th gear.

Also, haven't had the regen light - occasional episode of funny vibrations which may be the regen occurring in normal driving. Once had what may be the "engine surge" as drawing up to junction but this was because I was absent mindedly in what I call "too high a gear"! My old diesel used to cut in pretty firmly if you slowed down below idle revs.

So on the basis of no expertise and little experience I suggest anyone who's been trying to get max mpg through min revs has a go at a tankful staying religiously above 1500 rpm whatever the shift indicator says.

Alan

Threadbear

I take it your Dad's Bluemotion is the 1.6TDi? What sort of economy has he been getting?

No My Dad has a Golf Plus 1.9TDi PD Bluemotion

No My Dad has a Golf Plus 1.9TDi PD Bluemotion

He normally gets mid 60mpg but has been down to mid 50`s recently!!

Dropped the car off at the dealers this morning, got to speak to the "Master Technician" himself so I could explain the problems, asked him to remove the DPF and throw it away!!.

He is suggesting the car should have a new ECU fitted to resolve the issues. I don't care what they change just as long as they rectify the problems.

Interesting. Problem is, this ECU will have to learn everything again, which will set you back at least 2500 miles if not more. They really should be telling you why the ECU needs replacing. When they haven't got a clue, they just start changing bits and bobs at random. My dealership keeps insisting that the computer can identify any problems and if it can't see any problems, there aren't any. In other words, unless the computer tells them what the fault is, they haven't got a clue. No matter how good the computer, there is no way it can possibly identify every problem......

It does seem as though your fuel consumption is much lower than could be expected, I agree. The technician may have a point about changing the ecu. It may do the trick. I don't know for sure as I have never had any tech experience with SEAT, but it's my guess you may be running completely different software in the ecu anyway compared to Skoda units. This is sometimes the case to allow for differing weights and aerodynamics, different gearing etc of different models and makes of car with the same engine units. So making comparisons between your car and a Skoda my not be very relevant. But I can certainly see something somewhere is probably not right with your mpg. Again do please keep posting on this as the more information going online about it the better for everyone.

Hello again,

Not sure what the situation is with SEATs, but I was told by the dealership that the software update they put in my car had just been sent over from VW and had been in their cars for a couple of weeks. So, certainly my Fabia and at least one type of VW car share the same software.

To be honest your not far off a decent mpg. Add on about 8 mpg for summer diesel and warmer temps along with a bit more 'loosening up' your going to be near 60 mpg.

I get a little over 60 mpg in this cold weather driving normally without trying to be frugal. Just under 70 mpg in warmer weather is the norm. Mine will probably just about beat a standard CR for mpg as its been designed for frugality in mind, not just the engine but the whole package. If you look at the numbers I only really get 8 mpg more than you at the moment

If I had a CR 1.6 then 60 mpg would be acceptable to me unless it was a Greenline version. I would expect then to get the same as I do now at least..

If you had never actually read the ridiculous mpg EU generated 'test condition' figures, would 60 mpg be so bad ? The main issue is unrealistic test figures. I dont think new diesels will ever be more efficient than diesels of old. We just arent allowed to pump out any noxious gas we like anymore. Nox reduction in euro IV and V vehicles actually harms mpg........all that lovely oxygen rich air is turned in to not so oxygen rich air to reduce Nox via the EGR system.........its not going to do anything for improving the efficiency of the burn having less oxygen.

Pootling around at low rpm just like everyone used to in older diesels without a turbo just doesnt work for these engines. I did a little experiment. Pootling along using low rpm knocked a fair bit of my mpg. I then tried a run without ever using 5th on my 116 mile commute......the mpg was 2 mpg better than when I used 5th. Thats on 60 mpg A roads. Fifth gear is pointless for me unless I am doing over 60...its a bit like the old fashioned 'overdrive' button.

I can talk rubbish for hours so I best stop there :yes:

Hello raisbeck,

60mpg would be acceptable to me, but I'm far from that yet. Interestingly, the EGR system is claimed not to reduce mpg. In theory, provided you have enough oxygen (and preferably a bit more) to combust the diesel, having over that doesn't make any difference. As it's compression fired and the fuel and oxygen should be evenly dispersed througout the cylinder, excess oxygen levels will do nothing. Even with the EGR working, having too little oxygen would cause more partial combustants to be created and therefore that would damage emissions. I concur with you about not pootling around. The engine seems to prefer being at 1500 rpm at minimum and even a bit more.

Hello again,

Not sure what the situation is with SEATs, but I was told by the dealership that the software update they put in my car had just been sent over from VW and had been in their cars for a couple of weeks. So, certainly my Fabia and at least one type of VW car share the same software.

Not necessarily Mike. VW and/or it's agent writes all the software for the group and holds the licensing rights. So it's perfectly possible they have put you in an upgrade especially written for the Fabia, or just an upgrade from a Golf or Polo to see what happens. You are right about the egr's not in real life affecting mpg, they have been about for decades on diesels. They only degrade mpg's if they stick open as can sometimes happen when they get a bit old, tired or clogged up.

Edited 18 December, 201015 yr by Estate Man

As I have such a problem with poor economy why can't they upgrade the engine software from the 1.6 Bluemotion or 1.6 Ecomotive?

Not necessarily Mike. VW and/or it's agent writes all the software for the group and holds the licensing rights. So it's perfectly possible they have put you in an upgrade especially written for the Fabia, or just an upgrade from a Golf or Polo to see what happens. You are right about the egr's not in real life affecting mpg, they have been about for decades on diesels. They only degrade mpg's if they stick open as can sometimes happen when they get a bit old, tired or clogged up.

I was told it was official Skoda software and was a recommended update. Having said that, who knows...............

It is, however, interesting that most people report they should be driven in a way contrary to the computers own suggestions!! Makes you wonder if the engineers writing the code actually know how to get the best out of the car?

Hi again Mike, yes...you are right, official Skoda software that comes for VW, but written for Skoda's. Yes, the lights are pretty much useless. On my last Ford they advised me to select 5th gear at 36mph, totally ludicrous. The engine was turning over at 900rpm and vibrating itself to death. Consumption would plunge to upper 30's. But select it at 60mph and the consumption went up to 60mpg.

Hi again Mike, yes...you are right, official Skoda software that comes for VW, but written for Skoda's. Yes, the lights are pretty much useless. On my last Ford they advised me to select 5th gear at 36mph, totally ludicrous. The engine was turning over at 900rpm and vibrating itself to death. Consumption would plunge to upper 30's. But select it at 60mph and the consumption went up to 60mpg.

Doesn't this rather worry you? If they can't even get the gear indicators right, what hope for the rest? On my Fabia, it suggests 5th at about 40mph unless you have a reasonable bit of throttle on and am accelerating quite hard. So, obviously the software is taking account of the throttle position etc. as well as the speed. So, some logic and thought must have gone into it. In this case, why is it so wrong? To me, it rather suggests the people writing it don't have a clue, otherwise they should be able to get the indicator right. How difficult can it be? However, bearing in mind the lack of accuracy in the trip computer, presumably it can't be connected to the ECU, as otherwise, how can it be so wrong. The ECU is aware of the exact amount of fuel used (it controls it per squirt!!), and the mileage should be accurate (unless you're spinning wheels!!), so why can't it be perfectly accurate? Presumably, it can't be connected to the ECU and can't get to the exact information? Rather bizarre to me. I would have thought all the computers would be interconnected.

Doesn't this rather worry you? If they can't even get the gear indicators right, what hope for the rest? On my Fabia, it suggests 5th at about 40mph unless you have a reasonable bit of throttle on and am accelerating quite hard. So, obviously the software is taking account of the throttle position etc. as well as the speed. So, some logic and thought must have gone into it. In this case, why is it so wrong? To me, it rather suggests the people writing it don't have a clue, otherwise they should be able to get the indicator right. How difficult can it be? However, bearing in mind the lack of accuracy in the trip computer, presumably it can't be connected to the ECU, as otherwise, how can it be so wrong. The ECU is aware of the exact amount of fuel used (it controls it per squirt!!), and the mileage should be accurate (unless you're spinning wheels!!), so why can't it be perfectly accurate? Presumably, it can't be connected to the ECU and can't get to the exact information? Rather bizarre to me. I would have thought all the computers would be interconnected.

I cant imagine anything more annoying or distracting than a gadget telling me how to drive. I think I would ignore it on principle. If they set the gear recommendation system up on the 'rolling road' same as mpg figures then you have your answer

As for calculating fuel flow. I have to calibrate fuel flow transmitters at work. To be accurate they are seriously expensive and take in to account density etc. The one on your car would be an approximation at best. Saying that I dont know exactly how fuel flow is calculated on a Fabia........I just doubt it costs a fortune.

The speedo on my car over reads by 5 mpg (checked it against a car sat nav and an aviation spec satystem). Thats going to mess up your mpg figures for a start.

Oddly enough all the Fabias we had over read by 5 mpg.

Edited 18 December, 201015 yr by raisbeck

The neatest economy aid I saw was several years back on a BMW 3 series. An analogue gauge in the centre of speedo/rev counter pod (like a fuel gauge) which showed instantaneous fuel consumption (in ltrs/100km I think). Its response was such that as you changed the accelerator position, it would smoothly move to indicate better or worse economy. Much better than the crap digital readouts that are not much better than a joke.

But then again that would be too simple and old school for today's generation of so called software engineers.

The neatest economy aid I saw was several years back on a BMW 3 series. An analogue gauge in the centre of speedo/rev counter pod (like a fuel gauge) which showed instantaneous fuel consumption (in ltrs/100km I think). Its response was such that as you changed the accelerator position, it would smoothly move to indicate better or worse economy. Much better than the crap digital readouts that are not much better than a joke.

But then again that would be too simple and old school for today's generation of so called software engineers.

Friend of mine has a brand new company BMW. It has the analogue gauge in the centre.......

I really liked that idea.

I cant imagine anything more annoying or distracting than a gadget telling me how to drive. I think I would ignore it on principle. If they set the gear recommendation system up on the 'rolling road' same as mpg figures then you have your answer

As for calculating fuel flow. I have to calibrate fuel flow transmitters at work. To be accurate they are seriously expensive and take in to account density etc. The one on your car would be an approximation at best. Saying that I dont know exactly how fuel flow is calculated on a Fabia........I just doubt it costs a fortune.

The speedo on my car over reads by 5 mpg (checked it against a car sat nav and an aviation spec satystem). Thats going to mess up your mpg figures for a start.

Oddly enough all the Fabias we had over read by 5 mpg.

I was told a long time ago speedo's in cars are allowed in law to be out by upto 10% and the faster you go the less accurate they become. I was also told Police speedo's used to have to be calibrated to ensure they are accurate.

As for the gear selection you would think they would base the selection based on throttle and revs, which combined surely aloow for terrain, the probem probably being the selection is based on a run and fully lose engine.

It used to be that gear indicator lights worked soley off of the intake manifold pressure. In other words, how much throttle you were giving the engine. It didn't matter what gear you were in, when the engine revs reached a certain point and the manifold pressure and load on the engine was at a predetermined level, the light to change gear would come on. I don't have lights on my car so I can't tell you how this latest lash up works but given the inaccuracy, it is probably just the same as the older system.

I cant imagine anything more annoying or distracting than a gadget telling me how to drive. I think I would ignore it on principle. If they set the gear recommendation system up on the 'rolling road' same as mpg figures then you have your answer

As for calculating fuel flow. I have to calibrate fuel flow transmitters at work. To be accurate they are seriously expensive and take in to account density etc. The one on your car would be an approximation at best. Saying that I dont know exactly how fuel flow is calculated on a Fabia........I just doubt it costs a fortune.

The speedo on my car over reads by 5 mpg (checked it against a car sat nav and an aviation spec satystem). Thats going to mess up your mpg figures for a start.

Oddly enough all the Fabias we had over read by 5 mpg.

Hello,

I don't mean to say I would use one of these gadgets, it's just that the ECU is supposed to know just whats happening and could tell the trip computer. I don't see why fuel flow needs to be calculated if the trip computer talks to the ECU. The ECU should know exactly how many squirts of fuel it is using and how big each squirt is. This should be accurate to an extremely small margin of error. That's exactly how an inkjet printer works. So, that gives the amount of fuel your using, probably to a resolution of picolitres.

As to the speedo. I've been told that manufacturers deliberately set their speedos to overread as this makes their customers feel good. Makes them think they're going faster than they are!! Don't know if it's true, but I can't imagine multiple cars all reading over by the amount by accident. So, mileage covered should be easy and accurate given that it merely needs to count rotations of the wheel. Tyre wear will alter things marginally, but not much.

So, why can't it work it out accurately? My guess is, they don't want to.........

Hello,

I don't mean to say I would use one of these gadgets, it's just that the ECU is supposed to know just whats happening and could tell the trip computer. I don't see why fuel flow needs to be calculated if the trip computer talks to the ECU. The ECU should know exactly how many squirts of fuel it is using and how big each squirt is. This should be accurate to an extremely small margin of error. That's exactly how an inkjet printer works. So, that gives the amount of fuel your using, probably to a resolution of picolitres.

As to the speedo. I've been told that manufacturers deliberately set their speedos to overread as this makes their customers feel good. Makes them think they're going faster than they are!! Don't know if it's true, but I can't imagine multiple cars all reading over by the amount by accident. So, mileage covered should be easy and accurate given that it merely needs to count rotations of the wheel. Tyre wear will alter things marginally, but not much.

So, why can't it work it out accurately? My guess is, they don't want to.........

1. The ECU and the Trip Computer are effectively one and the same thing. All the calcs are done in the same box by the same processor.

2. Due to manufacturing tolerances and other factors, there is is always a spread of injection rates between injectors and these change with time/wear/contamination. Some manufacturers try to minimise the imbalance (e.g. Delphi) by binning the injectors (stamping rates on them) and programming those rates in the ECU.

3. Inkjet printers dont work anything like a car injector - they squirt fixed quantities multiple times at a constant temperature and into constant pressure environment. Engine injectors inject a wide dynamic range of quantities over a wide range of timing and pressures into a varying temperature/pressure hellhole (the piston).

4. Speedos by law must read between +10% and +0%. The manufacturers probably aim for +5% with half worn tyres/medium load. So in general new tyres/lightly loaded will read towards the upper end of the allowed band. Measuring speed from tyre rotation also has to be compensated with effects such as creep/slip and tyre distortion.

Edited 20 December, 201015 yr by xman

1. The ECU and the Trip Computer are effectively one and the same thing. All the calcs are done in the same box by the same processor.

2. Due to manufacturing tolerances and other factors, there is is always a spread of injection rates between injectors and these change with time/wear/contamination. Some manufacturers try to minimise the imbalance (e.g. Delphi) by binning the injectors (stamping rates on them) and programming those rates in the ECU.

3. Inkjet printers dont work anything like a car injector - they squirt fixed quantities multiple times at a constant temperature and into constant pressure environment. Engine injectors inject a wide dynamic range of quantities over a wide range of timing and pressures into a varying temperature/pressure hellhole (the piston).

4. Speedos by law must read between +10% and +0%. The manufacturers probably aim for +5% with half worn tyres/medium load. So in general new tyres/lightly loaded will read towards the upper end of the allowed band. Measuring speed from tyre rotation also has to be compensated with effects such as creep/slip and tyre distortion.

Some suggestions:-

1. If the ECU and the trip computer are the same thing, given the accuracy of the trip computer shows the ECU is totally incapable of running the engine efficiently. If the ECU has enough information to run the engine properly, the trip computer should have the information required to get the fuel consumption right. If the amount of fuel put into the cylinder is changed by the ECU, the fuel rate can be worked out, distance is known, so how is the trip computer so wrong. If it's the same data, the ECU must be running the engine wrong by the same amount!!

2. I understand this. That's why injector cleaners can be a good thing etc. Is that why they claim the ECU 'learns the injectors'? That's what they claim?

3. Errrr. No. Fixed quantities, yes. Although the same as for injectors is still true. Different batches of heads change the volume slightly due to manufacturing tolerances. Constant temperature....no. It does vary. Constant pressure....no. Again, it varies for various reasons, both atmospheric and internal (varies according to the ink left in the cartridge). Inkjets also eject ink over a range of timings into a varying environment, not least the type and quality of the paper!!

4. I think we agree on this one!! They try to adjust to make the car look good to the customers!!

I don't mean to say in any of this that the environment is not more extreme. However, if ECU doesn't know how much fuel it's injecting, it is effectively no better than older methods. So, if it knows how much is being injected and it knows how far you've travelled, it should be very accurate. They're not, they're hopeless. So, why? My guess is that ECUs are nowhere near as effective and good as manufacturers claim and there's a wide margin of error on them which accounts for the discrepencies.

Edited 20 December, 201015 yr by MikeHart

Xman is correct in mostly everything he says in his post. The main variable though Mike, and as xman points out is the tyres of the car. This is why speedo's, odo's, and trip computers measuring mpg's are a bit off sometimes. To say they are inaccurate or hopeless is completely wrong, rather the reverse is true. They are very accurate and this is why they return a sometimes slightly off mpg figure. Eh!...I hear you say. This is because the computer will accurately record every variable but cannot easily compensate for one of the most major fluctuations, the tyres. It doesn't know the tyres change size all the time. Mostly everything else it can cope with, but not the tyres. The circumference of your wheels is constantly changing due, not just to tyre wear, but fluctuating tyre pressures on each journey, the ambient temperature, the speed you drive at etc. Tyre pressure will fluctuate by several psi during some journeys causing significant change to the circumference of the wheel. Additionally, the faster you go the bigger the circumference of the tyres. All this will alter the overall size of your wheels enough to cause an inaccuracy just by a little. Then there's the load you carry. A full tank of fuel or passengers alters the size of your wheels and the temperature they run at. With properly inflated tyres you can notice (and easily measure) a reduction of tyre circumference of between 15-20mm when fully loaded. Measure from the centre of the wheel to the central contact point on the road. You'll see what I mean. You get the picture. And that's even before you take into account the slight errors that all flow meters give you. The longer the journeys the bigger the errors that build into the system. There's loads of other stuff too that combine to thwart the trip computer with total accuracy.

In reality, most of us find our trip computer pretty accurate for miles covered and mpg's. If tyre pressure monitors were more accurate that would be the way forward to improve further but there would be a cost involved.

A tyre on the road does not simply roll as you might expect. Basically its because at the road/tread level there are lots of push pull dynamics in 3d. It varies with speed, road surface, tyre composition/tread/wear, power being transmitted or dissipated (braking), and much much more and can account for +/- 3% in readings. Try this experiment, compare GPS measured speed against your speedo when driving up a steep hill with power applied, then repeat going down the hill on brakes.

The ECU is part of a closed loop control system, it does not need or indeed have accurate rate information from the injectors. A trip computer (which is a bit of extra software in the ECU) is calibrated in the factory on a production line(i.e. quickly). I've read you can trim it further with VAGCOM if you want to try and improve its accuracy as you can the speedo etc.

A bubble jet or inkjet printer head has no resemblance whatsoever to a car diesel fuel injector - the technologies aren't in the slightest similar. Resolution and accuracy are two totally different things and are not related.

The "learning" ECU (self calibration) is over egged. ECUs use adaptive algorithms to ensure transducer readings and control loop parameters stay within range. 90% of the "learning" is done in a few miles. It then does small adjustments when it see drifts in parameters caused by transducer aging etc. Some engine ECU can dynamically calibrate (balance) injectors by looking at the instantaneous changes in rpm (we would call it vibration or shudder) between injections.

It doesn't learn your driving style - that may however be the case for an auto gearbox ecu.

Edited 21 December, 201015 yr by xman