Looking over some old threads, I've noticed a few regarding exhaust systems. Some had questions about exhaust systems in general, some had specific questions about systems I'd built. Since I was not visiting the forum and did not see them, I was unable to respond. I'll try to rectify that in part now.

Let me start with saying our X100 XK8/XKR Jags have the worst exhaust system I have ever seen on a car--and I've seen a lot in 55 years of working on cars as a full blown car-nut. It was obviously a cheap adaptation of the pre-existing XJ8/XJR system which had no consideration for performance, just super-quiet sound.

Going back to 2004, I began developing an exhaust system for my own 4.2 XKR. I had previously done several for SCCA road racing cars. After researching the latest findings on the topic, I starting designing a system for the XKR and having it built (bent and welded) by a local exhaust shop.

Although my first priority was to have the car sound better, I was also interested in improving performance. I don't believe any improvement unless I can verify it with testing. Fortunately, The Dyno Shop was nearby, with three dynos, and a wealth of experience with accurately measuring vehicle performance.

Many prototypes later--different off-the-shelf X pipe fixture designs, different pipe configurations--each one carefully dyno tested to measure improvements in both sound and power, the final result was the "Mk I X-pipe".

Although the intent had only been to have one for my own car, I'd posted the saga of my pursuit on the old Roadfly forum (at the time the most popular Jag forum). When it was all done, I started receiving requests from forum members to get one for their cars. Guys were driving from all over the West to San Diego to have one installed. Next thing I knew, for those guys that couldn't come to San Diego, there were requests to ship them all over the world! UK, Sweden, Europe, Australia, New Zealand, etc.!!!

This was an entirely unforeseen result. The Mk I system had never been intended to be shipped. I had to figure out how to have it made in sections that would meet shipping dimension requirements, and then had to pay the shop to build jigs/fixtures with which to build it since they were not installing them on cars. That was expensive, but I was motivated to share it with as many guys as wanted it. Frankly, I was hugely flattered that so many wanted my creation!

After a couple of dozen systems were sent out, the shop had fallen way behind on orders--these were, of course, behind their regular everyday drive-up business in priority--with no prospect of ever catching up. I finally realized there had to be a better solution to so much demand for a really good exhaust system for our cars. I canceled the remaining open orders, lost the money on the fixtures (never amortized), and started redesigning the entire exhaust system from a blank sheet of paper.

The new system took into account shipping dimension regulations, the finest available stainless steel tubing, all stainless steel muffler material (internal and external), fasteners, brackets, etc. While I was at it, I went back to spending my kids' inheritance at The Dyno Shop testing new configurations, pipe diameters, and theories of exhaust pulse extraction, passive noise cancellation, (both related to X cross-pipe intersection angles and distance from exhaust valves) and other related parameters. Desired and maximum cubic feet per minute (CFM) flow rates of hot gases and laminar flow characteristics (from my aeronautical background) all became part of the new design. Flow bench testing often preceded fabrication and dyno testing. It became obvious that only all mandrel bending would be acceptable, but expensive.

My formal education, both undergrad and graduate school, was predominantly in research and experimental testing. I blame all of this way over-the-top behavior on that background. :-)

The final result of all this was the Mk II X-Pipe. Pictured in the posts below from other forum members.

Photos of the New MacLeod X-Pipe Mk II

MacLeod MK-II X-Pipe

Perhaps not coincidentally, this may be the most dyno-tested exhaust system on the planet. The Dyno Shop alone did many installations--took 1 to 1 1/2 hours, most of it spent removing the old OEM system--with dyno testing both before and after installation for the car owner's curiosity, and my desire to determine the statistical reliability and validity of the tests. These in addition to the perhaps dozen dyno tests on my own car with the Mk II system. Several other owners across the US also got back to me with their virtually identical dyno test results.

Regardless of the noteworthy power gains, I would still come back to say, these are not race cars and the predominant factor in choosing a system should be the appeal and pleasantness of the sound.

Some owners expressed a desire for a little quieter, or a little louder exhaust note--all were very pleased with the tone, just wanted more or less of it. I designed two more choices for mufflers, plus a straight-pipe muffler substitute.

Finally, I received some requests for an even more subtle sound, "like an expensive European GT, you know, an Aston Martin without the bypass, Maserati, etc., EU legal (more restrictive than USA), but obviously a bunch of power under the hood".

The answer was the "Euro Version" which added two straight 24-inch mufflers directly behind the "X" in place of the long legs aft of it. A little quiet for my personal tastes, but those that wanted that sound level have all been very happy with it.

Wide Open Throttle (WOT) with the Euro still produces an attention getting sound. :-) One just barely hears it at low and middle throttle.

So, bottom line, the Mk II X-Pipe ended up with 8 different sound levels. Each of the basic systems--Standard or Euro--have a choice of four different levels that can be changed in about 15 minutes with the car on the ground. (See Mike B's post about doing this--scroll down to "15 minute swap")

First Antipodean MacLeod Performance X-Pipe Instal

Sorry about this getting a bit long. The several old posts with questions about exhaust systems, and particularly those asking about my "MacLeod Performance Mk II X-Pipe", touched on a topic close to my heart. So, I thought it easiest to answer most of them in one post.

I'll be happy to answer any questions, as I'm able, about exhaust systems in general, exhaust effect on performance, system longevity, design and material considerations, etc.

As I go through past threads, if I see a question to which I may have an answer, or at least a little information, I'll respond to it on that thread.

Bill

 

That's not just an exhaust system, it's a work of art.

Graham

 

Is the exhaust system still available for purchase and installation (if local)? And for 4.0L engines as well?

 

Like many members, I have looked at the pictures many times.

Since your recent "joining the forum" post, I have been hoping for more details.

If you are at liberty to reveal them, I am sure that the critical dimensions would be of great interest to many members including myself.

 

tberg - looks like Mina carries it but currently out of stock

 

tberg:

Yes, they are still available, also with installation.

Although I've never actively marketed them (Mina did buy some 15 or 20 systems that they sold as their "Top of the Line" Exhaust System--they're all gone now), I've always had them available for Jag owners that contacted me directly. The only occasional problem is that the pipes are all mandrel bent on a computerized pipe bender and the shop has a minimum order of 20 (identical) pieces. So, if I run short of any particular pipe, such as if someone needs only certain sections for collision repair (I will sell only parts of the system in such cases), my inventory can get out of balance and I'm stuck waiting for them to bend new pieces. Several months ago this happened when Rob Enderle wanted a Mk II X-Pipe system. He is the most patient, understanding man I know. He kindly waited until I got it all sorted out with no more than a periodic email inquiring about the status. Thank you again Rob, you are a gentleman!

Rob's post about his new exhaust, scroll down to #36: https://www.jaguarforums.com/forum/x...t-82601/page5/

I have a lift in my hangar and might be able to do the installation if I can clear enough space, or The Dyno Shop is just on the other side of the field and they can do it.

There are three different types of catalytic converter to pipe connections: 4.0 N/A, 4.0 S/C and 4.2 engines. I have specific pipes to mate to each of the three styles.

Earlier cars also had a poor design hanger assembly at the rear. I made an improved version of the later style attach bracket and replace the old originals at the same time a system is installed.

 

I don't see it listed through the main Mina site but master modder Rob put one on not too long ago (post 36):
https://www.jaguarforums.com/forum/x...t-82601/page2/

I know I am among those interested, if it is still available.

 

plums

I have a spec sheet that compares the Mk II to other exhaust systems.

If I can figure out how to scan it and then post it to the forum, I'll do so.

 

Does anyone know where to get this system now?

 

An exhaust thread without sound clips is...useless. There are hundreds of pics online of various systems, the only ones that get attention are the ones that actually show what you will be getting when you spend your money(YouTube ).

And it's always important to remember, the under axle systems WILL hit the floor if you car is lowered

 

So... do you know where to find clips of this system? Or where to get the system or at least pricing from?

 

SanDiegoMac,

Looks like a great system but why don't you have it over the wheels? Those Mina systems I've seen look like crap hanging down under the wheels....I would be interested if I could get a set over the wheels.....Doesn't seem like it would be a big deal to do that....What is the advantage of the under the wheel design?

I'm not knocking your product Mac, just looks kind'a funny to me.....

Billy Clyde in Houston