I finally decided to pick up a supercharger pulley for my XF from Powerhouse. I emailed the owner a few times and he has always been very responsive and knowledgeable. The 4.2L SC has two options for upper pulleys (1.5lb ~ 6% or 2.5-3lb ~10%). I went with the smaller pulley (2.5-3lb ~10%) so I could try to eek out a bit more hp. The only downside is that the smaller pulley requires the supercharger snout to be sanded/machined down.

Step 1: Remove Pulley
I covered the engine bay with towels and cut the old pulley off with a angle grinder. Powerhouse sends instructions describing how to cut so you don't cut into the snout. Last year I swapped pulley's for a local SC 5L so I had my old pulley off after about 15 minutes.

Step 2: Sand SC Snout
This is where things get a little nerve wracking. First off you need to mark how far back you need to sand to. I used a zip tie which worked out pretty well. I had to swap on a new one a few times after bumping it during sanding. I have a few power/air tools for sanding and I could only get access to the top of the snout. The instructions state that removing the supercharger isn't a big deal so I started down that route. I quickly realized that this is no easy task due to the limited room back behind the supercharger (horrible). 3 broken vacuum lines later (brittle to the touch) I decided to call it a night.

The next day I drained the coolant and removed all the coolant lines around the snout. This provided much more access to the snout. I have a Milwaukee Bandfile which worked extremely well. The only difficult part is knowing when to stop. Powerhouse doesn't send a die to test fit (others do) which helps you verify you cut enough material off. I think that is a huge mistake. I'd easily pay $50+ for that. I have a micrometer so I was measuring non stop. The diameter needs to be reduced from 60mm down to 54mm. Measuring from the shaft to the snout needs to be 17mm all the way around. The new pulley is 55mm inside so tolerances are tight.

Step 3: Install Pulley
I popped the pulley in my oven set at 550F. I left it in there while I ate lunch and had a beer (requirement) ~30 min. Using my oven mitts I grabbed the pulley and ran out to the car to slide it on the shaft. It slid on fine and didn't appear to bind. It cools fast so you need to: #1 make sure there is no binding and #2 make sure the end of the pulley is even with the end of the shaft. If the pulley binds remove it. Well after it started to cool it started to bind up. Metal shrinks as it cools so I guess I had a slight high spot that grabbed when it cooled. At this point a few swear words popped out. I let the pulley fully cool because there was no removing it. I sprayed some WD40 behind the pulley at the high spot and I was able to get the pulley to spin with a vice grips and a rag wrapped around the front of the pulley to prevent any damage. I worked it back and forth and I feel like I won the lottery because I was able to work it through that high spot.

Step 4: Reinstall Everything
I had to fix the vacuum lines which was fairly easy. I had some 1/8" plastic vacuum line from my other car projects so I removed all the brittle line and swapped in some new line. You do not need to buy new lines from Jaguar ($50). Go buy about 1-2 feet of 1/8" line from the store ($5) and cut it to fit and swap over the boots. Everything else went back together without any issues. Start up was nerve wracking because I didn't want to hear a metal scraping sound due to that pulley and that high spot. I figured it could have issues under load. However, it started up and sounded completely normal at idle.

Step 5: Butt Dyno
Woah, this thing moves now! It's neck snapping with the new pulley. There is no doubt that the pulley makes a significant change. It really kicks you into the seat now. It is mostly low/mid range power with this pulley as it is well documented that the M112 looses steam up top due to heat. I'm VERY happy with the results. My MPG has taken a hit but that is only because I have been making wide open throttle (WOT) runs every time I drive it. The supercharger really screams at WOT now.

Future mods: Supercharger porting appears to be hit or miss with the M112, especially the new revision in the XF. There is a lower pulley option available for the 4.2L SC to push the boost up further but there are clearance issues with the oil filter housing. EuroToys appears to sell the lower pulley with a modified oil filter housing but it's $1,200. As far as a dyno tune, I may look into that but I know the S-type R guys haven't had much luck in that area. I'm not sure if the S-type R also had smaller intercoolers like the early XJ/XK cars. Powerhouse sells upgraded intercoolers for the early XJ/XK and the owner stated the XF didn't need it because it came with a larger intercooler already. I would like to take some temp measurements and determine how hot the air is getting coming out of the SC. The larger intercooler pump others have been swapping in is an easy/cheap swap so I may go that route.

Thoughts:
If you don't have much experience working on cars. Get the 1.5lb pulley which does not require sanding. The snout sanding is a massive pain in the ***.

 

I finished up two more maintenance items this past weekend and I figured I'd share for the 4.2L SC guys that may be searching for help in the future.

1. Supercharger oil change

Supplies:
-Oil sourced from Amazon (x2 bottles needed): -Clear tubing sourced from NAPA 1/8" (the smaller the better)
-Hand pump originally used to pump new diff fluid in/out. This one is similar to what I have: -Misc tubing to connect pump outlet to smaller tubing

Quick How To:
-Remove plastic air intake tubing
-Remove supercharger fill plug. I had the best luck removing the plug with a torx bit even though the plug is a allen head (4.5mm was the closest allen and it still seemed loose). My SAE allen set seamed worse which was odd. The torx bit is tapered so it fit much better. I had a 1/4" knuckle which accepted bits (1/4" end) so my torx bit fit into the knuckle. This is key because there is little to no room and this is as compact as you can get before you need to cut the bits down to fit.
-Rig your tubing up so that you can pump out the fluid. Tape the tubes or get barb adapters. Stuff the tubing into the supercharger.
-Suck all the fluid out. 7.3oz is the approximate capacity. The old fluid really stinks. Use gloves because the smell won't come out of your hands easily.
-Pump in new fluid until it over flows
-Reinstall plug
-Reinstall intake tubing

Conclusion:
The supercharger oil isn't going to do anything as far as performance. The fluid was pretty nasty after 70k miles and the fluid was only $18 so you can't go wrong with that.

2. Spark plug change

I was having slight idle issues (surges from 500 to 750 rpm in park) at times that was driving me nuts so I decided plugs could be the cause.

Supplies:
-OE Plugs from Amazon (x8):
-Dielectric Grease
-Anti-seize

Quick How To:
-Unbolt the coolant tank.
-Remove the coil covers which requires lifting the coolant tank up on the driver's side.
-Unbolt the coils
-Disconnect the coils and remove. Wire wrap is brittle so be careful not to drop particles into the plug holes.
-Remove the spark plugs. I has to use two knuckles to get at the back plugs on each side. I don't think you could do it without them so make sure you have those and various extensions.
-Re-install new plugs with dielectric grease on the boot end and anti-seize on the plug threads. OE plugs are Iridium which are pre-gapped.

Conclusion:
I had a noticeable improvement from the plug change. The idling issues I had were eliminated and the car appears to run smoother throughout the rev range. In my case it was well worth the cost for the plug change. The only differences from plug to plug that I could see was with the rear two plugs on the passenger bank. They had a little more build up vs the others on the porcelain near the tip. Overall, they looked fairly normal so other than mileage I don't know what could have been the issue. My coils all looked brand new. No cracks in any of them.

 

Wondering what size rubber coupler you used???

 

I purchased a 09 XF Supercharged 4.2 with 24k miles 6 months ago. I have put 8k trouble free miles. It is my 6th Jag, and the only reason I purchased this XF is the Jag mechanics I have worked with for years swear the 4.2 supercharged is the best V8 Jag has ever made. So, here are my questions to you guys that have already added some mods to your 4.2 Jag supercharged engines:
1. Is it worth it to get the upper supercharger pulley from someone like Mina Gallery who claims it will add 2.5lbs of additional boost and you won’t have to machine down anything?
2. would you add stainless steel exhaust from someone like Borla or Mina Gallery to enhance sound? I live near the ocean and the stainless steel mufflers are attractive for durability
3. would a ECU tune by someone who knows what he is doing really help? Or, should you just switch to Dynamic mode for quicker throttle response.
4. Plugs - the originals are in my 09 with 32k miles. It seems to run perfect, at what age,or mileage would you change them
5. Coolant - I am getting another synthetic oil change this week and have asked the guy to change the coolant and put fresh coolant in the car. How often do you guys change yours?
Anything you would recommend to insure optimum performance and reliability for long highway drives, which is why I bought the car
thanks- Jim

 

I've had the Mina Galleries exhaust on my 5.0 V8 for 8+ years and still love the sound every time I drive it. I'd imagine the 4.2 version is every bit as good. Easy install too.