330D running lamda 1.4 at constant speed?
Discussion
This cannot be right, surely?
This is a folliw-up to my "coolant temperature" post.
After an initial improvement to fuel consumption it is right back down, close to what it was (low 30s) and checking the running figures, I can see now a lamda of 1.4 nearly all the time, certainly 100% of the time at idle or constant speeds.
Using plenty of throttle the figure drops closer to 1, but I would expect the opposite, surely?
The dealer SA will groan when I call him again, so I want to be certain of my facts...!
This is a folliw-up to my "coolant temperature" post.
After an initial improvement to fuel consumption it is right back down, close to what it was (low 30s) and checking the running figures, I can see now a lamda of 1.4 nearly all the time, certainly 100% of the time at idle or constant speeds.
Using plenty of throttle the figure drops closer to 1, but I would expect the opposite, surely?
The dealer SA will groan when I call him again, so I want to be certain of my facts...!
What are you expecting MPG wise?
We've had an E91 330d (08 plate) for over 8 years so a long term owner. On local commute journeys, sub 40mph for say 6 miles each way it does a constant 26 to 28mpg - measured by brimming, driving 200 miles, then re-brimming. Feels about right for a 3.0 diesel with an auto box'.
Show it longer journeys it changes.
Originally I used to commute from Halesowen West Midlands to Trafford Park in Manchester every week, 195 mile round journey - I could just get 3 return journeys from each full tank. I can't recall exactly but that was over 44mpg.
We've done regular trips from the Midlands to South West France in it, fully loaded with a roof box on, always did at least 40mpg on those trips.
Extra notes:
1) I've read a lot of what I would call fanciful mpg figures for these on just local urban use. As above, late 20's on urban feels right given the age of the engine tech involved.
2) The MPG since reset reading should be taken with a pinch of salt, they can be way out. I've had ours showing 32mpg then when I do a measurement by brimming, driving 200 miles, then re-brimming it'll work out that the manual calculation is lower.
3) Just checked the dash binnacle OBC, it's done 33.2MPG over the last 3k miles. I'd say that's been 75% local urban with the rest longer motorway.
As a side comment, in some ways its the wrong car for my wifes commute, but given that it owes us nothing and has been really reliable we've hung on to it.
We've had an E91 330d (08 plate) for over 8 years so a long term owner. On local commute journeys, sub 40mph for say 6 miles each way it does a constant 26 to 28mpg - measured by brimming, driving 200 miles, then re-brimming. Feels about right for a 3.0 diesel with an auto box'.
Show it longer journeys it changes.
Originally I used to commute from Halesowen West Midlands to Trafford Park in Manchester every week, 195 mile round journey - I could just get 3 return journeys from each full tank. I can't recall exactly but that was over 44mpg.
We've done regular trips from the Midlands to South West France in it, fully loaded with a roof box on, always did at least 40mpg on those trips.
Extra notes:
1) I've read a lot of what I would call fanciful mpg figures for these on just local urban use. As above, late 20's on urban feels right given the age of the engine tech involved.
2) The MPG since reset reading should be taken with a pinch of salt, they can be way out. I've had ours showing 32mpg then when I do a measurement by brimming, driving 200 miles, then re-brimming it'll work out that the manual calculation is lower.
3) Just checked the dash binnacle OBC, it's done 33.2MPG over the last 3k miles. I'd say that's been 75% local urban with the rest longer motorway.
As a side comment, in some ways its the wrong car for my wifes commute, but given that it owes us nothing and has been really reliable we've hung on to it.
Firstly - thanks for the comprehensive response.
I absolutely take your point on the "lies, damned lies and OBC fuel consumption figures" thing.
However....I have had this car for nearly 13 years (bought it with 6k miles recorded) and for 7 years, when using for business trips I kept comprehensive mpg stats for every single journey, always using the OBC numbers.
Throughout that period I would be seeing 43-44mpg averages, including the low speed, urban miles. Split was around 220 miles m/way and dual carriageway, and perhaps 35 miles urban, per week.
Usage has changed over the last 4 or 5 years, and is now typically 50 miles m/way and 15 miles urban (weekly). The speeds on m/ways have dropped, thanks to the proliferation of average speed cameras, so this is another factor to consider.
Since the usage change, the mpg dropped to 37-38 mpg, until quite recently, when the number has dropped to 32-33.
That recent mpg drop, and the evidence that engine was running much cooler than it should have been, prompted my visit to the dealers, when glow-plugs and GP control unit, plus main thermostat were changed.
Temperatures now seem more reasonable, but I am very surprised by the lamda readings which should surely be around 1.0 when running at constant speeds, or idling?
Monitored the numbers a lot today, and lamda is consistently at 1.40, almost all of the time....except...when the catalyst heats up from its typical 280 to 350C, going up to around 580-590, which I assume is the regen process.
Only at that time does the lamda vary significantly, getting much much more throttle sensitive and closer to 1.0.
It seems odd, that apart from these times, it is so consistently at 1.4.
I wonder whether the sensor is faulty, as a 1.4 figure would indicate very lean running, would it not? And maybe at these times the ECU will attempt to supply more fuel, to return the AFR to 14.0 i.e lamda = 1.
And potentially this could answer the question - why is it getting more thirsty now?
Or is my logic entirely wrong?
I am going to use a different OBD reader and app, to see if I can recover any error codes (the BMW Drive Analyser just monitors running numbers without trapping error codes)
I absolutely take your point on the "lies, damned lies and OBC fuel consumption figures" thing.
However....I have had this car for nearly 13 years (bought it with 6k miles recorded) and for 7 years, when using for business trips I kept comprehensive mpg stats for every single journey, always using the OBC numbers.
Throughout that period I would be seeing 43-44mpg averages, including the low speed, urban miles. Split was around 220 miles m/way and dual carriageway, and perhaps 35 miles urban, per week.
Usage has changed over the last 4 or 5 years, and is now typically 50 miles m/way and 15 miles urban (weekly). The speeds on m/ways have dropped, thanks to the proliferation of average speed cameras, so this is another factor to consider.
Since the usage change, the mpg dropped to 37-38 mpg, until quite recently, when the number has dropped to 32-33.
That recent mpg drop, and the evidence that engine was running much cooler than it should have been, prompted my visit to the dealers, when glow-plugs and GP control unit, plus main thermostat were changed.
Temperatures now seem more reasonable, but I am very surprised by the lamda readings which should surely be around 1.0 when running at constant speeds, or idling?
Monitored the numbers a lot today, and lamda is consistently at 1.40, almost all of the time....except...when the catalyst heats up from its typical 280 to 350C, going up to around 580-590, which I assume is the regen process.
Only at that time does the lamda vary significantly, getting much much more throttle sensitive and closer to 1.0.
It seems odd, that apart from these times, it is so consistently at 1.4.
I wonder whether the sensor is faulty, as a 1.4 figure would indicate very lean running, would it not? And maybe at these times the ECU will attempt to supply more fuel, to return the AFR to 14.0 i.e lamda = 1.
And potentially this could answer the question - why is it getting more thirsty now?
Or is my logic entirely wrong?
I am going to use a different OBD reader and app, to see if I can recover any error codes (the BMW Drive Analyser just monitors running numbers without trapping error codes)
I have no way of measuring the lambda on mine to compare, someone else may be able to as there are quite a few owners on here of this model and engine combo.
Mine dropped to low 20's with worn out stats, both changed and it went back up to high 20's on just local short runs.
Will be interesting to see what else you find on this one.
Mine dropped to low 20's with worn out stats, both changed and it went back up to high 20's on just local short runs.
Will be interesting to see what else you find on this one.
sortedcossie said:
I have no way of measuring the lambda on mine to compare, someone else may be able to as there are quite a few owners on here of this model and engine combo.
Mine dropped to low 20's with worn out stats, both changed and it went back up to high 20's on just local short runs.
Will be interesting to see what else you find on this one.
Oops...just noticed that I had fallen into US-speak by referring to "lamda" rather than "Lambda"!Mine dropped to low 20's with worn out stats, both changed and it went back up to high 20's on just local short runs.
Will be interesting to see what else you find on this one.
Sorry - Is this a diesel?
...Because diesels /don't/ aim at Lambda = 1, at all; only petrol engines do - for emission purposes.
And at L=1.4 a petrol engine would be very 'lean' struggling, reluctant to pull, into detonation under load/sudden demand. But -t'sfine for diesel, where teh air path is wide open, and power == fuel added == direct measure of average power requested.
Sorry - I don't know enough about diesel engine management to 'help'/confuse, further.
...Because diesels /don't/ aim at Lambda = 1, at all; only petrol engines do - for emission purposes.
And at L=1.4 a petrol engine would be very 'lean' struggling, reluctant to pull, into detonation under load/sudden demand. But -t'sfine for diesel, where teh air path is wide open, and power == fuel added == direct measure of average power requested.
Sorry - I don't know enough about diesel engine management to 'help'/confuse, further.
ridds said:
Diesels don't tend to run Stoichiometric.
18:1 and all the way up to 25:1 is common.
20:1 would put you around 1.36.
OK - all my automotive learning/spannering has been with petrol engines so clearly I have some catching up to do with diesel concepts.18:1 and all the way up to 25:1 is common.
20:1 would put you around 1.36.
Taking your point above, I should expect to see far more variance in the Lambda numbers, as displayed by the app (which is a BMW app, and has a database of vehicles from which I have to select this specific generation of 330D).
So....I am still very surprised to see the displayed L so often static at 1.4. It only starts to vary significantly with accelerator position (must avoid talking about throttle openings) when the cat temperature is up in the high 500s. Then it fluctuates immediately with accelerator movement, whether opening or closing.
As soon as the cat cools down to more normal temps (250 to 350, which is most of the time) it hardly matters where the accelerator is.
So, I am still convinced that something is not correct (given the noticeable increase in thirst, over the last few months).
The car absolutely flies when asked, so I think it is still fundamentally healthy.
I shall be going back to the dealer, as whatever is causing the cool running has not been cured.
Therefore I am guess that the EGR thermostat - which was not changed - should have been changed as well.
25 to 30 minutes of running to get into the low 80s seems a very long time.
Question: Does the EGR thermostat operate in series with the main thermostat, or in parallel?
Given that there should be a much more variable AFR with diesels (apparently), I am surprised that it appears to be stuck either on 0.6 (immediately after starting) or 1.4 almost all of the rest of the time, apart from when the cat is doing its DPF regen thing (evidenced by cat temperature increasing to just under 600C).
Question: What sort of AFR would you expect to see at a constant 70mph cruise? The engine is probably running at less than 2k revs (from memory) at this speed on barely any accelerator opening.
Car has 64k miles, fully up to date service history, no smoke, and goes like a jabbed rat when asked.
But is now unacceptably thirsty.
Therefore I am guess that the EGR thermostat - which was not changed - should have been changed as well.
25 to 30 minutes of running to get into the low 80s seems a very long time.
Question: Does the EGR thermostat operate in series with the main thermostat, or in parallel?
Given that there should be a much more variable AFR with diesels (apparently), I am surprised that it appears to be stuck either on 0.6 (immediately after starting) or 1.4 almost all of the rest of the time, apart from when the cat is doing its DPF regen thing (evidenced by cat temperature increasing to just under 600C).
Question: What sort of AFR would you expect to see at a constant 70mph cruise? The engine is probably running at less than 2k revs (from memory) at this speed on barely any accelerator opening.
Car has 64k miles, fully up to date service history, no smoke, and goes like a jabbed rat when asked.
But is now unacceptably thirsty.
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