Don't even bother, for a naturally aspirated Jaguar those things either do nothing or are actively dangerous. Turbo cars will respond to a chip, but again your car won't get any real benefit from it. Just enjoy what performance it has; feel free to do bolt-ons mods like exhaust and intake, but be aware that those will make very little difference for actual performance, more so for the sound it makes.

 

Jaguar performance chip = snake oil....

 

the easier some car mod is to do, the less likely that it does anything. this is closely related to how good it looks or inexpensive. if you wish to go down this route, the shop performing this modification must provide you with before and after dyno results for your car and a warranty their work. extra performance can probably be obtained through polishing the cylinder head ports and changing exhaust manifolds, but both are easier done and sensible during a rebuild. additionally increasing cylinder bore and/or changing stroke will make a difference which is why the stroke was lengthened to make the 4.0 into a 4.2. please note that there is a trade off with this change. i have driven the newer XK with its larger displacement and more power. it is nice but not that amazing smooth delivery of the 4.0. this is why the engine to have might be the 4.0 supercharged. you have the 4.2 which some find to be more drive-able. perhaps you should look for an xkr and not decrease the value of your xk8. it is very difficult to make these cars into something else. this short discussion is to help you to have a plan and manage expectations.

 

I've always subscribed to the policy that the best way to up performance is to buy a car that has it. I wanted my XKR to be faster but it is too expensive and iffy to try to modify it. I
brought home a Mercedes E550 that will do 0-60 in 4.4 and is naturally aspirated, just a big engine. I keep the XKR in the driveway to look at and drive in the country on Sundays. It's much prettier than the Merc. Perfect solution for me.

 

I should have mentioned that most cars this old are down on power around 20% due to worn sensors and adjustments out of date. If you replace the plugs, ALL filters, MAF and O2 sensors, clean and match the injectors (done by an injector guy) switch to synthetic fluids you will get much of it back. 20% power increase is a big one. You would not get nearly this much from a chip, plus it will run better afterwards whereas chips can reduce drivability.

 

 

I changed all my plugs, all the fluids etc even thought about having the car tuned/chipped. I found though that replacing the MAF sensor gave the biggest change. After changing the MAF I visited a friend where you have to turn out onto country road. Problem is there is a blind bend in both directions and when you pull out you have to do it sharpish in case someone comes around the corner. So I stopped as usual. Could hear or see nothing so I put my foot down ............ and nearly planted the car into the hedge opposite. The power increase was not massive but noticeable.

Dead easy to do to :- https://www.jaguarforum.com/showthre...l=1#post940168

You will let us know if you try it wont you?