Looking through engine specs for the Mark VI Golf today, I noticed that the effect of adding a DSG gearbox seems to be reversed depending on whether you have a petrol or diesel engine.
tinyurl.com/qed7ks
Economy is increased by a few mpg for the petrol versions, and decreased by a few mpg for the diesels. There's a concomitant effect on CO2 emissions.
Can anyone explain why? Obviously one's gear-changing habits should change between a petrol and a diesel, but surely Volkswagen could take this into account in the programming of the DSG 'box?
Edited by gpmartin on 02/06/2009 at 20:09
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Most likely down to driving styles as much as anything. A DSG by its nature has to be programmed to prevent damage to its internals first and foremost. Therefore it will prevent the internals being overloaded as much as possible. Thus it's likely it will be in a lower gear than the manual might be.
Another potential reason is that a petrol DSG is likely to be higher geared than the manual as it can more easily drop a gear to maintain/improve performance. A diesel is already high geared so you'll get little extra benefit.
If you're considering one make sure you take a long test drive first in your chosen model and make sure you can live with its little nuances.
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The DSG's from VAG are usually either 6 speed or even 7 speed. The 7 speed usually on the petrols only due to torque.
So I too think this could be down to gear selection and therefore on petrols you have more gears to help. On diesels it might make little difference due to torque - you'd not change gear in a manual as often.
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IIRC it's because the petrols use the dry plate 7 speeder (less internal drag as well as the extra gear) and the diesels use the wet plate 6 speeder.
My personal experience of a 1.6 petrol + DSG was that it really is as economical as VW claim, if not more so.
Why this engine is limited to base S spec I don't know, as it was a decent combination.
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I've never driven a 7 speed petrol DSG, but the diesel is in top by 45mph and if you drive it carefully 1st gear can be virtually forgotten. Get it rolling slightly and it changes into 2nd immediately.
Mine's doing about 40 round town at the moment.
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A colleague who does drive very well bought a Seat Toledo with the DSG box, absolutely drank fuel, i posted on here for him and other's experience was the same.
He got shot of that sharpish and now has a manual Jetta and his normal enviably high mpg is back on form.
Each to their own, i can't abide any of these automated manuals whatever they're called.
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I have just read the answer to this question.....
The EU test for economy for a manual car stipulates the exact speed that the gears must be changed. They are
1st - 2nd 9mph
2nd - 3rd 22mph
3rd - 4th 31mph
4th - 5th 44mph
5th - 6th 62mph
These speeds must be used despite the cars gearing or torque curves.
Automatics have a get out clause that means they can be in any gear they want to be in. These gear changes will suit one over the other hence the difference.
It is in this months EVO magazine with the example of the Audi R8 V10, the manual version is 351g as oppose the DSG which is 327g
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Each to their own i can't abide any of these automated manuals whatever they're called.
Personally I'd much rather have a DSG box on my car, rather than the antiquated auto that I have with a torque converter and planetary gears.
But I am not claiming that you are wrong and I am right - it's just personal preference as you say.
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