What's your MPG?
Tank track example was my thought on this too. Imagine the track has 100 links in it. Doesn't matter of the track is sausage shaped, as it is fitted to the tank or a perfect circle. 100 links is 100 links. Every one of them will contact the ground at some point no matter what the shape is. Where one complete circuit of the track is carried out. The total distance covered will be the same.
What will change though is the torque required to rotate the wheel/tyre. Reducing the pressure will reduce the radius between the centre of the wheel and the contact patch of the tyre. Less radius equals less force needed to get the thing moving. Albeit this may be a bit offset by the energy lost when the tyre deforms more. Assuming the tyre isn't completely flat of course causing excess drag.
What will change though is the torque required to rotate the wheel/tyre. Reducing the pressure will reduce the radius between the centre of the wheel and the contact patch of the tyre. Less radius equals less force needed to get the thing moving. Albeit this may be a bit offset by the energy lost when the tyre deforms more. Assuming the tyre isn't completely flat of course causing excess drag.
EDIT: 150 bhp (CXFA) tdi carrvelle, AU7, bmt MY17 Executive (weighs about 2.2..) running on 17' montreals(?)
My experience is i get around 32mpg when the van is or has been doing an ACTIVE regen and i get 37-41 the rest of the time.
Diesels shouldnt be driven like a grandma all the time. They do need to be driven hard, at least, occaisionally - even more so with dpf (high exhaust temp regens are the most efficient)
I did viturally the same routes with my 1.6 diesel eu6 psa engine in a car that i owned and i got a similar drop of around 6-10mpg when the vehicle did regens.
in that i was getting normally an average of 620miles per 60l (trip said 53mpg.. which is close enough for my liking)
Ill use my trip back form place of work today as an example - normally i get 40-42.5mpg - today was 32.6. Difference between normal and the past 4 days? I pottered my van about over ten miles, stopping starting, but with 10-20mins at least between turn off and i dont think the vehicle ever got hot. and in a couple trips i made before going to place of work and watched the economy go gradually down and down....
Note: Dpfs can Actively regenerate (diesel being spitted in between combustion cycles to increase temperatures in the exhaust) or passively (the sort where bombing along the motorway at 70 for half an hour will do)
My overall average speed is about 27mph. but that because of where i live and the routes i do. I would suspect those with lower mpgs have a lower average speed as well to boot.
While of course driving at 70 is great for burning the soot in that piece of rubbish that is now on every new car, 34/35mpg. which for 70 in a brick i think is damn impressive (did i mention that this is a cheaper way to regenerate)
This whole dpf and poor mpg thing i remember reading about from some of the more older type dpfs (pre 2012..) where they got clogged and reduced performance and thus mpg and the range goes hand in hand with the experience you are suffering with. except with these things would get a whole lot worse (and more expensive..) that just poor fuel economy.
I guess my point is, if all other avenues have been exhausted (oh, damn, the pun machine is turned on...), maybe its time to look at whether your vehicle is stuck in active regen mode or your driving style/habits/routes... annoyance of routes.. and tractors.. cats.. peacocks... are causing it to constantly actively regenerate.
Knowledge of tyres is not great but from general gesticualtion on the topic with racing boffs is that it normally only affects a cars performance of between 0 and 5-7% 7% being the sort of thing that would happen is you put drag racing tyres on a poncy toyoda aygo...
If there was one thing i could take from my ownership of that little psa diesel car, is that the instruction booklet was extremely well written about fuel economy and dpf regeneration, and the same can be applied to any car with a dpf.
EDIT: I also remember that a vehicle that is stuck in active regen MAY NOT throw a fualt code...
My experience is i get around 32mpg when the van is or has been doing an ACTIVE regen and i get 37-41 the rest of the time.
Diesels shouldnt be driven like a grandma all the time. They do need to be driven hard, at least, occaisionally - even more so with dpf (high exhaust temp regens are the most efficient)
I did viturally the same routes with my 1.6 diesel eu6 psa engine in a car that i owned and i got a similar drop of around 6-10mpg when the vehicle did regens.
in that i was getting normally an average of 620miles per 60l (trip said 53mpg.. which is close enough for my liking)
Ill use my trip back form place of work today as an example - normally i get 40-42.5mpg - today was 32.6. Difference between normal and the past 4 days? I pottered my van about over ten miles, stopping starting, but with 10-20mins at least between turn off and i dont think the vehicle ever got hot. and in a couple trips i made before going to place of work and watched the economy go gradually down and down....
Note: Dpfs can Actively regenerate (diesel being spitted in between combustion cycles to increase temperatures in the exhaust) or passively (the sort where bombing along the motorway at 70 for half an hour will do)
My overall average speed is about 27mph. but that because of where i live and the routes i do. I would suspect those with lower mpgs have a lower average speed as well to boot.
While of course driving at 70 is great for burning the soot in that piece of rubbish that is now on every new car, 34/35mpg. which for 70 in a brick i think is damn impressive (did i mention that this is a cheaper way to regenerate)
This whole dpf and poor mpg thing i remember reading about from some of the more older type dpfs (pre 2012..) where they got clogged and reduced performance and thus mpg and the range goes hand in hand with the experience you are suffering with. except with these things would get a whole lot worse (and more expensive..) that just poor fuel economy.
I guess my point is, if all other avenues have been exhausted (oh, damn, the pun machine is turned on...), maybe its time to look at whether your vehicle is stuck in active regen mode or your driving style/habits/routes... annoyance of routes.. and tractors.. cats.. peacocks... are causing it to constantly actively regenerate.
Knowledge of tyres is not great but from general gesticualtion on the topic with racing boffs is that it normally only affects a cars performance of between 0 and 5-7% 7% being the sort of thing that would happen is you put drag racing tyres on a poncy toyoda aygo...
If there was one thing i could take from my ownership of that little psa diesel car, is that the instruction booklet was extremely well written about fuel economy and dpf regeneration, and the same can be applied to any car with a dpf.
EDIT: I also remember that a vehicle that is stuck in active regen MAY NOT throw a fualt code...
I know I said I wouldn’t contribute to this thread any more but here goes.
TPMS works by comparing pulses from the wheel speed sensors on each wheel - it doesn’t read the speed of each sensor, if it did it would go off if you went around a long corner or a series of same direction bends - it works by comparing the signals from each wheel looking for discrepancies between the wheels - imagine if you were sat on a half inflated football, it would feel squidgy and unstable - this effect modifies the signal from the soft tyre.
TPMS will pick up a couple of PSI, if you think this is because of a minuscule reduction in the rolling radius you‘re really not thinking it through. Try dropping 2 or 3 psi out of a tyre and see if you can measure the difference in rolling radius and then think about how much impact this would have on the circumference of 2m plus, the difference is minuscule - also think about when you set it - how would it know the rolling radius when it isn’t moving...
if you think you can accurately measure rolling circumference with a piece of chalk over 1 rotation - crack on but dont be surprised if you don't understand - IMO if the basics aren’t right you haven’t got a chance of understanding the problem. Also if you think you can measure it without the weight of the vehicle on it then you haven’t considered how a tyre takes the weight of a vehicle or how it maximises it’s contact patch.
With air suspension the van is much more softly sprung (isn’t that the reason people fit it) as such it will deflect in a completely different way (think less violently) - this will have an effect on the signal from the wheel speed sensors, if TPMS coming on is common on air suspended vans, I would bet the farm on the behaviour of the suspension being the reason.
A differential isn’t only about differences in driven tyres, its also about going around corners where the track taken by the outside wheel is longer than that of the inside...
Axle and wheel alignment can also have a big effect on fuel consumption and don‘t assume that your tyres are wearing ok so it must be ok. Think about a rear axle that isn’t quite at 90’ to the centreline of the van so the front wheels compensate to go in a straight line - this can have a huge effect and you wont even notice it - its very common on trucks and if you cant see it on a 13m trailer you wont see it on a T6.
We haven’t mentioned Ackerman angles yet
TPMS works by comparing pulses from the wheel speed sensors on each wheel - it doesn’t read the speed of each sensor, if it did it would go off if you went around a long corner or a series of same direction bends - it works by comparing the signals from each wheel looking for discrepancies between the wheels - imagine if you were sat on a half inflated football, it would feel squidgy and unstable - this effect modifies the signal from the soft tyre.
TPMS will pick up a couple of PSI, if you think this is because of a minuscule reduction in the rolling radius you‘re really not thinking it through. Try dropping 2 or 3 psi out of a tyre and see if you can measure the difference in rolling radius and then think about how much impact this would have on the circumference of 2m plus, the difference is minuscule - also think about when you set it - how would it know the rolling radius when it isn’t moving...
if you think you can accurately measure rolling circumference with a piece of chalk over 1 rotation - crack on but dont be surprised if you don't understand - IMO if the basics aren’t right you haven’t got a chance of understanding the problem. Also if you think you can measure it without the weight of the vehicle on it then you haven’t considered how a tyre takes the weight of a vehicle or how it maximises it’s contact patch.
With air suspension the van is much more softly sprung (isn’t that the reason people fit it) as such it will deflect in a completely different way (think less violently) - this will have an effect on the signal from the wheel speed sensors, if TPMS coming on is common on air suspended vans, I would bet the farm on the behaviour of the suspension being the reason.
A differential isn’t only about differences in driven tyres, its also about going around corners where the track taken by the outside wheel is longer than that of the inside...
Axle and wheel alignment can also have a big effect on fuel consumption and don‘t assume that your tyres are wearing ok so it must be ok. Think about a rear axle that isn’t quite at 90’ to the centreline of the van so the front wheels compensate to go in a straight line - this can have a huge effect and you wont even notice it - its very common on trucks and if you cant see it on a 13m trailer you wont see it on a T6.
We haven’t mentioned Ackerman angles yet
I know I said I wouldn’t contribute to this thread any more but here goes.
TPMS works by comparing pulses from the wheel speed sensors on each wheel - it doesn’t read the speed of each sensor, if it did it would go off if you went around a long corner or a series of same direction bends - it works by comparing the signals from each wheel looking for discrepancies between the wheels - imagine if you were sat on a half inflated football, it would feel squidgy and unstable - this effect modifies the signal from the soft tyre.
TPMS will pick up a couple of PSI, if you think this is because of a minuscule reduction in the rolling radius you‘re really not thinking it through. Try dropping 2 or 3 psi out of a tyre and see if you can measure the difference in rolling radius and then think about how much impact this would have on the circumference of 2m plus, the difference is minuscule - also think about when you set it - how would it know the rolling radius when it isn’t moving...
if you think you can accurately measure rolling circumference with a piece of chalk over 1 rotation - crack on but dont be surprised if you don't understand - IMO if the basics aren’t right you haven’t got a chance of understanding the problem. Also if you think you can measure it without the weight of the vehicle on it then you haven’t considered how a tyre takes the weight of a vehicle or how it maximises it’s contact patch.
With air suspension the van is much more softly sprung (isn’t that the reason people fit it) as such it will deflect in a completely different way (think less violently) - this will have an effect on the signal from the wheel speed sensors, if TPMS coming on is common on air suspended vans, I would bet the farm on the behaviour of the suspension being the reason.
A differential isn’t only about differences in driven tyres, its also about going around corners where the track taken by the outside wheel is longer than that of the inside...
Axle and wheel alignment can also have a big effect on fuel consumption and don‘t assume that your tyres are wearing ok so it must be ok. Think about a rear axle that isn’t quite at 90’ to the centreline of the van so the front wheels compensate to go in a straight line - this can have a huge effect and you wont even notice it - its very common on trucks and if you cant see it on a 13m trailer you wont see it on a T6.
We haven’t mentioned Ackerman angles yet
So will a vehicle move forward the same amount per single wheel revolution with flat tyres as it would with fully inflated tyres?.
Your earlier post suggests it would, or the difference would be negligible.
Daffy, I've got the definite impression that you know this subject very well, I am not arguing that you are wrong.
The reason why people like me think that the TPMS detects low tyre pressure because of a difference in the rolling radius and therefore the speed of rotation, is partly because of websites like this one:
"Indirect systems use the vehicle's anti-lock braking system's wheel speed sensors to compare the rotational speed of one tire versus the others. If a tire is low on pressure, it will roll at a different number of revolutions per mile than the other three and alert the vehicle's on-board computer."
The reason why people like me think that the TPMS detects low tyre pressure because of a difference in the rolling radius and therefore the speed of rotation, is partly because of websites like this one:
"Indirect systems use the vehicle's anti-lock braking system's wheel speed sensors to compare the rotational speed of one tire versus the others. If a tire is low on pressure, it will roll at a different number of revolutions per mile than the other three and alert the vehicle's on-board computer."
Somehting in the back of my brain tells me there are or were two types of TPMS once upon a time...
I had no idea that the ABS sensor on these vans measured vibration aswell as wheel speed.
You wouldn't have thought that the wheel bearing, abs ring and sensor would be able to vibrate against each other given how tight their fitting tolerances are.
Very clever.
I think it’s more about how a manufacturer markets these products, if they want people to buy them they need to convince the public that they are going to do a job and in these cases sometimes less is more - if you think about it the squidgy football will be unstable and it will have a variable radius and as such it’s not wrong to say the system detects changes in the rolling radius - although you might not find that the number of wheel rotations over a given distance will be different.
My guess is they have a much softened version of the system functional description to make it easier to digest by non technical people, although I might be doing them an injustice but I’m not sure the people at tire rack would be able to explain it If they tried.
Did you have a chance to try if more robust setting (in ABS adaptations) would help?
AndyVanT6
Member
I use Fuel Log App which tells me all possible statistics of my fuel usage. This is a screenshot of the latest fill ups. I do use the (2016 T6 102) mileage but wonder if mileage taken from sat nav or Google Maps would be more accurate as Google Maps tells me I'm doing 70mph when the van says I'm doing 63mph, ie 10% discrepancy. Not convinced that the van's speed and mileage are related. I believe this has been covered on other posts. 
Hi, I had a remap done last year to my 140 DSG, and though I haven't seen a noticeable improvement in mpg, it certainly hasn't got any worse.
