Guys,
I have a TM KZR2…. I have KG NITRO and KG Power airboxes….online I have read different reports about which is the latest…
I’m not consistent enough in lap times to decide which is better…. Can any of you hot shoes help a newbe brother out..
Thanks in advance,
Bill
I had the nitro for a bit, I have the power now. I had to go one richer on the MJ, and it seems like it picked up a half mph or so at 80. Laptime varies more from track conditions so I don’t know exactly what the gains are. Probably a few tenths maybe?
There are definitely differences from airbox to air box, but I’d put it this way…I’ve seen top level drivers from various engine builders win races on all different air boxes. There’s no pattern to suggest airbox “x” is the outright best choice, or at least by any significant margin.
The Power will lean out the bottom end vs the Nitro, especially upon initial throttle application.
Airbox’s effect the jetting, some boxs leave the engine runner leaner or richer.
In terms of anything else I dont think theres any improvements.
You have to jet the engine to suit the airbox your running, if you change the airbox you will have to rejet.
My hypothesis on airboxes is that they have different resonance characteristics. Usually most noticable at partial throttle.
I agree. We had to make a sound deadening setup for the Honda at Jax one winter tour, as we were just running the k&n air filter and they were cracking down on sound. Everyone was using the tic tac shaped airbox that was popular in europe, and was a touch down on power as a result. The rule however allowed open airbox, as long as the sound was in spec.
In an effort to not lose power, dad bought a 1 gallon bucket, cut a hole in the bottom for the air filter nozzle to fit through, and lined it with sound deadening foam. When mounted it perfectly covered the entire length of the filter with about a 1 inch gap between the foam and filter surface.
Not only did it not lose power, it picked up power enough for me to see it in my data, and it carbureted much better. I think picked up around 1.5 mph at the end of the long straight there, which is significant. I almost won the pro class with the advantage, but got punted by an exuberant youngster in the final few turns.
Ironically, we also had the quietest karts in the paddock.
Our device was outlawed at the end of the weekend.
Our hypothesis was that we were effecting the inlet resonance characteristics.
Raisonance that affects inlet airspeed at different ranges of throttle oppening, depending on airbox design.
I believe the leaning out of the power vs the nitro (at iso carburation) on the bottom end to be due to a a more efficient delivery of air at low charge due to the curbature / geometry of the bottom of the airbox (more curved and profiled than the nitro).
You jet accordingly to regain proper carburation, but will certainly lose elsewhere on the range as a compromise (as with everything 2Stroke related)
(also to note that engine design philosophies tend to marry an airbox better than another. IAME which has historically prioritized top end power in its design goals, uses the RR Active for both KZ and OK applications, an airbox known to provide more preferable conditions at the top of the RPM range.
TM, in contrary, almost exclusively works best with the Nitro. We have just recently seen Hildebrand use the RR in Portimao, with great sucess.)
For me, reversing the trumpets has had the biggest and preferred impact. I find when running them “backwards” it’s easier to land on the right jetting balance with a lower peak EGT (at just the right temp) and a higher min EGT, and more forgiving. I’ll let others explain the physics. Yes, I drop a couple of main jets, but it just seems more stable/consistent.
Absolutely. I had discussed this in another thread, but we have a famous tuner in france that has been running his trumpets backwards for ages. Only last year did another one copy him, then another, then another etc etc… A vast majority of tuners in France now will rent you their engine only at the condition that you run the trumpets backwards, as they have developed a carburation setup only under such conditions.
The way it has been explained to me is that you remove the variable of ram air speed that comes with forward facing trumpets, which is dependent on the speed of the kart. I’ve always thought that the filter element was enough of a buffer to remove this variable, but it is proven that carburation does become more “stable” with the rearward setup.
Couldn’t we just run with the rain cover to prevent ram air? Is that illegal?
Something that helps with the ram effect making the carb lean out is routing the carb vents into the airbox. Problem is, I think drilling holes in the airbox for the lines is technically illegal.
Yes, physically modifying an airbox would void its homologation and make it illegal.
You could however route the air vents along the airbox pointing forward so they would receive some of the forced air, would not be identical to what the airbox sees but theoretically would do something. Someone could even 3d print something to clip on the airbox horns that would hold the vents.
Heck yeah. I will probably try that.