Hello,

did the pulley upgrade and ecu remapped with extensives dyno runs before, during and after.

End results are 707nm of torque and 564hp for now.

Strangely now when hitting the pedal hard while on manual mode of 'S' transmission setting + dynamic mode, The tranny would kickdown on its own, rev all the way up and wait for a paddle gear change.

before the tuning, manual on S mode was manual with no automatic kickdown

Also strange, lets say we re on 3rd gear so number 3 is displayed on the dash.
When the unsollicited kickdown arrives, gear changes for 2nd but the display still shows 3 like if the gearbox was doing something on its own w/o telling rest of the car.

I read the gearbox is speced for 700nm and suspect the tcm does the kickdown for safety reasons or something. I dont want to step down to say 699nm if I am not sure it will fix this annoying behaviour that is more expected in non manual modes.

I am specifically looking for feedback from members who went north of 700nm, had same issue and came back just south of it for the problem fixed.

Thanks in advance

 

I don't have any answers for you but i'm interested to find out more. Subscribed to this thread.

 

Sure it's kicking down and not just locking up the torque converter really quickly?

 

Kickdown behavior as follows :
-gear 3 engaged
-pedal2metal !
-car pushes hard untill 2500 rpm
-then switches 2nd
-pushes hard untill end of rev range / limiter hit
-waits for you there to switch gear again (s manual mode)
-you switch up and then back to 3rd ratio

During the whole thing gear displayed is 3 ..

 

Wow, sounds as if you have quite the motor... more than I would need though
Have no idea why the indicator doesn't change, but why worry/care, the tach is all you need?
Surprised that the original program would allow WOT/pedal2metal to hold a high gear at sub optimum/low rpm... Think this is the most likely situation to cause serious engine damage due to the very high cylinder pressures (knock sensors may well be dialing things back) and it surely will not give you best acceleration, how many horses would you think around 2500rpm? (not many)
When I tracked a VW R32 (DSG auto)best laps always seemed to be in S auto mode, think our Jags likely be the same..
If you were cruising in 6th would it not drop down several gears if floored?
I am fighting the itch to own another real manual tranny, maybe an M3.
Regards

 

Before the mods, manual was manual, no kickdown.
There are many situations where you do not want an unsollicited kickdown to happen, especially during corners or on any splippery surface when you already focus on pedal vs traction.

I will have access again tomorrow to the torque power curves and will answer then the 2500 rpm question. You should get a manual if you like it I actally have a strong preference for manuals. My issue definitely tied to the automatic box.

I thought it is the TCM and apparently nobody knows how to reprogram it. Anyway, if I dont get anymore feedback, I will ask my tech to downgrade the torque a bit and we'll see.

 

Remaps often lift the torque limiters and/or change how and when the torque converter locks up. Locking up the torque converter suddenly can feel and sound like a gear shift, hence I asked the question - are you sure it is actually changing down a ratio in the gearbox and not just locking up the TC quickly?

 

But, if you are modulating the throttle for traction then surely it would not kick down?
If your dyno numbers are quoted at the rear wheels where measured then that torque value will be way higher at the trans.. like may be 800..
I have often been wrong, but I would not hold WOT in a gear that kept the rpms below maybe 4000, it will load up everything, pistons, rod/crank bearings, tranny, but you will get better mpg lol.... better for the drivetrain to use a lower gear, more rpm and part throttle for the same performance
The VW dsg would upshift at redline in manual, that is not good, at least on the track.. but easier for max performance on the street...
Also do not know when our torque converters lock up, I think the torque going to the rear will drop when it does... my experience is that they are mechanical clutches, not something that will be happy happening often at WOT I think...
Just a reminder, hp is calculated from torque which is what you measure on the dyno.. guessing the SCs have a fairly flat torque curve, so hp will be somewhat proportional to torque, might be less than 250 at 2500rpm..(if you reduce torque you will reduce hp)
Interesting

 

looking at dyno charts, at 2500rpm we're :
- torque 650nm vs 560
- power 230hp vs 200

 

Thanks 8bit and qcktvr for your inputs

Excess Torque is most probably the reason.

I will come back to the tuner for a brake job nest month.
anything I can learn from XKR tuning in between I will take

 

It''s not exactly torque, the engine nor transmission cannot measure torque, it'll be a function of airflow at rpm & load or throttle position which is used to estimate torque, and implement a torque limiter. The tuner played around with the torque limiters I guess...

Plenty of these cars have been tuned and none have been reported to have the problems you're facing. So what has he done that the other tuners haven't?

 

True. Thats more precise and will help with the discussion.
The tuner is very handy and will re-tune if required gracefully ( I guess from past experience with them )

 

I had only one hour drive since I got it tuned. Today is bank holiday. I will have a drive on b roads and check again if I notice special conditions when this happened

 

Thank you for sharing those curves, they make me wish for the same...
Enjoy that drive in the country, after all that work I would be reluctant to change it.... try leaving those low rpms for cruising... (it is not a diesel)
Good luck

 

No pb changing a bit some parameters and actually working on the car is a pleasure.
The car will undergo an alcon brake conversion next month from the same guys anyway.\

Today's cruise was inconclusive as I had a chance to let my brother drive it (former rally pilot ) and did not test myself. Today was 17C outside + sun so we were able to get the top down and enjoy weather and engine sound. I will use it again tomorrow and will be driving it most of the time. I'll see then.

BTW, the "remote top" that our friend Steve Klonsky is making is a treat. Made our ride simpler and more enjoyable with the small rear windows up with soft top down.
Every one should buy it

Well I realize this post had nothing to do with my issue but err, that's a forum !

 

Hello again.
After some business travels in this troubled period .. I had the chance to drive and relax with the xkr this we.

New behavior is : still kickdowns AND now displays correct gear
Maybe the ECU flash led to some learning phase of electronics ...
Under WOT, Could witness the kickdowns in 4th gear +

Do you have these kickdowns in manual mode as well ?

Thanks

 

If you have an ETG tune you need to drive the vehicle for about 110+ miles (about 180km) for the engine management system to "learn" or adjust to the new tune. That is probably the same for any other new tune.

 

Mine does a kick down in manual mode if I mash it. As far as I know my software is stock.

 

Thansk for the feedbacks. I guess I can stop worriying now

Next step will be alcon brakes conversion. Could be done by end of year if I am lucky

Cheers