New vRS CR Estate

 

With Manual Gearbox, Extra-Urban = 78.5 mpg

With DSG Gearbox, Extra-Urban = 65.7 mpg

 

I thought the drive ratio of both gearboxes was the same in 6th?

 

How can the DSG be 13 mpg less efficient in testing?

 

Cheers,

 

H

Does it really matter as they are both unachievable made up numbers for marketing purposes?

 

Extra-urban isn't driving at a constant speed in 6th either.

 

How is the fuel consumption test conducted? 

• The test is outlined in Directive 93/116/EC as amended by Regulation (EC) 692/2008, and provides results that are more than representative of actual average on-road fuel consumption than previous tests. There are two parts: an urban and an extra-urban cycle. The cars tested have to be run-in and must have been driven for at least 1,800 miles (3,000 kilometres) before testing.
• Urban Cycle
  The urban test cycle is carried out in a laboratory at an ambient temperature of 20^oC to 30^oC on a rolling road from a cold start, i.e. the engine has not run for several hours. The cycle consists of a series of accelerations, steady speeds, decelerating and idling. Maximum speed is 31mph (50km/h), average speed 12mph (19km/h) and the distance covered is 2.5 miles (4km).
• Extra-Urban Cycle 
  This cycle is conducted immediately following the urban cycle and consists of roughly half steady-speed driving and the remainder accelerations, decelerations, and some idling. Maximum speed is 75mph (120km/h), average speed is 39mph (63 km/h) and the distance covered is 4.3miles (7km). 
• Combined Fuel Consumption Figure 
  The combined figure presented is for the urban and extra-urban cycle together. It is therefore an average of the two parts of the test, weighted by the distances covered in each part.

I've noticed this before on DSG models and wondered why, especially as BMW claim an improvement in mpg and performance with their 8 speed traditional auto.  I don't get why it would perform worse on any given test, except that you are lugging around a tad more weight perhaps, but not so much to make much difference. The above post, whilst interesting, doesn't really explain why the DSG is so much worse on tests. My Octy II wasn't very economical with it's DSG either

Edited 22 August, 201411 yr by Lady Elanore

It might depend on how harsh the acceleration part of the cycle is.  The DSG may change down a gear or two whereas the manual may stay in the same gear.

DSG's also heavier, isn't it? So even with theoretical performance (i.e. gears change at the same time, same acceleration and breaking) the DSG will automatically be less efficient.

DSG's also heavier, isn't it? So even with theoretical performance (i.e. gears change at the same time, same acceleration and breaking) the DSG will automatically be less efficient.

But that doesn't explain something like the BMW auto which will be heavier than the manual. I don't think the extra weight would make so much difference either as it's only a relatively small weight penalty, Perhaps it's the gearbox fairies at work Anyone looked at any other DSG type car's mpg from MB or similar?

kitset.

In theory it might, but the proof of the pudding is the same driver driving the Manual Version & the DSG Semi Automatic version even if it 

is heavier when Laden (rather than given Kerb Weights).

 

Then that is the test as to if the DSG car is using more fuel when the same driver is doing the driving on real roads..

 

george

i have noticed that DSG tends to go down a gear to easily. When i drive on a country road i stick it into manual mode so that it would hold 6th gear. That brings consumption quite a bit down.

Will weight make much difference on a rolling road in lab conditions??

I've had a look at the Mercedes GLA 200 diesel and it comes in manual and 7 speed DSG equivalent.

 

The DSG is 30kg heavier, a teeny, weeny bit quicker to 60. but is 3 mpg better in the urban test, 3.5mpg worse in the extra urban and the same mpg in the combined test.

 

Something like the Yeti seems a little worse in PMG in all similar guises if it has the DSG it looks like :(

Edited 22 August, 201411 yr by Lady Elanore

I can't help but think some of it is down to programming the box to be better at the test. I think generally the differences are mostly due to the programming. The DSG may be quick at changing gear, but that seems to be its sole party piece. Ive driven DSGs and several other autos and they seem dumb as bricks, relying on fast changes to make up for poor decisions. The BMW ZF8 is likely much better programmed. The auto box in mine also has a 10% improvement over the manual version, despite extra weight, which is partly as its a CVT so can always remain in the optimum position (in economy mode) and cleverer algorithms on how to react to changes.

VWG just pick Numbers any Numbers for EU Fuel & Emission Test.

 

There are 5 VWG 1.4 TSI Twnincharger cars, 132-136 kw, DSG.

 

The Lightest is the Fabia vRS and is is 148 co2 g/km.  on 205/40 r17 Tyres, (& Skoda put 25 kg Ballast on the rear crash bar.)

The Estate is 70 kg Heavier but given a Official Weight 5 kg lighter, and the same co2.  

 

the 3 Sister cars have the same Engine & Gears and 215/40 R 17 tyres.

All 3 are heavier but the Official Test Figures have it  VED Class Lower, 139 co2  g/km

Higher Top Speeds, quicker acceleration and lower fuel consumption.

 

Then 2 years later VWG correct the Kerb Weights, but not the MPG, Emissions or Performance figures.

 

The Volkswagen Group deal with Fiction really.

Usually it is more expensive or more premium brand, better figures though.

 

 

 

george

Edited 22 August, 201411 yr by goneoffSKi

65.7!

Maybe, coasting down a long, long hill.

thanks for replies.

 

Lady - the BMW is more efficient as an auto because it's an 8-speed vs 6-speed manual.

thanks for replies.

 

Lady - the BMW is more efficient as an auto because it's an 8-speed vs 6-speed manual.

I can understand that the overdriven gears would help on the motorway, but of course all those extra gears will add up to more weight while accelerating. BMW reckon that 8 gears is the optimum number, as more than that is unnecessary and less efficient. So that must be why Mercedes, Jeep, Land Rover etc etc are all going to 9 speed autos now Eventually they will reinvent the CVT gearbox the hard way

I think what surprises me is that I was taught that an automatic with its torque convertor was always going to be less efficient than something with direct drive through a convectional gearbox. I guess the modern advances in technology and clever software in these auto boxes is something to praise.

With a DSG (or Auto), the shifting program can't possibly have a knowledge of drivers intent; a manual driver can upshift sooner at top of a hill or end of acceleration, and downshift sooner (with less "kick-down" use of fuel) on an uphill or passing move.

but the changes are in general much quicker, so the car wastes less fuel slowing down between shifts

I think what surprises me is that I was taught that an automatic with its torque convertor was always going to be less efficient than something with direct drive through a convectional gearbox. I guess the modern advances in technology and clever software in these auto boxes is something to praise.

Modern ones have a lock-up clutch. This effectively makes the torque converter into a solid coupling. So now autos only have a viscous coupling at the exact point of gear change when the lock-up clutch disengages allowing the TC to do is job of letting there momentarily be a difference in input/output shaft speed, once the shaft speed has equalised (which usually takes less than a second) the lock-up clutch re-engages making it a solid coupling again - so 99.9% of the time it is equally efficient as a manual/DSG.

In my SQ5 for the first mile or so on a cold start the lock-up clutch would not engage until the transmission fluid had warmed up. As a result it made it feel horrendous, cruising at 60 in 8th you could stab the throttle and vary the revs a good 2k rpm with zero effect on your acceleration/speed. Basically it was working like an old pre-90's auto as loads of the engine power was lost spinning some fluid around in the TC and not being sent directly to the drive shaft.

I see plenty of slip (well it's noticeable on the rev counter) with the lock-up on my 7G box, before it does lock. Still it makes it very smooth

I see plenty of slip (well it's noticeable on the rev counter) with the lock-up on my 7G box, before it does lock. Still it makes it very smooth

Which car/box is it?

Merc with a 7G box

Merc with a 7G box

I test drove a C180 with that box a year or so ago. Genuinely the worst gearbox I have experienced - ever! I was considering a C220 Estate as a work horse/long distance mobile, but changed my mind based on that test drive!

As you say, slipped all the time, and could you make it downshift and stay downshifted for deceleration - HELL NO!!

The difference to the 7G DCT in my BMW 135i was like stepping back 30 years!

I did like everything else about the car tho!

Edited 22 August, 201411 yr by josedebardi

I test drove a C180 with that box a year or so ago. Genuinely the worst gearbox I have experienced - ever! I was considering a C220 Estate as a work horse/long distance mobile, but changed my mind based on that test drive!

As you say, slipped all the time, and could you make it downshift and stay downshifted for deceleration - HELL NO!!

The difference to the 7G DCT in my BMW 135i was like stepping back 30 years!

I did like everything else about the car tho!

I should have said I have the 350CDi engine. The gearbox is way better than the smaller engine versions. They feel like they are connected by a big rubber band to the engine. My gearbox is definitely less slushmatic than those models. It needs to be more manly, it has at least 460lb/ft of man torxs

I should have said I have the 350CDi engine. The gearbox is way better than the smaller engine versions. They feel like they are connected by a big rubber band to the engine. My gearbox is definitely less slushmatic than those models. It needs to be more manly, it has at least 460lb/ft of man torxs

Mmmmmm torx :P