Dual Stage Exhaust

[YarisSi]

What is one and how work? Apparently used in 3.2 TT and a ferrari.
Also what is this about a "gate" used in Evo exhaust when go over certain speed opens and allows more out.

Thanks in advance

[Pigeon]

Sounds like an exhaust version of a variable length inlet manifold - you get what is basically a trumpet-valve type gadget to vary the length of the exhaust system and keep it in tune with the exhaust gas pulses. Probably worth more on a two-stroke than a four-stroke...

[alfa dave]

The dual stage exhaust has valves in that open to minimise back pressure at wide open throttle but close to keep things quiet and civilised at low speed - the Vanquish has these too. They are usually located inside the muffler box.

This also helps manufacturers acheive the required 74dB drive by noise requirement but keep the customer happy with a sporty exhaust note.

[dern]

If it's the same thing, and it sounds like it is, Yamaha used these on their bikes for years. They called it the exup valve. When their patent ran out it then started to appear on many other bikes including my Fireblade.

Mark

[andycanam]

would be interested if you could adapt one to fit on any exhaust.....
can imagine it being difficult to keep sealed but I only have an image in my head that may be totally different to what they are actually like (a throttle butterfly?)... funny as I used to have a FZR with an Exup.

[YarisSi]

Otherway i thought might work was like a shutter on camera. But could see this become jammed from soot.

[dern]

The answer (at least as far as my fireblade is concerned) is... neither I'm afraid...



...it's some kind of complicated barrel which is rotated with cables controlled by a motor (or 2) in (or near) the airbox.

The blade has a 4-2-1 exhaust system and the barrel controls how the exhaust gases flow through the system.

For the following assume the 4 pipes are stacked together in this way...

(4)(1)
(3)(2)

...looking down the exhaust in the direction of flow.

Right, from a quick read of the workshop manual this system works like this...

idle - 3000rpm:
The valve directs 1 into 2 and 4 into 3 so if this was looking at 1 and 2 side on it would like like this...

1 --
'
2 ------

3000 - 8000rpm
The valve lets all 4 pipes go straight through...

1 ------
'
2 ------

8000 - red line (about 12000rpm from memory)
The valve routes 1 into 2, 2 into 1, 3 into 4 and 4 into 3 (gawd knows why but I assume that it tunes the pipes by increasing the pipe length but that a guess) and at the same time it opens a ruddy great barn door of a valve in the airbox letting a *huge* amount of air in.

The idea is, apparently, to increase torque in the low and middle rev range but to maximise engine power at high rpm. I have no idea what the bike would be without it but it is bloody fast with it and yet pulls pretty cleanly and strongly from low revs.

Clever eh?

Mark

PS. Can't seem to get my ascii art right but I'm sure you get the drift.


>> Edited by dern on Tuesday 18th May 20:49

[alfa dave]

The one's I've seen in car systems are more like a simple flap valve that fits in side the muffler box within a solid tube section.

Does that explain it clearly?....