Changing Peak Torque

I have finally decided that KTM had identified this as a flaw from the design of the bike/s.. but found that the time and $ spent on the airbox would not yeild much improvements. Assuming that this is correct adn KTM have don a brilliant job elesewhere... that leave me with a great opportunity for gains.

Hence the airbox intake thread, and dual velocity stacks. I have good and bad news:
Good: I have an answer to 'fix' the airbox
Bad: It is extremely difficult to implement without plastic making equipment

Idea:
- single or dual tube runner/s, (dual - fitted side by side)
- with a bell intake stack/s
- bent smoothly to run into the airbox (hence flowing the air smoothly)
(obviously it/they would need to be bent at approx 45deg and run into
the box avoiding the throttle bodies)
- tuned length for airbox capacity (not intake runner length as noted here)

Bonus:
- fit a Hermoltz resonator onto the tube/s using a smal sealed plastic box
(this would need to be close to the stacks & need room under the tank)
- Size from my previous calculations - the size should be as large as possible

(I will post a diagram in the near future... for the moment - it is in my head)

Benefits:
- airflow = this would remove the massive turbulance from the square edged and changing direction of the intake and airbox.
- resonance = good tuning would allow the airbod to have a different peak turque
(in my case I would lower peak rpm resonance - but could be tuned anywhere)

- Resonantor = if fittable would improve air velocity and clean up the resonance point. It is alo a second point for tuning.

So here I go again: looking at the interesting design and config of the intake side of the SD. I am looking at deceasing the ROM of max torque without effecting top end power too much.

So I need to look at the runners to see how they will be effected as a final result. remember - do your homework first.

I am looking at the wholeistic plan for the airbox, so here is some info and formulas:
Stock Dyno graph:
Intake Runner Calc:

SD Info:
Capacity: 999cc = 60.9 ci
Optimum Intake runner area: 2.42 square inches
Optimum Intake Length: 12.00 inches long (from valve head to plenum)

More info....here is another basic formula:
84,000 / tuned rpm = runner length

for the SD: 8400/7000 = 12 inches


The runner length is measured from the back of the intake valve to the start of the radiused entry of the runner. Most people use the max. torque rpm as the "tuned rpm".

Also, as a general rule of thumb, the port cross section area should be ~83% of the valve area in the intake port and taper out at a 3.5 degree angle as it goes toward the entry of the runner.

There are more exact formulas that use the compression ratio, engine displacement, and cam timing, but this one is close.

This is care of Greenlight from http://www.eng-tips.com

Using the following auto calculation (for ease), I calculate the following:



Airbox Volume = 19.8 Litres
Intake Diameter = 7.2cm (my modified intake runner)
Optimum tuned peak RPM = 5000 rpm (where the dip is)
Runner length = 18cm


Although using a single 58mm tube (the jaycar speaker port item) this would need to be 11cm. Although I expect that this would kill the top end performance... possibly?


Approx standard airbox figures are:
Airbox Volume = 19.8 Litres
Intake Diameter = 6cm
Runner length = 15cm
Optimum tuned peak RPM = 4500 rpm (1/2 freq of peak power)


My summary assumption is that the stock airbox is tuned correctly for power... but as Sommer have identified it needs a littl emore air for top end breathing. This would mean that to obtain real gains - a very precise calculation would need to be done and applied to meet the specific bike's peak torque requirement.