Hello for the first time Jag Forums!

At 19, I just purchased my second car, a 2003 Jaguar XJR, in gorgeous dark navy blue with a tan interior. The grandpa car jokes from my friends were quickly silenced by the roaring supercharged V8 , and I love blasting brand new Mustangs and my buddy's new WRX out of the water from the lights, but being a bit of a car guy I'm interested in squeezing a little more juice out of it.

I do have a goal in mind, I want to theoretically be above 400bhp which should not be too difficult considering stock these vehicles are rated at 370bhp. Unfortunately, I live in a somewhat rural area and do not have access to a dyno (which is why I say 400hp "theoretically"). So does anyone have experience modding these vehicles? After some initial research the aftermarket for an 03 Jag is (unsurprisingly) thin. What have you guys done?

My plan right now is to get the s/c pulley upgrades and catback exhaust from mina gallery, a k&n filter and hydroshield for the intake. Will this be enough to add the 30bhp I'm looking for? And will I need more supporting mods, such as a larger intercooler or a retune? Are mina gallery parts quality? What other places supply good parts? Im curious and have a ton of questions, so feel free to answer the ones you can! I hope we can get some modding knowledge out here for anyone who might be interested in the same kind of thing.

Cheers!
Skiv

 

and while im at it, is there a good place to get some headers for this beast? I love the car, but the stock exhaust is just a hair too...humble...for my tastes. Car like this needs to be a bit louder

 

twin screw! twin screw!

I think pulleys and a tune will get you the bump in power you're looking for. I remember reading somewhere that the factory intake is good enough to the point that aftermarket upgrades don't actually improve power at all. Could be wrong though.

 

This is what's on my XJR-100, not sure if XK's still carries it. A bit pricey.

 

Pricey for sure but thats a huge gain, and looks like a simple mod. Labor ought to be cheap if its not DIYable. How does it feel on your car?

 

I've driven several XJRs and mine is by far more potent. Mine had the mod on it from the PO when I bought it so I can't give you a direct comparison of before and after.

 

i got my top pulley from powerhouse . real good quality stainless pulleys . i see that list a top and bottom pulley for the 4.0sc and are way cheeper than post #4's .
it is also much cheeper to get a custom exhaust built . and forget about headers .
as that are not the bottle neck here.
my biggest gain on the 4.2sc was 200cell catalytic converters .
and this was after the 1.5psi top pulley upgrade , full 2.5'' cat back exhaust with x-pipe
muffler delete with 4 resignations installed . mina cold air box and k&n pod filter.
and a replica caldoofy/quickets elbow . i recon there is +50hp in that lot .
I'm using a phone app to gauge hp increase . just so i know we are heading in the right direction . give dynolicios a go its a great app , and was designed for nascar test n tune days so is quite accurate .

 

This is in regards to JTsmks car under the previous owners care. I've done a lot of work to that car. Anyone that wants to install the smallest upper supercharger pulley along with the oversized lower crank pulley needs to be aware of a few things. First, because of the added extra boost, you better have some fresh 4.2 steel head gaskets and at least new head bolts. The car only had 30K miles on it when I installed the pulleys. Within 500 of those hard driven miles on it since they were installed, the car came back to me because under full throttle the heads were lifting and causing a serious smoke screen. Not only did we replace the existing steel head gaskets, I installed ARP head studs. Those fasteners were crazy expensive, but it's doing what it's designed to do... keep $hit together. When it was done, that thing ran like a cat shot out of a cannon. So if you intend to put both of the pulleys on your car and you have composite head gaskets and/or high mileage, you don't stand a chance.

Contributing to this thread concerning added power on the R cars, to be on the safe side and achieving 400 or so HP, I would (and still considering) adding a killer chiller. Since these Eatons put out serious heat, I'm sure that New freezing charge air temp would drastically be beneficial by this setup. I'm in Florida as well so I believe there would be a lot to be had from this system. I think its about $900-$1000 for the universal setup. It would definitely take some time and patience to perform a clean install. Hope this helps.