Purchased my XK8 a few months ago and was poking around under the sar and noticed that the center muffler was missing. It was a clean looking removal (nicely welded) but I'm wondering if this has any impact beyond the exhaust note?

 

Does your car have a nice rumble?

 

Other than increase in-cabin noise? It sounds louder outside too. That's about it though.

 

it doesnt give us another 100HP??????

 

Dave, I suspect you have an "X" shaped pipe in place of the muffler? These are widely available and commonly used. Many feel the Jag is painfully quiet for such mean looks. Whatever you have is most likely "all about the sound". Unlikely it is hurting anything and unlikely it is helping anything (like HP). Enjoy the sound while some of us whisper down the road.

 

No crossover connection between the left and right bank. They are totally independent. It does seem to have a nice rumble but not loud and the cabin is church quiet when cruising on the freeway. Since I havn't heard any other XKs I'm not sure how much louder I am but, I can say when you light the fuse you know it!

 

You get a little noticeable pick up on the low end just because you have less restriction in the exhaust process.

 

About a year and a half ago, I had my center muffler pulled off my 2003 XKR and replaced by two straight pipes to the first resonators - with an old fashioned H-Pipe connection, just after the transmission crossover.

I did it for the sound. "Whisper quiet" Jag was ruining my rep as the rowdy old gear head in the neighborhood!

Well, I don't think my rep was restored. It's a barely noticeable improvement in sound quality - but hey, it actually makes a slight rumble now and what DaveC said: "it's church quiet when cruising" is true for me too.

IMHO, Log manifolds, two cats and six muffling devices is ridiculous on a performance car! Next year, I plan high-flow (or possibly gutted cats with a fabricated MIL eliminators) and flowmaster mufflers.

The cat WILL growl then!

 

Any thoughts about the Mina rear muffler delete? I like sound but don't want to go nuts.

 

The Mina setup is quite pleasant and not overly loud.

 

Not sure what the difference is between Mina's rear muffler delete and what I did by just replacing the rear mufflers with pipes. I'll be trying something different as the drone at 2000-2200 rpm is too much. Climbing a hill at 60 mph will vibrate the whole car. I'm planning to put rear mufflers back on and try some variations on removing the center muffler. Probably start with complete separation then maybe try an x-pipe.

 

The biggest inhibitor of high quality exhaust note is the factory Jaguar catalytic converters. I got much more and much better sound from replacing those than I did replacing everything past them. Just saying...

 

xenophobe,

What aftermarket cats did you find that complied with CARB requirements?

 

There aren't any. I just have my fingers crossed. lol

However, the 200 cell cat that NP uses is CARB certified. But using the terminology "high flow" and "performance" in their product, it automatically disqualifies it from being usable.

I've retained my old cats in case they need to be changed out to pass. Every once in a while I do get a code, but it's irrelevant.

My logic is, how many smog techs are going to know the difference if they have to visually inspect? Probably none of them. And they're so tucked away that they're not easy to inspect. Add to that, the place I've been going for smog checks is the same place I've been going for 20 years. He won't fudge results, but I've never seen him inspect anything.

 

What I thought. I think I'll stick with what I have for now.

 

Granted its not directly related but I passed emissions in CO with Magnaflow high flow cats in my Galant VR4, passed with flying colors come to think of it.

 

When the engine is up to temp and running closed loop the cats shouldn't have all that much work to do anyway. Plus the comparison being made here is between a new high flow cat and an old low flow one that has been crudded up with who knows what over the years.

I'd expect that the lifespan of a high flow cat might be somewhat shorter since you are probably starting off further down in the acceptable emissions range, but that when new, they wouldn't be any worse than a middle aged stock one.

 

I had always heard mixed things about what happens when you change exhaust restriction. I seemed to recall that reducing restriction actually REDUCED low end torque but that horsepower was increased at high rpms. Anybody else want to chime in about this?

Doug

 

It's all over the map, each person I've encountered has had a different answer. In N/A cars, to my understanding, backpressure helps a little in low end torque but stifles high end power.

Turbocharged engines like as little backpressure as possible to help the turbo spool faster.

As far as S/C motors, I'm not sure of the general sentiment.

 

I've been toying with the idea of leaving the front box and the two rear boxes in place but getting a pair of straight through pipes to replace the middle two boxes , thought it may increase the growl but without any boom or resonance , don't want the car noisy at cruising speeds though , any thoughts guys ? ,

All the best

NikasilNik