i have a xk 4.2 2007 which is to quiet - can i remove the the two semi active units and insert two pipes to make it a quad outlet system like the r - will this improve the sound - regards big a

 

I assume that what you mean by removing the "semi active" units, you mean the spring loaded valves that are spot welded to the sides of the factory muffler?

I have not tried that but, I would remove the single resonator from between that cat converter and the muffler before I would play with the valves. Don't be surprised if you pick up a 1900 RPM drone when you take more muffling out of the system. I have that and it drives me up the wall. I presently ran the MinaGallery muffler with the quad outlet pipes that look and work good but, it does make that drone just bit louder.

The side valves appear to only divert a smaller portion of the exhaust gases. When I put on the Mina, which is a non-bypass muffler, the high RPM performance increased a LOT, proving that it flows better than the factory bypass muffler.

Albert

 

I know the exhaust "activity" has changed for the newer models and by pulling fuse 19 (between the rear seats) my exhaust valves are open fully at all times with no issues at any rpm other than great sounds out all four tips. I would try to keep the valves in the open position in a temporary fashion and see how it sounds before removing resonators or doing any welding etc.

 

Albert,
It sounds like you know how the 2 muffler valves work! I don't have a clue! Do they open to atmosphere at some certain rpm or what? If you can enlighten me please do so..............My 1200 rpm drone aint too bad; have got used to it!
Thanks, Adrian 2007 XK Coupe

 

Adrian

I actually do not know for certain how they work. I've been looking at it and it seems that there could be spiral springs operated valves in those two tacked-on units on either sides of the factory XK mufflers. These are NOT the same as the valves used on the XKR, which are ECU controlled. The spring-loaded valves simply open on back pressure thus, closed at small throttle openings and open at wide throttle openings. When the valves are closed all the exhaust is routed through the internal muffler passages. When open, apparently only a smaller portion is passed throught the bypass valves.

I posted here a recent performance comparison between the stock muffler with its bypass valves and the MinaGallery muffler which has no such bypass. The MineGallery muffler gave plenty of extra high RPM power to reduce the 70-110MPH acceleration times by nearly 3 seconds. That tells me that despite having no bypass valves, the MinaGallery muffler flows quite a bit better.

The 1200 RPM drone is NOT my real issue. There is a less audible but, more bothersome drone at 1900-2000 RPM with the standard and with the Mina muffler. Many owners probably do not hear it as on my car the drone only comes in after a good 30 minute highway drive when the stainless exhaust track expands and changes its exhaust frequency. Such drones, including the 30 minute delay, appear to be very common at these RPMs across most manufacturers and models when using aftermarket exhaust but, my XK also drones with the stock exhaust. Driving right at 1900 for extended periods gives me a headache. Drop to 1800 or go to 2100 and it is not there. Too bad that 1900 is 70 MPH, right where the traffic tends to flow much of the time and my normal driving includes nearly 3 hours of freeway driving in each direction.

There appears to be one solution that works for nearly all who tried it and it is called something, like the "Helmholtz pipe". I'm looking into trying it on my XK. I measured the drone frequency in my car and it occurs at 129Hz. There is a math formula that takes that into account in calculating the exact lenght of this "Helmholtz pipe" which would works as a noise cancelling device for that particular sound frequency.

Albert

 

I'd love to noise cancel that low RPM drone. How did Jaguar let that one go into production?

 

Albert,
Thanks for info; back in the 70's I added a cross over pipe between the twin exhaust pipes (before the mufflers) on my 3.4L salon. This made the exhaust note more mellow and got rid of the rasp.............
Just another idea............
I looked up the Helmholtz Pipe idea; think I'll leave mine alone unless a drone shows up at cruise(2000 rpm); didn't notice one driving to the Grandkids (100 miles at 60-70 mph).
I wonder if it's possible to jam the valves closed? worth trying?
I'll try to observe the valves at different rpm's with wife on the throttle! not sure if there is anything to see with no load on the engine.

Thanks again, nice to find someone interested in tech/engineer topics for a change!

Adrian

 

The cross over pipe does not seem to effect the drone. As a matter of fact a number of people think that it can cause drone. I have been tempted to put one in (X-pipe) since my drone is a pulsating one, thinking that the X-pipe could even those pulsations out. But, most of the online opinions claim no benefit from the X-pipe when it comes to droning. Also, I am pretty sure that the resonator muffler already has a built in cross over. Do note that the XKR has 2 resonator mufflers as opposed to the XK having only one. That maybe the difference in having or not having a drone.

Like I said the drone is less audible than the 1200 RPM one. As a matter of fact if there is tire noise it seems to mask out the drone. Fortunately or, unfortunately, much of the road surfaces that I drive are new and cause very little tire noise so, I can tune-into the drone sounds. It is almost a relief when I hit a noisy pavement section...ha...ha...ha...

Most of my time these days I try to avoid the 1900 RPM range by going at speeds up to 67MPH or over 72 MPH. In between, right at 70MPH, +/- 3 MPH, it is headache territories... The frustrating part is that the car is still under factory warranty but, when the service rep rides with me I can not reproduce the sounds as the exhaust cools off prior to the test drive. Naturally, they say that they can not fix something that they can not confirm during the test ride.

Albert

 

Have you been able to capture said drone in an audio or video clip? I'm really curious as to how it sounds...

 

No, I have not. I'll try to capture it on a voice recorder on my Android phone next time. Wonder if it will show up on the recorder? It is a pulsating exhaust sound the kind that gives headaches.

I did capture the frequency by using one of the Android spectrum analyzer apps, called "SPL and Spectrum Analyser" on my cell phone, that I paid something like $1.99 for. It displayed a solid 129Hz as the peak frequency while droning.

Albert

 

My 2007 XK Coupe had a noise which sounded like a bad wheel bearing or the drive shaft. Orlando Jaguar said that a drone at 1300 RPM is common ......
Reference SSM37257 02/28/2008 identified the problem to be exhaust hangers.
A redesigned exhaust hanger is available --- think I was told the repair is about $1000.......... covered under warranty if you still have one available.

2007 Jaguar XK Slate Coupe ......... 32000 miles.

 

What is SSM37257 that you referenced and how do I find it? I use ALLDATA for the TSBs but can't find an SSM.

Thanks.

 

I had taken my 2007 XK Coupe to Orlando ............ 32000 miles - no warranty

I had taken my 32000 mile XK to Orlando Jaguar to check wheel bearings or drive shaft noise. The Jaguar mechanic said he did not need to test drive. He provided me with a copy of Jaguar SSM37257........... Problem was a exhaust drone noise which had been previously identified as an exhaust hanger sympathetic vibration at about 1300 RPM .... drone is not heard at higher speeds.

Jaguar USA provided a courtesy $250 gift certificate to fix. Note my XK was about 1 month out of warranty when I purchased from Orlando Jaguar in June 2011. I have only driven my XK 4 times is the past 11 months ....... interstate 70MPH+ so I never had heard drone. I think the repair is about $1000 ........ parts $800.

I think if you access the Jaguar XK online shop manual .... TOPIX .........
they will provide addition information and repair procedure. I have not started or completed this repair.

Another issue ... AC CONDENSATION DRAIN TUBE CLOSED

I had AC condensation in the passenger side footwell .......... think this is a higher priority for me. $1000 to install a $8.00 redesigned drain hose. The recommended repair is to remove the instrument panel to fix ....
I have a concern that this is a high risk repair. Any thoughts?

Hope this helps

Alec Redfearn 2007 Grey XK

 

Just adding an FYI to this as I only have documentation 07-09 models.

For those years, it says the Stock XK has a "semi-active" system, controlled strictly by exhaust pressure acting upon a spring loaded valve. Th XKR got the "active system" controlled by the ECU...

Just more data for the thinking team...

Vince

 

Can someone post the procedure to fix the drone? I wonder Lou's Custom Exhaust can do it for much cheaper?

 

SSM37257 Title Vibration/Drone at cruise
Symptom 703000 Vibration Cruises

If any of the following vehicles (newXK, S-type, XJ) with an
AJV8 engine is experiencing a drone/vibration at cruise in
Content the 1300 RPM engine speed range, please contact the
Jaguar Technical Helpline for assistance with diagnosis and repair.

I could not find an repair solution in TOPIX Shop Manual.

Hope think gives all the published information I could find.

Alec Redfearn 2007 Grey XK Coupe

 

Additional information -- my 2007 XK is early model VIN .... B03959
Jaguar SSM37257 -- Vibration/Drone at cruise

My rear muffler appears to have a pressure operated by-pass in the muffler.
It does not have a "vacuum operated exhaust sound enhancement solenoid
assembly" .

The Jaguar Shop Manual includes the description of the vacuum/solenoid sound enhancement muffler component. I think I was quoted by Orlando Jaguar the repair was $1000 ...... suspect this is a new muffler and supporting vacuum pump assembly.................... not sure.

My normal driving is not 1300RPM ........... on I95 interstate no drown or
objectionable sound other than the JAG sound that we love.

Alec Redfearn 2007 Grey XK ....... 32000 miles/like new condition