Found the most likely cause of my vacuum leak resulting in lean codes on both banks, thanks to suggestions from you guys. I’m attaching some photos here. Will opt for a temporary fix but will finally get around to ordering a replacement part from SNG Barretts. I was surprised by how much the plastic around the lower sound baffle on the air intake duct had become brittle and broken off.

 

Yeah, that happened to me as well. I replaced it with the Mina Gallery Aluminum intake pipe.

 

I hope to do that eventually but for the interim I’ll patch it up. There may be other leaks elsewhere, will have to stay alert for them, although the usual suspects seem pretty good.

 

Do you have rodent problems at your parking location? It looks more chewed than just cracked.

Graham

 

Rodents must have 'crappy' taste buds!!!! I don't think most of what they chew tastes good?

 

Rodents have incisors that are constantly growing. Chewing and gnawing on hard objects such as wood and plastic Jaguar XK8 intake pipes help wear these teeth down and keep their length in check. If they do not do this, the teeth grow disproportionately, curl around, and begin to pierce their skulls.

This poor little squirrel is a victim of his own teeth. Warning, this image can be disturbing to look at.

 

These are closed echo chambers meant to dampen some frequencies coming from the blades of the supercharger and traveling back up the intake tract. These sound waves work against the supercharger's ability to bring more air in the engine and develop the torque/power as designed by Jaguar. It also tends to lessen the supercharger noise in the overall sound profile. The "better" answer is to stick with the stock part and all these chambers, but you have to factor cost and availability. An aluminum part is a simplified and more durable design, but not without compromise. I drove a local car with such an intake and did not care for the resulting sound profile (sounded more like a jet engine, overwhelming that nice V8 sound), but it is a personal preference. I could not tell if there was a loss of power as these cars are plenty fast, and certainly faster than my XK8.

FWIW, someone tried to repair this part before, but ended up replacing it as the particulars of the plastic material involved made it super hard to properly heat up for plastic welding (it apparently ***** up when heated). The other consideration is that any failed repair can result in loose parts getting sucked in the intake.

Best of luck, keep us posted.

 

These appear to be side branch Helmholtz resonators to alter the frequency dependent sound attenuation profile of the intake, like bass traps in speakers. Presumably they are performing their magic together so that there is a fairly narrowband reduction in sound amplitude across some range of frequencies.

Nothing is free, as with most things, so the attenuation directly implies viscous loss in the intake (mostly in the necks of the resonators), impeding flow. Mina appears to have done the experiments and found that a smooth wall curved pipe adds 8-15 hp for the XKR, according to them. So, I wonder what part of this design has anything to do with increasing the flow to the supercharger and what part is just getting rid of the 'jet engine' noise from the supercharger. Increased flow could have been accomplished by increasing the flow directly.

On the other hand, not clear how 8-12 hp matters in the overall scheme of things. Potential elimination of leaks in the XK8 (no resonator), priceless...

 

Interesting reading about the role of reducing the impact of sound waves. The level of technical knowledge on this forum is remarkable probably due to the fact that we have to do a lot of maintenance ourselves which means a lot of research. Graham mentioned it looked as if that section had been gnawed at by mice; the fact is it crumbled when I pressed on it. The original damage was just a long crack. I have made some temporary fix and will reattach it later today but I’m not confident my handiwork is going to hold for long so I’ll look around for a replacement.