Fuse 15

[Thunder Dump]

Under normal circumstances, mine starts with the valves closed however does run at higher revs for about 60 secs before it throttles back. If I push the valve button it opens them and the sound is considerably louder.

It will always start with the valves open. However, Jaguar calls it a 'flair' where it is open on start-up and then closes within 2-3 seconds. There is no way to start the car with the valves completely closed on the MY2020 and older cars, and no way in the MY21 and newer (with the electronic valves) *unless* you pull the fuse while the valves are in the closed state and then they will stay that way until the fuse is reapplied.

[davidls]

Fuse 15 is coming out then

[davidls]

I always let my v8 run high on start up, I never pull right away on cold start up. I wait for the revs to back off to normal tick over then engage D, or reverse. This time I beleive is to allow the cats to get hot and also ensures oil is reaching the top end of the engine. I have noticed on my car, that after driving for a while at and normal temperature has been reached, stopping for 5 - 10 minutes getting back in again, it starts to run through this higher rev time again?? Nothing to worry about I'm sure, just some quirk with the s/w. I don't bother to wait at this time I just continue as the engine is still pretty hot, I suppose the cats would cool quicker.

Anyone else experience this?

I remember in my VXR's, the stop/start....mode when activated and engine stopped, with car in neutral and handbrake on, opening the door to get out it would sense the voltage drop on the battery as the lights came on and start the engine when you were climbing out! A bit disconcerting, but perhaps over sensitive on the monitoring of the battery. I didn't make a habit of getting out of the car in start/stop mode it's just something I noticed.

If mine has reached temperature and run for a while and been stopped for 10/15 minutes, it does not go through the fast idle again, just starts at regular revs.

[scm]

In *any* mode, pressing the active exhaust button will open the valves at *idle only*. As soon as the RPMs start to move the valves close and then don't open again until higher RPMs, depending on mode and exhaust button. When the fuse is pulled, the exhaust is wide open all the time, including from idle to about 3500 RPM (lower in Dynamic mode). What you get from pulling fuse 15 is having the valves open from idle up through 3500, which makes a difference in regular driving where you're not constantly going higher into the rev range.

More definitively wrong information, unless you're referring to a specific MY (which you haven't). In my MY18 pressing the button at idle in *any* mode depends on the mode. At idle if you're in dynamic pressing the buttons closes the valves, in non-dynamic it leaves the valves closed, to open only when the revs pass 1500.

Not sure what you mean by "the exhaust is wide open all the time, including from idle to about 3500 RPM (lower in Dynamic mode)." Can the engine run at lower than idle in dynamic mode?

[Deleted User 4828]

Ok, darn it, I'm going to pull fuse 15 too, to see what I experience. I'll report back at some point. Have MOT on Wednesday, I'll probably leave it until after then

[Timbo]

Or just fit an aftermarket exhaust lol

[Thunder Dump]

In *any* mode, pressing the active exhaust button will open the valves at *idle only*. As soon as the RPMs start to move the valves close and then don't open again until higher RPMs, depending on mode and exhaust button. When the fuse is pulled, the exhaust is wide open all the time, including from idle to about 3500 RPM (lower in Dynamic mode). What you get from pulling fuse 15 is having the valves open from idle up through 3500, which makes a difference in regular driving where you're not constantly going higher into the rev range.

More definitively wrong information, unless you're referring to a specific MY (which you haven't). In my MY18 pressing the button at idle in *any* mode depends on the mode. At idle if you're in dynamic pressing the buttons closes the valves, in non-dynamic it leaves the valves closed, to open only when the revs pass 1500.

Not sure what you mean by "the exhaust is wide open all the time, including from idle to about 3500 RPM (lower in Dynamic mode)." Can the engine run at lower than idle in dynamic mode?

Well I should have specified that if they're already open and you press the button then you close them. I figured that was self-evident. Yes, if you're in a mode at idle that already opens the valves then the light will be lit on the switch (because it's active) and pressing the button will close the valves.

My post was more to point out that at idle (and only at idle), in any mode if the active exhaust light is on (switch is active) then the valves will be open. Depending on mode, as soon as the revs move off idle the valves will close.

And what I meant by 'the exhaust is wide open all the time' means just that--the valves never close (because they can't) when the fuse is pulled.

[munchie]

I’ve only ever taken the fuse out when the car was switched off on my 2021. The startup from cold is more raucous with the fuse removed and in lift off of the throttle below 3500mrom I get some overrun noise on the exhaust. If I have the fuse in but have the active button pressed I don’t get the overrun on such low revs.
So I don’t understand removing the fuse when the valves are open, does this create more noise then it does with fuse 5 removed when the car is switched off ?

[scm]

My post was more to point out that at idle (and only at idle), in any mode if the active exhaust light is on (switch is active) then the valves will be open. Depending on mode, as soon as the revs move off idle the valves will close.

That's where we differ - in my car at idle if the switch is lit and I'm not in dynamic mode the valves remain closed until I get to 1500 rpm. Only in dynamic mode are my valves open at idle (and all time, of course). So your statement may be true for your car, but it's not a fact for all, so shouldn't be represented as such.

[Lunar]

Yep, for my MY14 with no Jaguar software updates having been allowed, I just have to select Dynamic mode and the valves open too and stay open all the time from tickover upwards - no need to press the exhaust valve button also. This setting is also remembered if I’ve say stopped for a nice lunch and start up again.
The only thing I haven’t bothered to do is to plug the synopser, as I feel no need to adjust the noises I get.
Come spring and quicker engine warm up I do remove the engine cover for that nice bit of supercharger whine from around 2,100rpm.
On joining the motorway I do close the valves separately to the Dynamic setting, as I prefer the more musical sound of the V6 like that.