Besides the supercharger, wheels, seats and mesh grill, do they pretty much share everything the same? Same suspension, controls arms... etc, brakes (besides the R1/100 pkg) shocks... etc. I cant remember, is the trans different?

 

the XJR has a MB 722.6 trans and the XJ8 has a ZF. The engine is different, variable timing on the xj8 and higher compression aside from different induction.

 

As well as the entire air-intake system, coolant system, the electrical part around the engine and as much as I've seen - the exhaust system is also different.

 

Here are differences:

The Brakes in the front are a larger diameter than the XJ8's 12.0, upsized to 14" in the XJR. Rear brakes remain 12.0in diameter. They are 4 piston fron, 2-piston rear in both variants.

The interior of an XJR includes a subwoofer (rarely true on N/A cars, besides the Vanden Plas), and only supercharged short wheelbase cars get a 2nd cigarette lighter mounted in the rear. The XJR also included a wood steering wheel, a rarely fitted option in a N/A(normally aspirated) car. Heated seats were available across the range, and, again, more common on the R. (may have been standard equipment)

Also, despite the stereo setup looking almost the same across the range, supercharged models have a navigation system in there. It isn't even as much as a 256x256 screen, though, like a bigger screen in the XK. It isn't colour either. (very outdated.)

The XJR runs 8.0lbs of boost out of an Eaton M112 Supercharger. There are twin intercoolers. The VVT system was removed from S/C cars. Engine is otherwise the same basic 4.0 unit.

The shocks in the XJR are contolled by CATS, an adaptive damping system which scans the road to determine response. The N/A cars lack this, and has no adaptive suspension. Aside from the Sport, N/A cars do not have a rear sway (anti-roll) bar. The XJR also has a Mercedes 722.6 Gearbox (developed in part by ZF), whereas the standard car just has a ZF 5HP24.

The rear mufflers are different, with larger tips on the XJR. There is also less chrome trim on the R. The rear declid trim is painted on Sport and R models, chrome on the rest. The grill surround is the same story. (The sport retains slats, the R has mesh)

The shocks are Bilstein Sport on my XJ Sport, idk about the adaptive ones on the XJR. The N/A car has Bilsteins, but not a sports variant.

The setup for unequal-length wishbones is the same on N/A and S/C cars.

The Compression is 10.8:1 in the regular car, and 9.0:1 in the supercharged car.

The XJR has a kickdown switch, located under the accelerator, and the standard car does not. It has no kickdown switch, but responds in kind when flooring the accelerator.

 

Xjr has two fuel pumps and also a different EGR ( exhaust gas recirculation) mechanism, an electric fluid pump for the supercharger, a different s (sport) button...and...a rear sway bar, different thermostat housing, different TCM, and different communication path for internal computers than the xj8...I know I am forgetting a few other things too...

 

small niggle:

Not all "R" models came with CATS.

 

Another small niggle: not all supercharged models have navigation (mine doesn't).

 

I believe CATS started with the 2001's ........ but not all of them had it ...... all the 2002's did. In the USA all the R's had NAV by 2002 - upgraded audio -- rear heated seats

The XJR is one of the rare examples where buying the more complicated version of a car is actually getting more reliability.


The supercharger on the R's is very reliable and requires almost nothing. The R has better brakes -- no VVT -- and the MB transmission is extremely durable.


Buying an unmolested 2002-2003 XJR is the way to go when entering the X308 club -- the extra few thousand dollars will be rewarded in both fun and minimized pain.

 

What's the best/easiest way to check if an XJR has CATS?

 

Open the hood and see if the shock has an electrical connection going to the top it -- The shocks have a black plastic cap covering the top.

 

Up to VIN 853935 the XJ8 had 305mm discs,
From VIN 853936 the size was increased to 325mm
The R always had 325mm
The calipers were always the same across the model range

Obviously we're not talking about the brembo/R1

In the US CATS became standard only on MY 2002, as the NAV
The "R" has a cooling fan in the ECM box

 

what about front suspension components? Control arms, tie rods... etc

 

On the suspension, are the springs different between the 2 cars? I have an short wheelbase 99 XJ8 with 16" rims and what I believe is the normal touring suspension. I have worn out dampers and i'm considering replacing them with the Bilstein sport suspension dampers.

 

The main difference between sport and comfort suspension,

rear anti rolebar fitted
thicker front rolebar fitted (blue as against red in comfort)
springs might be stiffer rating - I'll check the parts cat - probably are...

Mine has 'SuperSport' suspension fitted ;-)

 

Much appreciated