[Tigers] Headers versus Cast Iron Exhaust Manifolds

[Rense, Mark (GE Indust, ConsInd)]

Tom,
Variable tuned exhaust has been used for years on high-performance
motorcycles. Yamaha pioneered it with their EXUP system, now Honda and
Kawasaki use it and BMW's new S1000 sportbike uses it (191 HP at the
rear wheel, 440 lbs. wet). Furthermore, several of these bikes also
employ variable intake tracts, with servos lengthening or shortening the
velocity stacks inside the airbox depending on engine speed and load.
Add variable valve timing, three-dimensional fuel and ignition mapping
and these engines make 200HP per liter yet are docile around town. Ain't
high tech cool?

Bugz

-----Original Message-----
From: Thomas Witt
Sent: Tuesday, June 08, 2010 2:24 PM
To: tigers at autox.team.net
Subject: Re: [Tigers] Headers versus Cast Iron Exhaust Manifolds

Which brings me to the concept of variable exhaust.  Just like there are
multi valve engines that allow for good intake velocity and the ability
to meet an added demand I'm surprised there aren't designs that follow a
similar concept on the exhaust side.  I'm thinking of a smaller primary
exhaust pipe with a sprung flap that vents to a larger pipe secondary
pipe on demand.  Anyway, just thinking out loud.
Tom