Dividing some x pipes between european and american is not flawless. Firing order has a role in sound making. But camshaft, intake and compression compilation has the biggest role. What comes to firing order then? Jaguar v8 has same firing order as Cadillac Northstar.
As these v8 engines have so called lame camshafts almost straight through pipes does not make justice to it's sound. It sounds nothing but cheap and tug boat like. It is completely different story when engine has old school type big overlap cam and lots of timing etc.

What I have is 2.5" to the second mufflers and after those 2.25" to the back mufflers.


Superturbos cured drone and did not change the sound.

 

OK, so the style of x-pipe really doesn't matter, and the straight-thru pipe (I'm assuming that your addressing the removal of the mid-mufflers) doesn't sound too good (I don't know what a tug boat sounds like). What about the straight-thru mufflers? Is that what causes the drone versus the Superturbos? Are they chambered?

 

Straight through mufflers aka absortion mufflers doesn't absorb lower frequencies that much or at all. Depending on its physical size. Superturbos in the otherhand kills mostly on low frequencies. Superturbo muffler is not chambered. Inside is kinda 3 times straight thru muffler. You can not see thru them. But there is no obstructions in a flow.

Here's what type mufflers I have. Everything is not Dynomax. But structure is the same.
Superturbos in the middle.

X pipe muffler in front

Straight thru at the back.

.I don't know how mutch paraller X makes sound difference to the true X. Basically tugboat sounds like slow paced lame exhaust pulses.

 

Thanks Vauxi. This discussion is making me reconsider my layout. I'm really looking for better flow without being overbearing on my neighbors. A friend here has a 30's-something hot rod with a 351 Cleveland; you can hear it about half a mile away.

 

How about if I replace the front muffler with a dual in/out with an internal x-pipe instead of the fancy x-pipe, then continue with the mid and rear as described in my original post? I'm still looking at Borla, with this one: https://www.borla.com/products/proxs...t__400492.html

 

What I have found on my setup is that after every mods I've done. I'd say 90% of the sound what this has after x pipe conversion, comes thru that dynomax muffler casing. There is no holes or anything. Exhaust pulses just are so loud and not cancelling each one out. Thats why filling it with muffler wool helped a lot. What I would (and i have done) do is modify the setup bit by bit. Otherwise I could not tell what eventually did what. And I have not had this kind experience before as this is my first v8 car. Noise cancelling is why I think that paraller x pipe stresses mufflers more what are after it than what x pipe muffler does.

What not filled dynomax x muffler sounds in xjr? It is not LOUD all the rev range no. It is quite loud all the rev range but LOUD on those certan thight rpm ranges where exhaust pulses doesn't override. Including of course v8 drone 1800rpm. Neighbours would't mind unless you are giving it beans. But if you do x pipe only. I don't know what the result will be. You have to test it. Sound will change thats for sure.

And what i can not stress more is that use flex pipes. These cars have very stiff exhaust pipe hangers. So using long and soft flex pipes "detach" engine more from the car. Plus stainless steel seems to strech a lot when it heats up. I measured easily 3cm increased lenght from cold to medium warm tail pipe. I have four flex pipes. Original place and axle overhang.

 

Thanks for the details, Vauxi. I like your approach to these mods by doing them bit-by-bit, which at this point would be installing the new downpipes and hooking them up to the existing setup. They're supposed to be "direct-fit" replacement for the stock downpipes. I'm not ready to do this yet as I had a total knee-replacement a few weeks ago. I have some other things that I'm going to do along with the downpipe installation; the SC snout needs to be rebuilt, new motor mounts, and new water pump. That should be a big enough project without trying to build a whole new exhaust system. Hopefully I can get going on it in a few weeks, and I'll let you know how it turns out.

 

My ideal setup is: Supersprint catless pipes, x pipe, no resonators and Supersprint rear mufflers. I've never heard that setup on any 4.0 AJ V8. It's expensive, but I'm sure I'll buy it when I convince myself to spend the money, lol!

If that sounds over powers the S/C whine, then I'll get the blower ported and put the +2.5 upper pulley.

 

I hadn't come across Super Sprint in all of my searches. Lots of good quality stuff for XJRs, but not only is it expensive, if you order now you could get your parts sometime in October. That does look like a good setup, though, and I think that you should go ahead and get the SC ported and put on the pulley for WHEN the exhaust over-powers the whine.

 

Agreed, lol! Sucks they have no pics or vids on them of these cars. But I love my car, so why not.

 

Do you think that the cat-less downpipes will get you through that pesky yearly inspection? I spent 17 years in the DFW area, but over on the FW side ...

 

Everytime i've taken a car to get inspected, they never look under it. Usually, if no codes, 6 out of 7 readiness monitors completed, it'll pass. If it fails, I wouldn't care. I'll just put cats on or drive to the country side for an inspection.

 

I had a place in Bedford that was like one of those "country" shops where I would take my truck to get inspected. That was in the 90s. The truck was a '77 Chevy C20 with a 292 straight six. Being one that can't leave anything as-is, I found headers, an Offenhauser intake manifold, roller rockers and a cam to put in it. I tried a small four-barrel Holley, then a big two-barrel Holley, but never could get it just right, even with an air/fuel ratio sensor in the exhaust. But, it always passed inspection ...

I live in area now where there are no inspections at all; not even to see if your brakes or all the lights work. I'm somewhat leery of going cat-less, so I went with the Nameless Performance downpipes with 200-cell cats.