Good day folks! As the title states, 400whp is the goal without sending myself into poverty. Can it be done? Maybe. Will I try? You betcha.

Here we go: This week I should be getting my new ride. 2005 XJR with 125k miles. Not ideal, but I think I can work with it. I have a lot of experience with older muscle cars, but this thing is going to be daunting. Too many wires. I've binged as much as possible on the content here, but I'm completely overwhelmed so here we go. I'm a brand new Jag owner and I know it's likely heresy for most of you, but I have zero desire to maintain originality and am willing to upgrade anything. I like to tinker and I like unique cars, so feel free to recommend or point me in the direction of any wild or crazy mods. I'm a muscle car guy at heart, so please let me treat this like one at least a little bit.

First Things First:
When I get my ride, it's going straight to my trusted mechanic for inspection and a good look over. After this, its fluid changes all around. Engine oil, power steering, brake, transmission*, rear diff, coolant, supercharger oil, etc. I was able to find the specs on all fluids necessary, so that's pretty sweet. Looking to get as close to factory performance as possible off the bat.

Questions- Is an "engine flush" recommended for this vehicle and the mileage? I'm a big Seafoam fan, but from working with dinosaur engines I know that often times the buildup is the only thing keeping the engine together. Is this the case? *Are there any aftermarket parts I can use to easily drain and fill the sealed transmission? For one of my vehicles I had a nifty little transmission drain plug that also had an adapter to fill it back up with. Does this exist? Also, is there a part number for better, more traditional lug nuts? I hear those things are a nightmare.

Next:
Next I'd like to continue with "preventative maintenance/general upgrades" on things that may generally need attention. I know it has a relatively new water pump installed, but it's my understanding that the SC cooling system could benefit from an upgraded Bosch unit. I'd also like to attempt to clean and/or upgrade the SC intercooler. Anyone have a quick and dirty guide for this?

Question- What is the specific part number for the Bosch unit? Also, tips on mounting would be greatly appreciated. I know it takes a custom bracket so I'm curios about what has worked for you. Are there any other parts that I should just replace immediately without hesitation? Also, I like to plan for the worst so any powertrain safety mods will always be considered. I noticed someone on here installed a supplemental coolant reservoir for the SC. I like the idea of this. How to attack this?

Performance:
Okay now into the fun stuff. I have the usual stuff planned; Intake tube, SC pulley (upper only for now), plugs, etc. By dumb luck I came across and picked up the Range Rover intake duct, so I plan on throwing that on there. Does anyone else utilize other RR parts and have good experiences with them? The gearhead in me likes the idea of utilizing truck parts on this sucker. I was considering a larger throttle body, but then I'm not sure if I need other stuff replaced like MAF sensor, O2 sensors, ECU mods, and stuff like that. I'd like to steer as clear of the computer as much as I possible can.

Question- Intake tubes; is there any significant difference between Caldoofy and Mina intakes? I like the Mina price, as well as the fact I can bundle it with a SC pulley to save some more coin. Is this copacetic? Is the jury still out on a upgraded cone filter vs the stock air filter box?

I know the Powerhouse pulley is typically the way to go, but the price tag has me a little turned off. Also, any tips on SC snout trimming would be greatly appreciated. I'm sure I can do it myself just need to know where to start. Any other bolt on performance parts I should consider at this time? I need to locate a coupler that will work for the slightly larger RR intake duct.

Exhaust:
Boy this is one hotly contested topic. I'll keep it short and sweet. I want a little deep bark but not sound like a tug boat or straight piped Harley. Also, once I start getting into the exhaust what do I need to consider regarding cats and O2 sensors? I've always just ripped out the cats and put in a test pipe or hollowed them out. I have no emissions tests in my area, but going back to the computer I don't want to deal with too much of a headache from this stuff. Whats the average recommended exhaust mods? Nix the big muffler and install X/H pipe? Swap the rearmost mufflers for Borla/Magnaflow? Remember, I'm a muscle car guy so think more small block Ford style. Obviously different engines, but I wish I could remember the mufflers I had on my 4.6 DOHC Cobra... sounded perfect before It blew up.

Computer:
Oh boy, this is where I get scared. Too many wires. Too many features. I purchased this car to fulfill my wife's desire for a luxury weekend cruiser and to wet my whistle on something fun to drive after selling my 351 Cleveland. I figure if I can even find someone to do a tune near me, it'll be the last thing I do. That being said, what electronic luxury features can be bypassed or eliminated? I hear horror stories about the alarm system. Can this be permanently deleted? Parking sensors? Unnecessary. Help me make this thing as user friendly and hands off as possible!

Thanks friends. I hope that you can chime in on any area you're familiar with. This forum has such a great wealth of knowledge, so much so that I'm completely overwhelmed. Let me know if you have any comments or suggestions! In the mean time, I'll be reading up on as many of the sticky threats as possible!


EDIT:
CARFAX Notables:
Pretty consistent oil change and maintenance. Always nice to see.
`08 - new rear window
`09 - electrical system serviced, engine/powertrain module replaced, transmission serviced
`10 - shift linkage repaired
`11 - throttle body replaced
`16 - Air suspension compressor replaced, spark plugs
`17 - water pump replaced
`19 - horn replaced, PCV valve replaced, intake maniforl gasket replaced,
`20 - lower control arms replaced, water pump replaced, drive belt tensioner replaced

 

Welcome and good luck! There isn't a lot of aftermarket support for these cars, so that makes them less than ideal as a hotrod platform. But, they are decent out of the box, so there's that. I can tell you that replacing my old original cats with high flowing ones and adding an H pipe where the resonators were made good butt-dyno gains, likely just restoring lost HP though. It's also a little louder, but still quieter than any new 'performance' car made today with fancy adjustable mufflers.

These motors are stout, and if there was a way to cheaply and reliably tune them, I'd be willing to bet that they would take to turbocharging well. But that would also be a packaging nightmare. Other alternatives are bigger/better superchargers, but those get very pricey very quickly. I wish there was a way to get cheap boost into these things.

Quickest way to 400 is to do intake/exhaust/pulley, and then go to a generous dyno.

 

buy the ebay 1.5lb pulley.

Range Rover Jaguar S-Type 4.2 4.0 Supercharger 6% Performance Pulley 98-09 M112 | eBay

pump number is

0392022010

400whp isn't happening without cheating or going broke

 

My take on engine flushes is that they do more harm than good. The idea is to pump oil or cleaner or something through the engine, in the reverse direction of normal flow, the idea being to push out any buildup anywhere. What happens, though, is stuff that is perfectly happy sitting in its little out-of-the-way corner, not bothering anything, is suddenly washed into the general oil passages, and perhaps gets stuck somewhere else. Some flake of crud that won't pass through where it wants to go. No it's just loose in there, and when you start pumping real oil in a running engine, that stuff gets as far as it can and maybe plugs an oil passage, gets between a ring and a cylinder wall, enters a bearing, whatever.

Engines flush all the time with the oil pumping through them. That's what filters are for. The flush services that the garages do are reverse-flushes, and to be avoided like the plague that they are.

 

I hear the you regarding the "muscle car" vibe. One question though, what is your end goal. Street sleeper, weekend dragstrip, highway cruiser or a road track terror? Without knowing what you intend to use it for it is kind of hard to plan on where to spend your money for the best result. I have not driven the R model but the stock NA has plenty of go. I can make enough noise with the rear tires to attract the unwanted attention of the local law if I would care to. However it is nice to drive a car that gives a much more refined impression than my Ranchero GT with magnflow exhausts that will set off car alarms in a parking garage. I don't know if a goal of 400 horses at the wheel is as important as using 350 horses well. Personally I have a feeling that a lot of fun could be had by adding a LSD with a little lower gears. Unless you like the higher speed and have a place to let her run free.

I would think just go with a few upgrades like the pulley, a better intake and a better flowing exhaust then see how you want to address the traction issue before doing much more. With 125,000 miles you will likely be looking at more suspension issues and some hoses that should be replaced. All of the procedures for servicing the transmission and other parts are documented very well in this forum and not to complicated if you are not adverse to turning a wrench. I believe there is a Toyota part number for the lug nuts also.

One thing I am constantly impressed by is how well the Jaguar engineers ave done in setting up almost every part of the engines they have produced. Nothing is ever perfect but if you did appreciate the design of the 351 Cleveland, you will not be disappointed by this motor at all. It even has the familiar, charging rhino feeling. I look forward to seeing what you do. Good luck.

 

Thanks friend! My goal is 99% street sleeper and 1% drag just for goofs. I’m not too accustomed to cars that hit the twisties and have a lot more experience driving in a straight line! I may consider the LSD, especially if I can find something on the cheap.

I look forward to seeing what I can do too! I’ll try to keep everyone posted on my progress.

Wfooshee- I’m inclined to agree with you regarding a formal flush. I might throw a little seafoam in the tank and oil prior to my first change and leave it at that.

Xalty- Thanks for the part number. I’ll see what I can get in to. If you have the cheat codes though, please share!

 

I use Seafoam in my motorcycle very regularly whereas I only put it the Jag maybe once every 1000 miles or so depending on my driving (town vs highway). I also use Techron just about as often. I do not use it in the crankcase nor do I use any of the other Seafoam products. It may well help wash the crankcase out when you change the oil. While it has helped on occasion I cannot say it is providing any real benefit. I mainly use them both because I do not often get to hit the highway and clean out the corncobs. In my 750 Vulcan I can tell absolutely that it helps keep the carbs clean. The Edelbrocks on my Fords also respond well to it as I can not drive them often enough either.

If you have good, comprehensive maintenance records that is great. I believe the use of good oil and regular maintenance will do more good than additives although I have not heard they hurt anything. For all the good the Jaguar engineers did I do wish they had included good dash gauges for oil pressure and water temp. Having a good reader with you to monitor the engine is helpful. I would like to install gauges but can not find any that will fit with the design of the rest of the dash. I am not crazy about gauge displays on the audio/climate screen.

I feel strongly about the limited slip as the current traction control works by braking the spinning tire. If I understand correctly. There should be a Ford sourced rear end that can be made to work since so many other Ford parts are in the chassis. As a street prowler the Jaguar is very well prepared when stock and any upgrades will payoff large dividends.

 

Welcome to the asylum.
Toyota lug nuts fit our cars

 

Go with the 1.5 lb fully no need to cut this now. 3 pound pulley is too much and will cause heat soak

 

This will get you there since there aren't too many performance parts for our cars. I'm running a 75 shot now but can go to 125 if I add an AFR gauge

 

I’ll tell you hwhat, the thought crossed my mind the other day after my wife demanded we watch the OG Fast and Furious movie (which I should say still holds up despite all the nonsense the franchise became). That being said, I have zero experience with nitrous but I think I could be sold on it. How big a job, what’s the price, and is there a good “how-to” I can check out?

This might be the cheats xalty was referencing.

 

I had no experience with nitrous either. It was probably about a 30-hour job but I also did the bottle heater remote opener and Purge system and extra bottle.. With a CAI pulley and 75 shot you will be right around 500 brake horsepower...

 

Having owned 383-Chrysler-powered Bristols with zero electronics (a luxury car with wind-down windows), buying an X350 Jag was like stepping into a parallel universe. I also got my first PC (IBM PC-XT) in 1983 when I was in the computer industry, and with buying an X350, I realised I was now driving a computer not a car - so if you don't have computer skills, start learning.

First thing to buy is an OBD reader because the on board computer is essential to know why the car goes into limp mode or lights up the dashboard with red and amber lights as well as useless messages that essentially say drop your car off at the dealer with a blank check.

Buy a new battery unless you have proof you have a proper battery less than one year old. Look on the forum for advice on what to buy. I bought a new JLR (Jaguar / Land Rover) branded battery, but in the US there are alternatives. Also buy a 50amp 13.8v battery backup so when you are messing with the computer you have clean power. Relying on the battery can drop below the voltage the computers need, and a normal battery charger is dirty power that can really confuse the computer. You will find a posting of mine where I used an Autel MP808 to clear the adaption memory of the transmission, and the shifting became horrible. Slam shifts, no shifts and finally the red lights, error codes and limp mode. Why? Not enough power in a brand new JLR battery. When I added external power, it cleared the memory and the transmission rides like a dream.

Removing anything that came with the car is much higher risk than in an analogue car. If you choose to do so, please document it in detail, so the forum can learn from your bravery. Remember the car has zillions of sensors and software that compares one to the next. Removing something can cause the dreaded MIL light (malfunction indicator lamp AKA -check engine light) causing the DTC (Diagnostic Trouble Code) code to appear on your OBD (on-board diagnostics) and rarely will it be in clear shade-tree mechanic English. Oh, and BTW, be prepared to learn a whole new set of acronyms like JLR, MIL, DTC and OBD.

Also be aware that about 50% of the time, there is nothing wrong with the car, it's the sensors or the computer. Your brakes are fine, but the OBD gets bad data so it says your brakes are bad. In a 2001 Mercedes SLK, I got a Christmas tree of dash lights, nasty limp mode and a long list of DTC's, but it turned out that when the circuit board gets old, it develops hairline cracks in the board. The DTC did not say "replace the computer", which is sort of like reporting yourself to the principal for smoking in the carpark, but instead blamed it on everything else. Finally I found an MB forum thread that pointed to the hairline cracks, and when I replaced the unit with a wrecking yard unit (with matching numbers), everything was fixed. It took 15 minutes to fix, but only after three months of ordering and replacing brake shoes, sensors, relays, etc. Had I been paying shop labour, it would have been an expensive adventure.

The primary issue with the X350 has to do with the amazing suspension. If you want to do preventative work, buy a full set of air springs, rebuild the compressor, replace all the O rings and then replace all the rubber, ball joints, etc that gives you the amazing ride. You can rip out the air springs and replace them with Arnott mechanical springs, but then you lose the point of difference, the ride. Installation is a DIY job for any reasonable-skilled wrench monkey.

I agree with others, flushing can cause more damage than it is worth. Yes, change all the fluids, and pull the transmission pan don't just drain it. If you want to be sure, waste fluids by changing, driving, changing again.

The rest of the car is well made. Thank Ford for spending a billion dollars.

 

Welcome Cneukum,

I'll be honest, 400whp is tough to attain on these and it will not be cheap (at least on the 04-05 for sure). I hit 390rwhp a few years back without nitrous and already had a good bit $$ invested into the car.


My current set up should easily make more power, hope to get it running again soon and dyno to prove it. Had everything ported, larger TB, 92mm MAF and new legit exhaust.

Here is a highway pull without nitrous from earlier this year (I have a 125 shot installed, haven't gotten video of pull using it though)


Its fun, but not cheap. And as mentioned, you have to be on top of maintenance. So short answer, possible? Yes. Practical? Not really.

I haven't been dailying my Xjr in 3 years, its a dedicated toy/project or show car. Too loud to daily, 12 or 13 mpgs, need to blend fuel etc

IMO 360-370 rwhp is the sweetspot of power, practicality, and reliability for these cars.

Regardless of how you decide to build it, enjoy it! And keep us updated.