XK exhaust to XKR modification
#21
12-12-2017, 04:45 AM
Veteran Member
As flow velocity and mass lowers from optimum flow, back pressure increases. So at lower RPM a huge open exhaust is increasing back pressure compared to one tuned to that flow.
#22
12-12-2017, 06:30 AM
I'll quote myself LOL
I posted this in the other thread, seems like the right place to post it again, given the subject matter.
I had a chat about this exhaust/cats subject, with my ex-JLR friend who writes tunes.
Here's what he said;
-------------------------------
Exhaust backpressure is very important on the torque based PCM's, i.e. the 2006 onward models like an X150, since this parameter is used to calculate engine VE (volumetric efficiency).
So, put in an x-pipe or remove the cats (or install 200cell, 100cell, etc) and the fuelling would be off, because the VE of the engine no longer matches the stock parameters, resulting in high LTFT/STFT %'s.
This would limit the perfomance somewhat and/or cause some hesitation in certain RPM/load regions.
VE, in turn, is used in the torque calculation (driver demand, calculated indicated torque, which are compared to the estimated torque table in the PCM). In HEAVY cases SOMETIMES it may even trigger limp mode (been there, done that).
-------------------------------
And this makes perfect sense to me now, since we had the experience of flashing the factory XKR-S tune into a standard R and it did not make good power. Yet we have also flashed the stock XKR-S tune into other cars that were fitted with the XKR-S exhaust (with the x-pipe) and it made great power.
There are dozens and dozens of maps/tables and factors in the PCM of the X150, even things like the supercharger pulley ratio are in there and can (must) be modified. So with an X150, any mechanical changes you make to the car, be it exhaust/cats, pulley's, intakes, they have to be acommodated for in a custom tune.
Yes the PCM will adapt somewhat, but it won't be perfect, and in some cases I guess you could even go backwards, if the tune is not matching the mechanical changes.
I had a chat about this exhaust/cats subject, with my ex-JLR friend who writes tunes.
Here's what he said;
-------------------------------
Exhaust backpressure is very important on the torque based PCM's, i.e. the 2006 onward models like an X150, since this parameter is used to calculate engine VE (volumetric efficiency).
So, put in an x-pipe or remove the cats (or install 200cell, 100cell, etc) and the fuelling would be off, because the VE of the engine no longer matches the stock parameters, resulting in high LTFT/STFT %'s.
This would limit the perfomance somewhat and/or cause some hesitation in certain RPM/load regions.
VE, in turn, is used in the torque calculation (driver demand, calculated indicated torque, which are compared to the estimated torque table in the PCM). In HEAVY cases SOMETIMES it may even trigger limp mode (been there, done that).
-------------------------------
And this makes perfect sense to me now, since we had the experience of flashing the factory XKR-S tune into a standard R and it did not make good power. Yet we have also flashed the stock XKR-S tune into other cars that were fitted with the XKR-S exhaust (with the x-pipe) and it made great power.
There are dozens and dozens of maps/tables and factors in the PCM of the X150, even things like the supercharger pulley ratio are in there and can (must) be modified. So with an X150, any mechanical changes you make to the car, be it exhaust/cats, pulley's, intakes, they have to be acommodated for in a custom tune.
Yes the PCM will adapt somewhat, but it won't be perfect, and in some cases I guess you could even go backwards, if the tune is not matching the mechanical changes.
Others have reported no gains at all after changing cats, exhaust, etc, but that's because the tune was not corrected for these changes.
The following users liked this post:
Chris77 (06-11-2022)
#24
12-31-2017, 12:49 AM
hi,
the xk and xkr rear exhaust are very similar except of the bypass. Is the interior the same ? I assume they are identical, because of the cost savings during production and even the connection of the bypass is there. When I weld new pipes to the main exhaust body, I actually would get a xkr exhaust with a better sound for my XK, am I´m right ?! What you guys think ?
Cheers
Frank
the xk and xkr rear exhaust are very similar except of the bypass. Is the interior the same ? I assume they are identical, because of the cost savings during production and even the connection of the bypass is there. When I weld new pipes to the main exhaust body, I actually would get a xkr exhaust with a better sound for my XK, am I´m right ?! What you guys think ?
Cheers
Frank
or opening up your back box?
I want to do the same!!
#25
12-31-2017, 09:34 AM
Get An XKR Rear Muffler!
I have a stock 2009 XK and wanted my exhaustto have a little more rumble and sound throatier - but I didn't want it to beobnoxious or 'race-track' loud like so many of the aftermarket exhausts. Then Iread on the Jag Forum that by removing the rear muffler (aka 'back box') frommy XK and replacing it with the 'back box' from an XKR, it would really improvemy XK's exhaust sound.
Fortunately, a friend of mine recentlyreplaced the entire exhaust on his XKR and gave me his back box, which a localmuffler shop charged me $55 to install onto my XK and it only took them a halfhour. The sound is now fabulous - throaty, with a slight muscle-car rumble … andthe quad exhaust tips look amazing! It has totally enhanced my owning anddriving enjoyment!
There are guys on the Forum from time to timewho have a back box from an XKR for sale. That’s the first improvement I’d make if I was you! Note: Since the XKRback box has 4 exhaust tips instead of 2 like an XK, I alsoneeded the XKR rear valance which was an easy andcheap item to buy (part # C2P8245 from Parts.com for $35 plus $10shipping). Good luck!
Fortunately, a friend of mine recentlyreplaced the entire exhaust on his XKR and gave me his back box, which a localmuffler shop charged me $55 to install onto my XK and it only took them a halfhour. The sound is now fabulous - throaty, with a slight muscle-car rumble … andthe quad exhaust tips look amazing! It has totally enhanced my owning anddriving enjoyment!
There are guys on the Forum from time to timewho have a back box from an XKR for sale. That’s the first improvement I’d make if I was you! Note: Since the XKRback box has 4 exhaust tips instead of 2 like an XK, I alsoneeded the XKR rear valance which was an easy andcheap item to buy (part # C2P8245 from Parts.com for $35 plus $10shipping). Good luck!
#26
02-19-2018, 12:33 PM
I have researching ways to modify the existing 5.0 XK muffler. I came across this drawing of a semi active valve. I don't believe it is from Jaguar but it looks awfully close. I removed the little rubber plug that is located on the side of the semi active valve (2) that are located on the side of the 5.0 XK muffler and internally it looks just like the drawing.
So I was thinking about cutting thru the 3 spot welds that attach it to the muffler. Remove the spring pull the valve to the open position and weld it into that position. Re weld the valve back onto the muffler. Basically the muffler would be functioning as it would when the valve is open due to the exhaust pressure from higher RPM and thus giving a more aggressive exhaust not thru out the rpm range. What do you think? Any inputs or suggestions would be welcomed.
So I was thinking about cutting thru the 3 spot welds that attach it to the muffler. Remove the spring pull the valve to the open position and weld it into that position. Re weld the valve back onto the muffler. Basically the muffler would be functioning as it would when the valve is open due to the exhaust pressure from higher RPM and thus giving a more aggressive exhaust not thru out the rpm range. What do you think? Any inputs or suggestions would be welcomed.
#27
02-19-2018, 01:46 PM
Veteran Member
Join Date: Jan 2015
Location: Naperville, Illinois USA
Posts: 4,581
Received 1,901 Likes
on
1,289 Posts
Sounds reasonable. You probably wouldn't need to weld the valve open, just in case you wanted to reverse your change in the future. If you think it might rattle (should be able to tell when you have it apart), you could clamp something on that shaft when its in the open position, to keep it secure from sliding in and out.
#28
02-19-2018, 04:12 PM
Veteran Member
Interesting thread. I deleted the rear muffler on my XK. Its not for everyone, but I like it. I can’t drive it in D anymore because it shifts into high gears too soon, and all the way to 6, which gives me some crazy drone. Its not how these engines should be driven. 6th gear at 35mph is lugging the engine even though some want to believe that the computer wont let you lug it. I can feel the lugging with an open exhaust way more. So my solution is to drive it like it was meant to be driven, Sport mode and/ or I manually shift at 2k rpms on warm ups all the way to 5th gear and after warm up, I never go over 4th gear and always drive at 2500rpm. The car sounds lovely and has the sound and hum you’d expect from high end luxury sports car. The only drone I hear happens at 1500-1600 while reving it up to 2 gear, but it smooths out so fast you really aren’t gonna be bothered by it. My MPG has also gone up to 20mpg on mostly surface streets. As for DS, Ive trained my car to upshift around 2500rpms when driving normal, my foot has gotten lighter, because I’ve taught it to shift without it taking me to RPMs above 3k. It holds the gear and has power to move if needed. Many worry about getting too much wear, “oh my god! I’m straining the engine and overheating the transmission. Nonsense. The ZF is solid and will last as long as you replace your fluid with timely intervals. If you want more noise, and feel, straight pipe it and never use D. This thread was originally started by a fella who wants to modify his existing naturally aspirated XK muffler, back in 2016. Like I said, its not for everyone because the brain on most of XK drivers is too used the quiet ride, so the rise in exhaust will be bothersome. Especially if you’re convinced that driving in D will save the car from destruction, and save you petrol. I say keep the revs up at all times, it will keep carbon from building up, and the clutchpacks in good health. Also, its not obnoxious to my neighbors on startup, I asked. Straight pipes have made my driving experience more engaged, and Im no longer bored with the lack of sound, lack of feel, and Excitement. Mind you, Im an older guy with sense and I don’t race on public roads, but damn it feels good when the guy in the Challenger/Mustang/Camaro spins its wheels just to show me who’s boss. Its like trying to compare a run of the mill stripper to Victoria Secret supermodel. It’s silly.
Last edited by Brewtech; 02-19-2018 at 04:17 PM.
#30
02-20-2018, 11:32 AM
Veteran Member
Hey Steve! I do wonder about getting new cats but I was told that I cannot find them here in California. I haven’t gone past one source. Im definitely considering an XKR box. But I will miss the mean sound the car produces if I go back to a box. I have had nothing but compliments on the exhaust. Its a pretty car, but it feels powerful and all of my passengers have been captivated by that combo. It wasn’t really lke that, before the sound got turned up.
#31
02-20-2018, 11:57 PM
I have researching ways to modify the existing 5.0 XK muffler. I came across this drawing of a semi active valve. I don't believe it is from Jaguar but it looks awfully close. I removed the little rubber plug that is located on the side of the semi active valve (2) that are located on the side of the 5.0 XK muffler and internally it looks just like the drawing.
So I was thinking about cutting thru the 3 spot welds that attach it to the muffler. Remove the spring pull the valve to the open position and weld it into that position. Re weld the valve back onto the muffler. Basically the muffler would be functioning as it would when the valve is open due to the exhaust pressure from higher RPM and thus giving a more aggressive exhaust not thru out the rpm range. What do you think? Any inputs or suggestions would be welcomed.
So I was thinking about cutting thru the 3 spot welds that attach it to the muffler. Remove the spring pull the valve to the open position and weld it into that position. Re weld the valve back onto the muffler. Basically the muffler would be functioning as it would when the valve is open due to the exhaust pressure from higher RPM and thus giving a more aggressive exhaust not thru out the rpm range. What do you think? Any inputs or suggestions would be welcomed.
the semiactive exhaust actually releases gases from the sides of the
box when you go past 3500rpm.. now its open all the time.
Maybe not for everyone but worked quite well, not too loud also.
#32
02-21-2018, 01:58 AM
Veteran Member
Hey Steve! I do wonder about getting new cats but I was told that I cannot find them here in California. I haven’t gone past one source. Im definitely considering an XKR box. But I will miss the mean sound the car produces if I go back to a box. I have had nothing but compliments on the exhaust. Its a pretty car, but it feels powerful and all of my passengers have been captivated by that combo. It wasn’t really lke that, before the sound got turned up.
The following users liked this post:
Sean W (02-21-2018)
#33
02-21-2018, 07:51 AM
Veteran Member
On a car with a simple engine management system, yes, but that is not the case with the ECU's in our XKR's.
I'll quote myself LOL
I can tell you that this is 100% the case, after putting the 100 cell cats and straight-through 2-1/2" with x-pipe on my XKR, replacing the choked up cats and stock centre pipe, the car LOST a lot of pep, but then after correcting the exhaust backpressure values in the tune it felt heaps faster and actually trapped 5mph faster in the 1/4 mile, https://www.jaguarforums.com/forum/x...9/#post1785378
Others have reported no gains at all after changing cats, exhaust, etc, but that's because the tune was not corrected for these changes.
I'll quote myself LOL
I can tell you that this is 100% the case, after putting the 100 cell cats and straight-through 2-1/2" with x-pipe on my XKR, replacing the choked up cats and stock centre pipe, the car LOST a lot of pep, but then after correcting the exhaust backpressure values in the tune it felt heaps faster and actually trapped 5mph faster in the 1/4 mile, https://www.jaguarforums.com/forum/x...9/#post1785378
Others have reported no gains at all after changing cats, exhaust, etc, but that's because the tune was not corrected for these changes.
#34
01-09-2021, 03:43 AM
[QUOTE = tarokyama; 1845968] J'ai percé les vannes de mon 5.0 XK, content des résultats,
l'échappement semi-actif libère en fait des gaz sur les côtés de la
boîte lorsque vous dépassez 3500 tr / min .. maintenant il est ouvert tout le temps.
Peut - être pas pour tout le monde , mais a très bien fonctionné , pas trop fort aussi. [/ QUOTE]
Hello, did you feel a difference in engine and power when you pierce the valves? because I would like to do the same but it changes the couple?
l'échappement semi-actif libère en fait des gaz sur les côtés de la
boîte lorsque vous dépassez 3500 tr / min .. maintenant il est ouvert tout le temps.
Peut - être pas pour tout le monde , mais a très bien fonctionné , pas trop fort aussi. [/ QUOTE]
Hello, did you feel a difference in engine and power when you pierce the valves? because I would like to do the same but it changes the couple?
#35
01-09-2021, 06:17 PM
Veteran Member
Jagtoes as I’m seeing it there are 3 tunes from the factory 510, 530 & 550ps the latter two having the PAE fitted
XKR/XKR175 standard exhaust twin resonators - 510ps
XKR75 PAE - 530ps (factory X-pipe, standard rear box )
XKR-S PAE - 550ps (factory x-pipe , bespoke rear box for RS)
#36
01-09-2021, 06:19 PM
Veteran Member
The following users liked this post:
steve_k_xk (01-09-2021)
#37
01-10-2021, 01:59 AM
Veteran Member
Jagtoes as I’m seeing it there are 3 tunes from the factory 510, 530 & 550ps the latter two having the PAE fitted
XKR/XKR175 standard exhaust twin resonators - 510ps
XKR75 PAE - 530ps (factory X-pipe, standard rear box )
XKR-S PAE - 550ps (factory x-pipe , bespoke rear box for RS)
XKR/XKR175 standard exhaust twin resonators - 510ps
XKR75 PAE - 530ps (factory X-pipe, standard rear box )
XKR-S PAE - 550ps (factory x-pipe , bespoke rear box for RS)
#38
01-10-2021, 07:25 AM
Veteran Member
#39
01-10-2021, 10:29 AM
Veteran Member
I think it was Cambo who posted some pictures of an XKR box and an XKKR-S box both cut open, with a diagram showing how to convert the XKR box into an XKR-S style.
They were somewhat different, with bypassed baffles in the -S variant.
Maybe the Parts Catalog knows that there aren't any more -S boxes available so it lists the /R ones as Suitable Subs?
They were somewhat different, with bypassed baffles in the -S variant.
Maybe the Parts Catalog knows that there aren't any more -S boxes available so it lists the /R ones as Suitable Subs?
#40
01-10-2021, 10:11 PM
Veteran Member
Unless you have changed the backbox on your '10 you don't have the PAE. The standard XKR system is just know as the active exhaust system, as opposed to the semi active on the XK.