I've been running with the lid and snorkel tubes on for about a month, and installed hose clamps on plenum last week. While tinkering with my bike today I took the seat off and revved the engine to look for any distortion or collapse when something weird happened. As I leaned over to watch the plenum, air was hitting me in the face. I lost the plug in the top of the box (its somewhere in LS, Ok.) and air was coming OUT of it when it revved!!! Maybe velocity from the tubes pressurizes box???

This, to me any way, proves MrHps theories. At times I thought he may be on crack, if he is I WANT SOME TOO!!!! Now I wish I'd ordered the Lectron 46 instead of the tm45 like he said!!! WTG MrHp!!

 

[img]i/expressions/face-icon-small-wink.gif[/img]

 

Hey Butt,

Are you using twist or thumb?

And where did you get your nic? Hope its not a medical condition!

 

That is his High school annual picture!! He's much hairier now!! [img]i/expressions/face-icon-small-shocked.gif[/img]


LMAO!







Bigger.

 

Kyle, is right!...lol It's a long story. I using a thumb throttle that was modified.

 

What you experienced was reversion caused by the pulsation of the air movement through the air box. When the engine draws in air it is not a smooth draw, it is a series of pulsations determined primarily by RPM. When air is drawn into a confined area such as an air box it builds velocity concurrent with demand. When the demand pulses, the excess air came out the hole where there once was a plug. No pressurization, just a reversing of flow happening about a hudred times a second. This is the same theory that powers pulse type fuel pumps.

 

DCryder

OK, you had to make me think on this one. But I have the solution, bear with me on this it might be hard to follow (difficulty in explaining things with out the use of my hands)...

If air is coming out of the hole in the top of the air box, the only reasononing could be the pressurized interior of the box.

The reason for this is not increased velocity inside the box (as velocity increases, pressure decreases... Bernoullis theorum on pressure and velocity), it is because of a back pressure caused by the carb. When the throttle is opened with the engine not under load (makes a big difference) air is pulled into the air box, thru the filter and into the carb. This creates a low pressure area inside the airbox, this in turn causes more air to be pulled into the box. When your jockeying the throttle open and closed, the airbox is switching between a vacuum and pressure (the throttle plate is opening and closing).

The pressure comes from the air entering the air box, as the throttle is being closed. The vacuum caused by the preceeding throttle actuations causes the air to rush up against the throttle plate, but with the trottle plate closed (even for a millisecond), a chain of events happens. Air since it is compressable begins to back up against the closed throttle plate and up into the airbox... at the same time the air is still rushing into the box. This in turn causes the air to look for an escape point.... the little hole in the top of the air box.

Easy way to test this is to get something that smokes (like a smoking incense stick), hold it next to the little hole and start revving the quad, .. watch how the smokes go.. it will go in the hole under acceleration, and push away from the hole under decelleration.

Ther is no reason why this should make your engine react better, actually, because of the long tubes required to get air to the engine, this should make throttle crispness less (longer tube means a higher pressure drop along the tube).

I run an open K&N with a home-made adapter to the carb. It works real well for me, and I'm able to run large jets (192.5 mikuni main jet). I'm still running a little on the lean side at the top end area also. My quad pulls hard... at least that is what aothers tell me when they try to catch me.. (Baja DS, and a tricked out Banshee).

Hope this makes sense.....

Good luck in anything you decide for your DS... I was merely trying to explain the puff of air from your airbox.

Glenn

 

KenDS..

I should have waited... my fingers wouldn't have gotten sore.


But, I think were talking about two different (but the same) conclusions to his "puff" of air...

Glenn

 

DCRyder - why would any of this make you question the carb - Mikuni vs. Lectron?

Lid removal leans the fuel/air mixture, therefore it must be getting more air flow. more air + more fuel typically equals more power. the intake boot from airbox to carb may very well have some validity, just as a reverse cone megaphone on the exhaust works, but if we are to all of sudden realize lid removal is wrong then it goes against every race motor ever made since the beginning of time. there may be something to leaving the lid on with the stock carb, due to its vacuum operation and the fact that it has a vacuum hose going to the intake boot, but I'd have to see a chart for other carbs.

What airbox setup does Buttfungus's charts represent?

 

Chris, which charts are you referring to?