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.

 

 

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?

 

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?

 

Got it - thanks very much Cee Jay. Will go check.

 

 

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.

 

I notice a huge difference between having the dynamic on and off, as far as sound goes.

 

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.

 

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

 

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).

 

Does your XFR have the "Active Exhaust" option?

 

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

 

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.

 

thanks! I wonder if there's a way to keep the valves opened at all time

 

Bend a coat hangar around the actuators.

 

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

 

There you go ! This only applies to 5.0L 4.2L have different set ups ! !