Issue link: http://trailridermagazine.uberflip.com/i/919511
January 2018 31 PowerCDI - Power and Control? By Mark Johnson There's always a will to innovate, especially when there's a need. If you think about how sensi ve an engine is to igni on advance, you'll realize its hidden poten al although unimagined by most. Electronic control units is a fi eld where we've seen very li le innova on a er the introduc on of digital units— and that happened many decades ago. Ideally, we look for clean, responsive and powerful engines to help us when climbing steep hills (nobody likes to be forced to downshi in those situa ons, especially when trac on is scarce), or when we suddenly and unexpectedly fi nd a log or a deep hole in front of us and we need to li the front wheel instantaneously. But we also want mellow engines to have op mal trac on and to not make our bodies re quickly because of hard, o en unnecessary, sudden accelera ons. These two needs — a powerful reac ve engine and easily managed at the same me —contradict each other. It's a simple ma er of physics: if you want torque, the tendency to slip and diffi culty in controlling the engine will increase. These are simply the two sides of the same coin. As is well known by various engine modifi ca ons (reduced compression and/or squish, very rich je ng, heavier fl ywheel, etc.) you can improve trac on and manageability of your engine, but this will come at the expense of power and responsiveness — you can't have both quali es in an engine. It's always a compromise. There have been a empts to transfer trac on control technology from road bikes to off -road bikes but they failed because what works on the road doesn't necessarily work off -road. An -spin and an -wheelie systems certainly make sense on a road bike but when you're in the woods, some mes you really need to wheelie to jump obstacles. You also need to slip the rear wheel to close ght turns or to actually move in the sand or in deep mud. Clearly, a trac on control — generally defi ned as a system where the speed of the front wheel is con nuously compared to the one of the rear wheel. If the la er is sensibly higher than the former, power is cut to reduce wheelspin — won't work off -road. The wish for a powerful and reac ve engine for maneuvering slippery and rocky terrain— typical of the enduro of his zones — mo vated a so ware programmer with a past in developing commercial videogames. Experienced in computer hardware design, this programmer has a huge passion for enduro and mechanics and a will to develop an engine control unit that was fi rst meant as a powerful laboratory. This laboratory would have no compromise in features and the ability to test every possible idea about engine op miza on and control. Will a very powerful spark truly improve combus on? Let's try and measure the eff ects via telemetry. Will retarding the igni on cause enough reduc on in power to allow eff ec ve control of engine power? Let's verify it. But, mostly, what are the best control strategies? The ques ons were many. The more experiments completed, the more telemetries were examined, and the more new ques ons arose. All of this started at the end of 2009 when the original CDI of the programmer's bike died and, although a replacement original CDI was s ll needed, this was the decisive s mulus to make his own engine control unit or engine control laboratory as he saw it at the me. The fi rst prototype was bulky but a er a few