I'm working on making it happen (I've only had it a week and a half). But it's not as easy as giving a credit card to JEGS or looking through eBay.

I'm particular on these projects too. And getting a feel for it first matters. I was skeptical of its handling for lack of feel. But that changes when you push it. I pushed it around an wide intersection at around 40-45ish - it didn't balk in the slightest. I'm not into drifting but the XKR does it so well. When pushed on the turn it seems to let you know exactly what it can do - and it can do a lot!

The best XKR You Tube video in my view is:

http://www.youtube.com/watch?v=X1jN87hMqSI

Any XKR owner's gotta love it.

It's worth the 8 minutes. Does that guy have a great job or what?
He so often has raved of the XKRs on television that Jaguar should give him one. He's their best promo-man.
His comments are accurate. It looks better than it's German counter parts. "It's brilliant" and "spectacular" ... "but imagine how good it'd be if it had more power" (the 4.2) Well put and he defined how it can best be improved. "more power."
Critical analysis at first. Then excellent high speed power drifting video cuts worth watching in the middle. Finally a work-course driving contrast to the Aston Martin trying to lose the XKR at the end.

 

That's the special edition that never was

 

Wait a minute...does the Aston have a limited slip diff? And whats the gearing in the aston?

Furhtermore: -----> http://www.ajsengineering.com/Services.html

notice the "powerlock upgrade"

 

To answer my own question....

http://www.remarkablecars.com/main/a...artin-db7.html

"A limited slip differential and new rear axle mountings ensure optimum traction."

Now to find out if the trans is the same, and if it where we can get the software....

 

On the other hand you'll still be handicapped by a 30 year old frame hacked up into a convertible...what the hell, you should just give me your Jag it's clearly hopeless ;P

 

[QUOTE=dfwx;179659]
I'm particular on these projects too. And getting a feel for it first matters. I was skeptical of its handling for lack of feel. But that changes when you push it. I pushed it around an wide intersection at around 40-45ish - it didn't balk in the slightest. I'm not into drifting but the XKR does it so well. When pushed on the turn it seems to let you know exactly what it can do - and it can do a lot!
[COLOR=Red]
and it handles very well at 50-60 under over passes in the uturn lanes, and walks out sideways with alittle oversteer with trac off...I meen not that ive done that to a customer car. I do have to drive preowned and lease returns to make sure ALL systems function correctly

 

You know...

This idea that the rear end is fixed and cannot be changed because there is no way to modify the software hardcoded into the TCM, got me thinking. I've been lurking around on this thread for a while. Mostly because I wanted to see what someone who thinks a 400hp XKR is too slow and has the funds to play would do to it.

I'm an EE, and I came to this conclusion. The only obstacle to changing the rear end gear ratio is the fact that the TCM will complain if a different gearset is used and the output shaft revolutions don't jive with the math of what the final drive is SUPPOSED to be right? While people have been unsucessful in finding someone who will reprogram the gear ratio in the TCM, despite that the same 6 speed ZF autobox is used in BMW, and Mercedes applications which apparently someone has managed to develop software for. If you can't modify the internal programming of the TCM, why not modify it in another way, externally.

So, the output shaft speed sensor is what's telling the TCM how fast the output shaft is turning with pulses. All we would need here is a microcontroller of some sort between the TCM and the output shaft speed sensor, to take the pulses from the sensor, and slow them down as to replicate the original rear being in there as far as the TCM is concerned. since the final drive will be altered by a known percentage, all it would have to do would be to slow down the output by a fixed percentage and as far as the TCM is concerned the rear never changed right?

Now I believe the car also uses the output shaft sensor to determine vehicle speed. These boxes exist for that purpose in other applications (correcting speedometers due to gear ratio or tire size changes). The thing I wonder is could you feed the real output of the sensor to the PCM (which I believe drives the instrument cluster) - I haven't looked at the XK's schematics. Yet modify the value at the input to the TCM, as to keep it from complaining about the gears.

Just food for thought.

George

 

And on the tcm and gearing, while i havent seen anyone yet swap gearing, i have seen tire/wheel changes and no adverse affects other than sometimes a overly sensitive trac/asc system intervention. And when programming new instrument cluster it asks for wheel sze. I dont know why you could not program the ipack as new and tell it it has smaller than actual tires whic eis the communication between abs(speed of vehicle) instrument and tcm. the trans does NOT calculate the speed but the ABS module does through the wheel speed sensor. this info is sent through the network ABS>I PACK>TCM for shifting purposes

 

Now we're talking.

SO how difficult would it be to make such such a thing? Knowing next to nothing about electrical engineering I'm picturing PCB with some resistors on it

 

It makes perfect sense. The question is actually applying the concept, ie do it in a real usable form.

 

Let's just say not quite that simple. BUT. It's been done already. These things are popular with the jacked up truck crowd, that puts much larger than stock tires on their trucks.

This one lists all the specific VSS wire locations.

http://www.truckcustomizers.com/prod...alibrator.html

Now the key point is if one of these units can be adapted to the Jag Vss signal then it would be cake.


What's the specific model of the transmission in these cars? Let me see if I can dig up the vss output on them.

Brutal, I realize you can calibrate the dash, but does that affect the TCM? Or is it simply for correct display of road speed and odometer mileage recording. Do you know? Also, you mention programming the instrument cluster based on wheel size. Do you have infinite adjustment, or just the options that came on the car as possible factory options. Can you tell the dash it's running on 12's if need be?

George

 

I'm positively tingling.

 

Yes!
Do you think this might ACTUALLY lead to something workable? As in workable in MY 05 XKR?

 

What's the exact model number of the trans in that car? There seem to be 3 types of these speed correction devices, for different vss signals. Let's see if we can adapt something.

It's not that far fetched. It's just a matter of telling the computers what they want to hear.

George

 

I have no idea or even where to look. It's an 05 XKR. Had it 1 1/2 weeks. No shop manual found yet. I suspect others on this thread can look up what the trans code is on an 05 XKR. I'm mostly in the dark on any details.

This is very exciting! This has been THIS has been the only serious question left on my modification goals.

 

So it works like my wife then?

 

LOL... That's great.

So as far as I can tell the car either uses the Mercedes W5A580 (722.6) 5 speed, or the ZF 6hp26 6 speed, like my S-type.

Seems like the 6hp26 made it into the 07+ XK/XKR , and the Mercedes Trans was in the earlier 00 - 03 ones, but I can't find a definite answer on 2005.

I'm sure one of the Jag techs can tell us.

George

 

Sometimes it seems like the 04-05 XKR the mystery one. Time to time those two years are just off parts lists. No luck finding a shop manual - CD or hardcopy.

Follow up to Brutal...
Other than little things I'm doing (KN filter, emblem, change thermostat, probably something done cheap to add a little exhaust tone) I plan to do it all at one time - exhaust, motor work, gearing, wheel/tire combo - rather than piece-meal. The specific reason is that AFTER all it on it, then have it ECU tuned probably by Eurotek. Since ECU tuning is not cheap, doing it piece-meal wouldn't go right. Second, I tend to lose interest - as in moving on to the next whatever project or goal. So when I do something it best take it to the end. That also is why you may sense some impatience on my part. I want to round up all the components and get it done.

 

Did i miss the 2.5 - 3.5 lb boost pulley in all this? That seems like a no brainer...

 

No you cant pick and choose, but at least you can pick the smaller avail on screen. The vehicle speed is given to all modules from the ABS module. not from the trans. thats what the wheel speed sensors are for and how the vehicle speed is calculated.