2012 XKR: Is my active exhaust working?
#1
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.
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.
#2
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#3
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#6
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#8
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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#10
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.
#12
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).
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).
#13
#14
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
My XFR doesnt sound any different dynamic or normal.....there's a noticeable growl change at 3500rpm in either mode
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
#15
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.
#16
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
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
#17
#18
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
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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LockNumber25 (02-19-2018)
#19
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