Multitronic CVT question

[BrianWM]

A "normal" auto uses a torque converter that uses a non contacting oil filled drive system that creeps naturally. The clutch in the auto A6's (except biTdi) is like a clutch on a manual car but it's controlled by electronics. When the car creeps, the electronics is just slipping the clutch like you would in a manual car.

[jbanfie]

Well in a manual car, when stationary, the engine is spinning, but with your foot on the clutch and 1st gear selected, the wheels, gearbox gears and clutch plate are stationary - obviously. When you let your foot off the clutch slowly, the clutch starts to bite up against the spinning flywheel and torque is transmitted and the car gently moves forward - it creeps.

In an automatic, you have a torque converter which is two pelton wheels (like a water wheel), one attached to the engine and the other attached gearbox input shaft. A viscous fluid surrounds both. The engine spins moving the fluid which pushes up against the second water wheel transmitting torque and the car creeps - if you don't hold your foot on the brake.

Now, in the Multi-tronic and the s-tronic or DSG or whatever, their is a mechanical clutch in the car, but it is controlled by a computer with an actuator in place of your leg! Therefore the creep has to be 'engineered in', that is the computer allows the clutch to bite a bit when the car is stationary to simulate the creep of an auto box which people like for maneovering without having to push the throttle pedal.

The questions then asked are whether this small amount of bite is still applied when the brakes are on and I guess the answer is yes, unless the brake pedal position and inclination of car is also monitored and factored in, otherwise on slopes it would all be a bit nasty with creep on or off as a binary point in the release of the brakes, if you follow.

That said the s-tronic owners obviously find that the amount of creep is not enough when reversing up hills, which must be a nightmare! If you park on a steep steep hill, then the manual and auto cars will have the same problem? Which is why your then get the hill start option.

Give me a manual box and a handbrake anytime!

[fysmd]

I'd like to know if the drag on the clutch, which is essential for the feel of the car, still happens with your foot firmly on the brake or when the hill hold is in operation. It'd be a pointless waste of energy, clutch lining and you'd think the software would know it isn't needed.

Me too - I suspect it's still happening with foot on brake AND auto break AND parking break active. I've tested all three and the small RPM drop is there in all cases. in N or P the engine speed will lift by approx 400 RPM.

Not tried it but I guess there are electronics to stop this after some time, much like auto hold will deactivate when the "stuff" gets too hot and then engage the parking break.

[rizday]

Great summary - I posted last year about how much worse my multitronic was compared to my old auto reversing up my drive's slope. It's a delicate balance and it's made my wife reluctant to reverse the car out at all. Lots of play and dead spots moving between brake and trottle.

[retired99]

S Tronic (VW call it DSG) has two concentric clutches. One controls gears 1,3,5,7 and the other 2,4,and 6. As there are two clutches when you are in a gear driven by one of the clutches a gear operated by the other clutch can be pre-selected. To change gear one clutch is disengaged and the other engaged. Because a gear selection has been made prior to changing gear the change can be made very quickly. Porsche call this PDK, Porsche Doppelkupplung; Porsche Double Clutch.

Multitronic is a continuously variable transmission connected by a multiplate clutch to the engine. The ratios are virtual in the sense that they are predefined points within the variable range. Prevents the situation where the engine stays at a constant speed while the speed of the car varies. Suspect this because people don’t like this behaviour.

The gearbox fitted to the BiTurbo is a ‘conventional’ 8 speed auto box with a torque convertor.

[shabazmo]

I must be the only one that loves my multitronic. I have not had any problems yet and find the driving ver smooth.

[bmoster]

I have had my C7 multi for a few weeks now and have no problem with it. It is ultra smooth. I can see why drivers who like to push their car to the limit may not like it but it does encourage a relaxed driving style.

[Timothy Nathan]

I agree that at any speed above 5mph it is great.

For very low speed and critically tight manoeuvring it is truly frightening.

[fernar]

I second that - especially when there is any type of gradient.... on the flat I have no problem...

I wonder if there is any chance that Audi will release a software update that will help low speed gradient manoeuvring...

[Timothy Nathan]

Of course, the clutch slipping when stationary issue is resolved by Start-Stop.