Tiptronic Kickdown in Top Gear

[GJD]

Hi

 

I can see this issue is being discussed in the "Advantages of VVTI thread" (and loads of other past threads), but I'm after confirming as best as possible the particular detail.

 

There's lots of mention of the problem with speed delimited Tiptronics where at high speeds they can kick down from 4th to 3rd, redlining the engine (or even exceeding redline?) and presumably hammering the gearbox hard. But it's a bit vague what exactly causes this "feature" to happen.

 

For people who've experienced this or know what's going on, does this only happen at FULL throttle, or is it triggered by reaching a certain speed? In other words, can I confidently drive as fast as I like in top gear as long as I don't push the load pedal ALL the way to the floor?

 

Thanks

[Carl]

I cant explain technically why this happens on the VVTI but I can confirm the same thing occurs on my Auto TT. If I kick down(foot to floor) at 80 mph then it drops two gears causing the engine to rev to redline and bounce of it. If I kick down around 100 then it will only kick down one gear and is fine... (Of course only on a track)

I always thought it was because the delimiter put the clock out so that the ecu thinks the car is going slower than it really is and is miscalculating when it can actually kick down but I have been since told that this would not be the case as the delimiter does not take a signal from the speedo.

I am led to believe that it is either faulty gearbox, kickdown cables are in need of adjustment or else kickdown sensors need resetting.

Im probably talking rubbish tho so I'm sure someone more knowledgeable will correct me shortly asnd in turn possible en-lighten me to.

 

Carl

[Pete]

This old chestnut.

 

Basically the VVTi was limited to 120(ish), this we know.

To overcome this limit a delimiter will cap the speed signal returned to the ECU. It thinks you're doing less than the limiter - but in fact you can be going much faster.

 

Now - you put the peddle to the floor, the ECU/gearbox map thinks - that's fine, we can go to third as we're doing 115 (or whatever the cap is) so it does, but in actual fact you might be doing 150+

 

Only way to overcome this I believe is to replace the ECU or hack it to remove the internal limiter (unknown territory). The gearbox change programming may not even be mapped beyond this point even if you could do this.

[GJD]

Thanks Pete

 

I know it's an old chestnut, but reading some of the old threads about it I wasn't clear exactly what the trigger is and what I should avoid doing. From what you're saying, it sounds like you think it's a case of pressing the right foot far and/or fast enough to trigger a kickdown from 4th to 3rd - is that right?

 

I didn't buy the Supra for serious track use, but it would be a shame not to put it through it's paces so I'm considering taking it on a track. I can see in some of the other track day threads that people seem to survive it with Tiptronics (including yourself Pete?) but I wouldn't want to do it without being confident that I knew how to avoid this "feature" knackering the car.

[Pete]

From what you're saying, it sounds like you think it's a case of pressing the right foot far and/or fast enough to trigger a kickdown from 4th to 3rd - is that right?

It'll do 150 leptons fine if you don't put your foot flat to the floor - so I've heard.

I can see in some of the other track day threads that people seem to survive it with Tiptronics (including yourself Pete?) but I wouldn't want to do it without being confident that I knew how to avoid this "feature" knackering the car.

Depending upon the track of course you'll probably find it hard to get beyond 120/130mph max speed anyway.

Certainly at Llandow I was only somewhere around 100 (not that I really looked as I was too busy focused on not hitting anything!)

[wile e coyote]

Mine will kick down if you plant your foot but i have been over 150 leptons (once and not again)and not kicked down

I think if you want to go on a track this will not be an isu as dout your be doing those speeds

 

Doh you beat me to that

[Pete]

Doh you beat me to that

That's why you never catch Road Runner! MEEP MEEP

[wile e coyote]

I know mate constantly chasing the dream

[vvteye]

The kickdown problem took out my old gearbox (with Lucifer at the wheel)

In the end I went manual so if anyone wants a recon tip gearbox with less than a 1000 on the clock.. then get in touch.

 

I love threads for a free bump

[nige]

My J-Spec auto will kick down at 100leptons but change up again at 120/125,and just about redlines and I dont have any gearbox problems,my two mates supras do the same.

[vvteye]

It's a specific issue with tiptronics which have been delimited