Fuel Computer MkV 2.0TDI innacurate ?

[cetane]

Has anyone used the Caltex special vortex noted on their web site available only at a few selected outlets in Sydney?

"Special vortex" is not available here....

I use "ordinary" Caltex diesel in Mk1 Golf, Mk5 Golf TDI, Nissan Patrol SD33, S1 Landrover Discovery Tdi, Deutz 90hp tractor, Inter 65hp tractor, MF 70hp tractor and NONE of them smoke. The reason that they don't is they're all tuned properly (except the Golf TDI which I can't touch until the warranty expires...but then it doesn't smoke anyway even if I floor it..... with 30,000km on the clock it's not run in yet).

Oh, and according to the MFD I get 4.7L/100km on hilly, windy country roads to and from town...50km, 5.0L/100km on a 300km round trip to the nearest big city on highway running, and 5.2L/100km with mixed highway/city running. Not that I go to the city if I can avoid it. I guess with the error you guys are talking about these figures will look a lot less good

[gregozedobe]

Sad thing is I rely on that readout, to keep my sometimes poor driving habits ( sinking the slipper into it ! ) curbed.

If you want to use the MFD to help you save fuel, display the instantaneous fuel consumption, not the average. It tells you when you are really slurping fuel at that moment, which encourages you to back off a bit.

The average will tell you whether you have been sinking the slipper over the total journey.

[BeigeJet]

Hi All,
Have 15,000k on the odometer, so my 2007 TDI 2.0 Comfortline should be performing okay in the fuel usage stakes.
The onboard computer reading average fuel readings says that I'm consuming 5.0 litres per 100k or less.
Reality, when measuring at the fuel pump says that I'm actually using 6.6 litres per 100ks.
The all time fuel reading suggests my average over the distance travelled is 5.4 l/100k. The reality is 6.5.
I get approximately 700 to 750ks for 50 to 52 litres of fuel. That is 14ks per litre = 7.14 l/100ks to 6.9l/100ks. This is my " real world " average. Car readout suggests as above, approx. 5.4l/100ks.


My questions are
1. Does anyone else keep records which record a similar disparity between what the readout suggests and the reality ?
Thanks I look forward to your replies.
cheers
richard

Hi Richard,

I'm fairly anal and have kept detailed records for almost 2 years on my Jetta TDI manual.

I have found that my MFD is optimistic by about 0.5 lt /100. So when it shows 5.6/100 on the computer its more lik 6.1/100.

Life of car is 6.13 lt /100 km.

Below are totals for life of car and FBT year ending March Mar 2009 so far.

total km total lt total $ cpl km/lt mpg lt/100km $ p km
2009 6,080 376.0 642.59 170.9 16.17 45.7 6.18 $0.106
since new 44,644 2,736.7 3,713.12 135.7 16.31 46.1 6.13 $0.083


I hope it makes sense.

Cheers

Neil.

[cetane]

Typographical errors (that's more than 10 characters )

[cetane]

We all know that the speedo is optimistic by ~10%. So if the speedo is optimistic then won't the odo also be optimistic? Which means that you're actually covering less kms than you think (by 10%?) and so your fuel consumption will look less by ~10%.

Check out my logic, guys, it could be flawed.

[BeigeJet]

We all know that the speedo is optimistic by ~10%. So if the speedo is optimistic then won't the odo also be optimistic? Which means that you're actually covering less kms than you think (by 10%?) and so your fuel consumption will look less by ~10%.

Check out my logic, guys, it could be flawed.

Hey Cetane,

I checked that out against the numerous speedo checks around where the roads depts in each state have 5km stretches measured out. My Odometer appears to be out by approx 50 metres in 5 km so not an appreciable error. Surely NSW, VIC and SA all can't be wrong!

I know the speedo reads under as most people on freeways seem to zip past. The wife though does most of the driving around town and she ain't light footed.

[Greg Roles]

The speedo, no you cant adjust it but you can adjust the consumption in the mfd.

Im in the process of adjusting mine at the moment. So far ive made one adjustment but it requires more.

Geez, I feel like a dunce, how'd you get so smart with Vag-com? Let us know the tweak mate!

[cetane]

Hey Cetane,

I checked that out against the numerous speedo checks around where the roads depts in each state have 5km stretches measured out. My Odometer appears to be out by approx 50 metres in 5 km so not an appreciable error. Surely NSW, VIC and SA all can't be wrong!

I know the speedo reads under as most people on freeways seem to zip past. The wife though does most of the driving around town and she ain't light footed.

I'm going by GPS speed readings. Assuming they don't lie, there is a consistent 10% error in the speedo readout.

[gtimk5]

Hi Jackafrica, You failed to mention that your golf has the plug and play tune? Maybe something going on there if it blows a lot of soot out the back mate?
Cheers, Andrew

[gregozedobe]

We all know that the speedo is optimistic by ~10%. So if the speedo is optimistic then won't the odo also be optimistic? Which means that you're actually covering less kms than you think (by 10%?) and so your fuel consumption will look less by ~10%.

Check out my logic, guys, it could be flawed.

My experience (my version of reality ? ) is slightly different in one aspect.

IIRC, for various reasons (as discussed in previous posts) VAG typically design their vehicles to display optimistic road speed (usually 5-10% fast), low fuel consumption (anything up to 20% optimistic), but their odometers are much more accurate (possibly something to do with law suits re warranty in the good ol' USA).

If the odometers were also 10% out then the fuel consmption would be even further out (ie 10% more), as we use the odometer (or trip) reading to calculate fuel used for distance travelled. Unless we have some other way of calculating distance we have to rely on the odometer for the distance. Thankfully I haven't heard of anyone with a particularly inaccurate odometer.

I've read numerous posts that show you a way to display a more accurate speed via a special function in the climatronic controls, so if you have that fitted it might give you a good idea of just how optimistic your speed is. You have to press various buttons in special ways to access it, and I can't recall just what it is (do a search on climatronic in the various VW forums and I'm sure you'll find it).