KTM 690 Tuneboy

  •  KTM 690 SM Airbox mod
  •  KTM 690
  •  KTM 690
  •  KTM 690
  •  KTM 690
  •  KTM 690

July 2009

We've spend another good part of a day on the dyno to test a new mod and setup the fueling with TuneBoy. Scene of the crime was the dyno and EFI specialist in NL; Ruud Frederiks. We did my mates' 690 SM P and my 690 SMR. Our bikes were well setup already and running great with a full Akra (mine) + map, gas flowed head, Duke/SMC cam and K&N drop-in filter.

We modified the airbox with 36 10mm holes, 18 on each side as pictured. This mod comes from the German KTM forum. A guy Highscore started the topic on 690 fueling and airbox mods a year ago: "neues-aus-der-tuning-k├╝che". Excellent work and a wealth of information.

These 36 holes double the intake surface area compared to stock.

Next was to setup the fueling with TuneBoy to match the drilled airbox. And it worked perfect.

Tuneboy is still the only solution that can modify the fuelmap itself and write the new tune back into the ECU. Just like KTM does with the stock and Akra maps. No piggy-back boxes like PowerCommander or Rapid Bike with extra wiring looms & connectors on your bike. Tuneboy also has the most features and offers full control over all fueling parameters, ignition, rev-limit etc. IMO there is no doubt that TuneBoy is the most advanced & sophisticated way to remap a KTM available today. But not a tool to start mess'n with in your shed without any knowledge.

As the graph shows the drilled airbox gives a big improvement in low-end and midrange torque between 3000 and 6500 RPM, ie the most important rev-range. The graph looks a little messy but it shows the bike before without the holes (as said, pretty good already) and two runs after with holes and the fueling & ignition setup to match. The mixture is set leaner and richer at various places and the ignition slightly re-timed at the mid and top-end. All with a few mouse-clicks. This beats fiddling with jets, needles and float levels big time!... The bike puts out 68 HP and 74 Nm at the rear wheel. But these figures alone don't tell how much better bike feels and rides. The gain in low-end torque is a huge improvement. It's smooth and powerful throughout the range.

But what the graphs don't show is the most important. The O2 sensor is switched off with Tuneboy. Big deal? Yes. With the O2 sensor the FI system will always try to adjust the mixture towards Lamba 1, A/F ratio 1:14.7 on a steady-isch throttle (closed loop condition) to meet emission regs. The dreaded super-lean mixture so many FI bikes suffer with jerkyness, a hairy throttle response and hunting on steady loads. Tuneboy is the only tool that can switch off the O2 sensor in the ECU.

With the O2 sensor switched off the bike runs on the fuelmap alone (open loop) and won't try to lean off the mixture towards Lambda 1. The result is a massive improvement in throttle response and feel. Crisp, powerful and snappy without jerkyness or glitches. It feels like a well setup FCR Flatslide carb now. Better actually...


Update:  I've removed the O2 sensor and plugged the hole in the headerpipe with the bolt pictured. Looks cleaner and makes the pipe flow better. The tip of the sensor that sticks into the headerpipe is about 1/3 of your little finger. It's close the exhaust port and disturbs flow. The grey color of the sensor confirms the mixture is good. With the sensor removed the engine seems to run a little better again.

Note: The thread in the hole for the sensor is M12 x 1.25 pitch and this not very common (same thread as a 12mm spark plug). The thread of a plug to close the hole should be around 8 - 10mm long.

Last modified: 31-08-2009