Disclaimer: Everything I'm writing applies to the XKR; I understand that the exhaust components of the XK8 are different, so what worked for my XKR may not work for your XK8.

I've been playing around with how to get a good yet civilized exhaust note for my XKR. When I bought it, the previous owner had deleted the rearmost resonators and replaced them with straight-through pipes, which gave the car a vocal exhaust note, but also came with an annoying drone between 1500-2500 RPM, aka normal cruising revs. As it happens I managed to find a guy selling an entire stock exhaust system from a 2006 XKR with all five pieces. With these spare parts in hand, I felt comfortable hacking up what was already on the car without worrying about being unable to return it to stock.

My first move was to try and quiet down that drone by putting the rearmost cans back on, leaving me with basically a stock exhaust system, but with the 2006's quad exhaust tips. Incidentally, those quad-tipped exhausts bolt right up and fit mostly well, though if you look closely enough they do hang a little lower than the stock tip cutouts on the bumper. This got rid of the drone, but as people know, the stock exhaust note on these cars is woefully quiet, so I had to do something else.

My next move was to get rid of the big resonator that joins the exhaust streams from the two cats. Based on research from this site, I had the exhaust shop (Lou's Custom Exhaust in Waltham, MA) weld in an X-pipe to merge the pulses for both sound and performance. At the time of this job, I'd put the rearmost straight pipes back on, so now that I had only two out of the original five exhaust cans in place, it sounded pretty gnarly:

Kinda like a 4.6-liter Mustang GT with Flowmasters, come to think of it. Unfortunately I could only get this sound with the droning rear straight pipes in place; if I put the back resonators back on, leaving it with four cans in the system, it still sounded overly muffled, a lot like that almost-quite sporty exhaust note that comes out of a stock V6 Infiniti.

So a few weekends ago I put the rearmost resonators back on, went back to Lou's, and had them delete the two small cans right in front of the axles, leaving it with straight piping (including the X-pipe) between the cats and the resonators right behind the tips. Now it sounds like this:

I'd say it's comparable to what you'd get from a modern V8 Jaguar with a sport exhaust, and it even crackles if you lift off while holding a gear. And, best of all, it doesn't drone at all, so you can cruise around comfortably between bursts of speed. It seems that what I had done is similar in principle to one of Paramount's offerings, though I kept a lot of the original piping (including the crush bit over the axles).



One thing I discovered after all this was that all five of the pieces in the XKR's exhaust system were straight-through chambers, without directing the exhaust flow through packing or baffles. This surprised me as I remember reading that all four cans behind the big front on XK8s were packed with sound-deadening material. Can anyone who's hacked up XK8 mufflers confirm this?

Anyway, hope this has been useful; we have tons of exhaust threads around here, but they tend to be light on sound clips to go with descriptions, so I tried to fix that with this thread.

 

Good job! That sounds great!

In the end, you ended up with an setup identical to mine.

I have to take mine to the exhaust shop. It developed a leak at the welds where they replaced the before rear axle mufflers with straight pipes.

 

That sounds great. Good job. Did you notice an improvement in power?

 

Awesome, glad to be on the same page. Hope the shop can fix those welds quickly.

I haven't noticed any difference in power; maybe a dyno could give exact numbers, but I don't expect it to have done much power-wise, as everything that was removed was straight-through resonators, and their impact on flow would've already been minimal.

 

Just recorded a series of clips showing how it sounds on the road, mostly with something nearby to reflect the sound, whether it be a bridge, a wall, or a tunnel. Sorry about the audio quality, my camera's microphone isn't all that good.

 

I used you as my inspiration however I did 2 things different

1. 2.5" pipes
2. Went under axle instead of over axle

Strange thing, Im not getting pops and bangs, something I did wrong?

 

Very, very interesting. Maybe one of these days I'll catch you driving in person and hear the live footage.

Recommend Lou's in Waltham?

 

That looks like a much cleaner setup than my mishmash of stock and aftermarket piping. My pops and bangs aren't the near-gunfire ones you'd get from modern performance cars, just muffled burbling after lifting off the throttle, so perhaps yours is just subtle. Exhaust sound tuning is a mysterious art anyway, so your unique piping and H-pipe setup might be set up perfectly to discourage pops and bangs.

I'm going to Cars and Coffee next Saturday at Larz Anderson (you have to sign up on their website, but it is definitely happening) so if you're there you can hear it. I highly recommend Lou's in Waltham; I've been there a few times both for this XKR and a previous MR2 and they're great at walking you through your options and explaining what exactly they do to the exhaust.

 

 

Only if you somehow stuff a V12 under the bonnet.

 

I deleted the last 2 pairs of my '06 XK6's mufflers. Got full roundered pipe over rear axle. Sounds like a '60 Muscle car when 'triumped'. Other wise, a real nice combo.