Slow Riding on The RC 390 single

[KwicK To Master KTM]

Just wanted to get RC 390 owners thoughts on how they find riding their bike in the slower rev range?

Des your bike splutter allot when under a certain RPM ?

Don't get me wrong I am not trying to pick fault as I enjoy riding my bike just find it takes allot of effort to ride the bike smoothly in the

lower RPM range this just something that happens with a high reeving single?

 

[B7ACKTHORN]

I can share the emotions. It's almost it has a mind of its own at slower RPM, it jitters and the throttle is kinda snatchy at low RPM, perhaps one way the bike says, do it or die it!

Cheers!
V

 

[KwicK To Master KTM]

Well said Don't get me wrong I find the bike a real blast to ride its just those times when you are stuck in slow traffic with no real throttle on or off it makes me feel like I don't know how to ride! but when the beast is unleashed - well the fun begins -

 

[gbabyracing]

My new bike does not like low RPM running

 

[micahpearlman]

I don't have my bike yet so I can't claim to know what it is like in low RPM. But as far as I understand how the KTM 390 Bosch ECU is setup and designed is that it runs on a "closed loop lambda" system below a certain RPM (I've heard anywhere from 4-5K). Meaning that it uses the oxygen sensor to work out how much fuel the injectors should spit out. Or specifically:

Closed loop lambda: Lets the ECU monitor a permanently installed lambda probe and modify the fueling to achieve the targeted air/fuel ratio desired. This is often the stoichiometric (ideal) air fuel ratio, which on traditional petrol (gasoline) powered vehicles this air:fuel ratio is 14.7:1.

With what owners are describing is that the "lambda" setting is too lean, causing low RPM stuttering. The leanness is likely on purpose for emissions. For fuel injected bikes this is usually "fixed" by re-flashing the ECU with a new map. Unfortunately it is not easy to reflash these ECU's (I have a separate post about this) as they are locked down by KTM. An alternative is to use a piggyback ECU like the PowerTRONIC. I'm not clear if the PowerTRONIC actually modifies the O2 (lambda) sensor signal or not -- I already have one on order and will check when it comes in. If it doesn't and you are an electronics tinkerer, it wouldn't be too difficult to build your own. All you are doing is intercepting the lambda signal (a voltage range) and tweaking it on the fly. One could use an Arduino microcontroller placed between the lambda sensor and the ECU, read in the O2 (lambda) voltage using the analog to digital converter (ADC) and then write a modified voltage out to the ECU thereby tricking the ECU to richen things up.