Over axle exhaust pipe diameter

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    • #13345


        Does anyone know the maximum exhaust diameter you can fit to a pre facelift XJ-SC to get clearance over the rear axle.



      • #13364
        Norman Thomas

          Hi Alan,

          I’ve just fitted some stainless aftermarket pipes to my car (from Simply Performance) – these are 1.8″ /45mm diameter.

          Whilst there is generally plenty of room around these pipes over and around the drive shafts and through the suspension subframe, they run very close to the bleed nipples on the inboard rear calipers, so I would say these are about as big as possible – unless you repostion the pipes to give clearance which puts them at unsuitable angles for the connections at each end. Remember that these pipes are hanging on brackets at the top of the curve over the axle, so there is no much scope for repositioning them.

          I can’t recall now if these were larger than the originals, but the originals had greater clearance to the bleed nipples, although this could be down to the form of the pipe.

          In conclusion, I would say its not so much an issue of pipe diameter, more down to the shape of the pipe.

          Hope this helps, Norman.

        • #13381

            Thanks Norman,

            The new system I have had fitted is about 2.5” and my original were just under 2”.   The car runs better with these pipes but I was getting a slight tapping noise at the rear end.  Before going to a classic car show I checked the tyre pressures and they were under inflated. After correcting the pressures this the noise has gone so this must give a bit more clearance from where it is catching. I have informed the fitter that I believe these pipes are too large and await his answer.  I found a site on the internet that recommended larger pipes for upgrading the exhaust but not to go above 2.25”.  My system is bespoke so the shaping of the pipes is down to the quality of the fitter.   At this moment I am confident that nothing is catching but my concern is if you get some little wear on the hangers the noise will return.

          • #14697
            Geoff Pedlar

              Never mind fitting through the sub-frame, per the original; just go straight pipes under the sub-frame.

              I did this to two Double Sixes, without any negative consequences, and never grounded them, even with four people in the car. I’ll do the same with my XJS when the time comes.

            • #14760


                My Longlife system is now sorted.  I got a 50% refund from them and got my Jaguar mechanic to sort it out by repositioning the hangers on the over axle pipes.  The good news is that I now have good clearance between the axle and the pipes + saved about £200 on the original cost.


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