I see some posts on active exhaust and was wondering how it worked , what it did and was it standard equipment on the XKR. Thanks

 

I see you recently joined the forum. It would be helpful to know what year XKR you have or are looking for. You can note that in your signature.

Active exhaust is standard on 07-up XKR models. When activated, it works like an exhaust cut-out valve, bypassing the muffler for less restriction and louder exhaust note.

There has been a lot of discussion about the XKR active exhaust. Using Advanced Search for "active exhaust" under current models XK XKR resulted in 75 threads. Not sure if this link will work: Jaguar Forums - Jaguar Enthusiasts Forum - Search Results

How does Active Exhaust work? See this thread, in particular Post #7 by jallitt, for details (07-09 4.2L XKR): https://www.jaguarforums.com/forum/x...se-19-a-62736/

You can also pull Fuse 19 to keep the muffler valves open all the time.

 

I did pull my fuse 19 on my 07 XKR and love it! It's still very much Jaguar, but roars a bit more.

 

Specifically, the two outer pipes of the quad-pipe setup on the XKR bypass the rear muffler box and are controlled by a flap which is open below 1100 RPM and above 4000 RPM. In between, it closes in order to push all the gasses through the muffler to keep the noise down. However, on the 5.0L models, if you select manual gear change using the paddles, the valves open.

 

Do you know where in the documentation it says the valves open when the rotary shifter is set to "S" or when the paddle shifters are used? However, it is my experience the valves remain open when the shifter is in "S" and and the paddles are used, which is my normal driving mode.

 

From the workshop manual:

So, based on that, Sport mode doesn't open the valves, only manual shifting.

 

I always thought that by selecting the "S" mode the valves opened. However, the valves open permanently when "S" mode is selected and a paddle shifter is depressed. If a paddle is not depressed then the valves remain closed and behave according to the chart (based on rpms and throttle depression %). Based on this when a large gear number appears on the LCD the exhaust valves are open (sequential shift, manual mode, is engaged). Consequently, no need to remove fuse 19.

 

I was under the impression that on the Performance Active Exhaust that putting the car into "S" bypasses the valves. Interesting to know the XKR is only using 2 tailpipes most of the time and not all 4!! So if I go into "D" most and drop the gear manually to pass someone do the valves open? That might scare the bajeezus out of someone!!

Loth

 

it also looks as if I need to start using the paddle shifters dag nabbit!!!!!!! Ive gotten too lazy otherwise!!!

 

They do, and it does - especially cyclists

 

Is there ever a situation where exhaust flows through all 4 pipes?!?

 

When the outer-pipe valves open, the inner-pipe route via the muffler remains open - while most of the flow will be via the outer pipes, some will still go through the muffler. Here's a picture (top half shows valve closed, bottom shows it open):

 

THAT IS AWESOME!!! You have a special book that gives you these diagrams showing exactly how the car works!?!?! Would love to read one some day!! Your the man!!

Loth

 

Didn't someone have a table that showed exactly under what conditions the valves opened? (Throttle position and RPM.)

 

I got it off eBay - just a CD with PDF copies of the manuals:

JAGUAR XK - XKR 2006 - 2012 WORKSHOP SERVICE REPAIR MANUAL - X150

A lot of useful stuff in there...

 

Comme ça?

This is for the 5.0



This is for the 4.2



Of course, this only applies for the Active Exhaust on the supercharged models.

 

That table was posted by jallitt on 10-29-2011. I cited it in this thread in my post #2, above, with the link to his table for 07-09 (4.2L) XKRs. Here's a copy of that table:


The 4.2L XKRs do not take the transmission mode into account as do the 5.0L XKRs. Compare the 2 charts posted by Ngarara, above.

If you want the active exhaust to stay fully open below 4,000 RPM and under light throttle simply remove Fuse 19.

Stuart

 

The XK's exhaust is "active" also, but differs in that the valve assembly is spring loaded. The muffler is tightly sealed and there appears to be no way to access the spring assembly for either repair or modification. Has anyone peeled back the sheet metal of the muffler to access the valve assembly?