MK7 GTD - Real Life MPG

[monkeyhanger]

Maybe VW have changed the point at which the MK7 is run in by either being exceptionally tight, or clever ECU limitations gradually lessened over a long period? With my Scirocco 170TDI, I was initially disappointed, it felt like it had the performance of the 140TDICR Scirocco that came before it, but after 320 miles/500Km, as if a switch had been flicked, it opened right up (and others had the same experience). mpg was always good - very hard to get under 50mpg indicated/45 actual except in the worst of winter.

I had the chance to test my performance benchmark by which I have judged my last 4 cars, now i've passed 1000 miles. Getting onto the coast road and accelerating hard (about 3/4 throttle) to the point at which I pass a certain sign: 140 PD MK5 = 70mph, 170 PD MK5 = 80mph, 140TDI CR Roc = 78mph, 170TDI CR Roc = 83mph.......MK7 GTD, throttle down to click point = 79mph. 

Not sure whether there is a lot of improvement to gain still or whether in the past TDI output was less tightly controlled. A well run in one would go a fair way over book output, maybe now they can be accurately limited to book output with a more sophisticated ECU? Did I have a 170TDI putting out about 190PS, or do I have a GTD putting out less than 184PS? Roads were dry, so seemingly no grip issues. Scirocco had 235/18 tyres vs GTD 225/18 tyres, could that be significant if the traction control didn't intervene?

One other factor to consider - i'm on V-power right now, will have to see what standard Shell does to me with higher Cetane.

[virginVWman]

Driving to St Andrews yesterday from Stirling in my three year old a3 i got 67.1mpg...turned out to be so addictive trying to constantly improve. I have evidence if know one believes me. Surely the gtd will manage 60 if you kbow how to drive it

[Skinnee D]

Driving to St Andrews yesterday from Stirling in my three year old a3 i got 67.1mpg...turned out to be so addictive trying to constantly improve. I have evidence if know one believes me. Surely the gtd will manage 60 if you kbow how to drive it

Looking possible I'd say with a restrained right foot.  Will be interesting to see how people get on with a few thousand on the clock; I won't be there for a while myself...

[monkeyhanger]

Driving to St Andrews yesterday from Stirling in my three year old a3 i got 67.1mpg...turned out to be so addictive trying to constantly improve. I have evidence if know one believes me. Surely the gtd will manage 60 if you kbow how to drive it

The GTD could do this fully run in and doing a constant 55mph on a clutter-free motorway, but what's the point of sitting at 55mph on the motorway? It should be capable of doing this at a constant 70mph. My last car could exceed it's published combined mpg doing a constant 80mph on a clutter-free motorway. How fast were you going to achieve those figures and is that a 1.6/105, 2.0/140 or 2.0/170 TDI?

[virginVWman]

Driving to St Andrews yesterday from Stirling in my three year old a3 i got 67.1mpg...turned out to be so addictive trying to constantly improve. I have evidence if know one believes me. Surely the gtd will manage 60 if you kbow how to drive it

The GTD could do this fully run in and doing a constant 55mph on a clutter-free motorway, but what's the point of sitting at 55mph on the motorway? It should be capable of doing this at a constant 70mph. My last car could exceed it's published combined mpg doing a constant 80mph on a clutter-free motorway. How fast were you going to achieve those figures and is that a 1.6/105, 2.0/140 or 2.0/170 TDI?

I was going the back roads, well anything non motorway (A977 and the A91). I had to join the motorway for a few miles or so sitting at 75mph but pretty much sat at 60mph all the way there. Not much traffic on the roads surprisingly so just sat at a steady pace. Its a 2.0 140ps A3 with the best part of 60k miles on the clock (3 years from new). Great car, just hoping the GTD is as good as I hope it is.

[monkeyhanger]

I was going the back roads, well anything non motorway (A977 and the A91). I had to join the motorway for a few miles or so sitting at 75mph but pretty much sat at 60mph all the way there. Not much traffic on the roads surprisingly so just sat at a steady pace. Its a 2.0 140ps A3 with the best part of 60k miles on the clock (3 years from new). Great car, just hoping the GTD is as good as I hope it is.

In every aspect but mpg and output (which may be attributable to my choice of fuel as much as needing running in), the GTD is a big jump over the previous gen VAGs - ride/handling/comfort/standard equipment are all excellent.

[corgi]

I had the chance to test my performance benchmark by which I have judged my last 4 cars, now i've passed 1000 miles. Getting onto the coast road and accelerating hard (about 3/4 throttle) to the point at which I pass a certain sign: 140 PD MK5 = 70mph, 170 PD MK5 = 80mph, 140TDI CR Roc = 78mph, 170TDI CR Roc = 83mph.......MK7 GTD, throttle down to click point = 79mph. 

Assuming you are going through the gears... there are only three factors at play here: power, weight and , as speed increases air resistance (frontal area is the major factor here)... And the weight and frontal area are known or could be calculated... power is the unknown. There is one other unknown... whether your throttle openings amount to the same thing... The only real way to rule that out would have been to run the cars at full throttle...

A well run in one would go a fair way over book output, maybe now they can be accurately limited to book output with a more sophisticated ECU? Did I have a 170TDI putting out about 190PS, or do I have a GTD putting out less than 184PS? Roads were dry, so seemingly no grip issues. Scirocco had 235/18 tyres vs GTD 225/18 tyres, could that be significant if the traction control didn't intervene?

It could be any of the above scenarios (and you'll probably never know unless you could run both cars back to back on a rolling road). The tyres will not make a significant difference assuming their rolling resistance is similar - and increase in section from 225->235 is ~4.5%... another factor could be the mass of the wheel/tyre combo but I suspect there's not a lot in it...

In the end there are too many unknowns to make a judgement on whether (a) there is a significant difference between your Scirocco and your Golf (b) if there is whether it is because your Golf is down on power or not

[monkeyhanger]

Corgi:

I suspect the use of V-power (which the Scircco was never fed) might be a significant factor. Less potent fuel (V-power ave Cetane = 52, Shell standard ave Cetane = 56) could explain poor performance and poor mpg. I won’t know for a few weeks – probably got about 10 days-worth of V-power left in the tank at the rate I use it. The relative limpness of my GTD in 5th and 6th gear acceleration compared to my Scirocco makes me hopeful that it is the fuel. Another regen today – the car’s fan was deafening when I parked up. 2 people chased me from the works car park to tell me I’d left my car on! Despite the regen, my mpg was not bad for the journey compared to what I have been getting on my commute – an indicated 46.9mpg.

Also, the Scirocco is more Aerodynamic than the Golf, I suspect not massively so, but might make a 1 or 2 mph difference on my roadsign marker test, as might a strong headwind as opposed to no wind or a strong tail wind.

[Skinnee D]

Corgi:

I suspect the use of V-power (which the Scircco was never fed) might be a significant factor. Less potent fuel (V-power ave Cetane = 52, Shell standard ave Cetane = 56) could explain poor performance and poor mpg. I won’t know for a few weeks – probably got about 10 days-worth of V-power left in the tank at the rate I use it. The relative limpness of my GTD in 5th and 6th gear acceleration compared to my Scirocco makes me hopeful that it is the fuel. Another regen today – the car’s fan was deafening when I parked up. 2 people chased me from the works car park to tell me I’d left my car on! Despite the regen, my mpg was not bad for the journey compared to what I have been getting on my commute – an indicated 46.9mpg.

Also, the Scirocco is more Aerodynamic than the Golf, I suspect not massively so, but might make a 1 or 2 mph difference on my roadsign marker test, as might a strong headwind as opposed to no wind or a strong tail wind.

MH - do you reckon that V-Power diesel might be detrimental to efficiency?  For gasoline I recall Shell and others promoting improved efficiency for their higher octane "V-power" type products. 

[monkeyhanger]

For the diesel version at least, V-power's likely gains are from your car running cleaner because it is a purer fuel. It used to be pure GTL content (apart from the additives, and now it is a blend of oil derived diesel and GTL derived diesel. V-power is less dense than normal diesel, because the GTL derived part has shorter average hydrocarbon chains than the oil derived part. Basically it has less hydrocarbon content and therefore less chemical energy than standard diesel. If it can burn more completely than standard diesel then there could be no disadvantage, but as people running normal aren't being inundated with regens then i'd say standard is combusting just fine in the GTD. Lower Cetane rating with V-power (52) than Shell's standard (56), should mean that standard has a head start in combustion.

I wish i'd used my Chemistry degree and thought it through before I filled up with V-power.

Assuming I do get better performance with standard diesel, I'd say V-power shell is better for cleaning out an older car than keeping a new one running perfectly.

V-power petrol to improve a car optimised to run the higher RON fuels is different, plenty of petrol users will swear by V-power.