Rear valve in the exhaust box on my 3.0

[Southernboy]

Can anyone tell me the purpose of the valve in the one pipe of the exhaust on my 3.0.... Is it an emissions thing or something to modify noise or an economics gizmo ?
What I don't like about it, is that one pipe outlet is black from the exhaust emissions, whilst the one with the valve looks pretty unused... so, if it's not being used, why have 2 pipes?
I look forward to soem enlightening comments...

[('_')Z3]

It's to change the exhaust note at certain revs, I had mine blanked when I had the eisennann exhaust fitted a couple of weeks ago.

[Southernboy]

Aha !...please describe to me what the "blanking" process involves...

[('_')Z3]

When I asked mike fishwick for his help with the same problem he sent me this,

"Just disconnect the vacuum pipe frm the valve cylinder, and plug it with a suitable smalll bolt - that's all that is required. The valve opens the shorter (and noisier) path within the silencer about about 3000 rpm to increase the exhaust noise, but with the Eisenmann you will get more noise at all speeds!"

Hope that helps, my local Indy only charged £30 to fit the eisennann and blank the tube so it can't be that bigger job!

[Southernboy]

Cool...I'll lift the car up and have a look under there....thanks !!

[Captain]

Commonly referred to as the golf tee mod, where a golf tee is used to block the vacuum pipe

[Southernboy]

... Thanks for the size indication Hilton...I assume this pipe is located under the car adjacent to the exhaust somewhere?

[gookah]

When I asked mike fishwick for his help with the same problem he sent me this,

"The valve opens the shorter (and noisier) path within the silencer about about 3000 rpm to increase the exhaust noise!"

From what is described then it will be quieter after 3000 revs as the valve will never open?

I looked at my exhaust and the valve was open anyway..
I disconnected and plugged the pipe and noticed no difference, unless mine was stuck open ( the way I would want it anyway)

[Southernboy]

I'm not sure when it should be open and when it should be closed under normal operation...I have seen it in both open and closed positions...both times whilst the car has been stationary, and the motor not running...so go figure... I seems it's a gimmick that can be elliminated and I think I prefer both holes open all the time...

[mnbrennan]

... and I think I prefer both holes open all the time...

That's what she said...

[beerbelly]

if you think about it it will be open with no vacuum pipe connected as vacuum in the inlet side of an engine decreases as the revs rise the valve opens as revs rise simples . my 330ci had the same thing but was stuck closed I just removed the vac pipe and sprayed wd40 at it and wiggled it a bit until it opened

[Robert T]

Nice theory, but there is actually an electric valve that controls when the vacuum is applied.

The purpose of the flap is to reduce exhaust noise at low engine revs, for example when driving in towns.

Cheers R.

Sent from my GT-I9300 using Tapatalk

[Southernboy]

...Thanks for all the input guys....Does the exhaust make more or less noise with only one pipe open or two open? I would have thought that with two open and less restriction, it will be quieter ?? ....I have just been out on a short run of around 2km, and looking up the spouts, with the motor turned off, they are both open... the moment I start the motor, it shuts...so it would seem one pipe is quieter than two..... I think I need 4 pipes again... the neighbourhood is becoming complacent.....

[Robert T]

The less area of exhaust ventage the quieter - you get less of the booming low notes akin to those that the boy racers get from their baked-bean can exhausts.

By your description, the flap is normally open, held there by a spring. With low revs the electric valve will open, thus applying a vacuum and holding the flap closed. When the engine revs increase the electric valve closes, releasing the vacuum and the spring will open the flap. This also ties in with what Mike says in that if you disconnect the vacuum line and plug it (so that you don't have a vacuum leak) then you can safely bypass the mechanism and it will be open all the time.

Cheers R.

[Southernboy]

That'll be one plugged vacuum line then...

[gookah]

I did this expecting great things but noticed no sound or volume difference whatsoever..

[Woody1000]

I never noticed any vacuum pipe when I fitted my Eisennman back box. Where is it located ?

[Southernboy]

I haven't looked for it yet, but when I do find it, I'll let you know...or someone else here will come along and we'll both know...I suspect it will be under the car somewhere...

[Zedbedee]

IMHO the best way to deactivate this valve is to remove the carpet from the left hand side inside the boot and remove the vacuum tube from the engine to the electronic controller mounted in the bottom of the well which is revealed. Then block the pipe with a suitable bolt or a golf tee. This enables the system to be reactivated in the future if you wish to without the problem of the dirt and debris which builds up under the car. You will get a much nicer exhaust note, especially at lower speeds.

[gookah]

I You will get a much nicer exhaust note, especially at lower speeds.

I wish.....

[Zedbedee]

You could check your valve in the rear silencer. It may have already jammed in position, it needs to be open all the time to get the best sound. I was very pleasantly surprised at the difference this simple mod made.

[Southernboy]

..... Just popped out and plugged the tube with a nice luminous pink golf tee... Job done.