Okay then; how about one X-pipe right off the cats, then another one back as far as possible?
I don't recall that ever being done. Ranch............ got some free time?

 

I don't see a huge benefit in using two cross overs in an X form.

The original purposes of the X was to both use one banks exhaust pressure pulse to help create a momentary negative dip as the opposite bank has that banks cylinder exhaust valve opening to help draw that pulse out of the cylinder. It works similar to a venturi only the pressure pulse passing the window opening to the other bank is creating the negative pulse going up that bank. Everything pulse moves at different speeds depending on heat, amplitude and distance.

The 2nd purpose is to allow each banks pressure pulse two paths to follow past the crossover. So effectively at 2000 rpm you are getting 500 exhaust pulses per minute out of each bank in the head pipe and 1000 pulses after the X as both banks are using both mid pipes. The other side is you basically double your effective volume available to each bank after the X.

So all that brings us back to the original question. If you add a 2nd X pipe what's going to happen to the pulses coming from the first? If things are out of phase enough do you end up with 8 pulses out, or remain at four? Does it improve things or just add another variable that may or may not work?

There's just a ton of interesting stuff going on at any instant to definitively quantify any one modification as good or bad. Find a free copy of the "two stroke tuners handbook" that was written back in the '70's for the dirt bike crowd. Absolutely fascinating stuff understanding how a 2 strokes expansion chamber uses the exhaust pulse pressure wave to act as a supercharger at certain RPM's

 

Modern n/a Ferrari do exactly this (supercharger effect at a certain rpm) on their variable inlet manifold

 

"Theory is theory until application makes it either live or die"
- Some guy somewhere

 

The X-pipe is not 100% efficient in getting equal cross over. There will be a pressure wave location that is good for a 2nd X-pipe and there can be benefit. The problem is bends can also cause a loss, so you're adding in an extra set of bends. The benefit of a 2nd X-pipe is not going to be as big as the 1st.

It won't be a big difference as it is not a linear benefit from the 2nd X-pipe. However, it also won't be negligible.

 

The Newtonian physics for air flow did not account for the compression of air. This resulted in several leading physicists saying air planes would be impossible.

However, by experimentation, it was found scientific knowledge and reality were at odds with each other. We got airplanes.

 

Although not asked, the problem with a triple X-pipe, is you start to change the sound from "V8" to a two inline four Fast'N'Furious cars racing each other. It will start to get flatulent in sound with three X-pipes unless you also reduce the pipe size at each X-pipe.

Single good, double ok, triple, don't go there with a XKR.

 

 

2-stroke tuners handbook really is fascinating. they are brilliant. not efficient, but brilliant.

 

Yes, I like it because it gives a great foundation on how to control exhaust pulses and what can be done with them. Understanding pressure waves, header lengths, merge collectors and different crossovers is all in good fun. With the XKR I've also learned about controlling resonance and drone. Not nearly as good or thorough as an OEM but pretty neat making it do what I want and sound good too. Granted, it's 80% SWAG, 15% luck and 5% skill but who's counting...

 

 

I can do the standard XKR-S tune, or the big power tune like we put in u102768's XKR. https://www.jaguarforums.com/forum/x...-177494/page3/

It's a bit of a drive from the Sunshine Coast to here though...

The exhaust fabricator I use here in Sydney would need a 5.0L XK or XKR to make the exhaust to send up to you, or we could procure an OEM one from an XKR-S, it'll be more expensive though, the last two 5.0L I did were OEM pipes, I have one of the 4.2L version here on the shelf...




Here's the one's we get made for the 4.2L



Fancy a roadtrip?

 

 

I sent you an email, there's a few ways we could make this happen for you.

 

I can recommend that

 

Sorry Cambo.
I was searching for the email ( no email) then realised I changed server about three years ago with new email address. I've now updated on Jaguar forums.

Can you resend please.
Thanks.