Hey Tech Doctor!
I have a question. (well a couple actually)
I have no idea whether the stock new gen 750 airbox is a compromise or that it already supplies more than enough readily available air or how to test that.
What if anything could I possibly acheive by simply increasing the capacity of my airbox? Would that simply serve to reduce the pressure in the airbox given that the ram air inlets would retain the same 'flow' capacity.
Is the amount of air the engine breathes in governed purely by the engine's 'charging'(filling) stage.
I noticed some major airboxes available on the net for 1Ks which have twice the capacity of the stock airbox. They are claiming some good gains. Is this just for majorly modified machinery? ie big bores, big cams etc.?
I don't expect you to part with the trade secrets or anything but a few hints would be cool. graemlins/cheers.gif . This area really interests me and has me wanting to experiment a bit.

There are 2 main aims of increasing the capacity of an airbox.
1. It gives a greater volume of air ready to be used at any time which helps improve throttle response.
2.It helps reduce turbulence in the airbox, which helps getting the air through the throttle bodies straighter. This increases horsepower by allowing more of a charge to enter the cylinder before the valve closes.

The ideal airbox is a plate that runs around the throttle bodies and seals against the frame. The tank is then receives minor modification to seal onto the frame making it the top of the airbox.

Hope this clears it up a bit for you.

Dean.

Thanx Dean, that's just what I thought. i guess the trick is to work an air filtration system into that somehow(for a road bike). I am thinking that the positioning of the filter/s should be right where the air is entering the main box from the ram ducts because of the velocity of the 'ram' effect which would assist the air in penetrating the restriction and therefore making a larger volume of 'still' air available to the engine. as opposed to having the engine actually sucking the air through the restriction and therefore reducing the available quantity. would this could cause a 'back log/too much turbulence' in the ram ducts? I’m thinking that the imbalance of pressures on either side of the ‘restriction’ would actually cause the airbox to have a ‘negative pressure’ and therefore possibly act as a vaccuum itself. As You didn't mention the 'pressurised' aspect of the airbox which I assumed played a role does that mean that it is secondary to the volume of readily available air?. You don’t have to answer these questions if You don’t want to. I know it’s getting a little complex now. Man, now I’m getting real excited.
Cheers
…Dave
Am i still on the right track?

[ 01-29-2003, 02:48 PM: Message edited by: Kiwi750y ]

It would be preferable to have the filters "IN" the ducts, but since this is not practical, they have been positioned over the throttle boddies for cost reasons.

It is preferable to have a positive pressure of air in the airbox as this forms a natural supercharger effect. This really only comes into play above 230kph.

Dean.

P.S. I will answer ANY question you throw at me, so keep them coming.

[ 01-30-2003, 04:00 AM: Message edited by: Tech Doctor ]

Thanx for the replies dean that's really helpful. I am starting to get a good feel for this now. my last 2 questions i just want your opinion really, what do You see as the main weaknesses of the stock airbox. Do You think that the stock ram air ducts are capable of supplying an air box of around twice the capacity of stock below 230kmh?

Originally posted by Kiwi750y:
Thanx for the replies dean that's really helpful. I am starting to get a good feel for this now. my last 2 questions i just want your opinion really, what do You see as the main weaknesses of the stock airbox. Do You think that the stock ram air ducts are capable of supplying an air box of around twice the capacity of stock below 230kmh?<font size="2" face="Verdana, Arial">I don't really understand your question. Can you re-word it please.

Dean.

Sure,
Do You think that if I modified my airbox, along the lines discussed, that I would get a big improvement on the street? Would it be worth the effort?
Thanks Dean

Originally posted by Kiwi750y:
Sure,
Do You think that if I modified my airbox, along the lines discussed, that I would get a big improvement on the street? Would it be worth the effort?
Thanks Dean<font size="2" face="Verdana, Arial">Really only if you are outright horsepower, or are after every little improvement possible. I would do it if it was me.

Dean.

Would you try to keep the same cross sectional area as the std airfilter split over the two duct area ones. Kiwi looks like you have a nice project brewing, keep us informd images/icons/smile.gif

Thanks Tech Doctor graemlins/cheers.gif
Would you try to keep the same cross sectional area as the std airfilter split over the two duct area ones.<font size="2" face="Verdana, Arial">is that a question for tech doctor?
I would imagine that that wouldn't be necessary as long the air getting in was filtered. I think that as the filter is a restriction, the smaller the better.

But is that the trade of, too little filtering and potential bad news. How are you going to work out how much filter to apply to trap enuf nasties. And what type of filter media do you have in mind. Keep us updated...

You are actually better off with a filter that has a large surface area. It is eaiser to suck air through a larger area than a smaller one. Get a straw and a 2" peice of PVC pipe. Which one flows better when you suck on them? The larger one of course. Also, having a larger filter will help place it further away from the throttle bodies which will help in reducing turbuliance.

Dean.