Purpose of airbox

[Guest BoBOKik]

The most commonly spouted bollex about ram air is that the bigger the scoop, the better the air pressure. Utter shite I'm afraid.

 

Your bikes' airbox exists as a kind of air reservoir - purely there to provide the engine with cool clean fresh air 'on tap'. Imagine if you didn't have an air box - the air would be rushing over the carbs or throttle bodies at anything up to 200 mp - bloody difficult to get it in the engine when it's in the engine when it's whizzing past at that speed. Hence the airbox holds a near-still supply of pressurised air directily over the carbs to feed them effortlessly with as much air as they need, every time they need it.

 

The airbox has to be much larger than the capacity of the engine too. If you take the GSX-R1000 as an example: Each cylinder as it fires will need 250cc of air to be sitting there ready to flow into the cylinder, and as the next cylinder fires it will also need another 250cc of air, and so on.

 

Now, obviously with each 250cc gulp of nice fresh air disappearing from the airbox - there needs to be enough to sustain each of the next 'draws' too, which means that the flow of fresh air into the airbox must be sufficiently high that the rapidly diminishing air can be replenished beforre the pressure drops significantly inside the airbox. Therefore the airbox needs to inflow more than it can outflow - but no more, although even that's a lot of air. Each cylinder uses 250cc , which is 1 litre of air per four revolutions. At 11,500 rpm that's 2,875 litres of air a minute, or 48 litres a second. Going back to the size of the intake and, taking the example of the Gixer Thou again: it has 42mm throttle bodies, which means that the intake needs to be bigger than 42mm to flow more that the cylinder can take - but literally 43mm would do the job, it doesn't need to look like a '50s hot-rod.

 

The total pressurisation of the airbox is dependant purely on the speed at which the bike is travelling - again, nothing to do with the size of the intaks. Static air has higher pressure that air moving at high speed because air has fixed amount of energy - raise the air speed (kinetic energy) and the pressure energy drops to keep the total volume constant. This is why bikes have airboxes.

 

In all reality the maximum pressure you're gonna see in the airbox at normal riding speeds is significantly less that 1 psi - so you might be wondering 'why bother?' Well, if you consider that the effect of not having an airbox which even only held the air still would mean that you'd actually be losing power the faster you went - the effect of having positive pressure in the airbox is simply a boost - literally.

 

Fast Bikes - Apr 03

[Demon]

The most commonly spouted bollex about ram air is that the bigger the scoop, the better the air pressure. Utter shite I'm afraid.

 

I can't agree with your statement that "ram air" is to boost air pressure. There is no way you could boost air intake pressure unless you are running turbo or supercharging devices. Ram air devices serves the purpose of providing cool air to the engine for combustion. Cool air is more dense than hot air so technically you get more bhp, everything being equal.

[S750WP]

The 'Ang Moh' like to remove the airbox and put individual pod air filters when jetted with stage 3 jet kit.

[Guest GuiNNeSS]

So..... how to achieve this on the dyno cos the bike sitting still?

 

Even with blowers running i can't see the fans blowing as hard a bike running hard.

[joshy]

then y some guys modify their airbox?

will this way push the performance of the bike?

[stanboy]

i took out the snorkel...bikes feels better but louder...

the louder sound shldnt b a prob wif tp hor? further more i punch mi exhaust liaoz...

[Strife]

If replace the orginal with an air filter isit better and can make the bike more powerful. Cause think my bike no air box only an air filter connected to the carb.

[tOngEh]

1 thing to clear my doubts. Does it mean that the purpose of the airbox is to hold the air still so that the pressure of the air box is higher then that of the carbs. (air flow for high to low pressure)

[L3stat]

1 thing to clear my doubts. Does it mean that the purpose of the airbox is to hold the air still so that the pressure of the air box is higher then that of the carbs. (air flow for high to low pressure)

 

my humble opinion would be that the air box allows for STABLE and PREDICTABLE air pressures for carb or EFI tuning to work on, for predictable performance. as mentioned in the first post, varying windspeed with an awkward position of the carbs in the bike makes for unstable air pressures that vary at different riding speeds. with or without air box, air will definitely enter the carb body when the engine is running, due to low pressure (vacuum) induced by the engine (piston on intake stroke).

[wolverin]

I believe the air box has 2 main functions. 1) to feed air into the throttle body. 2) Regulate air pressure. To combust requires 2 elements, fuel and air. At high rpm, the engine requires more air than the air box can provide thus ram air duct uses the bike's forward momentum to have cool air rammed into the airbox. this creates a higher pressure to cope with the combustion. People taking out the air box will also work provided the scoops are located in such a way that takes advantage of uninteruptted air flowing into the carbs.

[Guest Vpower]

Airbox is there to guide & channel filtered air into the throttle bodies. If you notice, most sportbikes capable of going at fast speed have airbox under fuel tank and air intakes at the front. Other than that, air box can be at the side or open without a box construct.

 

Sometimes we wonder why there isn't a universal airbox design for every bike. We have air vent/tube to channel the incoming air into the air box. Straight, slightly bend at certain angle, single or dual air intakes create diff air pressure at diff speed and all must be taken into considerations together with the bike aero-dynamic design and air-coefficient drag ratio.

 

The diff types and designs of air intakes create diff air pressure when the bike moves. Often than not, designers have come a long way to build the most efficient airbox, alongside with the change in bike exterior.

 

Running without air filter is a personal choice as one believes that air-filter induce restriction to air flow. Others argue the fact without air-filter has ill effect on impurities going into combustion chamber. We leave this to individual.....

 

R&D bike scientists have discovered, other than the fact air temperture changes (although not significantly but in biking technology, mm creates cm, g creates kg) as speed does over a medium, air pressure inside the airbox is NOT LINEAR too! Read up on articles on air on Hurricane and Tornadoes you'll understand more.

 

Since then, ram air technology is introduced! Read on how Turbo works, ram air borrows the general idea from it into bike air box. Ram air hences regulates air pressure at diff speed when needed to manage better combustion power.

 

This is how a boost is created when reached a power band. Usually someone likes to removes ram air from their air box as they want to run the bike with move linear power, so to speak!

[wolverin]

[Biker]

wow.. i thought air box is to stop dust particle from getting into the funnel onli... newbie x

[Terrible One]

i remove the airbox from my bike to try and see if there's any difference...my pickup really improves alot...but my top speed ended up reaching only 100km/h...the noise is really cool...but wen it gets high rev...it doesn't have dat "kick" anyomore..so I guai guai put back the airbox...my bike is more predictable wif it...

[learner22]

can anyone tell me where is the air box for s4 vtec1. thamks.

[Andy]

can anyone tell me where is the air box for s4 vtec1. thamks.

 

lift up your tank. There's a black box with 3 screws. Unscrew it and lift off the cap, you will see your air FILTER in that box.

[Andydy]

For sp, if take out the airbox leh?

got wad effect other than the sound...

wad are the pro and cons..??

[stanboy]

For sp, if take out the airbox leh?

got wad effect other than the sound...

wad are the pro and cons..??

tink bike may run smoother(feels lar) but b prepared 2 hav a dirty carb soon....so better 2 keep it there lor...juz mi 2cents worth...

as 4 other efx i nt sure lor...

[Andydy]

tink bike may run smoother(feels lar) but b prepared 2 hav a dirty carb soon....so better 2 keep it there lor...juz mi 2cents worth...

as 4 other efx i nt sure lor...

 

 

oic...

[stanboy]

hey lao jiaos out there...i yesterday washed mi bike n i took out the filter 2 wash...washed in water then realised i dun hav blower 2 dry it throughly...so bobian i squeeze out as much water as i can then put it bac...izzit ok like dat???

[Guest FireSpitter]

hey lao jiaos out there...i yesterday washed mi bike n i took out the filter 2 wash...washed in water then realised i dun hav blower 2 dry it throughly...so bobian i squeeze out as much water as i can then put it bac...izzit ok like dat???

 

Please make sure it's 100% dry. You wouldn't want water in your engine. It is neither combustible nor compressable, the results are not pleasing.

[stanboy]

 

Please make sure it's 100% dry. You wouldn't want water in your engine. It is neither combustible nor compressable, the results are not pleasing.

 

if i hav been riding since yesterday n (touch wood) everiting seems ok shld b alrite???

[Throttle]

wah stanboy , you think your original air filter is K&N washable?

 

better dont try it again.

 

the effects = choked throttle response

[tonyhawkzx]

hey lao jiaos out there...i yesterday washed mi bike n i took out the filter 2 wash...washed in water then realised i dun hav blower 2 dry it throughly...so bobian i squeeze out as much water as i can then put it bac...izzit ok like dat???

 

U sure u can wash with WATER?? eeeh, I think yr filter by now should have been torn already! did u oil after u dry?

 

Just my 5cents thought!

 

Tony

[jsn]

remove airbox will have faster pick up speed but will not reach the top speed...i test out on a normal motor (just engine with filter kit and carburator) for those big cc one if the air is not enough their engine may overheat easily that why big cc bike need alot of air to cool so they need to have more speed to have more air...correct me if i'm wrong