member Unders said< The two best mods I ever did was to swap for XKR-s center pipes (new from Jag) then leave the fuse. The XKR-s has the standard rear exhaust box so fits in 30 mins. Then the Supercharger wheel change.
Changes the whole car with a re map. Better fuel economy too with this. These engines are bullet proof, so no sleep lost.

For those of us wanting to follow a known path, can somebody give us Source, Part numbers, sizes if applicable for the Center Pipe and the Wheel?

Are both of those DIY?

Is a re-map Dealer-specific, or can most service centers do it, or do we need to locate a shop before spending time and money on the parts?

 

The R-S has an X-pipe instead of dual resonators yours has. There's nothing special about it other than placement of the crossover, easy to make your own. He also likely went to a small supercharger pulley, which with a tuner, can give 25-50HP power increase as discussed in your other thread. With the 5 litre, there's a factory R-S map which can be loaded to give non-R-S cars a boost, but that doesn't apply to the 4.2 you've got.

 

Lost in translation across the pond.
Unders speaks British English : supercharger wheel
Rick speaks Alabama English : pulley

As Jahummer said, the the X150 4.2L SC engine was available from the factory with only one state of tune, namely, 420HP. Jaguar dealers will not install an aftermarket ECU tune.

You previously asked about ECU tuning in this thread: 600HP or BUST!! and got many replies. Read it again.

 

After I had my pulley and tune done on my 5.0L years ago, I had the X pipe installed at a local muffler shop. If I recall it was only about $200-225 including the pipe and installation. It did make the sound of the exhaust a tiny bit deeper. It was a quick and inexpensive installation.

 

I have not done the pulley swap, but I do have the X-pipe and R-S tune, so that's not horrible. I was all set for the Silver State Classic in a faster bracket since I also raised the Top Speed limiter to 185 mph to get out of the Honda and Toyota brackets, but stupid 'vid made that a problem. Maybe again someday.
"Best Mod" should be two-fold; Two for mechanical, and two for appearance/tech.

 

The XKR-S and for that matter, no Jaguar has a factory fitted smaller diameter pulley. For the 4.2 a smaller pulley will increase boost, but the efficiency and capacity are limited by design. The later TVS blowers fitted to the 3.0 and 5.0 have great volume and better efficiency and benefit more from being spun faster but a custom map will still be needed in all cases to fully benefit. There are some supercharger builders who've managed to push the limits on the M112 fitted to the 4.2 with custom porting, polishing and other mods.

 

This is a good starting point. After your pulley and tune, what did you notice, and did you get the car dyno'd to see the difference? er, belay that....I just read the post above this and have learned that any substantial HP gains are going to come at a cost, either P&L, or R&M, that is more than it's likely going to benefit the car.

Based on a few threads and posts, looks like adding 100HP to our 4.2L will not be timely, fun, or in-expensive. I'm going to live with a nice HP that was put into it, OEM.

 

Really? From 600hp to OEM, that is what I call a real compromise! Sometimes cost vs desire raises its ugly head. Enjoy your ride.
wj

 

hmmm, I was trolling for ideas about mods for my and others' benefit. My car having 90K miles makes it iffy for additional pressures, and learning that just about any mod will cause need for a tuner (which isn't available within an hour's drive) made it an idea-killer for me. Others might have lower miles or closer shops to indulge their needs.

With any new brand, it's nice to know what's available in the way of improvements, right?

 

Right
wj

 

A skinny, old philosopher from Dartford, UK once sang:

 

Aside from cost, this's one that's most concerning. The only way to safely increase power would be to bring all parts to date, hoses, fittings, gaskets, seals, expansion tank, belts, tensioners, etc. All easy to do and at this mileage you're ready to begin doing this any way as maintenance. Good news's these motors can easily do over 200K with proper care.