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-   -   Air box options (/showthread.php?t=85509)

Spjallen 29-Jan-2012 12:08

Air box options
 
What's the real benefit of removing the air box? I read in the regs that you can remove it, but what do you gain? More induction air I guess?:eureka:

skidlids 29-Jan-2012 12:39

Debateable I guess
Airbox is big enough to supply the 900/1000 with enough air to make 85-95bhp with standard restrictive filter and makes for a good Plenum Chamber, upgrading to a race filter can only improve things. Most restrictive part of the standard box is the lid which is easily disposed of.
i have seen plenty of bikes running a standard airbox, race filter and no lid making the Class limit on BHP.
Some airboxes get cut to seperate the Battery and Electrics so they don't have to be removed everytime you want to work on the carbs or the throttle bodies

Jolley 29-Jan-2012 12:43

My B bike made better midrange (around 5bhp more) with the airbox and standard lid.

bradders 29-Jan-2012 12:48

only reason I'm junking mine is so I can accommodate the tank swap, otherwise I'd leave as is with high flow filter and no lid

Spjallen 29-Jan-2012 13:38

Thank you great info. I was going to just take the lid off but it also made good power on the dyno with the lid on and a k and n. Just for info had it done at the dyno centre. It's run by ex bsb racer Stuart Nicholson and great value for money. Well I thought so!! 01609 760466

bradders 29-Jan-2012 19:01

so was it like Jolley says; better midrange with lid on?

Spjallen 30-Jan-2012 10:31

Yes better with it on.

antonye 30-Jan-2012 10:55

Have a read...
http://www.ducatisportingclub.com/sh...ad.php?t=41331

Spjallen 30-Jan-2012 22:42

That's one brilliant post.

bradders 30-Jan-2012 22:59

But not relevant to our little bikes. Superbike a have a chamber with pressurised air, where our tiddlers don't. Certainly not from research I've been reading

Only way to know is back to back dyno which SP has done, hope to do the same and see the outcome. Shame if it's worse tho, have to keep the weight and look of the monster tank

Ghost 30-Jan-2012 23:07

Quote:

Originally Posted by Spjallen
That's one brilliant post.



+1 to that.

antonye 30-Jan-2012 23:42

Quote:

Originally Posted by bradders
But not relevant to our little bikes.


Not quite true - there's a lot of good information in there about the venturi effect, the plenum effect, Helmholtz resonation and filter performance which are all relevant to any bike and the power it makes as well as the way it makes it.

skidlids 31-Jan-2012 00:06

Also makes a difference wether your running CV Carbs, Slide carbs or fuel injection
Engines are essentially air pumps but to work they need need a air fuel ratio within a certain range. One end of the range will give good economy the other the best power.
So its not only a matter of drawing in two lots of 300cc (probably less as engines aren't 100% efficient, especially older two valve SOHC ones) 5000 times a minute but also getting not only the correct amount of fuel but also getting it to mix with the inrushing air as best as you can.

What I would like to know at exactly what point do the injectors switch on to fit in with the opening cams duration

badgerpilot 31-Jan-2012 11:43

Quote:

Originally Posted by skidlids
What I would like to know at exactly what point do the injectors switch on to fit in with the opening cams duration


Purple.

You techy boys are ace, I press the red button and twist the grippy thing and it goes vroom till the fuel runs out or I crash.

Cranker V2 31-Jan-2012 12:16

Crash....................:(

ells 31-Jan-2012 12:17

Yep,
very interesting, but I am with Badger on this one (apart from the crashing bit)

Mark

skidlids 31-Jan-2012 14:28

Quote:

Originally Posted by ells
Yep,
very interesting, but I am with Badger on this one (apart from the crashing bit)

Mark


Thats because you both have carb'd bikes

When they start sucking in fuel is determined by when the inlet valve opens, and the amount of fuel sucked in is governed by the size of the jets and the vacuum above them hence why the airbox plays a part.

@ 10000rpm the engine only has 6mS for each 360 degree crank rotation, Cam duration is around 280 degrees on the injected bikes so only about 4.65mS to suck a fresh charge into the cylinder when flat out, yet injector opening times are often in excess of this, meaning fuel is being added while the valve is closed.
I may have to hook up the Oscilloscope one day and see how the injector pulse conpares to the pulse from the crank sensor and also to the Ignition timing

bradders 31-Jan-2012 14:41

twist hard, go fast, simple as :D

from reading and listening to lots of this, the difference at the speeds we travel isn't huge. Yes there will always be a difference, as long as its 1 or 2 hp, and I lose no midrange, thats fine. When you start talking 180 hp, 1 or 2 for ours can be 10 or 20 - so worth the investment and time.

Aim is simple; good strong wide range, good fat torq and 63 hp flat balls out...and dont brake!

nogaromill998 31-Jan-2012 16:49

Well I've gone from twin front discs to none on my Class A bike this year.....I may add a set of rubber brake blocks if its REALLY needed to outbrake you Paul......Lol.....

bradders 31-Jan-2012 17:03

wouldnt worry - I ran one disc no pads for lots of last season ;)

badgerpilot 31-Jan-2012 17:24

Quote:

Originally Posted by bradders
wouldnt worry - I ran one disc no pads for lots of last season ;)


Big balls no brain more like! :lol:

bradders 31-Jan-2012 19:43

that as well :D

mat2hew 07-Feb-2012 12:52

love it.
 
Quote:

Originally Posted by badgerpilot
Purple.

You techy boys are ace, I press the red button and twist the grippy thing and it goes vroom till the fuel runs out or I crash.


love it, thats my philosophy as well! (and most in DD I think)

bradders 07-Feb-2012 18:50

Quote:

Originally Posted by mat2hew
love it, thats my philosophy as well! (and most in DD I think)


mines even better now - no key to turn either :D


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