no air box
 

thinking of ditching the airbox ..

i've seen a few of you out there with filters on instead .. any recommendations?

is there a downside?

Think I'm going to have a do with this too - or maybe just the top of the air box so I can still house the K and N. Took the trumpets out for the last two races and the bike was dragging in more air - induction.

lid off as a minimum!! With high liuft s,tage 2 filter of some form

Think most of the front guys have junked their airbox and use pod filters and none so far seem to have what I was worried about; water in wet races affected it. Think many will have fitted some form of deflector to the front of the frame so you dont get direct flow in one pot and disturbed air in the other



see skids, I was listening ;) :lol:

ooooooooo .. direct flow and disturbed air !!! wassall that about then?

anyone tried a ram air type system?

was half considering just having open inlets

one trumpet points forward, one up, so airflow isnt consistent....I think :puzzled:

IMHO: There is only likely to be one 'gain' in junking the complete airbox and that is the weight saving. You are extremely unlikely to make any performance gains sticking filters in the end of the inlets. Most 'Classic Racers' dream of still air boxes/plenum chambers. Get it built properly and a 620 will do 65bhp with the air box (lid cut open and foam filtering place) fitted!

mine made nearly 64 with it on, just open lid and good filter. Only reason I wanted to was makes access easier and wanted to fit different tank

Ditto, if memory serves about 1.6kgs :D

at the moment its lid off with no filter.

i didn't expect to get any extra horsies .. just want to lose the weight and gain some space

definately take the lid off .. makes a big difference

Not the best of ideas, you really need a filter, it only takes one trip into the kitty litter for the engine to ingest gravel or any other foreign object to play havoc with your engine internals. Remove the lid, but leave a performance air filter in place.

Did a dyno run a few years ago on a 583 class B, very little gain in hp, less than 1bhp.

If weight saving is your main aim, look at other items, the battery is the biggest area to lose weight, trim the frame of excess bits, make sure your fairing is as light as it can be etc.


Chris:burn:

agree - some filter is needed and helped witrh power rather than reduce on my 583...not sure of difference on a 620 as didnt try it. But dyno man tried with pods v with airbox and set up with pods would have been much harder he said

ran my 800 for a year in minitwins with no filter

back to back dyno runs showed a 4 - 5 horse increase all through the curve without one

had a good classics set up in the w100 club .. always liked the look and sound of the open carbs

admitedly i'd be a little nervous just having the throttle bodies open to the atmosphere at least the airbox affords some protection

Did you have different maps done for both, or was it a case of adding the filter richened the mixture and lost 4 - 5 bhp

had a custom map for both

I fitted some of these to my 900ss engined Monster:

http://www.unifilter.com/online%20ca...universal.html

Got a nice induction roar as a pro!!

Yorkie

looks just the ticket

hmmmm ... what about a couple of small air scoops with an in line filter?

I think AK tried ram air several years ago without any real success.
As my 620 uses the same size airbox, throttle bodies and injectors as my 1000SS I doubt there is much that is holding back the performance once the airbox lid is opened up.

As Andy Pike says a Plenum chamber is one of the best ways to go so as to create a large reservoir of still air for the engine to be able to draw on, so long as that air can be replaced as quickly if not quicker than the engine uses it then it should be able provide the desired air/fuel ratio through out the rev range and not be effected by speed

ah but it's not just performance kev .. it's the joy of creating something different .. and something you can blame when your slower than everyone else :lol:

does the airbox create a reservoir of still air? ..after all it's being constantly drawn

i can imagine with the trumpets in place you could expect the incoming air to be sucked in in a nice laminar fashion .. but with the top hacked off??

Once the air has been drawn into the air box from the previouse induction cycle the air will be still (still as in not swirling around the airbox) this allows maximum induction suction on the next induction cycle.
The stiller the air, the larger amount can be drawn in, the more air the better the fuel air mix and the bigger the bang:D


Chris:burn:

but with this happening a couple of hundred times a second .. hardly a sea of tranquility

how much air is required for max combustion .. think i remember reading somewhere it was 130% of the cylinder volume

so at 9000 revs that's about 120 litres per second (if my maths is right)

Do you think any front runners have consulted Einstein on this? They just ride the thing. Its not about the nth degree of HP. Look how Chris Clarke and Spence and me last year mixed it at the front with the A bikes.

The B bikes are 10bhp less than a good A bike. All about corner speed more throttle and less brakes.

i hear einstein was pretty fast in his day :lol:

not really after eeking an extra hp .. just like fettling .. and learning

So what would it be for a twin cam, 4 valve per cylinder with flowed heads, high lift cams etc.
Must be where Ducati went wrong with their Moto GP bike with the Carbon airbox, the 400 litre airbox was dictating the whole layout of the bike to be wrong.

:lol:

and i was suggesting the volume of air travelling through the box would suggest the air is never still

although ... you could put it on a trailer .. or maybe a large balloon

There is a difference between turbulent air and pulsed air, the underside of a 916 tank in conjunction with the airbox is specially designed to use the pulsing to help produce power by way of acting as a Helmholtz resonator, something Shazaam! did a great post on years ago.

Not sure what you think your air useage is

here are a few questions that may help you answer that

A, How many cc's of petrol do you use in a race
B, What air/fuel mixture do you run
c, How long is the race in minutes

Here's Shazaam's post
http://www.ducatisportingclub.com/sh...ghlight=Airbox

in it Larry mentions 130% of the capacity. so for a 620 thats 803cc so less than a litre between the butterflies and the air filter, for my 1000SS it woule be a figure of 1300cc so as they run the same airbox I doubt if my Class A bike is finding it a restriction

Geat post, I've been blowing on milk bottles all morning!

Should have listened to Bob Dylan Si, the answer is blowing in the wind. :D

You have the lid off yours phil, how do you secure your filter?

you can either cut the lid out, mine was, or use lockwire/duck tape (done that too!)

Mine is fully open, to suck the birds in. :D

Thats almost a sexual offence (ill get my coat).

I just through away everything that seemed heavy and I might not need...... including the air box.....

then replaced most of it 'coz it turns out that I did need it.

I put a couple of sponge filters on the end of the inlets,, did the job.