I have a stock 2009 XK and I'd like the exhaust sound to produce a little more noise with more rumble and throatier. But I don't want it to be obnoxious or 'race-track' loud. I've read on the Forum that installing the 'back box' from an XKR and/or adding an 'x-pipe', and/or '100 cell cats' can really improve my XK's exhaust sound. First, I'm not sure what the 'back box' is, same for an 'x-pipe' and 100 cell cats. A friend (Lothar52) recently upgraded his XKR exhaust by installing a complete Spires Stage 3 exhaust and has offered me his stock XKR exhaust. Should I install his entire exhaust on my XK or just parts of it ('back box', etc.)? What about an 'x-pipe'? Does his XKR have an 'x-pipe'?What about '100 cell cats'? Does his XKR have '100 cell cats'? As you can easily tell ... I'm in over my head ... so any advice would be greatly appreciated. Thanks.

 

A buddy of mine has a Mina rear muffler on his XK. Sounds wicked without being obnoxious. This muffler has 4 outpipes so you have to get the R version rear valance. There are 3 sections to the exhaust system. Converter section, mid-pipe and muffler. The XK has an interior flap in the muffler that bypasses the muffler at high RPM. It does NOT have a vacuum controlled valve like the R. Cheapest thing to do is replace the mid-pipe resonator with an X pipe or straight pipes. You'll increase the overall volume but still be quieter when at lower RPM then a little more at higher RPM. You could always weld the resonator back in place if you don't like it.

 

I replaced the XK back box (peek underneath your cars rear end, it's that big honkin' muffler box) with one from an XKR, and I really like the increased volume. At low RPM it has a bit more rumble, but not obnoxious, and when you punch the 'go' peddle you get a satisfying 'brrappp' (the guy you're passing knows you mean business).
Yes, you'll need to change the rear valence too, but that's only $50 for a new one.
I love the look and sound, it was a great 'mod' for the car.

 

Another thing, the XKR has two silencers (small mufflers) ahead of the back box, whereas the XK only has one. So by putting the XKR back box on an XK, it will be (in theory) a bit louder than the XKR. XKR owners often replace one of those silencers with an x-pipe which gives them a bit more sound.

 

I had the Mina back box on my XK. It came with the XKR valence. It is about a 45 minute simple install. Loosening and tightening bolts (must wait for the system to cool). I now have the Mina system installed on my XKR. got great comments when it was on the XK and continue to get similar comments now that it is on the XKR.

 

To answer your questions more directly, you probably only want his back box, not the whole system. The 'cats' are the catalytic converters (one on each side), and if I recall, someone said the OEM cats are 600 cell, so a 300, 200, or 100 cell cat will have more flow and sound. I doubt if you were being offered his cats, and if so, they'd be the same as what you have already. Another member here makes and sells custom cats.
Also, a vanilla XKR would not have an X-pipe.

 

Kj and myself both have the xkr rear box it definitely livens up the 4.2 and gives it that really sports car sound, intoxicating to put it simply.

In terms of increasing power that's were the x-pipe and free flowing cats come into the picture which will run into the $1000s

 

Lots of discussion on the new XJ Forum about 200 cell cats, including videos with the exhaust sounds and CEL horror stories . Pros: more aggressive exhaust sound and increased power. Cons: angry neighbors, high cost and CEL code aggravation. If you swap out your stock OEM cats for high performance 200 cell cats it appears that you will also need a custom ECU tune to compensate for the increased exhaust flow and prevent recurring CEL codes. For details, see: https://www.jaguarforums.com/forum/x...j-x351-158300/

 

kj07xk ... You said a new XKR rear valance only costs $50. Where do I buy one ... from my local Jaguar Dealership or an aftermarket provider? Thanks for all of your help! You and all of the others who have responded to me have really helped, and I greatly appreciate it!

 

When my friend upgraded his XKR exhaust to a Spires Stage 3, he left whatever part of his XKR exhaust that was removed, laying on his Dad's garage floor. When I go over there to retrieve the back box, can I remove it from the rest of the exhaust by simply loosening a couple of clamps or will it need to be cut off at a certain exact place by a professional? Thanks.

 

When I had the Mina system installed it was strictly a nuts and bolts operation. Took less than 45 minutes.

 

Yes, it simply unbolts from the forward sections.
I bought the XKR valence online from a Jaguar parts supplier (probably a dealer's parts department). The price was ~$46 if I remember correctly, for a genuine Jaguar part.
I find my receipt and post which supplier I got it from.

 

I need to double check, but I think the part number is C2P8245, and it appears the price has come down on it. Gaudin lists it for $36.xx and parts.com has it for $34.xx.

 

The late model XKR comes in 2 versions . One with the 2 silencers and the othe with the active exhaust which has the X pipe.

 

I replaced the boring stock exhaust with the Mina Gallery about three years ago.


I still love it. Doesn't "pop" but it sure gets the neighbors attention.


Nice throaty sound in "S" mode but mild otherwise.


At $1600 delivered and installed I view this a bargain.

 

Can't find the receipt, but C2P8245 is the part number (probably in the box with the original XK valence, stuffed away in the attic). Most places call it the bumper 'lower extension'.
Compare prices with tax and shipping/handling online, for your best deal (you can try your local Jag dealer, but online is likely cheaper).

 

Since Lothar's XKR back box was already separated from the rest of his old exhaust, this morning I took his XKR’s back box and my 2009 XK to the local indie shop I use.

A half hour later they called to say that after taking off my XK’s back box, his XKR’s back box pipes did not line up with the rest of my XK’s exhaust system. In fact, they said it wasn't even close!

I know they weren’t talking about valance opening width issues because yesterday (while waiting for the new XKR valance that I ordered online, but not yet received) I took off my XK valance and trimmed the width of both openings to match the ones on Lothar’s XKR.

From what I read on the Forum, it sounded like swapping an XKR back box onto an XK was not a problem - loosen the clamps, slide the old one off - slide the new one on, tighten the clamps - done.

I guess the only thing to do now is to take it to an exhaust specialty shop so they can make whatever ‘connectors’ are necessary.

Did I read wrong, do I need another piece of Lothar’s XKR exhaust, or is there some other explanation? I’m confused! Thanks in advance for any help you can offer!

 

sorry you are having problems. these things can be frustrating. can any forum members post any photos documenting the retrofitting of the "back box"?

 

Lothar has a 5.0 car hasn't he? If yours is a 4.2 then that's not going to work, not without modifications or a custom middle section to be fabricated. The 5.0 cars have a different (read; bigger) rear differential so the paths the pipes take are wider to go around that.

A 5.0 XKR silencer will go straight onto a 5.0 XK, and a 4.2 XKR silencer will go straight onto a 4.2 XK but neither will fit the other generation of car.

 

Bingo