Best X-Pipe Location on 5.0 XKR
#21
#22
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
#24
#25
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
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
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 following 2 users liked this post by Tervuren:
Panthro (12-23-2018),
Ranchero50 (01-31-2018)
#26
However, by experimentation, it was found scientific knowledge and reality were at odds with each other. We got airplanes.
#27
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.
Single good, double ok, triple, don't go there with a XKR.
#28
#29
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
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
#30
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...
#31
Hey Cambo.
A fellow Ozzie with a passion for the big cats.
I want to get a remap for the extra 50 bhp including the x pipe. Do you know anybody in Australia who does the tune, also, do you know anybody who can make up the centre pipe with the x, so I can fit it at home.
I have a 2013 XKR and upto now I've replaced pads with red stuff, fitted new wheel bearings all round, trans oil/filter change, eng oil changes every 6 months (yes, the oil does get dirty quick)
A fellow Ozzie with a passion for the big cats.
I want to get a remap for the extra 50 bhp including the x pipe. Do you know anybody in Australia who does the tune, also, do you know anybody who can make up the centre pipe with the x, so I can fit it at home.
I have a 2013 XKR and upto now I've replaced pads with red stuff, fitted new wheel bearings all round, trans oil/filter change, eng oil changes every 6 months (yes, the oil does get dirty quick)
Last edited by XKate; 12-04-2018 at 03:50 AM.
#32
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?
#33
Love your work Cambo!
Yes, a bit if a trek to Sydney with the car, is their a way to put it on a laptop then OBD. Maybe a cheap Harvey Norman laptop and buyer of the tune pays for the laptop postage ( seen somewhere on the forum it being done in the states)
You'll have to pm me with pricing for the tune, did you buy the 2.25 X piece in Australia, do you prefer any particular manufacturer, or are they all pretty much the same.
I also liked that the X piece keeps the pipes close together, probably to fit better in the exhaust tunnel under the car
not sure if there are any advantages/disadvantages of going stainless regarding power output.
Yes, a bit if a trek to Sydney with the car, is their a way to put it on a laptop then OBD. Maybe a cheap Harvey Norman laptop and buyer of the tune pays for the laptop postage ( seen somewhere on the forum it being done in the states)
You'll have to pm me with pricing for the tune, did you buy the 2.25 X piece in Australia, do you prefer any particular manufacturer, or are they all pretty much the same.
I also liked that the X piece keeps the pipes close together, probably to fit better in the exhaust tunnel under the car
not sure if there are any advantages/disadvantages of going stainless regarding power output.
Last edited by XKate; 12-04-2018 at 03:00 PM.
#34
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#35
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