When you pull the fuse and leave the valves open, does it completely bypass the muffler?

Thanks!

 

Nope, still goes through the muffler just takes a different path

 

Thank you.

 

Here is a diagram of the flow

 

Thanks for the diagram!

So when the fuse is removed it is my understanding that the valve is fully open at all times? Is that correct? I have my fuse removed and My only concern is at idle... On cold start it sounds fabulous! But once it warms up it quiets down... Any idea how I can get a healthy rumble at warm idle? I know the revs change a little when warm but it still seems like the exhaust becomes more silent somehow...

 

When you first start your car there is no vacuum to close the valve so you get the nice growl. But it fades as vacuum builds and the valve closes. Edited - had it bass ackwards

 

Vacuum closes the valve, not opens it.

 

Got it! Thanks!

 

The fuse runs a vacuum pump, which creates the vacuum for the valve's to close. Engine vacuum is not run to the rear to operate the valve's..aka the fuse = the pump.

When you first start your car, your in cold start operation..its a higher rpm and different afr.

Once the engine is warm your back to commanded lambda 1 and a lower RPM idle @750rpm(actually it's 736rpm, but no one's complaining)... This creates the quieter sound.

If you want louder, an aftermarket muffler and cats are gonna be on your wish list! ;-)

 

Thanks Irish!

I already have the 100 Cell sport cats. - sounds like from your advice there is noting I can do other than free up the exhaust more? - I enjoy the sound now with the exception of warm idle. In the future I only intended to do headers so I could increase power and a rear silencer to reduce weight but was concerned I would get too loud on open throttled for my taste.

 

There's 3 options really - change out the back box for a louder one or muffler deletes, change out the sport cats for decat pipes (barely any difference), or fit headers with the late MY config sport cats (your OEM manifolds still have a 600 cell primary cat.)

If you want to end up with headers, don't bother with options 1 or two, decat pipes would become redundant anyway, and a back box that is the right volume now would probably be too loud if you switch up to header/sport cat combo later.

 

Does Fuse 22 apply to DB9's as well ? I haven't bought the car yet, hopefully next week, but when I pick her up I want to be ready to bypass the quiet mode