Velocity Stack

[PHIL_B54]

http://www.gtthunder.com/velocitystack.html

I just ordered my HMF/k&n for my 300ex, and Im deciding what to do with the airbox. I have seen that several people have these, including Rico.

How do you benifit by having one of these velocity stacks versus just a hole drilled in the box? I understand the airbox regidity benifit of a hole vs removing the entire lid. And I can see that the lip may help prevent mud/water from entering vs a plain hole. I was just wondering if there was a reason I was overlooking.

Thanks
Phil

[Eddiesanders250]

just take it off dont mess around with the holes unless you ride in the snow or mud or any water. then id drill some holes

[PHIL_B54]

ive never really had problems with my open topped alum. air box on my 400ex... i was just looking for any available power i can find

[cals400ex]

i run this too. there are a few things i like about it. first off, it is a two inch tube. by removing the lid you not only loose rigidity of the air box but you all have tons of air (volume) but little velocity. this two inch hole will provide less air but at great velocity as it is sucked through the hole. i am a firm believer that the speed of the incoming air is important. i am not saying you will get 10 more horsepower, but the filter says much cleaner too than with an open lid. also, this velocity stack is probably a couple inches long. i preferred to put this stack in the very rear of my lid. this way, the hole isn't right over the filter. when you hit water, it will go in this and be drained to the bottom of the air box, bypassing the filter. i really don't ride in those conditions but rico said his filter says dry. with enough water, anything is going to get wet though. a regular hole in the lid might have more of a tendency to pull the water towards the filter as it enters the hole. all in all, i would get this again if it came down to it.

[Aceman]

From what I see the benefit it has over a plain hole in the airbox lid is if water/mud should make its way down the velocity stack it will go right to the bottom of the airbox where it can drain. If it was just a hole there's a chance the water/mud would land on the filter before running off the side to the bottom of the airbox. That's the only advantage I can see over a plain hole or removing the airbox lid completely.

[cals400ex]

now that i read that you run an open air box lid, i bet you don't gain power by adding this. however, the maintenance on the filter is less. i personally never cared how mine ran with the lid off. i actually choose to run my air box lid on and unmodified on my 406 and 426 motors. my buddy is the same way with his 416. it feels like we have more of a bog at midrange with the lid off. we did a lot of testing and when drag racing our bikes were not one bit quicker with the lids off than with the lids on. the key is to have the bike jetted correctly which ever you do. i noticed my jetting would change almost 2 mainjet sizes by just removing the lid.

[PHIL_B54]

sorry, im being confusing

my 400ex has an open box, and ive never had water/mud problems

my 300ex is soon to be modified, and im considering this stack

[PHIL_B54]

i catch the idea of the increased velocity being good. but if this is the case, how is this different than the stock breather tube? would you need to plug the sock inlet for this to get added velocity?

[Rico]

I run it to keep mud and crap out of my airbox. In my riding conditions an open airbox is begging for a motor overhaul 4 times a year.. LOL


The stack is MUCH better than just drilling a hole in your airbox. You still get crap in there with the holes and you won't with the velocity stack.

[400exredrider]

wouldent it be cheaper to get some strong glue and afew inches of rubber hose thats 2 inch hose? put a zip tie around the top and glue it into the lid,.... seems like it would do nearly the same thing. im currently tring to figure out what to do with my snorkel. i have an FCR40mm and its too short so i had to move the airbox forward and now the snorkel needs shortend or canned.

[300exOH]

Originally posted by 400exredrider
wouldent it be cheaper to get some strong glue and afew inches of rubber hose thats 2 inch hose? put a zip tie around the top and glue it into the lid,.... seems like it would do nearly the same thing. im currently tring to figure out what to do with my snorkel. i have an FCR40mm and its too short so i had to move the airbox forward and now the snorkel needs shortend or canned.

I would think it would work as long as the diameter is the same and it extends into the airbox to direct water away from the filter. I have a similar setup that I was told was made by mickey dunlap. It's an aluminum tube with a screen on top that I epoxied in place. It works great for me.

[PHIL_B54]

300exOH, are the 2 frame tubes plugged with your set-up?

[400Rider022]

300exOH how exactly did you make that and does it give u a lil gain??? im interested in making one of those because i dont wanna remove my lid because i encounter mud and water occasionally

[speedy400]

I am a firm beliver of that velocity stack isnt any diffrent than a straight tube, but it sure does sound cool! I think you only need velocity right before the carb. in the carb to atomize, then in the intake ports themselves to help one way port flow design and just basically more velocity of air and gas flowing in the combustion chamber.... in the airbox, before the filter... I think it wont make a bit of diffrence, conidering as soon as the "high velocity" air goes in the big air *BOX* the box will kill all of the velocity you may have gained.-darren

[400exredrider]

makes sense,, but its still better than running no lid,,, because it can suck quite a bit of air thru that

[300exOH]

Originally posted by PHIL_B54
300exOH, are the 2 frame tubes plugged with your set-up?

The frame tubes are still the way the came stock.

400Rider022-I puchased the tube from another member on here. I think it was made by mickey dunlap. I think any 2" tube would work. This one is aluminum but you could use pcv pipe if you wanted. I do get a small gain in top end power. Enough to be worth doing IMO.