Hey guys, Newby Newberson here. Just picked up a 98 XJR that I am ready to really play hard with. I have done all the maintenance this week (got the car Tuesday night) and have replaced (or on the way) all the worn suspension and brake tidbits.

So now its time for power. I cut the rear mufflers off more for sound since they don't appear to be restrictive. I also have a pulley and puller on the way from Euro Toys and a cold air intake on the way from.... crud, forgot the name.
That will be it for round one while I getcomfortablee with the car. After that I may fabricate a 2.5" cat-back with some Borla XS Pros and add the larger lower. My question is what do you folks use to tune? I used to have SCT Pro software but need to buy a new copy and wondered if anyone uses it? I realize for round one Idon'tt need to tune but with the boost potential of the lower pulley I think in addition to a larger fuel pump that I would need totweakk the fuel map and maybe upgrade the MAF meter.

Next question, any other simple-ish mods to make power?Don'tt wanna spend the coin on a twin screw and I have ported Eatons in the past (Mustang Cobra guy) but theydon'tt really make much more HP for the work so I prolly willfore-goo that as well.

What can thesemotorss take RWHP wise before I have stress or cooling issues?

Am I right in assuming the pre 04 Brembo brakes are a direct bolt on with larger rotors? Do the S-Type and 04+ calipers fit or is the mount holes too far off?

Are there anychassiss reinforcement upgrades or larger sway bars available?

What are the lowering spring of choice?Don'tt want to slam it anddon'tt want to make it a slot car. Want to retain a bit of civility.

 

arent you on the svtperformance forum?

 

Pulleys (either s/c or crank) move the 'on boost' lower in the rev range. Added to a good cold air filter (not a cone stuck under the bonnet) and free flow exhaust adds a decent power gain, the cooling system needs to be in good shape, along with the s/c.

The crank pulley is easier to install. To add a smaller s/c pulley requires some material to be removed from the snout for clearance. A new slightly smaller belt and renewing the bearings in the tensioner and idler pulleys is always a good tip.

To be honest Jaguar have pretty much got all they can out of the system already - if adding both crank and s/c pulleys, then serious mods are to be done to the cooling, i.e. bigger surface area intercooler and separating the coolant loop from the engine coolant, along with a water/meth kit. This is just to keep the gain (around 30bhp)
Reason being heat kills the power gain almost immediately by ignition retardation to limit knock. This is why performance guys refer to the Eaton as a Heaton, it gets hot quick. You'll already know the score here....
If monitoring intake temp on boost compared to ambient you'll see what I mean. Heat soak kills the gains, period. To test, just do a few wide open runs, engine cold is noticeable, then as the system heats up, the power goes down.

Diff's are a weak link - see the diff rebuild thread for more info.

Brembo's - you'll have to find the pre 04' units.

Chassis - Sports suspension OEM, nothing aftermarket to stiffen that I know of.

As they're an import saloon, not a performance Ford, most things are custom. If you want serious h.p. the twinny is the route.

 

Yes but I hardly ever go there any more. Usually can find me on Stangnet or LVC as I have also had many Mark VIIIs and even built a supercharged one.