Exhaust Bypass or not switch available?

[macpaul]

Evening' All,

Done to death sort of subject but can anyone tell me if there is such a thing as a switching system that allows you permanently to keep the bypass valves closed, that is, gases always going through the back box for a smooth and quiet ride?

I've got 200 cell cats and at 4,000 rpm+ the noise is er, considerable.

This can be a bit of fun sometimes but I've been black flagged on trackdays for too much noise which means circulating at 4,000 or below which is not great.

My cure has been jubilee clips to clamp the valves in position which is a pain to do and gives no flexibility.

Done a search and can't find anything.

Any suggestions?

Best,

Simon.

[KarlFranz]

I don't think it would be too difficult to wire the solenoids to power via a switch.

[mikey k]

Easy enough
Simply put a switch in to the pump side of fuse 22 fed from live supply with the ignition on

[macpaul]

Thanks for the replies.

I am by no means an expert on this so forgive a basic question.

Is the sub-4,000 position that the valves are 'sucked shut' by the vacuum pump which then switches off at 4,000+? (Forget start-up)

I assume so as I have to jubilee clip the valve actuator rods against the effort of the spring.

In that case it would be a matter of making the live to the pump permanent unless switched off but what I'd ideally like is standard operation and quiet (which I didn't make clear in my earlier post).

A permanent live would either be open all the time or closed all the time when switched off, no?

Simon.

Edited by macpaul on Monday 26th August 20:36

[Neil1300R]

I always thought the valves opening was dual purpose - increase the noise but above 4000rpm to aid the volume of exhaust gases to escape.
If its too noisy surely the answer is to put the standard cats back on.

[Jockman]

The default position is OPEN

[macpaul]

Neil1300R said:

I always thought the valves opening was dual purpose - increase the noise but above 4000rpm to aid the volume of exhaust gases to escape.
If its too noisy surely the answer is to put the standard cats back on.

Last seen on the roof of Rick's office at DMS.

And I wouldn't get the benefit of the breathing improvement.

So, unpowered position is open (must be on reflection, if removing fuse 22 does what it does). Thanks Jockman

Easy enough presumably to liven up the pump permanent on/off but can't see how to make standard operation an option. Don't know where the +4,000 signal comes from.

[V12woollie]

As I understand it:

0-1500rpm - open
1500-4000rpm - closed
4000+ - open

I have heard (as Neil stated) that the valves need to be open above 4000rpm to aid the flow of exhaust gases. I think you may have problems if you keep the valves shut at over 4000rpm

[macpaul]

Well I've done quite a few trackdays with the valves clamped shut with no ill effects.

This will have put max gasflow repeatedly through the system which would only rarely happen in day to day use.

Its just the difference between through the baffles and not I think.

[Stuart Dickinson]

macpaul said:

Last seen on the roof of Rick's office at DMS.

And I wouldn't get the benefit of the breathing improvement.

So, unpowered position is open (must be on reflection, if removing fuse 22 does what it does). Thanks Jockman

Easy enough presumably to liven up the pump permanent on/off but can't see how to make standard operation an option. Don't know where the +4,000 signal comes from.

The valve opening & closing is also governed by the ECU. You can reprogram the ECU to alter the RPM at which the valves open, or keep them shut, or keep them open if desired (within some limtations.)

If you have a 'trackday' map which shuts the valves you could quite easily switch it back to your preferred opening point after you've finished tearing it up.

[macpaul]

Thanks, Stuart, getting somewhere.

I'm always nervous of interfering with ECUs and have the wrong OBD machine anyway but I see you are in Dorset (me Surrey).

I'll give you a call if I may.

Simon.

[yeti]

Bamford Rose have set up mine to open at 5500rpm (DB9), this was the maximum they were happy with due to exhaust gas flow.

It'll get you through a track day test but at full chat, you'll trigger any on-track noise meters!

Give them a call.

[macpaul]

That's exactly right.

I'll get through the static noise test but get called in once at full chat.

From what I've picked up on here, your exhaust system might be working quite hard at 5,500.......?

[Noisy]

Could you get a track day silencer?

[macpaul]

Could do but a hell of a faff to fit and refit every time.

Jubileeing the valves is bad enough!

[mikey k]

macpaul said:

Could do but a hell of a faff to fit and refit every time.

Jubileeing the valves is bad enough!

Exhaust bungs are your friend

http://www.migweb.co.uk/forums/engines-transmissio...

(no I don't go on there )

[macpaul]

Not pretty but a thought, thanks.

Had a note from Mike Bamford, so will see what might be possible electronically....

[PiloteAM]

V12woollie said:

As I understand it:

0-1500rpm - open
1500-4000rpm - closed
4000+ - open

I have heard (as Neil stated) that the valves need to be open above 4000rpm to aid the flow of exhaust gases. I think you may have problems if you keep the valves shut at over 4000rpm

BR changed mine from 4000 to 5000, apparently that's fine.

- Steve