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BMW 520d B47 Engine Fuel Consumption

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7 hours ago, DarkEnergy said:

Sorry guys, but I would like to be convinced with hard numbers that in equal conditions the B47 is less efficient that the N47.

I would like to see the result of at least 10 mile flat motorway run at constant 60 or 65 mph, zeroing the trip computer after at least 10 miles running to start the test with a  warm engine and transmission. The test has to be done in a dry and windless day, removing all load from the car, no A/C and normal tyre pressure.

If in this conditions a mileage of at least 50mpg  at constant 65mph or 55mpg at constant 60mph is not achieved with a B47 with more than 5000 miles in the odometer, then I would agree that there is a case to be worried. 

 

Any volunteer?

 

Remember, to save fuel accelerate normally, avoid high speeds and do not brake!! 

 

This would be virtually impossible as you'd need a billiard table flat section of road with absolutely zero gradients up or down for the whole duration of the test. Even an imperceptible gradient will make any results completely unreliable.

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59 minutes ago, IanS100 said:

 

This would be virtually impossible as you'd need a billiard table flat section of road with absolutely zero gradients up or down for the whole duration of the test. Even an imperceptible gradient will make any results completely unreliable.

I'm really confused now. Apparently we are willing to believe a result obtained without much concern about any parameter that influence fuel consumption  but recognize that  "Even an imperceptible gradient will make any results completely unreliable".

If this is really the case, then all results discussed here are indeed completely unreliable ?

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Results reported are from 520d owners with intimate knowledge of both N47 & B47 engines driven for extended periods and often over known routes whereas you're suggesting a few miles back to back on a motorway. I know which figures I'd find more reliable!

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Guys, I am with IanS on this. I am confident that if we did do this small test run, it would totally confirm our suspicions in any case. I did a journey Sunday just gone that I have done many times in many different vehicles. 

I reset my trip computer at the beginning of a certain stretch of road, very much like mentioned in darkenergy's proposal. After cruising on a very flat road, with a fair few long downhills at a constant 65, the computer returned 47mpg.

Now, I have done that same test in many cars I have owned over the years and, although not a direct comparison, I remember my 335d getting very similar results on that exact same test. 

In summary, there is simply something not right here for sure. 

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Had a quiet run out yesterday - nice and steady on A road dual carriageways.  Towing a double boat trailer wrecks the fuel consumption!  Did the same trip today without boats and got 63 mpg.  Car is still a fantastic comfortable place to be however much fuel it drinks.

20160423_195628_001.jpg

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Hello all, as the B47 gets more commonplace and the weather gets warmer how is everyone finding the fuel consumption? Is it slowly getting to N47 levels or still being disappointing?

 

Thanks all.

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Hi nbains, not for me sir, still at the same levels, but, I am planning to make a couple of really long journeys soon, so, will feedback the results from that. It will be higher than the "average" figures for my car for sure, but I am going to state now, they will not be as high as an equivalent N47 doing the same journey.

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Not for me either, my 520d is now coming up for 18 months old and almost 21k on the clock but I'm not seeing any signs of improvement. With fairly gentle driving, lots of long runs and very little town work my mpg is still languishing down in the low 40s. Whilst I didn't expect a car that would compete in the Shell Eco-Marathon, I did expect somewhat better than I'm getting :(

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Thanks for the updates. The mpg figures are shocking and to be honest I am surprised that there is not more people complaining about this especially as the B47 is now in other models too.

 

I look forward to seeing what you are getting with your upcoming long journeys nashdm2.

 

Bring back the N47 (with no timing chain issues! ^_^)

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5 minutes ago, carrman said:

Now across France tomorrow with plenty of range left before hitting the autobahn's.

 

 

Hi Carrman, be interested to see what the french fuel crisis is really like when you get over there as I am due there in a couple of weeks also, let us know please.........

 

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17 minutes ago, nashdm2 said:

Hi Carrman, be interested to see what the french fuel crisis is really like when you get over there as I am due there in a couple of weeks also, let us know please.........

 

No issues apparent at the moment - will be setting off at 730 (local) tomorrow.

 

Haven't seen anything in the UK press this last week of note and will be heading straight across the autoroutes with 500 miles of range to go against 400 to destination.

 

A "local" update from Ram Rod would be useful??

 

Edited by carrman

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1 minute ago, IanS100 said:

What sort of speed were you doing to average 52 mpg because at 70 mph, my car would need to be downhill with the wind behind me

75-80 except M25 round Heathrow - with usual stop-start traffic.

 

See my post in 518d thread quoting my improvement in mpg since around 15,000 miles.

 

My old 520d trip computer overstated my fuel consumption by 3 mpg.

 

Changed the MFD to show kilometres and headlights to dip to the right for the next week in Germany!!

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2 hours ago, carrman said:

See my post in 518d thread quoting my improvement in mpg since around 15,000 miles.

 

As stated earlier, I've done almost 21k now with no sign of any improvement, and I'm certainly not going to work it out brim to brim because that's bound to be worse, so I just don't want to know :(

 

carrman: there's absolutely no way I'd get anywhere near 52 cruising between 75 - 80, I reckon Midlands to Calais must be downhill all the way ;)

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Or on the back of the RAC lorry :)

 

On a serious note I would be wee wee'd off also if my figures was as above but at the end of the day it is a 2 ton car and the smaller engines will struggle a lot more than a 6 pot one.

Edited by n0chex

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5 hours ago, IanS100 said:

 

Carrman: there's absolutely no way I'd get anywhere near 52 cruising between 75 - 80, I reckon Midlands to Calais must be downhill all the way ;)

 

But it is of course!!

 

Town driving hits the consumption with this (and any) car - I am lucky I do do very little urban driving and when UK traffic slows to 50 mph on motorways the consumption reduces.

 

Obvious comments off course but all of our circumstances vary - and we do not drive in a Laboratory.

 

In my pre-LCI 520d I once got 75mpg driving down from Pen-y-Pass to Betws-y-Coed in North Wales - barely needed the throttle all the way!!

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I appreciate anything other than constant cruising will increase consumption but what I meant was: I don't see 50 mpg at 70+ mph even on a billiard table flat motorway driving on permanent cruise control. I'm totally perplexed why some B47s seem ok whilst others are totally the opposite. I think it's a great engine in all other respects but still very disappointed in fuel economy, or lack of it.

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Update from France.

 

Things have settled down for the moment, but there is a general strike on the 14th. Diesel has jumped up in price to €1.15 a litre on average.

 

Regarding my fuel consumption, I have kept a record of every tankful so far and will post after the next fill up.

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7 hours ago, IanS100 said:

...I don't see 50 mpg at 70+ mph even on a billiard table flat motorway driving on permanent cruise control. ...

 

The problem with Cruise Control is that it is a sledgehammer to crack a nut - it doesn't see up hill and downhill sections and therefore is always reacting after the event with a relatively large throttle movement even with the new gearbox linked Sat Nav.

 

Also with the newer models coasting does not work on Eco Pro when using Cruise Control..

 

Throughout the UK I was not using Cruise Control and was using Eco Pro - speeds varied and hence some coasting was seen.

 

BTW I do not use Eco Pro too much as a rule - just trying to save fuel at the start of the holiday.

 

FYI - 48.2mpg across France today using Cruise Control in Comfort mode with aircon on at a broadly steady 133 kph.

 

As Ramrod says Diesel appears to have jumped in price to c. EUR1.30 on autoroutes - but appears easily available (i.e I saw no indication anyway of shortages).

 

No autobahn today (bugger!) but now in Germany with 26 degrees - in the Black Forest and will be curious to see the Fuel Price here.

 

Looking forward to beer and wine for the next few days.

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