Intake Flapper Valve

Results I instantly noticed after doing this mod:

(keep in mind I do have a PCIII USB with a map I have been working on installed, but I think others even with stock ECU's will have equal & maybe even better results when they do this mod)

Intake induction noise is increased to a nice howl even at low rpms when opening the throttle

Low rpm engine noise is better, the engine sounds much less labored when taking off from a dead stop.

Definite improvement in upshifting & downshifting. The gearbox is just more willing to do what it is supposed to do. We've seen this before with other mods that affect the fueling when you chop the throttle from residual fuel left in the intake tracts. Sometimes we even add or remove fuel with the Powercommander to mimic these results. Throttle blips seem more natural now too as if the engine is just more willing to breathe.

The Basics

This type of Flapper valve can be found on most new Honda sportbikes.
The marketing propaganda says the intake flapper valve is there to increase low rpm intake velocity & improve throttle response. This theory is very sound, but inside sources from Honda have told us the real reason is for noise abatement testing. It seems getting an engine to pass EPA emissions testing is easy nowadays, but getting them to pass the noise level testing has been difficult at best & many times the induction noise is actually louder than the exhaust noise.

So they slap one of these flapper valves in place that only works with the bike in gear, the clutch engaged & a sufficient load on the motor so NO you cannot rev the bike & try to watch the flap open & close...

Anyway, even though we haven't dyno tested it on this new 1000RR (yet), we have tested it (as have many others) on the RC51 & the 919 & on both bikes the mid-range horsepower was increased slightly (usually 1-2 hp) with no perceivable loss of throttle response at low speeds/low rpms.

What is actually happening

At low speeds the flapper door completely closes off & forces the engine to breathe through 2 tiny little air flaps that open as the main ram-air flapper door closes (one piece of plastic does it all). They say this increases intake velocity for better peformance, but once you try this mod you will know that is all BS.

When the bike is breathing through the 2 small openings it is bringing in nothing but hot air from the engine bay.



How to do it

The mod is soooo simple!

From the left hand side of the bike you can see the flapper diaphragm valve with the vacuum hose connected to it. Simply reach in & remove the hose then plug it with a screw or golf tee or anything that will seal up the hose & prevent it from sucking air in. Then tuck the hose out of the way where it won't get hung up on anything. Once you have removed the hose the diaphragm valve will be stuck in the open position keeping the flapper door propped open at all times

You can also simply disconnect the electrical connection to the solenoid & the flap will always remain open, but you have to remove the side fairings to get to this connection.

If you remove all the parts as seen below keep in mind that there will be one vacuum hose left that runs back to the throttle bodies. That hose MUST be blocked off or the engine will suck in air & run poorly.

This is the simplest mod you can possibly do & if you don't like it then just reattach the hose & you're back to stock.

Later on we will show you how to completely remove the entire assembly, but I don't have the time right now to go into that much detail.

Eventually all these pieces (the cannister, solenoid & hoses) will be removed

All the pieces you will have if you decide to remove the ENTIRE assembly
(which is not neccesary if you don't want to, but many have chosen to do so)