after being around the houses in form of a 996 Carrera, mkiv supra and sl500 I find myself back in a jaaaag

Ive bought myself a 2001 4.0 xkr in black and im very happy with it. I intend on keeping this one for a while so ill be tinkering with it as I like to do.

I have had a good read around the forums and web I have come across lots of confliction info in regards to tuning the 4.0 xkr so ill hope to get some clarity on the subjects through experience of members who have done it

the first few point id like to clear up are;

exhaust,
ive read that messing with the oem exhaust for a bit more v8 growl can lose you lots of low down torque, the chap I spoke to said his xkr wouldn't even spin the wheels after he had his exhaust done. is there any truth to this

smaller charger pulley.
some say it false gains and builds up lots of temp, other say its a great improvement ? what do we think.

upgrading the eaton m112.
ive heard the kenne bell name mentioned a lot but I know little about it. also I understand the 5.0 xkr now has a twin screw charger that is much cooler . will this it the 4.0?

thanks for all the input . ill try and load a quick pic of the car

 

Very nice looking xk!
Enjoy it.

 

Looks great and welcome! Time to get searching on here for that info.

 

I can't answer your question on the exhaust as I've left mine stock. I do a fair amount of long distance driving (my reason for buying an GT in the first place) and did not want to end up with an exhaust that "drones" at highway speeds.


In regards to the supercharger pulley, I went with a larger diameter lower pulley vs. the smaller upper pulley. I've been told (don't know for sure) that a larger lower pulley gives you more torque in the low to mid-range. Regardless, I am very happy with this mod.


I also added a limited slip differential and changed the stock 3.06 rear axel ratio to a 3.27. This was by far the best mod I have done.


Welcome back to the Jag family and to the best forum on the Internet. Happy tinkering,


Mark

 

Can't say about the exhaust as I haven't upgraded it (yet). Plan to in the not so distant future so can report back.

The 5.0l uses and Eaton TVS, which is not quite a twin screw but it is certainly more efficient than the M112.

The Kenne Bell is the way to go for big power but it is not for the feignt of heart or wallet. It requires a substantial amount of modification and custom work to install.

The pulleys are the best bang for your buck. If you want to go a further, you can have the supercharger ported and polished, port the intake and go with a larger intake.

Welcome to the forum, and happy tinkering.

 

Welcome to the forum! Has your car been retrofitted with an 05 front bumper cover? It looks nice.

Back to the exhaust... my 05 loves my exhaust mmodifications. Sounds great and has a better throttle response I can tell the difference. I'm going with the lower pulley upgrade..

Enjoy your XKR and enjoy this wonderful site!

 

thanks for the replys guys,


I think ill just get on with it and get it done then. ill report back my results .


the car has an aftermarket grill an lower plate holder, its still the oem bumper skin. glad you like it

 

Reducing back pressure drops boost which and pushes the powerband higher.
The eaton loses its efficiency in the higher power band.

However your engine can breath easier.

So, you have to increase boost to make your exhaust mods work.

You will see a gain of 40-50 HP with exhaust and pulley in the mid range only ,your top end will always suffer.If you port the blower, it will also decrease boost, put improve airflow.Doing all 3 have shown about 450HP at the engine, no tune.

Supercharged cars love cool engines,93 octane and so do the knock sensors that retards and advances timing. You can be pushing all 380hp, in one second, 310hp in another lol.

 

thanks,that's some great info


I think ill go with the powerhouse 10% top pulley and a rear box delete with the over axle part replaced with 2.25" straight pipe under the axle.
im also going to look into additional/improved charge cooling.
again. all input on this is much appreciated.

 

Here is some more information on the twin screw, should you change your mind:
https://www.jaguarforums.com/forum/p...59/#post243827