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MG MGF Technical - Driving the MGF CVT
|I'm looking for technical driving observations from owners of the ZF VT1F CVT in the MGF. I'm trying to clearly understand how it works and how it how this device functions, and how to drive it effectively.|
This same transmission is in the new MINI One or Cooper.
Each of the modes has a distinct set of behaviors. D is different than SD, which is different than Steptronic. I believe that the SD mode to have slightly better acceleration than Steptronic or D. There is good engine braking in all modes. The transmission seems to be near bulletproof, and fun to drive.
|I'm shown as a non-member above, which isn't correct?|
I've done some significant time recording observations on this transmission and trying to carefully sort out how it works. There are many functions and subroutines that operate behind the three primary modes given to the driver (D, SD, Steptronic). These functions help with setting off, low speed situations, and engine braking.
I'm looking to share and validate this information.
|I don't know too much about the technical details of the CVT box in my 2003 TF 120, but since I have had it I have experimented quite a bit. In general highway driving I tend to leave it in D after reaching highway speeds. For passing or more spirited driving snick it into SD and the performance is markedly better. Have not figured out how much the petrol consumption suffers though.|
In steptronic I find it is easy to miss the change points. With 6 speeds the revs rise quite quickly in each gear. Going down the box it is easy just to let it decide for itself when to change down, and this is probably not getting the best performance out of the car.
Recently I tried both SD and steptronic in a tar sealed motorkhana. Short twisty little courses, so speeds were very low. One run in each mode for 4 different tests. I did not come to any conclusion as to which was best. The difference was only a few tenths of a second in general, and this may have been all due to driver errors. Massive understear and lack of enough grunt to break away the sticky rears did not help my times. Last year on the same car park in my MGF, very wet, and I could get the back end to break away and help me get around the tight twisty bits.
One run using SD, I inadvertently managed to get it into steptronic, from reverse, and as it defaults to 2nd gear, it bogged down for a few seconds until I realized and knocked it back to first again. I need to do some tests in a straight line some time.
I would be interested in seeing your findings on timings.
|I've been driving a Steptronic for nearly two years now. It was my wife that bought the car and went for the auto box. Not long after that she got a company car and I inherited the F. If the car had been for me at the time I would probably have gone for a manual box but now I love everything about the car and would buy another Steptronic / Stepspeed tomorrow if I had to. Very underestimaded type of transmission in my view.|
Anyway, I normally drive about in "D". This is great for urban and motorway driving and I find it quite economical. On a trip to Le Mans this summer I was getting about the same MPG (37) as someone with me that had a VVC. Only drawback is that because the revs are usually under 3000 rpm I find is that when you lift off the throttle the engine doesn't help to slow the car and you have to use the brakes more than normal. Other drawback is that it's a bit slow on acceleration and I sometimes have to knock it into Sport Mode to keep up with other Fs when they floor it, particularly on hills.
In Sports Mode the car takes on a different life. It revs higher and so when you lift off it behaves more like a manual car and slows you down without having to brake. It also accelerates much better and has no trouble in keeping up with other Fs (MPi and VVCs) particularly round the twisty bits. It keeps being said that you are always in the right gear and it's true - your engine is always "on the boil".
To be honest I rarely use the 6 speed sequential mode. I find that I can go quicker in sports mode and don't need to bother about changing gear. However, the thing to bear in mind is that the car won't let you over or under rev the engine - it changes up and down when it reaches its upper and lower rev limits. So, why not let the gearbox do all the work and keep the engine at more or less the same speed where it produces maximum torque. The only time that I use this mode is when it's slippy and I want to keep it in the one gear and control the power with the pedel.
In general this type of transmission is a bit slower off the mark but they come into their own once they get moving and don't let anybody kid you into thinking that they are the poor relation when it comes to speed from A to B. The only thing that I've done to my/our car is fit an ITG Maxogen air filter and that made a big difference in getting rid of the slight lag when you hit the loud pedel.
Hope this helps.
This thread was discussed between 26/10/2003 and 27/10/2003
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