Fuse 22/15 out, but hardly any change?

[Johnny42]

As the title says, I have a device that disconnects Fuse 15 remotely. The change in exhaust note is barely noticeable, I find this really surprising, everyone seems to rave about pulling the fuse out...

The V8 has an enormous back box that's being bypassed, it must do almost nothing? Although looking at the pictures of these it's possible it's only being partially bypassed.

There's no change at all at idle. There's a bit more of an edge to the sound when the valves are open and the car is accelerating. I really have to do a back-to-back comparison to be able to tell though. I have the parcel shelf removed. I'm thinking that most of the sound is behind the car, and everyone but me is getting to enjoy this! Is this normal?

Thanks to Manwhoneverwas who pointed me at this, it's nicely made and works well:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[Jibberingloon]

Check the valves are not seized shut.

Go under the back of the car and you will see the valves, just push the rod in and out to make sure they are moving.

[Johnny42]

Thanks, I just tried to check this... there are guards under here limiting access, I can reach through and move the left hand one OK, can't get to the right hand one as it's in a slightly different position.

I'm certain they are working as I can detect a small change, and surely this is the kind of thing that either works or not...?

[douglas67]

I have the 4.7
There is a clear difference in sound, especially with the parcel shelf out.
If you have the remote fuse system with a remote control, then maybe you' have the fuse blade wire the wrong way round?

[Jon39]

Johnny42 said:

There's no change at all at idle.

That would be correct.

My understanding, is that normally (with the fuse in) the valves are;
open between 0 and 1,500 rpm.
closed between 1,500 and about 4,000 rpm.
open between about 4,000 rpm and max revs.

[JonV8V]

When you drive normally do you hear a distinct change in noise at say 4k revs? If you don't hear that then I imagine you have a problem. (I'm assuming all cars do what mine does in that regard). Removing the fuse just means the louder noise is there all the time.

[8Tech]

Jon39 said:

Johnny42 said:

There's no change at all at idle.

That would be correct.

My understanding, is that normally (with the fuse in) the valves are;
open between 0 and 1,500 rpm.
closed between 1,500 and about 4,000 rpm.
open between about 4,000 rpm and max revs.

Correct, and open at high throttle settings which is controlled by the ECU watching the throttle position sensor signal. The exhaust should be louder when driven carefully between 1500 and 4000 when the valves would otherwise be closed. If you are caning it with the fuse in, then the valves are open anyway.
I believe it was Aston Martins way of complying with noise regulations during certification, a bit like Volkswagens emission testing criteria!

[Johnny42]

Yes that's what I'm getting, there is a bit more of a growl at low to medium revs and moderate throttle. But it's not night and day...

I do get the impression it's just been done to sneak past the noise regs, it's a shame it doesn't make a bit more noise though! I'm guessing 200 cell cats would be the way forward?

[ds2000]

Start the car, let it idle and try to operate the values. Your car could be like my V12 and the vacuum actually buggered so the values are stuck open. I'm getting this sorted next year at BR but I quite like the noise as it is

[IanV12VR]

Having seen this thread and thanks to Manwhoneverwas link I got in touch with Clive and been up to see him today toget my exhaust switch fitted. Drove back with the top done ,out of the way - the difference is just awesome Very happy with result and such a neat fitting.

[kbooker]

I recieved my kit from Clive yesterday, looking forward to getting the car back from AM Leeds early next week so I can get it installed...