MK7 GTD - Real Life MPG

[jmc]

It's getting better....

[monkeyhanger]

8 mile trip home tonight from the city centre, 75-80mph on the coast road - 49.2mpg. The warmer weather is probably helping, it was 8.5C.

Now I can't help thinking about spoiling it all with a box.

[KyleB]

Now I can't help thinking about spoiling it all with a box.

Boxes are tempting me too. Think I need the extra power...

[monkeyhanger]

9.5C today, stuck behind a procession of cars doing 22mph on a 40 road for a good few miles of the journey and still managed 45.5mpg. Had to fill up and the penny has finally dropped for the local JET station (usually 3p more than everywhere else, now as cheap as anyone).

[Andrew@DTUK]

8 mile trip home tonight from the city centre, 75-80mph on the coast road - 49.2mpg. The warmer weather is probably helping, it was 8.5C.

Now I can't help thinking about spoiling it all with a box.

yeah, but how much fun would you have 

[C2K]

It's getting better....

Now that's more like it. As long as my night blue does the same i'll be happy.

[monkeyhanger]

A bit of a twist on the mpg banter with the DTUK box addition. I filled the car up this morning so I can see how the box really affects mpg:-

168.7 miles covered, 18.78L used = 41.1mpg, 44.3mpg indicated. Overall 168.7 miles, MFD is 7.8% optimistic.

Prior to box fitment, car was reading 41mpg indicated at 105 miles. Probable 40mpg actual (assuming MFD is 2.5% optimistic, as is usually the case) = 2.625 gallons/12.02L used.

6.76L (1.48 gallons) used to travel 63 miles since the box was put on = 42.6mpg actual.

A 3.3mpg indicated improvement (44.3 vs 41) since fill up on 63.8 miles since box addition = extra 8.7mpg weighted for the 63.7 miles only.

42.6mpg actual + 8.7mpg (indicated improvement) = 51.3mpg probable indicated had the car been full from the box addition. Car is 20% optimistic on the MFD display vs actual.

That's fine, as long as I look at the MFD and know that if the computer is reading 52.8mpg, I got 44mpg. The box isn't for me to get improved economy. The extra torque might help economy (a little) for motorway cruising, but around the doors I don't think it will.

The above calculations are all a load of extrapolation on mixed circumstances.

I filled the car up this morning so I can get a proper MFD vs actual when I use a tank full of fuel.

Early indications prior to adding the box and after are that Jet fuel is sh!te for mpg. I will be sticking to Esso and BP in future.

[karlak]

Yup,

I have noticed that on my current car, the MFD readout was pretty close to the real world MPG.  I have had a superchip remap though and it has made a larger margin of error.

52 mpg pre-remap would be around 49mpg real

52 mpg post-map is around 44 mpg real.

Something to bear in mind when reading reviews of peoples mapped cars.  Unless you are doing brim to brim checks, the MFD readout cannot always be consistent between mapped and non-mapped.  Perhaps explains some reports of mapped cars having improved MPG with better performance...

Not sure why this is though.

[monkeyhanger]

Karlak: The MFD is calculating fuel economy based on what it thinks it is consuming. Actual usage when then the box is taking the fuelling signals and amplifying them (over what is essentially a 2D map, if I understand it right) is higher. To main 70 mph with the box on takes less press on the throttle pedal than without. The MFD interprets this as needing less fuel and so you get a higher mpg reading. Actual mpg will be the same (unless some marginal torque gains come into play).

[karlak]

Karlak: The MFD is calculating fuel economy based on what it thinks it is consuming. Actual usage when then the box is taking the fuelling signals and amplifying them (over what is essentially a 2D map, if I understand it right) is higher. To main 70 mph with the box on takes less press on the throttle pedal than without. The MFD interprets this as needing less fuel and so you get a higher mpg reading. Actual mpg will be the same (unless some marginal torque gains come into play).

Ahh,, I see.

When I mentioned this to Superchips, they said they could alter or do something the map to account for the change in MFD reading.  Mine was the first car they had done, so they were on a bit of a learning curve with my model. 

I never went back to them as I had pretty much decided to order the Golf anyway.

Just for information, they were very interested to "get hold" of a Mk7 to try and get a map sorted.  They did this on my current car, so you basically get a remap for free.  I already had the Bluefin, so they just adapted for that my current car.