Hi all,

Collected my '57 Elegance (and christened it 'Nelly'* ) today and immediately went on a run to drop some parts off. No rush, so I had cruise engaged most of the way 60/50 (roadworks).

At one point I had the theoretical range at 940 miles. (miles done + remaining range)

-and-

The computer recorded 72mpg.

How beliveable is the on-board computermabob? What's the furthest anyone's gone on a single tank?

This was a 4 hour round-trip, no stress when getting out at the end....felt like a 5 minute run. Think I'm going to enjoy this :D

(* as in 'Nelly The Elegance')

Edited 15 October, 201114 yr by RainbowFore

1.9 TDi 105 PD? If so 72mpg is possible on a long steady run.

The OBC (Onboard Computer) is normally pretty accurate, hoewever there are plenty of members reporting over-reading by as much as 15% (me included).

Best to brim it, reset the trip meter do the same run, brim it again, note the miles covered and the litres used and calculate manually and compare.

The OBC can be adjusted if you discover it is out...

Edited 15 October, 201114 yr by silver1011

1.9 TDi 105 PD?

The OBC (Onboard Computer) is normally pretty accurate, hoewever there are plenty of members reporting over-reading by as much as 15%.

Best to brim it, reset the trip meter do the same run, brim it again, note the miles covered and the litres used and calculate manually and compare.

The OBC can be adjusted if you discover it is out...

Yes, 105 PD. Not going to win any drag races, but at that MPG, I don't care (Plus I have plans to re-map later if that's going to help the MPG too)

Thanks for that, I'll give that a go when I next fill up.

The 1.9 PD engine is a cracker and has the most to gain from a remap.

So much so it now has legendry status, it is often spoken about in the motoring press for its durability and thermal efficiencies.

Personally I've never quite got my head around how you can have both an increase in performance AND improved economy with a remap but there are too many people on here telling me it is true for me to dispute

Personally I've never quite got my head around how you can have both an increase in performance AND improved economy with a remap but there are too many people on here telling me it is true for me to dispute

I thought that to start with too.

From what I understand, especially with a diesel, the re-map makes the engine run at peak efficiency, so more power with the same fuel or same speed/less effort. The write-up on Shark's page made for good reading and was very informative, as well as a general google.

Edited 16 October, 201114 yr by RainbowFore

I tend to put in £30 at a time and run till light comes on and work out mpg that way. Divide cost per litre convert to gallons (cos I'm an old bugger). Computer does tend to be a bit over optimistic but not too far.

In the two years I've had mine I've ranged between 47 and 65 mpg. Winter conditions and short journeys obviously don't help. It's done 105k now and seems just as economical as when I got it

I would give fuelly a go (click on the icon in my signature) to track mpg. It works best when you fill to top, then down to almost empty. Its not difficult maths I know to calculate MPG, but fuelly tracks data over time and can be updated via mobile.

So long as you consistently fill to the same point, i.e. first cut-off, or second pump cut-off to get a bit more in, it seem to work quite well.

My computer shows approx 50-51mpg average, pump average shows more like 48mpg, so about a 5% error for mine.

I too use fuelly - run it down to just before the needle goes in to the red each time to get a good spread of different types of journeys off of a tank.

On a 2.0 TDi PD140 my best actual MPG is 59.8, 522 miles off of 39.66 litres. My trip computer was over 10% on the optimistic side, but I have now got it adjusted pretty much spot on. According to the trip computer I had over 180 miles left so could have theoretically got 700 miles out of a tank - it was still a notch and a half above the 1/4 tank mark.

The most I have actually got off of a tank is 660 off of 53.6 litres at 55.9mpg.

How / where do you get the OBC adjusted?

Cheers

It needs someone with VCDS to be able to make the adjustment for you.

VCDS is a special cable / software that allows you to access the cars CANBUS system via a laptop.

There is a list of VCDS members on here so you can find out if there is one local to you. A few beer tokens usually do the trick

Do a search for VCDS, there are loads of other neat things you can change at the same time too!

How accurate is the speedo? its all good you work out MPG from briming the bank and average over so many thousands of miles. If the speedo (normally fast upto 10%) then the mileage covered its wrong. I had a few cars in my time and all of then were fast ie. speedo saids 70mph, Gps will said 64-5mph so the overall mileage cover is wrong by upto 10%

How accurate is the speedo? its all good you work out MPG from briming the bank and average over so many thousands of miles. If the speedo (normally fast upto 10%) then the mileage covered its wrong. I had a few cars in my time and all of then were fast ie. speedo saids 70mph, Gps will said 64-5mph so the overall mileage cover is wrong by upto 10%

Am going to check that against GPS, when I remember to put the GPS in

(Also handy for when I hit cruise in the roadworks)

My theory is that cars are originally calibrated on the largest wheels the the manufacturer will put on.

My Felly Fun is bascally bang-on as it still sits on the 13" wheels which were the biggest Skoda put on there.

My dad's Focus reads 5mph higher as it sits on 15"s and I think Ford put 17"s on that model at some point.

Am going to check that against GPS, when I remember to put the GPS in

(Also handy for when I hit cruise in the roadworks)

My theory is that cars are originally calibrated on the largest wheels the the manufacturer will put on.

My Felly Fun is bascally bang-on as it still sits on the 13" wheels which were the biggest Skoda put on there.

My dad's Focus reads 5mph higher as it sits on 15"s and I think Ford put 17"s on that model at some point.

Note though that the overall diameter of the 15" and 17" is normally the same (within 1%) since the 17" would have a lower profile to compensate for the larger wheel.

So on a vRS the standard 18" (225/40/R18) wheel diameter is within about 1% of a 205/55/R16 that is fitted on other Octavia models.

However I acknowledge that if the speedo is not correct the mileage may not be either (unless they calibrate the mileage better)

How accurate is the speedo? its all good you work out MPG from briming the bank and average over so many thousands of miles. If the speedo (normally fast upto 10%) then the mileage covered its wrong. I had a few cars in my time and all of then were fast ie. speedo saids 70mph, Gps will said 64-5mph so the overall mileage cover is wrong by upto 10%

Indicated speed on the speedo and mileage are not related.

If you have the correct tools you can see that the ECU recorded speed is within 1% of what a TomTom will tell you, whilst the speedo will still be showing up to 5% over.

If you have a pre facelift with full dual zone climate you could get one of the climate dials to display the speed in mph that the ECU was recording, and it was bang on what my TomTom said I was doing, not what the speedo needle said.

Adjusting the trip computer mpg display is just applying a correction factor to the mpg calculation, not the speed the ECU or speedo are displaying. They can be corrected elsewhere if you know how.

With the cruise on 60mph on speedo, the ecu reads 57 (5% out in my favour). GPS is flat today, but it doesn't get used often.

On the subject of tyre sizes I found a tool that allows you to compare: (Tyre info taken from the Skoda accessories website)

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference

205/60-15 4.8in 12.3in 24.7in 77.6in 817 0.0%

205/55-16 4.4in 12.4in 24.9in 78.2in 811 0.8%

225/45-17 4.0in 12.5in 25.0in 78.5in 808 1.2%

Bigger wheels do make a little difference. However, I'm not entirely sure that something using 17's would have the same gearbox as something on 15's. (Kinda expecting the vRS to have a different gearbox to the "normal" ones)

surely if tyre thread is from 8mm (new) to 1.6 legal minimum the rolling radius is different, how can the car odometer be 100% accurate

Indicated speed on the speedo and mileage are not related.

If you have the correct tools you can see that the ECU recorded speed is within 1% of what a TomTom will tell you, whilst the speedo will still be showing up to 5% over.

If you have a pre facelift with full dual zone climate you could get one of the climate dials to display the speed in mph that the ECU was recording, and it was bang on what my TomTom said I was doing, not what the speedo needle said.

Adjusting the trip computer mpg display is just applying a correction factor to the mpg calculation, not the speed the ECU or speedo are displaying. They can be corrected elsewhere if you know how.

If you go to Section 19 subsection 1 in the Climate Control Data it shows you a digital readout of vehicle speed in Mph. I have found this matches perfectly the GPS speed from my Tomtom even though the speedo is showing about 3mph faster.

If you go to Section 19 subsection 1 in the Climate Control Data it shows you a digital readout of vehicle speed in Mph. I have found this matches perfectly the GPS speed from my Tomtom even though the speedo is showing about 3mph faster.

Given the variances already discussed, I have to wonder where the ECU gets the data from, and then why it can't tell the needle where to sit. Seems a 'lil strange to me.....

At one point I had the theoretical range at 940 miles. (miles done + remaining range)

-and-

The computer recorded 72mpg.

How beliveable is the on-board computermabob? What's the furthest anyone's gone on a single tank?

This was a 4 hour round-trip, no stress when getting out at the end....felt like a 5 minute run. Think I'm going to enjoy this :D

(* as in 'Nelly The Elegance')

I like data and have followed my 1.9TDi consumption closely since buying it last year.

The furthest I've gone on a single tank is 675 miles, but the fuel light had only just come on. It took 47.00 litres to fill up giving 65.3mpg. Over the same distance the on-board computer said I averaged 69.0mpg. A difference of +4mpg for the on-board computer has been average for my car over real calculated mpg.

At 65mpg I calculated that a range to empty fuel tank would be 787 miles. Not bad for a 55l tank!

I too have had average figures of over 70mpg on long journeys at 60mph, but I'm bored of that now and have settled for doing the the speed limit, 70mph and still get 63 or 64mpg on the computer.

I once tried driving 120 miles at 53mph at night on the M5. It was very boring and at 72.2 mpg gave no better mpg than at 60mph.

I used to have to fill up my old Rover 2l petrol every 350 miles and it had the same size tank, 32mpg average it gave me so loving the Skoda!