Dyno Tuning

BSD Performance uses a Dynojet 250i Load Control rolling road Dynomometer and the ability it gives, to control engine rpm at any throttle opening, is crucial for consistency and the precise build of a performance fuelling map. Ironically, the knowledge earned in the pre-fuel injection era, working on the dyno with CV and flat slide carburettors has proved an invaluable foundation for everything we do with EFI.

When a bike goes on our dyno the first thing that happens is that it’s strapped down correctly – this is very important. Next, we check the engine oil level, rear tyre pressure and position of the bike. A connection is made to the ignition system to get an rpm reading and we plug our Lambda sensor into the exhaust (if available) or use the ‘Sniffer’ to read the exhaust gases.

The bike’s then brought up to running temperature, usually under load to make sure the engine’s fully stretched and ready to work. The fans then go on to control the engine’s temperature and add airflow into the airbox. A Power Run is made; this consists of a roll-on from around 2000rpm revving feely, and again under load. After three or four Power Runs the engine’s performance will drop off and, assuming a constant temperature, has peaked.

At this point we stop and analyse the power, torque and air/fuel ratio, assessing the engine’s performance as stock.

If necessary we’ll perform some part-throttle runs. This needs another connection to the Throttle Position Sensor (TPS) via the analog channels on the dyno, and after adjustment allows us to ‘read’ TPS, dial in an actual throttle position and do a run. This is perfect for identifying fuelling/ignition flats spots or glitches in the power delivery; and large numbers of today’s bikes are cluttered with emission control units that cause small-throttle opening and bottom-end running problems.

Many of our customers, road or race, fit free-breathing exhaust cans or full systems and are after horsepower and torque gains; we recommend fitment of a suitable after-market air filter at the same time to save doubling up of dyno time. With these changes an engine’s fuelling will definitely need work and we offer two routes for our customers to take, either with Power Commander or our ECU Reprogramming Service.

Power Commanders are a relatively easy fitment; disconnect the injector wires, connect in the PC and earth it to the battery. The work for us lies in looking at the fuelling on a part throttle run and then, via Tuninglink (a piece of software on the dyno, which puts the Power Commander in a closed loop with the Lambda and computer) analysing and adding the ideal air/fuel ratio. This builds a basic map, but what works on the dyno does not necessarily work on the road…

And this is where our experience and detailed knowledge make a tangible difference; we go back and manually ‘trim’ at small, less than 40% throttle openings, where the bike spends most of its life. Once we’re happy that what we have on the dyno will suit the customer’s requirements, the bike is ridden on a 10-mile loop that includes a mixture of fast and very slow corners, to assess its performance in the real world at a variety of road speeds, engine rpm and throttle openings.