Hi everybody,

I have a fairly specific question for you guys. I understand that the 4.2L XKs feature a kind of acoustic channel between the engine bay and the cockpit, to enhance the perceived engine noise. Could anybody tell us the details of this system and where it is hidden, or show us a diagram of the related HW ? It is maybe a simpler / static version of the symposer fitted to the 5.0 engine inlet, for which there's some documentation available online (except through where goes the sound into the cabin?).

We discussed the subject on the french XK forum but haven't yet fully closed the loop for the 4.2 variants.

Thanks !

 

The 'noise feedback system' seems to more than just the symposer - they are described separately in the workshop manual, with the symposer being a sub-assembly (see attached). further on, it says: "The resonator directs the sound from the feedback tube into the passenger compartment. The resonator is installed in the passenger compartment side of the engine bulkhead, on two mounting grommets each consisting of an isolator and a compression limiter."

This manual applies to both 5.0 and 4.2 cars; it does not say the noise feedback system is specific to the 5.0.

 

Hi,

That's a quick and accurate reply ! Thanks a lot. What made me think that the system was different on the 4.2L is that, among other things, Mann+Hummel, the manufacturer of the airbox, dates the active symposer to the introduction of the 5L engine. See p.4 here:

https://www.mann-hummel.com/fileadmi..._2013-1_en.pdf

Several people I discussed with also had this in mind...

 

Here's two jpg of the Intake NOISE tube on a 2007 non turbo XK. Hmmm, noise......bad. Remove asap.

Noise Tube is number one in the first jpg...............resonator is number 8 in the second jpg.

 

Apologies - when I looked further up the manual, it does say "Intake Air Distribution and Filtering - V8 S/C 5.0L Petrol". Unfortunately, my version of the manual doesn't have the 4.2L stuff.

However, I did some more digging, and the Noise Feedback System on the non-S/C 5.0L cars is much simpler - there's no symposer, just a simple tube from the throttle T-piece in the intake system to the resonator. My guess, and it's only a guess, is that the 4.2L cars have something similar.

 

Hi,

As usual, I just can't believe how you guys can answer any unexpected question on the spot. Many thanks again to you two, and "bravo" to these wonderful forums and their expert contributors !

Side question : is this shop manual available somewhere on the web ?

 

I bought mine as a CD on eBay - not sure if it's 100% 'official', but it has the manuals and wiring diagrams.

And I've just discovered I do have the 4.2 manual, and the 4.2L non-S/C has a direct pipe from the induction system T-piece at the front of the engine to the resonator on the bulkhead. For some reason, it is not described for the S/C variant - if the symposer wasn't introduced until the 5.0L S/C engine, my guess is that the 4.2L S/C has the same direct pipe.

 

Ok. I'll pass on the info to this side of the pond ;o)

 

06-09 XK Workshop Manual [Jaguar XK XKR X150]

I think this is the site I downloaded my manual from. It took only minutes to download.

 

Call me weird, but I will never get my head around making a refined GT car noisier on the inside. I had my fill of noisy cars when I was young and all I could afford was old cheap stuff from the 1970s.

 

If you drive it 'normally', it's pretty quiet, even with the optional performance exhaust. When you twist its tail, it growls in a most satisfying fashion. Nicely Jekyll/Hyde.

One of my neighbours has bought an XK, and it's definitely quieter than my XKR 75. When he starts his up, it sounds similar, but he has the standard oval-pipe system and it is not as 'muscular' sounding. I would imagine his is quieter inside, even under hard acceleration.

 

I'm still not clear on if the 2010 5.0 XK non supercharged engine has a symposer. My service manager and shop Foreman said it does. Is this correct or is it only the 5.0 Supercharged version?

 

The symposer is supercharged-only. The NA engine has a simpler 'noise feedback' tube that runs from the intake system to a resonator on the bulkhead:

 

"Inlet resonator" isn't always what you think. Most are there to REMOVE specific intake resonances.

 

Ok. So it's not called a symposer, but does it still help to resonate the engine sound to the passenger compartment under aggressive driving anyway?

 

Yes, it's just not as sophisticated as the symposer, which has a valve that controls when induction noise gets fed to the resonator, which is like a speaker attached to the bulkhead, feeding sound into the cabin. Basically, it only feeds sound through at high load and/or high RPM.

The noise feedback system is just a tube, so the resonator is always being fed induction noise. However, I suspect the noise is less intense on the NA engine, which is why it doesn't need the same level of control as the SC engine.

 

Thanks, great info. Of course at Jaguar I was told my car had a symposer so there's where I was confused.