A bit more detail on the 690 Duke (R). It's a 2017 model (the last of the line of the R models) with the latest, twin balance shaft, engine. It's Euro 4 and the slow speed fuelling has always been snatchy when running in the closed loop part of the map. To meet emissions targets it has to run impossibly lean in the closed loop, leading to rideability problems. Euro 4 compliance hits big singles the hardest, which I suspect is one of the reasons why KTM have called time on the Duke 690 range (the engine lives on in the SMCR , Enduro and Husky bikes).
Back in November 2019 I took the bike to Andy at BSD Performance to try and fix the low speed fuelling issues. The dodgy-by-design fuelling was compounded by the rather aggressive nature of the fly-by-wire throttle, which gives an instant reponse to the throttle in all gears, including the lower ones. On one of my favourite roads, which has a lot of hairpins and 2nd and 3rd gear corners, a combination of the above meant it was difficult to maintain smooth progress. In the higher gears it was great, instant grunt, but it was all a bit too much in the low gears.
Unfortunatelly Andy found that all the maps on the bike were write-protected. He could read the maps but not alter them, so all he could do was disable a couple of sensors. However a year later when I contacted him, he told me that he now had software that could defeat the write protection, giiving him modify access to all maps. So not only was he able to correct the low speed closed-loop fuelling, he could also modify the throttle behaviour in the lower gears, making the initial response softer and more gradual. Full gas in all gears was still available at WOT but the 'slope' of the response was gentler initially, ramping up the more the throttle was opened. He also managed to find a couple of extra horses lurking at the top end, bless him...
Here's the dyno trace. 72.61 bhp at the rear wheel is not shabby for a 690cc single. What it does show is that there's precious little to be gained by hanging on after 7000rpm. Best to change up at 7k and use the fat part of the torque/power curves.
- Duke_690R.jpg (94.36 KiB) Viewed 1248 times
