Exhaust Valves - Misbehaviour?

[Moss]

Now then, - over the past few months the car has randomly thrown a dashboard message “Dynamic Mode Unavailable” sometimes after five miles, sometimes after fifty miles, sometimes never during much longer journeys.
There are no faults or error codes stored.
Progressively, though, I seem to have “lost” my pops, spits, farts and bangs on the overrun.
However, my flappy valves on the exhausts appeared stuck shut.
An overnight spray with PlusGas release agent eased them off, but they’re not as “free” as I’d expect them to be and, appear to turn independently to the actuator lever/cam.
The actuator rod itself seems very resistant to movement, which seems odd given that it relies on air pressure to move?

Primary question is, are the Actuators stuck?
Secondly, would they likely throw the Dynamic Mode Unavailable message, on the dash?

TIA for looking…

 

[gasgas]

is it a lower grade fuel issue, mine pops much better with hight octain petrol

 

[Moss]

is it a lower grade fuel issue, mine pops much better with hight octain petrol

I am almost certain it is mechanically-related to the jammed (damned) flaps…
Which, in turn, is (possibly?) affecting the Dynamic Mode system.

I was wondering what the collective’s opinion of this might be?

Viewing @SCTony helpful YouTube video gave me something to think about:
https://youtu.be/wploh4sCtoY

 

[scm]

First thing I'd eliminate is the battery - give it a good charge and diagnose from there. Won't help the exhaust flaps but might sort the dynamic mode unavailable message? And if it doesn't at least you know it's not a low voltage thing (which has been known to cause all sorts of random and spurious error warnings).

 

[Moss]

First thing I'd eliminate is the battery - give it a good charge and diagnose from there. Won't help the exhaust flaps but might sort the dynamic mode unavailable message? And if it doesn't at least you know it's not a low voltage thing (which has been known to cause all sorts of random and spurious error warnings).

Thank you scm
Battery/voltage were my initial thoughts and start point; although I do keep the vehicle on a battery tender.
I’ve also tried disconnecting/reconnecting the battery positive terminal, to see if that made any difference; but, nope.

 

[Moss]

After an impressive 250-plus views of this topic, I am beginning to wonder whether I’m asking the wrong questions…
So, having freed-up the valve flaps, and actuators - along comes another question….

On start-up, do the flaps remain closed/shut, regardless of the position of the dash control switch?
(There seems a confusing series of interpretations available covering just about every conceivable “condition” of the dash switch/dynamic mode/engine rev/accelerator position/year of manufacture…..)

Any help gratefully appreciated.
My cornflakes didn’t go down well this morning when I saw the price of two SVR exhaust silencers on fleabay especially with the same valve/actuator arrangements.

 

[Kev]

This may help to further understanding of how the system works



View attachment EXHAUST SYSTEM - V6 SC 3L PETROL (G1809212) DESCRIPTION AND OPERATION.pdf

 

[mickjaguar]

The valves should be open when the engine is not running. On start-up it depends the age of car and software updates applied

in simple terms, I think early cars (before say mid 2018 ish) can use the button or dynamic mode to simply open/close the valves (the MY16 V6 I had was like this). Later cars had to comply with drive by noise regulations and the valves are kept closed more at lower revs. On these cars the valves will be open until the engine starts and then close partially at idle. When you move off they close further and don't fully open until 3500 revs or under full load.

Apart from the very latest cars MY22+ which I believe have electrically controlled exhausts, all the previous models are closed by vacuum by way of a solenoid switch. The default being open until vacuum pressure is applied.

Your valves should be open until you start the engine. An easy way to force that is to remove fuse 15 (plus fuse 43 on very early cars). This disables the solenoid etc and the valves will stay fully open irrespective of revs, driving, switching. If the fuse is then put back in the behaviour will change and the valves can close themselves.

The valves vacuum works against quite bit of spring pressure. I give mine a wiggle (the valve actuators by hand) periodically, as my fuse is always removed and whilst they operate smoothly it takes a fair bit of grip to get them to move.

 

[Moss]

This may help to further understanding of how the system works
EXHAUST SYSTEM - V6 SC 3L PETROL (G1809212) DESCRIPTION AND OPERATION.pdf

Thank you @kev - your upload is really helpful.

The valves should be open when the engine is not running. On start-up it depends the age of car and software updates applied

in simple terms, I think early cars (before say mid 2018 ish) can use the button or dynamic mode to simply open/close the valves (the MY16 V6 I had was like this). Later cars had to comply with drive by noise regulations and the valves are kept closed more at lower revs. On these cars the valves will be open until the engine starts and then close partially at idle. When you move off they close further and don't fully open until 3500 revs or under full load.

Apart from the very latest cars MY22+ which I believe have electrically controlled exhausts, all the previous models are closed by vacuum by way of a solenoid switch. The default being open until vacuum pressure is applied.

Your valves should be open until you start the engine. An easy way to force that is to remove fuse 15 (plus fuse 43 on very early cars). This disables the solenoid etc and the valves will stay fully open irrespective of revs, driving, switching. If the fuse is then put back in the behaviour will change and the valves can close themselves.

The valves vacuum works against quite bit of spring pressure. I give mine a wiggle (the valve actuators by hand) periodically, as my fuse is always removed and whilst they operate smoothly it takes a fair bit of grip to get them to move.

And also thanks to you @mickjaguar for confirmation of the function and operational sequencing of the valve(s)…
The car is a 2018 vehicle and am confident hasn’t been silenced with the software update patch
Now that I’ve spent some time with the PlusGas and copper grease spray, I’m happy that the valves are free to rotate on their spindles, and not gunked-up with soot and crud.
I’ll spend tomorrow with fuse 15 check.

 

[scm]

I think I read on the US forum that there's a further complication on the latest cars MY21+(?) - in that the valve position is remembered so if the valves are closed when you remove fuse 15, they'll stay closed. That conversation cropped up because someone was discussing putting a remote controlled fuse device in place of fuse 15 and was experiencing bizarre behaviour - the above was the explanation. As always, I'm prepared to be proved wrong.

My MY18 had one software update but the only things effects were the dynamic mode reset on startup (the mode was originally preserved for 6 hours after switch-off) and non-dynamic valve opening by the switch doesn't occur until around 1500 rpm. Valves open from tickover in dynamic mode, and lots of pops and bangs still!

 

[Moss]

…..

My MY18 had one software update but the only things effects were the dynamic mode reset on startup (the mode was originally preserved for 6 hours after switch-off) and non-dynamic valve opening by the switch doesn't occur until around 1500 rpm. Valves open from tickover in dynamic mode, and lots of pops and bangs still!

Hmmm.
That’s interesting and reminds me the dealer did that patch update when I purchased the car. Dynamic mode always resets to “off” on ignition switch-off. I recall emphasising to them that I didn’t want the “quiet” software patch, if it were ever supposed to be applied.
Appreciate your input @scm
Ta.

I suppose, after all, it wouldn’t be a Jaguar if it didn’t have all these odd idiosyncrasies

 

[scm]

Dynamic mode always resets to “off” on ignition switch-off.

Pedantically, it doesn't actually reset to off until the next ignition switch on - you can verify this by seeing that your dash is still lit red when you turn the car on, but then it reverts to your non-dynamic lighting scheme. I'm assuming you don't have red as your default lighting colour!

 

[Moss]

Dynamic mode always resets to “off” on ignition switch-off.

Pedantically, it doesn't actually reset to off until the next ignition switch on - you can verify this by seeing that your dash is still lit red when you turn the car on, but then it reverts to your non-dynamic lighting scheme. I'm assuming you don't have red as your default lighting colour!

Thanks for that; every little piece/nugget of information helps to understand the system

Red backlighting only shows when in DM, for me. But I will take note next time I fire up!

 

[scm]

Red backlighting only shows when in DM, for me. But I will take note next time I fire up!

Hope I'm right! :lol: