Here are the shots of before and after with the MacLeod system. I started off doing this piece by piece and it just got ugly. Should have done MacLeod from the start or just stopped at the rear muffler delete and gone to the Nameless cats. Good lesson in not doing something by hit and miss. This got really expensive though the short run with the cutouts was kind of fun.

 

Hi Rob,

I'm back from Peru and will contact you offline as well.

The area where the Euro mufflers are located is in front of the rear wheels and thus doesn't have the advantage of maintaining the same ground clearance as the wheels go over bumps, etc. , as do the pipes when they go under the axles. We will replace the Euros with pipe sections, as discussed.

Also, as you know, but for others' information, I was working on different cats at the same time as Jason (Nameless) and collaborated with him about them. I didn't see any point in both of us making them and much preferred for him to do it as it is a business for him and only an expensive hobby for me. We had both ended up with the same catalytic converter model to adapt to the Jags and it was the best I could find at the time, but it is an earlier generation, 200 cell, not legal for retrofit (it's only a $10,000 fine :-) ), and adds a lot of noise to the system--as many have seen. Although it flows a little better than the OEM cats, it only adds 2-3 hp (XKR), if that, when installed with an OEM exhaust system.

My interest was more in being able to have the entire exhaust system have a 2.5 inch diameter. The exhaust manifold outlet is 2.5 inches, but the cats' outlet is 2.0 inches, so even with the Nameless cats, it is still like trying to push a baseball through a garden hose at the cats' outlet.

I recently found a new generation, legal for retrofit in 49 states (California requires that they individually test and approve any change) cat that has the desired 2.5 inch inlet and outlet. It flows much better than the older 200 cell cat and is EPA rated for 600 hp (each). Talk about flow!! It seems there is no (or very little) noise level increase (over OEM), but I haven't yet tested it with a sound meter (which I have).

It also allows me to eliminate the cat to pipe flange and gasket attachment and have a gasket-less V band clamp instead. This results in a totally smooth laminar flow inside the pipe.

I'm really anxious to get this setup on the dyno as it will eliminate the last significant restriction in the exhaust system--when paired with the Mk II X-Pipe exhaust. There's a lot on my plate at the moment and finishing this project is a little down the road.

Bill

 

I'll admit my ignorance in advance and pardon me if it's a stupid question but I'm just trying to understand. The nameless cats are a 250 cell cat and have an approx 2" diameter outbound. Even though they have fewer cells they are more restrictive than the 400 cell cats you've found that have a 2.5" diameter outbound... thus. cell count in the cat has significantly less effect on the outbound exhaust flow than the diameter of the outbound pipe ?

 

I'm not a catalytic converter engineer by a long shot, but I did speak with one from the manufacturer while looking for the best replacements. He recommended the cats I ended up with and gave me the specs, EPA ratings, etc. Since they are the same manufacturer as for the ones in the Nameless cats, I knew they would have the best info on them. Incidentally, the cats themselves have a 2.5 inch outlet, but the union at the flange is 2 inches.

I looked back at my notes and see that he didn't specifically say they were 400 cell, so that was my, perhaps incorrect, assumption, but he was very clear that the latest designs flow much better, were more efficient and that the EPA horsepower ratings were the best way to compare flow.

Looks like they don't even specify the number of cells anymore.
The ones I have don't say anything about how many cells per square inch, but they are definitely denser than the 200 cell ones. They are larger and have more surface area. He did touch on changes in wafer design and other things improving flow, and that the ones he recommended would flow much better than the older ones. There's a lot more to these than just cell density. E.g., number of wafers, distance between, surface area, etc. I'm just repeating things he mentioned.

The case size and design is also different than the older ones. Anyway, these will flow better, be quieter and are 49 state legal. That's why I decided to go with them instead.

 

Does anyone know if the MacLeod MKII X-pipe system is still available commercially? I cannot find it online anywhere. Very interesting thread.

 

SanDiegoMac.. Thank you very much for the explanation. When funds allow; I'm thinking of upgrading my exhaust system to help it breathe a bit better. I was initially thinking about replacing the cats, replacing the center resonator with an x-pipe, deleting the two mufflers near the axle and retaining the ones in the rear. After reading many threads about how restrictive the existing cats are I know a change there would help things quite a bit and I now know that I probably need to pay just as much attention to the input/output diameter as I do to the cat. Valuable information indeed. My thanks.

Regger21 ... I'd like to know the same thing.. very interesting thread indeed ! (thread subscribed and btw..regards from another DFW resident)

John

 

Yes, they are available.

Email me at MacLeodPerformance at gmail.com

I've never gotten a web-site, but am working on that now. Also never advertised them. It's always been "word-of-mouth" between XK8/R owners kind of recommendation/endorsement marketing.

It all started when some other owners saw and heard what I had made for my own XKR and asked me to make a system for them. Some would be at the dyno tests on Dyno Days. It just kept growing.

Some have even bought more than one system as they changed cars.
I thought that was the highest compliment.

 

[QUOTE=zjdmm1;970410]SanDiegoMac.. Thank you very much for the explanation. . . I was initially thinking about replacing the cats, replacing the center resonator with an x-pipe, deleting the two mufflers near the axle and retaining the ones in the rear. After reading many threads about how restrictive the existing cats are I know a change there would help things quite a bit . . . Valuable information indeed. My thanks.

You are most welcome, thank you.

Could you refer me to the threads you read about the cats being restrictive?

The catalytic converter engineer I spoke with told me that the early pellet type cats were very restrictive, but that the wafer style (as on our cars) that replaced them were much higher flow and not very restrictive. He was pretty candid about thinking there was not much, if anything, to be gained with replacing the OEM cats on an otherwise stock engine. (As long as they were not plugged, damaged, etc.) Some of this seems to be related to EPA requirements, limits on back-pressure, etc. But I don't have any expertise in that area.

I would like to flow test the OEM cats and will try to do so. The only way to be sure.

The most restrictive part of the XK8/R and XJ (essentially the same) exhaust systems is, by far, where it goes over the rear axles and the pipes are crimped to 0.75 to 1.0 inches in two places on each pipe. If those pipes are not replaced, one is just wasting time on other changes.

 

Most of the posts I read, if I recall correctly, regarding restriction in the cats were as much or more related to diameter and shape (almost 90 degree bends) than actual flow rate through the cat. I'm not an experienced member and since the day I joined I've been reading hundreds and hundreds of forum posts obsessively trying to get up to date and gain as much knowledge as I can. At this point 'what was said in which post" is more or less a blur. I'll start looking back through what I've read to see if I can find specific posts.
here's one though... https://www.jaguarforums.com/forum/x...35/#post373296
And another.. https://www.jaguarforums.com/forum/x...e3/#post837981


Regards and thanks !

John

 

There have been some measurements on R cars that showed about 11 rwhp gain, which must probably be about right. I have never done a good before and after test, but my best estimates would also be in the 10 rwhp range.

Be careful though if you already have a sport exhaust, as the combination will make it much louder. For me most sports exhaust systems are already a bit too loud, fun for short trips, but less for long trips (am already at 240Kmiles), but the combination of the stock exhaust and the sport cats make it perfect for me sound wise (and no drone).

 

Phew, what a thread! I've now read it all as I was able the last couple days. I was about to buy a x-pipe on eBay and have a shop fab it in, but it looks like I need to wait and do this the right way, possibly from the cats back. I'm loving the under-axle plan as well- will look more 'classic' to boot. I'll likely keep my stock tips on that same note, if they don't hinder other efforts upstream.

I'm especially interested in how this develops more for the 4.0 XKRs- lots of XK8s in here with impressive results!

 

Chris.. I'm very interested also. I asked about the new cats and MK-II exhaust system via email. I did receive a quick reply asking for a wee bit of patience since things were a bit hectic in San Diego at the moment. Once things settle a bit he'll get back to me with specifics and more detail. I'll keep you in the loop with the info I receive. We're both in DFW so it should make it even easier.

John

 

I had an X-Pipe installed in place of the straight pipes that replaced my middle muffler. The low-end torque has been largely restored. That was a priority over the sound.

However, I miss the rowdy sound at full throttle but not some of the trill-like sounds.

Glass packs....

 

Great, neighbor- please do and thanks for the PM!

Glad to hear that for the XKR as well. It seems the x-pipe is the way to go as keeping the low-end torque is also priority #1 for me. But what's the point if there's not an appreciable level of growl added, y'know? That's what concerns me, and makes me want to preemptively cut the small restrictors forward of the axle out as well, leaving just the rear mufflers at the back. Dunno. Wish there was a greater pool of 4.0 XKRs who have already been our test subjects!

 

Full throttle sound is great with x pipe and rear muffler delete, but normal driving sound drone increased from just rear muffler delete. so hot runs in the canyons great, 0-50 first gear great. Trolling with traffic, blah goes the drone. Now I envy the Mustangs, Challengers etc for their casual V8 sounds, probably just some glass packs or Magnaflows away.... and we get to enjoy the fab Jag interior

 

Thanks- which rear muffler delete? Is there a preferred x-pipe yet?

 

My rear muffler delete was custom, and not according to plan to simply explore ideas with mechanic. Cost me $450, not convinced that was a good price.

I had a $30 Jones X-pipe put in, $10 to ship (from summitracing.com). For $130 at Midas, I drove around 2 weeks with no center muffler but with clamped in straight pipes. I brought in the X-pipe and they welded it in for no extra charge. Yes, the sound is better for accelerating.

The proven solution by several people was replace center muffler with x-pipe, and replace rear mufflers with Magnaflow or Dynamax VT mufflers.

However, I want more sound even when not accelerating, so glass packs are next in a week. Think muscle car. I am usually a city-bound driver so excitement for my always different 10 minutes of driving are key. Weekends I hit the mountain roads and canyons. Off to Peak to Peak highway near Denver/Boulder.!!!

 

OK want to get the Jones X pipe, have seen several different pipes sizes noted on here. Anybody know which size I need to order for a XK8 2003?

http://www.summitracing.com/search?S...nes%20X%20pipe

 

I advise you not do the x-pipe just yet (2.25" pipe by the way). My rear muffler delete had acceptable drone BUT center muffler replaced with x-pipe and rear muffler delete is an unacceptable drone monster on the open road. I just finished hours of touring through mountain canyons and passes and I was not happy (nor my passenger).

It's ok in the city, but otherwise don't do it.

Now if you left your rear mufflers on perhaps ok. Those who were happy did X-pipe and replacement rear mufflers. I can attest to it.

For the record, straight pipes were hilariously glorious on those same canyon roads. Too bad the first gear torque loss at lower revs was so bad.

 

OK, I'm looking at X pipe and flow masters on rear, everything else removed.

Or possibly just X pipe and leave stock with the exception of removing the center muffler which the X pipe would replace.