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alpha/n injection systems

EFI Tuning Fundamentals

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Hi again, bikes again!

alpha/n systems are by far the most widespread injection systems used in motorcycling no matter if a stock or standalone ECU is being used (or even a very common ‘piggyback’ module). Motorcycle engines employ mainly one throttle body per cylinder.

Nowadays, most systems have included ‘speed density’ fuel tables but these are just used due to emissions regulations. As airflow to the engine varies dramatically at small throttle openings, alpha/n systems proved incapable to deal with the ever tighter emissions regulations, so there is a MAP sensor and fuel table to ensure proper lean AFRs required. Above around 15-20% of throttle opening, AFR control is held by an rpm/alpha fuel table. In between, the ECU uses some blending algorithm to ensure a smooth transition between both. So, in some systems it is important to have both coordinately tuned in order to avoid AFR sudden changing when the system changes from one table to the other.

Again, it would be useful to cover these systems in some depth as they’re relevant for an important part of the motorsport industry!

Thank you!

Hi Eduardo, thanks for the message. I have done a little tuning on a Yamaha R1 and they use the same technique with blended MAP and TPS tables. At this point we don't have the ability to dyno bikes unfortunately so I don't know how much I can realistically promise on this front sorry.

Thank you for your answer, I understand this. Anyway it is true than most learning on car engines are pretty close to suit bikes’ needs too. To my relief, your EFI fundamentals course have ensured that my practice on motorcycles goes the right way... the very good results and customers’ satisfaction too!!!

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