Has anyone ever put a Thunder products TPI valve in their sportsman's airbox, I just finished installing one of them and have another to go. They really don't give a guy much room to work with. And to not to mention the seat comes down really close to the top of the airbox, I think there will be enough room for it to breath though.
I think I have my work cut out for me if I plan on installing the other one.
I don't usually go in deep water or deep mud so I figured I was going to be safe to put it on my airbox lid. If I decide to scrap it I'll just by another lid, I think there cheap.

How many guys/girls are running the E-series white brothers exhaust on their machines, how do you like it? how does it sound?
They don't make one for the 500 HO yet but I have seen guys use the universal E-series and make them fit.

Brambles

 

I would like to see your take on whether or not you see a difference in performance with this product. I am kind of skeptical. The 500 HO engine uses a CV carb which requires a certain amount of vaccum to operate the carb slide correctly. This is the reason why you see people advising against drilling holes in the lid or removing the lid on the airbox for this engine. You reduce the vaccum and the slide will not function properly. To correct this takes more than just changing the main jet. For instance, my HPD airbox/carb mod kit came with a new 170 main jet, modified needle jet tube, and a different slide spring, as well as a recommended air/fuel screw adjustment.

 

BigBad did you notice a difference with the hpd kit. i order one about a week ago for my scrambler. hopefully its a noticable difference.

 

Yes. Better throttle response and a harder hit when you crack the throttle. That is what I noticed with it.

 

Lets see if I can explain my theory on this matter. I will use Vacuum instead of negative and positive pressure.

The airbox shouldn't be the restriction causing vacuum, if this were the case the engine would never be able to build RPM because it will constantly fighting for air. The engine itself is what causes vacuum, primarily the intake stroke, and its the carb ( the slide in this case and throttle valves in other carbs, plus the throttle bore diameter) which is the restriction. The engine vacuum is a combination of rpm and throttle opening(slide position). At full throttle their should be no engine vacuum, the throttle slide will be fully open and the engine is breathing freely. On the low end the throttle slide is closed causing more engine vacuum which results in the increase in intake velocity once the slide is open which is what your feeling as throttle response. The problem with ATV's are if they put a airbox on a properly tuned carb they would choke it out, the engine vacuum would suck more fuel though its passages because you have just restricted air flow. The manufacturers have to jet the ATV super lean to deal with the extra fuel that is being drawn in due to the airbox restriction. I took the airbox off my sportsman and started it up, it ran like crap but it did rev way quicker up to 4000 rpm then coughed and farted because it was so lean.

In real simple terms
Essentialy your lungs are the engine and your mouth is the carb, your lips are the slide. Make a tight circle with your lips and inhale deeply and feel the speed at which the air hits your tounge. The larger you make the hole in your lips the slower the air moves through. Now cup your hands over your mouth and repeat. You have just installed an airbox.

I would be able to better explain it in person, I don't feel I can explain all aspects in writing but I hope this helps

Brambles