So when will you be removing it?

 

Can anyone answer a few Q's for me.

Would a larger "box" yeild a larger pulse at a lower frequency and would this tune your Peak power at a lower rpm?

Does this work in the opposite scenerio?

Does the material the box is made out of have any effect (Alum. vs. Plastic)

Any relation to tuning a sub box. Port length/dia. and size of box effect the frequency.

 

So far I've only seen charts that show precisely what I'd expect to see. Neeeext.

--
Mikko

 

Not necessarily "larger pulses" but at lower frequency yes. And yes, that would tend to move torque peak to lower RPM.

As in smaller box -> higher frequency? Yes it does if other variables are kept constant.


Not directly. But indirectly maybe. You want the box to be air tight and rigid to make the resonant waves as powerful as possible. A soft and leaky box wouldn't produce any resonance at all.

Exactly same phenomena is used in both applications. Same equations and same challenges.

--
Mikko

 

I believe someone mentioned that the FI KLX's have the first 3 gears or so running a restricted timing or fuel map.

 

Phew! That beats all theories I've seen before...

Remains to reconcile that with the curves shown by Jeffward.

 

Ok let me throw something into the mix since we are talking about air boxes.

I have yet to take the smog plumbing off my bike. Wouldn't the tube from the crank case to the air box (92191A) totally throw the air box math out the window since it kind of moves air in and out or is the effect negligible?

 

And what is that ? I see more peak power with either the KDX200 snorkel or the lid removed and less with the stock snorkel.

Sure the stock snorkel seems to keep peak power longer towards redline, but since i shift at around 8-8.5K this is a moot point for me.

 

In the first place, why assume the stock box is the "ideal" resonation frequency?

Taking the snorkle out may yield closer to ideal....

Also, optimizing the resonance of an inferior design (perhaps the definition of the stock setup), only improves the results of that inferior model.

Perhaps "less restriction of air flow" is akin to "more displacement". While removing restrictions to the airbox design may disturb resonance, the overall effect is an improvement in power, such as boring out a cylinder gives more power...even if the overall setup is lacking in other areas (ports, valves, cam lift/timing, carb throat diameter, etc.).

I'm just saying I don't necessarily buy into the initial premise: that the stock airbox might actually be anything near perfect. It fits the space available, is cheap to make, and houses a filter....maybe that's about advance as the technology was that was used in it's design.

 

FlyingFinn, Jeff's graphs appear to show a much improved torque curve for both the cases where the airbox lid is fully removed (middle graph), and when the stock snorkel is replaced with the KDX220 snorkel (bottom graph).

For example, comparing the airbox lid removed to the lid on w/stock snorkel, the torque progression is smooth all the way from 4000 RPM to where it peaks at about 6500 RPM. From there is trails a little steeply but then less so beginning at 8000 RPM and finishes out at 1.0 (Kgm) at 9500 RPM. Where in the stock airbox/snorkel, the torque curve looks crookeder than a dogs hind leg at first, peaks a little farther up the RPM scale at about 6750 RPM, then trails off pretty crooked again and finishes out at about 0.8 Kgm at 9500 RPM.

The KDX220 snorkel shows a much more linear torque curve from 4000 to where it peaks at 7000 RPM, then trails off pretty uniformly. At 9500 RPM, it's torquing at around 1.3 Kgm. So the stock airbox/snorkel is far less smooth than either the no airbox lid, or the lid + KDX220 snorkel. And it peaks lower than both, and produces the least torque at higher RPMs.

Also, the "flat spot" at RPM=5000 in the torque curve for the stock snorkel seems to be gone for that RPM using the KDX220 snorkel (1.65 Kgm vs 1.7 or so). But it's really gone in the no airbox setup, it's producing 2.0 Kgm at that point in the no airbox lid setup.

Is that what you expected to see?