KTM EXC with Keihin ECU: What the Software Changes

A stock KTM EXC is a compromise. It has to pull hard on an enduro trail while meeting homologation, noise rules and emission limits, and it has to run on very different fuel all over the world. You notice this mostly in the throttle response at low revs and in a very cautious overrun fuel cut. Much of that is not in the mechanics but in the software of the control unit. On many EXC models from 2012 to 2016 this is a Keihin ECU, and that is exactly where the tune starts.

Which EXC models have the Keihin ECU

The unit discussed here carries the KTM part number 81241031100 ("EFI 11" at KTM) and replaces the older 81241031000. There is a Keihin sticker on the housing; the second line shows a number starting with 812.41.031. The last three digits differ depending on the software version, for example .033 or .100.

Model	Years	Displacement	Stock (approx.)
KTM 250 EXC-F	2012–2013	248.6 cc	approx. 42 hp / 27 Nm*
KTM 350 EXC-F	2012–2016	349.7 cc	over 45 hp / approx. 37 Nm
KTM 450 EXC	2012–2016	449.3 cc	approx. 51 hp / approx. 45 Nm
KTM 500 EXC	2012–2016	510.4 cc	approx. 62 hp / approx. 52 Nm*
KTM Freeride 350	2012–2017	349.7 cc	23 hp / 22 Nm

* Figures taken from the identical engine (250 SX-F, or torque of the FE 501). Six Days and Factory Edition models are included.

What counts is not the model in your papers but the sticker. If it shows a different number, a different control unit is fitted, and then we need to check first what is possible.

What happens inside the ECU

The Keihin unit controls fuel quantity and ignition timing through maps: tables that set a value for every combination of engine speed and throttle position. On top come the rev limiter, overrun fuel cut and corrections for temperature and air pressure. The unit has four map banks, normally used through the map switch for different riding characters.

The tune edits exactly these tables. One important point: the file is not taken off a shelf. It is matched to the original software of your ECU, which is read out first. That is also why there is no file-only option for motorcycles. We program the ECU ourselves, either on site or after you send it in.

The three options at a glance

Power increase. Revised ignition and fuel maps for more power and sharper response. You choose what it is tuned for: Super 95 runs on any regular premium fuel and is the safe choice if you cannot always get Super Plus. The Super Plus version uses a little more ignition advance, but then you must always fill up with 98 octane. We deliberately do not quote horsepower figures here, because condition, exhaust and air filter vary a lot on enduros.

Pops & bangs. Crackling and popping on the overrun. It only works while you keep the throttle slightly open. With the throttle fully closed it stays mostly quiet; at high revs it can still pop. You set the character on a scale from 1 to 5: level 1 gives quick, light shots, level 5 slow, strong ones.

Party mode (hard cut). At the rev limiter the ignition is cut and the timing is retarded. Fuel keeps flowing. The result is bangs and flames from the exhaust. You choose the sound through the hysteresis, meaning how long the ignition stays off per cut, from a fast "brrrrr" to "boom boom". The stock cut-off stays in place above it as a safety net.

Always on or via multi-map

You can switch one or more options on permanently. Then they are active whatever map is running. Alternatively, multi-map lets you spread the options freely over the four map banks. A typical layout is map 1 stock, map 2 power, map 3 power with pops & bangs and map 4 adding party mode. Every map carries its own strength settings.

Multi-map needs a map switch. KTM's stock switch (part number 77239974200) works, but on the handlebar it only reaches two maps: map 1 and the map set on the rotary switch for the base setting. All four maps directly work with our own Stealth and Clean switches. These are still in development and can be pre-ordered.

Prices and process

The pricing is simple:

• one option, always on: €150
• several options, always on: €200
• multi-map with four freely assignable maps: €230
• map switch on top (multi-map only): Stealth +€40, Clean +€80

You put your tune together in the motorcycle configurator and choose how it gets onto the bike. Either on site with us in Stödtlen on a date you pick, or you remove the ECU and send it in. By post the whole thing takes about 3–7 days including shipping both ways. How to remove it is explained in the ECU shipping guide. You will also find the details on the product page, for example for the KTM 350 EXC-F or the KTM 450 EXC.

What to check beforehand

Software can only work as well as the mechanics underneath. Before you have an EXC calibrated, a quick check is worth it:

• Air filter and intake: A dirty filter or a leaking intake boot upsets the mixture, no matter how good the maps are.
• Valve clearance: On enduros with many operating hours in particular, check it according to the service schedule, otherwise idle quality suffers.
• Exhaust: If an aftermarket silencer is fitted, tell us when ordering. That is useful information for the calibration.
• Battery and connectors: A weak battery or corroded contacts are needless sources of trouble when removing and programming the unit.

Stress and legal position

Pops & bangs and party mode mean unburnt fuel in the exhaust. That puts more load on exhaust valves, header and silencer than the stock calibration, especially on enduros with short, light exhaust systems. If you use party mode a lot, keep an eye on the silencer and its packing.

Legally the situation is clear. Changing the engine software voids the vehicle's type approval. All functions are intended exclusively for motorsport and are not permitted on public roads. That also applies to a road-registered EXC. Details are in the motorsport notice.

Conclusion

On a KTM EXC with Keihin 812.41.031, much of the character lives in the software. A calibration matched to the read-out original gives sharper throttle response and more pull. The sound functions are optional, either always on or neatly separated with multi-map. Check the sticker on your ECU before ordering and you know everything fits. More on the terms in the glossary under Keihin and multi-map.