Reed valves and intake reversion on 4-stroke

[Circlotron]

Has anyone ever tried having reed valves upstream of the intake valves for the purpose of blocking reverse airflow at low rpm e.g. idle with a lumpy cam? Probably do more harm than good as far as high speed airflow is concerned but 2-strokes seem to get by okay.

[Lockwire]

Yes.excellent.

[LCaverly]

Always thought that would work on a v8 but manifolding would be complicated.
Len

[groberts101]

Although, the 2 stroke stuff seems to make damned good power with fairly small valves, I would have to wonder about the increased restriction created overshadowing any potential gain to be had from the reversion reduction.

Maybe it could be oversized enough to reduce severe restriction and only used on applications requiring a very wide powerband? We could cam it up without paying such a huge price down low.

[Dan Timberlake]

Honda (who else ?) tried reed valves for a couple years on a 500 cc single dirt bike.

http://images.cmsnl.com/img/partslists/ ... 2_ff2c.gif

Then they didn't.

[Lockwire]

Although, the 2 stroke stuff seems to make damned good power with fairly small valves, I would have to wonder about the increased restriction created overshadowing any potential gain to be had from the reversion reduction.

Maybe it could be oversized enough to reduce severe restriction and only used on applications requiring a very wide powerband? We could cam it up without paying such a huge price down low.

I guess what you are saying is that all Reeds are the same size ???????? I did'nt think they were and are used in many different applications.

[Dan Timberlake]

Accel turbo kit "priority valve" from prehistoric times.
Allegedly bypassed the turbo to help reduce turbo lag.
Not a "reed"exactly, but more of a spring loaded disk or poppet

http://www.jalopyjournal.com/forum/atta ... pg.718957/

http://www.hotrodders.com/forum/attachm ... 1223602616

[MadBill]

Over a period of ~ 20 years, I saw two reed valve systems get close to production, but then get cancelled for unknown reasons. (Buick V-6 and Corvette) Also, I believe Alfa Romeo had a such a system in production in the early eighties.

[wheelsup330]

I have often visualized this same concept for blower motors, especially for protection from "banging" the blower... without a forced induction, this would require some very special cam timing to work around / take advantage of the absense of reversion in the intake tract and its "supercharging" the adjacent or opposing cylinders... Just thoughts...

[LCaverly]

Always thought if you could position the reed valve at one of the major harmonics you would get a big boost in torque.
Have been trying to convince one of my friends who races lawn tractors to try it.
Len

[kirkwoodken]

If all engine designers were to ride a 55 HP, 390 Husky with a reed valve and a works barrel, all engines would be two strokes with reed valves. You can't imagine the chain snapping, lugging power of one of those engines. I lugged one down in 6th gear to the point at which I thought it would stall, cracked the throttle wide open, and it felt like someone was hitting the piston top with a sledge hammer. Very impressive engine.

[4sfed]

I know of at least one manufacturer has experimented with the concept. As you might suspect, the improvements at lower speeds are significant. The difficulty is insuring the reeds seal perfectly. Here are the results from a two liter 4 cylinder engine. I'm not sure the report I have is public, so this is all of it I can share.

Reed_Motor.jpg

[MadBill]

Wow, 35% torque increase at the bottom end!

[groberts101]

So what would be the optimum location for a reed in most typical OHV stuff? Closer to the valve?.. or a bit further away to hopefully "trap and hold" more mixture and inertial energy for the next cycle?

[MadBill]

I'd say close as possible, to minimize reversion mass.