I've noticed an increasing discussion around reed valve induction. What are the advantages & disadvantages of using a bore kit with reed valve compared a simillar kit with port induction?
I've noticed an increasing discussion around reed valve induction. What are the advantages & disadvantages of using a bore kit with reed valve compared a simillar kit with port induction?
The reed valves will give you a little bit more low rpm power. They both should produce the same peak power if everything else was the same. Thats my understanding
this is mostly because of the av10 motobecane engine i assume.
having the reedvalve on a moby engine helps, but the real help is in that all the kits are made for a reedvalve moby, not the piston port AV7
As I understand it the reed valve closes the in-flow of mixture as soon as the piston begins it's downstroke and the crank case begins to pressurize immediately, where as with a piston port engine, it takes part of the stroke for the port to close completely, during which some of the mixture escapes back out the intake port as the case pressurizes. The higher case pressure keeps the fuel suspended in the air better and pushes more mix into the burn chamber, kind of like with a stuffed crank.
rpm!
Another thing that a case inducted reed valve setup does it free up room around the piston so that it can be dedicated to transfer ports, not controlling the timing on the intake port. There are clever ways around this limitation but usually requires strange port design or shallow boost ports that line up to holes in the piston wall. Reeds help make the port design a lot simpler. Reeds can also sustain much higher air flows than piston controlled ports. To have the same air flow the opening duration or the size itself become so large that either the piston will catch in the opening or the bike won't be able to draw enough vaccum to start until 3-4000 rpm. So yea reeds.
Also they are much simpler than rotary valve intakes and less of a pain then crank timed intakes (like on Vespas).
good points about the benefits of case induction, let's not get it confused with the valving though. You can have a case inducted rotary valve engine as in vespa, or a cylinder inducted engine with reed valves like a polini puch.
no,a lot of case inducted motors have reeds
yes, I never said they did'nt, like the performance vespa cases with reed-valve.
The point I am making is not to confuse some people that might think they are synonymous, you can have one without the other. Case vs cylinder induction is a separate matter from piston or/vs rotary vs reed valving. Although piston controlled valving can only be utilized with a cylinder induction port, reed-valving is a better performing alternate to either.
your bike will also stay cleaner with a reed valve system :)
lotsa fast bikes are piston ported. I think a piston ported engine can be just as fast as a reed valve motor
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