Ducati Sporting Club UK > DesmoDue Race Series > DesmoDue - General Questions and Chat > Air box options

[Spjallen]

That's one brilliant post.

[bradders]

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

[antonye]

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]

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]

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]

Crash....................

[ells]

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

Mark

[skidlids]

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

[mat2hew]

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]

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