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+--- Thread: Which computer to believe? (/Thread-Which-computer-to-believe)
Pages: 1 2
RE: Which computer to believe? - XFullFatTim - 08-05-2014 02:43pm
OK Trip A and Trip B read 43.4 and 43.3 respectively, neither has been reset since the car was delivered. I now have 1850 miles up so the engine is still a bit "new" but it is lively enough for my style of motoring.
Philskill - Yes it's quite happy to stay in 9th at 70mph, just that in my normal driing i have to manually put it there or exceed the local speed limits to get it to go up automatically!
RE: Which computer to believe? - Silver Fox - 08-05-2014 07:28pm
Hi,Just completed 2698 miles in my 2014 SD4 5 door 9 speed auto.
Fuel used is 64.72 galls that is calculated on the basis of the quantity that the dealer included in the purchase of the vehicle and the last fill up to the first cut off point and a calculation of 57 litres of fuel in tank after fill up.
Therefore the overall MPG from new is 41.7 (rounded up the decimal point)MPG.
The MPG has generally been improving with increased recorded mileage and the last actual calculation was 43.6 MPG over 698 recorded miles.
The computer average MPG generally shows a figure of approx 2 MPG better than the calculated figure.
I also complete the fill up at the first cut off of the pump and appreciate that this can be influenced by fill up rate and foaming etc.,
Running includes 40% motorway,40% rural and 20% town.
Hope that this assists the debate.
Does anybody know the reason why owners are recommended not to brim fill the tank as this is more definitive in recording the true MPG.
RE: Which computer to believe? - mark_n - 09-05-2014 06:29am
A further source of inaccuracy is the odometer which typically records revolutions of the prop-shaft and translates that to distance by applying a conversion factor which may or may not be accurate depending on the rolling radius of your tyres (which itself depends on tyre wear and inflation and the load the car is carrying) and things like corners and hills.
My odometer was about 2% out when I measured it over a 50 mile run compared to a GPS tracker.
RE: Which computer to believe? - speary - 09-05-2014 08:12am
(08-05-2014 12:41pm)PhilSkill Wrote: I was expecting to see upto a 6-7% improvement. Mainly from improved efficiency in the gearbox (maybe 3%) and improved gearing (maybe 3-4%)
If Tim, you've moved from 36 - 39.5 then that's a 10% improvement! and if your fuelly signature is old and you are getting 40+ then that's actually an amazing improvement for a gearbox change. E.g. 43mpg would be a 20% increase in efficiency!
Does it stay in 9th at 70ish mph happily Tim? If I have one glimmer of regret on the Manual, it's the top gear seems too short and is costing fuel due to higher revs than neccessary at higher speeds (but then I don't drive it loaded to the gunnels with stuff!).
I hardly think that 2000 rpm at 70 is low geared. At 2000 rpm the diesel has only just got into the peak torque range. I presume that the 9speed auto is running about 1500 rpm at 70. That is below the peak torque figure therefore can't be that efficient
RE: Which computer to believe? - timhum - 09-05-2014 11:13pm
XFFullFatTim,
Very interesting to read your mpg comments, I've asked on this forum a couple of times how on earth the 2014 model is achieving 30% improvement in fuel consumption with no changes to the engine; it appears that it isn't. I'm very surprised that you've been trusting the trip computer calculations and publishing the figures after previously quoting the 'fuelly figures'; I can't remember ever having a trip computer give accurate mpg figures. This information certainly makes me question the economic benefit of changing our Evoque to a 2014 or even 2015 model. How do BMW and VW get such better figures from their cars than LR can achieve, much more modern engines I suppose.
RE: Which computer to believe? - Silver Fox - 11-05-2014 09:48am
(09-05-2014 08:12am)speary Wrote: I hardly think that 2000 rpm at 70 is low geared. At 2000 rpm the diesel has only just got into the peak torque range. I presume that the 9speed auto is running about 1500 rpm at 70. That is below the peak torque figure therefore can't be that efficient
Hi the 9 speed SD4 auto is quoted by LR for max torque at 1750 RPM.
At 60 MPH a figure of 1400 RPM and at 70 MPH a figure of 1600 RPM was recorded on a flat stretch of motorway.
It would be interesting to review the LR figures/graphs for torque and power but I can't find them in any published LR information.
This is particularly interesting such as when towing a caravan as torque is important to maintaining performance.
The 9 speed auto will automatically engage 9th at 60/65 MPH but this is very dependant on the use of a light throttle setting but under normal driving conditions goes into 9th at 70 MPH.
I sometimes engage 9th manually in drive at 60MPH but unless the car is travelling on the level or downhill then the engine noise does not sound totally comfortable and when dropped to 8th sounds more healthy.
RE: Which computer to believe? - XFullFatTim - 11-05-2014 10:20am
Silver Fox, I concur completely with your findings regarding 9th gear and the RPMs at 60/70 and manually upshifting. The upshift seems weird as the car is quite happy to cruise at 60 in 9th and maintain 9th even after the gearbox has over-ridden the commandshift and returned to D.
I would urge anybody with a 2011/2012 car who is considering changing for something else to get hold of a 2014MY auto and have a test drive in it, it is a much better car now than the earlier cars were.
RE: Which computer to believe? - PhilSkill - 11-05-2014 08:49pm
(09-05-2014 08:12am)speary Wrote: I hardly think that 2000 rpm at 70 is low geared. At 2000 rpm the diesel has only just got into the peak torque range. I presume that the 9speed auto is running about 1500 rpm at 70. That is below the peak torque figure therefore can't be that efficient
You don't need to be in the peak torque range for cruising and fuel saving, the peak toque range is best for acceleration or climbing Hills/Towing where you need torque, you only need to be generating enough power to stay cruising with as little fuel as possible that will usually mean a lower rpm that generates that power, the lower RPM means less intake decompression strokes drawing in fuel over the distance and less friction (obviously too low and the engine will become harder for it to generate enough power), hence your up change indicator when not accelerating is often asking you to up change by 1800rpm unless you demand more torque if you meet a hill or accelerate.
RE: Which computer to believe? - harveyg77 - 17-05-2014 09:00am
Hi Tim,
Interesting comments on your 9-speed auto.
I drove an Amarok 8-speed and it either slurred along at not much over tick over or screened along at 3500rpm. But the Fl2 6-speed was cracking, better than any other auto I've used previously, well bar the 4-speed RaRo P38 auto. Looks like I would get on with the 9-speed too
Side issue, "Fuelly" is that the Gas Cubby free app by Fuelly LLC, or another app?
All the best,
Harvey
VW aren't achieving the figures they quote. I know people with manual Audi A4 2.0TDi 177 getting about 42/43 general commute ( mainly dual carriageway) and could touch 50mpg on a long run. Now got an A4 all-road 2.0tdi 17? auto doing 38-39mpg same commute and 44mpg long run.
I had a 105ps 1.6TDi Golf SE Bluemotion for a day and it was terrible around town, worse than the S-Max 2.0TDci 140 and Fl2 150ps manual GS.
My wife's Focus estate 1.0 125 ecoboost is better on fuel than the Focus 1.6TDCi hatches I ran!
The only cars I've seen achieve anywhere near what they claim are BMWs. I had a 118d that was pulling in 60+mpg on a run. My managers 320d ED 8-speed auto is hitting high 50s to low 60s mpg, it can get into low 70s on a very long, slow run.
I do not think anyone with a different brand is any better off than us!
Cheers Harvey