A huge intake sound difference below and above ~3750rpm - why is that?

Hi guys! I bought a 1999 Honda VFR a bit over a month a go. I removed the snorkel from the air box, and I also disconnected the pipe going to flapper valve. I noticed a big difference in intake sound, also I think the power curve changed somehow, maybe for a smoother direction.

Anyway, I noticed also that that big intake roar almost disappears when going over around 3750rpm. Does anyone have a explanation what is happening in the engine at this point? When the rpms drop, again below something about 3750rpm, it's like something would open in the intake system as the intake sound gets noticeably louder. I found this very interesting but I got no idea what is happening there....

Thanks people!

 

first off the snorkel directs air flow and also dampens noise... therefore when you remove the snorkel you open a huge hole int eh front of the air box.. as far as the noise going away at 3700 RPM.. who nows, maybe it has to do with the amount of tourque and gear that you are in.... my 86 if I have it in 3rd gear and roll full throttle the intake noise is outrageous until the RPMs catchup with the gear your in.
Just my guess....

 

I'm gonna take a shot at this one and say the sound your hearing is some engine lugging noise. Mine doesnt like heavy throttle under 4k. The valve timing makes the motor "chug" at low rpms and could produce the sounds your hearing.

 

V-4's do not like to run under 4000 RPM's once you are out of 2nd gear.

 

my snorkel was missing when I bought mine...I found one at the salvage yard and put it back on....

 

Some update... Now that the snorkel has been removed and the flapper valve is disabled, the engine power output has changed into a somewhat more boring direction. The power kick at some point of the rpm range has disappeared, now the power comes off more smoother.

The sound is nice, anyway, especially under that ~3750rpm. If going up from there, it sounds like something would be shutting the air box intake or something.

 

Agreed as said above about keeping the engine above 4k rpms. Your lugging the engine which is just as harmful as constant high rpms.