Espen's Reed Valves

[nhoj at cd.chalmers.se]

You wrote:
> 4,000 on a 175cc per cylinder engine (4 stroke).
> As the air flow goes up your gonna need large reeds, inertia goes up, and
> they drop in max rev effectiveness.
> Or go to LOTS of little one, and then port volume goes to h---.
> Again, the is just on th Yamahaha, and old info, but I haven't head of any
> manufacturer going to reeds lately for auto use....

Crank case pre compression on a two stroke wouldn't work very well if the  
reeds stayed open.

The key to performance at high RPMs is low weight, high stiffness and the  
proper shape. To get performance at low RPMs also, Boyesen's multi stage  
reeds can be used.

Remember that 2000RPM is only 33Hz. Locking open at that frequency sounds  
improbable. 20,000RPM, sound more like it.

Composite reeds, often using graphite, work well into the 9000's on  
outboards. The problem with composite reeds is that they don't last very  
long, however, the failure is not very dramatic. Metallic reeds, on the other  
hand, while long lasting, will tear an engine to pieces if they break at an  
inopportune moment.

Maximizing reed cage area is important since larger reeds will give better flow. 

Now, anyone for a homegrown EFI system for 2-stroke outboard ?

Regards,
John Hornkvist