How the Scalpel's ride-by-wire throttle works in the different modes
We're sort of missing the KTM 790 Duke already here - but we're still working through a load of info on it, and preparing a full road test of the beastie. In the meantime, here's a nice little snippet for y'all. When we were at the dyno shop last week, we thought we'd look at the four riding modes, and how they affect the power delivery. The smart new KTM comes with road, sport, wet and track modes - and you might be surprised how they work.
When Sean at Big CC ran them at 100 per cent throttle, we ended up with the same peak power and torque for all four modes, more or less. So what's the difference? Well, with the old-school 'manual' method of power restrictions, on something like a 2010 Suzuki GSX-R1000, the different engine modes just give less power, by keeping the secondary throttle valves from fully opening. That, plus maybe having different ignition advance and the like can soften off the power, and restrict the peak figures accordingly. That meant that in the rain, for example, you were less likely to spin up the rear and crash on the power out of a bend, say.
Now, though, we have super-smart traction control systems, which will stop you crashing in the rain from careless throttle use. And we also have ride-by-wire throttles, where the engine ECU has total control of the throttle valves, and can change both how far they open, and also how quickly they open and close. Meaning you can have much cleverer riding modes - like on the KTM. The TC setup is watching for any loss of grip, and will step in at that point to save your sorry arse. But if nothing bad happens when you turn the twistgrip to the stop, then the ride-by-wire can give you 100 per cent throttle and you're still safe as houses.
What the different modes do, though, is give a softer power delivery - by opening the throttle more gradually. So while you will still get 100 per cent throttle opening when you twist the grip fully, the ECU opens the injector body valves at a slower rate. And if you only turn the twistgrip part-way, the ECU will give less throttle valve opening accordingly. So in 'Track' mode, 50 per cent twistgrip will give you 50 per cent throttle opening quite rapidly, while in 'Wet' mode, 50 per cent twistgrip might only give you 20 per cent throttle opening, and will get there at a slower rate.
With all that said - here's a dyno chart to show it in simple terms. We put a mark on the twistgrip at about 30 per cent opening, and Sean did four runs, one in each mode, holding the grip at that mark. You can see quite easily how the modes give widely differing results. In rain mode, there's only about 9bhp available at that throttle opening, while in Track mode you get almost 30bhp - a big difference. Sport is quite similar to Track, while the road setting is about halfway between rain and Sport. The ECU is registering which mode you selected, and applying a much gentler map to the rain mode, opening the throttle valves much less than it does in the sportier modes. Meaning you get a lot less power at smaller throttle openings, like on the way out of a bend. But when you get onto the motorway, and want full throttle to accelerate up to speed, you can also have maximum power. The perfect solution...
