There are no changes made to the transmission (TCM) however because of the way the PCM and TCM work together, a more aggressive engine tune results in more aggressive operation of the transmission, kick down, shifts, etc are also more aggressive.

Changing the pedal operation would be a very time consuming process, not really interested in going down that hole.

In the stock XKR-S tune there's no real difference in the pedal sensitivity over the XKR, however in the modified tune since the torque limiters are raised the throttle pedal does become "more sensitive".

 

Apologies I was not aware, everything I've read indicates that the tcm was standalone and that no changes to the ECM would change the map or driving characteristics of the TCM. For instance the gear change points/speeds would remain the same.

I've had my TCM flashed and even with the engine in stock form it's made a world of difference when driving in a 'spirited' (allegedly officer) manner.

On the pedal front there are several companies that offer a piggyback pedal system upgrade and it's not too expensive.

 

Piggy back devices such as Spring booster do absolutely 0 for performance. All they do is raise how responsive your pedal is. This is not a tune although many tuners change these parameters in the tune to fool the customer into thinking the car is faster.

 

Did you mean a Sprint Booster?

No granted that such gizmo's only give you the same power for less pedal travel, however given the 'less effort' surely it might feasibly shave a few 100ths off?

Also if the TCU was flashed surely it could give you better change points for a 'launch control' situation out of the traps, or are exclusively using the paddles?


Soz for the newbie questions, been at least 15yrs since I did a track or airfield run

 

We had the last drag meet of the season today. Unfortunately the track temperature wasn't high enough for them to prep the track properly so it was probably a lot more slippery than just bare tarmac. My 1/4 mile times were therefore dire with a best of 12.450. The 60 foot times were all over 2 seconds as well but the supercharger loved the cooler temperatures so I smashed my previous highest terminal speed of 121.89mph.

In post 88 of this thread I said this:

Today I proved it with a best terminal speed of 124.63mph!!!!







I also visited the track on Saturday because the local Jaguar Driver's Club had hired the whole circuit for the afternoon. Once again the conditions weren't ideal and as you can see from some of these videos it was raining at times so the track had standing water on it.

This video is of me hunting down a 2014 Dynamic R XKR and demonstrates why you don't buy cheap Chinese tyres!


This one demonstrates the difference in power between an X100 XKR, a 4.2 XKR and my car and features an X100 sandwich:


This is one of me hunting down a couple of 4.2 XKR's:


This one is of me dicing with a racing Mark 2 Jaguar. It handled a lot better than mine and the guy driving races it so is a much better driver than me but, in the end, power wins


This is one of me chasing an Aston Martin DB9. We were supposed to be doing a low speed session with speeds no higher than 120km/h but we might have exceeded that slightly

 

Since tracking Perhaps it's time to upgrade to the BC coilovers and two piece rotors .
Jahummer has a whole thread on the coilovers

 

The track day is just a once a year thing that the club puts on so it isn't worth throwing too much money at it.

I was feeling quite jealous of the guys with the drag radials yesterday though but don't know if it would put too much strain on the drive train if I bought some for my XKR.

 

I went back to the track today and there was a national competition being run so I think they spent extra time prepping the track and the difference was incredible. Little or no wheel spinning which luckily coincided we me trying out first gear/normal drive rather than snow mode after seeing the results of H Jones on the XF forum in his modified XFR-S.

I was startled on my first run as to how hard the car launched and was surprised to get an 11.764 at 123.31 mph, smashing my previous best of 11.925!

I therefore tried a harder launch for my next run and got an 11.645 at 123.09 mph but then didn't get another run for over an hour and a half because they wanted to get the competition cars through.

I thought the track may have gone off by then but managed to do a new personal best of 11.567 @ 123.19. The 60' was a new best as well at 1.756 and I think I would need drag radials to improve on that!

 

Well done mate!

For a while I was thinking we would have to ship the car over to Sydney to get some numbers out of it, it's amazing what a little track prep can do.

 

Now that's more like it!!! way to go!!!

A 1.7 60' and a 11.5sec 1/4 mile is more like it...

Maybe next time you can experiment with Dynamic vs non-Dynamic, and with Traction Control On vs Traction Control Off, either way I think you are finally getting to see what your Jag is actually capable of.

 

Thanks. It is a shame the track was so busy yesterday because I only got half the usual number of runs in otherwise I would have experimented a little more. Once the competition was over and things quietened down towards the end of the day the sun had come out and my car was back to wheel spinning off the line again.

They also only prep the first 100 feet or so of the track because it joins the start finish straight of the race circuit at that point so the car can break traction again when you reach that.

The next meet is towards the end of November so I will see if they have prepped the track as well again.

 

The video from the run:


There was a Dodge Challenger SRT Hellcat there as well. I didn't get to race him but his best time was around 0.1 secs slower than mine as he was struggling with traction. The funny thing was that he had bought a couple of new Michelin Pilot Sport 4S's but put them on the front leaving some part worn Pirelli's on the rear so I suspect that contributed to his traction issues!

 

Probably wanted to burn ‘em up, so he could justify replacing them.

 

Yes, and the contribution is that his traction was IMPROVED with the worn Pirellis.


Michelins suck.

 

u102768 amazing 60ft ! What tires are you on?

 

Thanks. It is amazing what a difference a well prepped track makes. I can see why you guys can launch so hard now.

As mentioned earlier though, the track went off a little in the afternoon so I was back to the usual wheel spinning off the line but I am using Michelin Pilot Sport 4S's.

 

What's size are your tires ? No matter how the track is prepped my best ever was 1.88 , any faster than this I will spin . I'm on RE71r 285/38/19 very sticky, Maybe your ediff makes a difference here ..

 

If you guys want a better launch, why not install a mini-spool? It'll mess with normal cornering, but what the hey?

 

It would probably render everyday driving impossible

 

285/30/R20 so stock.

I think that the e-diff must make some difference and I actually just left the traction control on this time whereas I have used TracDSC on previous outings.

The 60' on my first run was 1.919 which is where I discover how grippy the track was so tried a harder launch and got a 1.795 so tried an even harder launch and got the 1.756. Once the track had gone off in the afternoon I was back to 2.086 and 2.067.

The best 60' I ever got in my 4.2 XKR was 2.22 so you are doing a lot better than me!