VAG - DSG or CVT?

[PerfAdv]

Which is better? Sadly VAG only offers the DSG in transversely mounted engine, so the A4 does with out it. In the A4 you'll have to settle for either the innovative CVT or a regular automatic (or Triptronic).

The A3 features the DSG, as do certain VW models. This is the dual clutch system, a clutch pedal-less manual. It can operate in auto mode or the gears can be selected by gear selector or paddle shifters.

The CVT is a very different type of automatic as it doesn't use any set gear ratios as such. What it has are two pulleys that change diameter, this effectively changes the gear ratio between engine and drive wheels.

Not so much a poll of which people will vote but just a thread to gather some opinions. So, which technology do you consider superior? Have you any experience with either?

[fpv_gtho]

Havent experienced either, but from reports CVT's are rather awkward to get used to, but in theory should be faster. I would rather a DSG though for still operating like a normal gearbox and giving you that difference in engine note

[pimento]

I'll take a normal manual over anything else.

[PerfAdv]

Hard to argue with manual but some of the auto-shifted options are becoming more appealing. The DSG, which is VAG's sequential manual gearbox, gets better city mileage and is quicker to 60 than the manual. (Jetta DSG v. 6-spd man.)

Between DSG and CVT, I prefer the DSG as well. It's just that the CVT is a novel and seems like the next step in automatics. As an engine makes most power at certain RPM, the CVT holds that RPM and gradually changes gear ratios to increase speed.

I test drove a Honda CVT, they used to have it in the Civic HX in the late 90's. It's a strange feeling as the tach stays at the same RPM and the speed keeps increasing. In the Civic atleast, they'd set it up so that under partial throttle the car picked a lower RPM to maximize economy but at full throttle acceleration the CVT sets the engine RPM for max torque. It is a strange feeling and I decided against it then as it just felt weird and didn't think I could get accustomed...

[drakkie]

Originally Posted by PerfAdv

It's just that the CVT is a novel and seems like the next step in automatics.
...

the first CVT in a production car dates from the 60's (edit: correction, in 1958)

Originally Posted by fpv_gto

but in theory should be faster.

A hell of a lot !!! Before they were banned in F1 for being too fast they drove 10 seconds a lap faster than other cars

so for me i'd definately get the CVT, less components so less to go wrong,proven concept,perfect for driving n the mountains,and same reverse speed as forward (and it is a Dutch invention offcourse )

[Matra et Alpine]

Originally Posted by drakkie

A hell of a lot !!! Before they were banned in F1 for being too fast they drove 10 seconds a lap faster than other cars

Calm down jsut a wee bit, it was compared to manual gearbox and pedal clutch controelled by the driver.
The BIG advantage it added was the driver kept both hands and more control on teh steeering wheel.

The BIG drawback CVT continues to have is that it relies on friction surfaces. So is limited on power and complex ( the days of the simple Daf rubber band and cones are no more )

It's infinite variability is the BIG win to be able to keep the input engine either runnign at maximum power, maximum torque or maximum efficiencey dependant on wht the driver wants. BUT, modeern ones are running "psuedo" normal gearboxes with ranges adn shifts put in by computer so the drivers are comfortabel with it.

[mikelzapi3]

one question, are the maximum torque rpm and the maximum efficiency rpm the same rpm ?

I ask this because in thermodynamics they teach us that one engine gets the maximum efficiency when the combustion is the most perfect, and at the same time the presure against the piston is the greatest, producing the greatest torque.

About CVT and rpms, If you want the maximum power (in racing for example) and you keep the engine all the time for example at 8000 rpm, isn't the engine going to blow?
With other gearboxes the engine takes a break when you change gears.

[PerfAdv]

Originally Posted by mikelzapi3

one question, are the maximum torque rpm and the maximum efficiency rpm the same rpm ?

I ask this because in thermodynamics they teach us that one engine gets the maximum efficiency when the combustion is the most perfect, and at the same time the presure against the piston is the greatest, producing the greatest torque.

In scientific circles "efficiency" is used differently than in normal speak. Normal use of the word means using the least amount of fuel. The engineering definition of maximum efficiency means; an engine's ability to do the most work, which is max torque. At least this is my understanding. Maybe someone can more accurately describe this.

Also, I've wondered why are engines referred to as air-pumps. Seems when you don't know what just say, "Well you know an engine is just an air-pump." I mean, where are all the air pumps that they've become the example to describe the common IC engine!!?

About CVT and rpms, If you want the maximum power (in racing for example) and you keep the engine all the time for example at 8000 rpm, isn't the engine going to blow?
With other gearboxes the engine takes a break when you change gears.

Max torque is usually a lot lower RPM than max horsepower, which is closer to redline. Also, pulling under load from very low RPM and over-revving are more detrimental than constant running at say 70-80% of redline. Max torque is where an engine pulls hardest, so that's where a CVT would work most efficiently, meaning be able to do most work.

[drakkie]

Originally Posted by Matra et Alpine

The BIG drawback CVT continues to have is that it relies on friction surfaces. So is limited on power and complex ( the days of the simple Daf rubber band and cones are no more )

The (dutch) company VanDoorneTransmissions (VDT) have found a way around this problem. I don't know the details but it is able to cope with very high levels of torque and hp...

[Matra et Alpine]

Originally Posted by drakkie

The (dutch) company VanDoorneTransmissions (VDT) have found a way around this problem. I don't know the details but it is able to cope with very high levels of torque and hp...

It's a steel chain insteadn of rubber.
Modern "lubricants" actually used to make the steel surfaces "stick"
Not seen any info on weight of a raliable high torque version OR expected lifespan.
They've been working on this since the late 90s.

[hightower99]

Umm doesn't an engine produce the most work at Peak HP? I mean because HP is a direct measure of how much work a motor can produce? Torque being a stationary figure and a measure of force only? So if you want to accelerate as fast as possible shouldn't the engine be revving at peak HP?

Personally I think I would love an adjustable CVT (where I can adjust what RPM the engine is doing) so I can choose between max milage and max power. I get shivers when I think about a constant 400hp launching me forward...

[drakkie]

Originally Posted by Matra et Alpine

They've been working on this since the late 90s.

A couple of years ago they succeeded.One of the first applications of the CVT for bigger engines was in the Nissan Murano... I'm sure there have been more cars...

[quattro_20v]

You forgetting Audi's multitronic? They use it for quite some time already now. It's also based on the CVT and uses a chain aswell.

[Matra et Alpine]

Originally Posted by drakkie

A couple of years ago they succeeded.One of the first applications of the CVT for bigger engines was in the Nissan Murano... I'm sure there have been more cars...

THere have been a few public reported problems with the CVT tho'
Of course it means nothing unless we know how many DONT report problems

[hightower99]

It seems to me that everyone has forgotten about the must effective and best CVT there is!?!

It is used on most diesel burning trains in many countries.

Basically the engine revs at whatever you need (max mileage or max power) and it turns a large generator. The power from the generator goes to electric motors at each wheel meaning lots of torque and very low losses. Hydraulic versions of this system exist but they are not as efficient.