I have a 1992 XJS V12 (convertible) w/ 29k on the odo and the center portion of the exhaust system will require replacing soon. Not up on all the lexicon but basically, the two center "design to fail" sections (one per side, under the seats) are what I'm talking about.
Instead of just replacing those 2 sections I've heard there's a longer straight through piece for each side which eliminates one of the mid mufflers, giving a throatier sound to this otherwise silent creature. Baltimore, MD based so if there's a mid-Atlantic expert, I'm sure I'll be in touch for other odds and ends. Thanks! peterbbell@gmail.com
Submitted by 89cat on Thu, 07/11/2019 - 14:27
(Regarding North american model )Here is my 2 bits worth and what I plan on doing come fall when I take the car off the road for the winter. I've read god knows how many pieces of info regarding improving the v12's exhaust on all the different XJS forums ( as long as you no longer want the silence ). All have a few things in common.
Ditch the middle muffler,keep the rear resonator. Use 2.25 inch pipe-2 reasons for 2.25.. #1 That is all there is really room for and #2, The jaguar v12's firing order in effect turns it into two 6 cyls of 160 c inches each. A & B bank, so anything over 2.25 is overkill.Use mandrel bent pipe. A 50/50 decision is regarding installing a H pipe. Again due to the firing order,this supposably won't make any difference in sound or performance, so why take the chance ?
So, here's what I plan on doing.My mechanic has already hollowed out my two cats.I'll be removing the center mufflers, replacing them with the rear resonators,and have the exhaust exit in front of rear wheels. All with 2.25 inch mandrel bent pipe. Haven't heard of anyone trying this yet. ( other than a gentleman who has both pipes going into one large side pipe on one side of the car only. Too loud for me, any seems a bit funny having only 1 large side pipe on the car )
My thinking is, all agree on removing those mufflers for better sound and a bit more power. Nice sound just using the resonators.So, why not just move the resonators up. Common fact the further exhaust travels the more restrictive the exit is. Especially over the rear axle with all those bends etc. Thus the exit in front of the rear wheels.Also exiting in this area, exhaust fumes should not get sucked into the cockpit ( mine are convertibles ). Quit a few people have had this experience when changing the exhaust tips while installing " custom" exhausts with different tips. Want bigger tips? Buy a set of the original dual tip TWR or XJR-S installed exhaust tips. They work. So,anyone have any thoughts as to if this won't work, please chime in.
As a side note. For sound and again a bit more power I modified my air intakes. Added K&N filters, got rid of the long intakes. Cut them off at the box, drilled 2.75 inch holes, and installed 2 inch long velocity stacks. Also drilled 2.5 inch holes in the under part of the boxes next to the above intakes and again added velocity stacks.Approx 5 times the volume of air now. Silent when cruising but step on it and a pleasant " growl " erupts. Not too loud, but nice.Side benefit, everything the " trumpets" use to hide is in plain view and easy to reach now. I didn't want to drill holes through the body of the car and end up with just to get colder air. The air going in is no warmer than factory set up, may even be a bit cooler due to the stacks underneath. Boils down to the easier breathing the better.
So there you have it, my two bits worth.