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2012 XKR: Is my active exhaust working?

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Old 02-06-2018, 09:42 AM
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Default 2012 XKR: Is my active exhaust working?

Hi.

I can't for the life of me hear a difference with or without dynamic mode. Was under the impression that dynamic mode = exhaust 'active' all the time, not just 4k+ revs. Do other people notice a marked difference (stock exhaust) in dynamic, revving the engine at standstill or do I just need to pull fuse 19?

Also revs seem to be limited to 4k when revving in N (warm engine) with the handbrake on, is that normal?


Thanks.
 
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Old 02-06-2018, 09:55 AM
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The 4k rev limit is normal, its in the manual.
 
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Old 02-06-2018, 09:57 AM
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Thank you and Sorry. I haven't got as far as the manual. Also just pulled 19 and doesn't sound much different so I wonder if my exhaust valve is stuck. Anyway of knowing without booking it in?
 

Last edited by LockNumber25; 02-06-2018 at 10:00 AM.
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Old 02-06-2018, 10:57 AM
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With the engine running and in Dynamic (or no fuse 19), check for exhaust blowing from all four tail pipes. If Yes, then ON. Only two, something is wrong. Maybe they are held "ON" all the time so there is no difference regardless?
 
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Old 02-06-2018, 11:01 AM
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Got it - thanks very much Cee Jay. Will go check.
 
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Old 02-06-2018, 11:34 AM
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Was the fuse good? May have been always active.
 
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Old 02-06-2018, 11:46 AM
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Cold weather is good for something. Could clearly see 2x exhaust non dynamic & 4x with dynamic or fuse pulled, that's a relief. So the fuse is now out and will see how we go.

Thanks again chaps
 
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Old 02-06-2018, 12:40 PM
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Originally Posted by LockNumber25 View Post
Cold weather is good for something. Could clearly see 2x exhaust non dynamic & 4x with dynamic or fuse pulled, that's a relief. So the fuse is now out and will see how we go.

Thanks again chaps
When you get the opportunity you should look under the center of the car and see if you have the stock XKR exhaust (has 2 silencers) or the performance X pipe exhaust.
 
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Old 02-06-2018, 02:06 PM
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I notice a huge difference between having the dynamic on and off, as far as sound goes.
 
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Old 02-12-2018, 04:03 PM
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I have the Performance Active Exhaust (x-pipe), and there's a significant difference between Dynamic Mode on/off. Basically, with the diversion valves open, it's almost open pipes from the cats to the tips. The standard XKR exhaust still has the centre silencers in-circuit when the valves are open.
 
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Old 02-13-2018, 11:49 AM
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i wonder if this is an XK thing?

My XFR doesnt sound any different dynamic or normal.....there's a noticeable growl change at 3500rpm in either mode
 
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Old 02-13-2018, 12:27 PM
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Well, the disabling of the active valves in Dynamic Mode is not documented in the workshop manual - that only talks about it happening when the transmission is in Manual mode. But it is a genuine effect; perhaps it was only done on the XKR.

There are a few oddities in the programming of the XK - for example, my 75 is supposed to be limited to 174 MPH, but it is actually set to 186 (and the ECU is unmodified).
 
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Old 02-13-2018, 12:51 PM
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Originally Posted by carzaddict View Post
i wonder if this is an XK thing?

My XFR doesnt sound any different dynamic or normal.....there's a noticeable growl change at 3500rpm in either mode
Does your XFR have the "Active Exhaust" option?
 
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Old 02-14-2018, 04:35 AM
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Originally Posted by carzaddict
i wonder if this is an XK thing?

My XFR doesnt sound any different dynamic or normal.....there's a noticeable growl change at 3500rpm in either mode
The exhaust on the XFR is totally different to the XKR.

XFR has spring-loaded valves that open at a certain pressure (exhaust gas flow) the valves are closed at idle and low engine load, regardless of what mode you select.

As you describe, the exhaust gas flow overcomes the spring pressure at around 3500rpm
 
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Old 02-14-2018, 07:06 AM
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On my 2012 there is a difference at idle when I go into dynamic (flags) mode. I have also checked at the back box that the outer valves open when you hit the button. I can watch the lever move as the valve opens. Also the fail state is "open" as the vacuum closes the valve on start. As I mentioned I have the performance active exhaust (PAF) option which is the X pipe. It lists as a $1400 option. In normal mode they open at around 3500 rpm when you peg the throttle. Just my observation.
 
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Old 02-14-2018, 12:15 PM
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Originally Posted by Cambo View Post
The exhaust on the XFR is totally different to the XKR.

XFR has spring-loaded valves that open at a certain pressure (exhaust gas flow) the valves are closed at idle and low engine load, regardless of what mode you select.

As you describe, the exhaust gas flow overcomes the spring pressure at around 3500rpm
thanks! I wonder if there's a way to keep the valves opened at all time
 
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Old 02-14-2018, 02:41 PM
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Bend a coat hangar around the actuators.
 
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Old 02-19-2018, 01:04 PM
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Disconnected vacuum lines to valve actuators then they will stay open. No vacuum valve stay open needs vacuum to close valves against spring pressure in diaphragm.
Valves are open on 5.0L at tickover. Rev slowly to 1,100 & you will hear Exhaust note change slightly. If you hold revs at say 1,200 & press Dynamic mode at same time while hold revs you will hear Exhaust note change slightly as valves open. Slight delay of about a second or 2 ! If you have an X pipe this change in note is more noticeable.
Also when using flappy paddles valve will stay open too.
If you open valves using Dynamic mode suspension damper rate will increase & also allow a bit of side/slidewheel spin as traction control is relax a bit,also engine will be more responsive & run a more aggressive map for a more sporty feel
 

Last edited by Grimreaper; 02-19-2018 at 01:11 PM.
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Old 02-19-2018, 01:07 PM
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There you go ! This only applies to 5.0L 4.2L have different set ups ! !

 
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