I own a Yamaha YS125 which is fuel-injected, and a lot of times I am flogging the bike on full throttle, which increases fuel consumption.
I was thinking of restricting the air flow intake of the engine, which I believe would yield:
Are my assumptions correct? Am I missing anything out?
Let's go through your assumptions about the effects of restricting air flow (assuming a mechanical restriction is implemented):
Slower top speed and acceleration
Definitely. Restricting the air flow will mean there is less oxygen available to the cylinders for any given RPM.
Reduced fuel consumption on full throttle
Yes, but only because you're not going to be able to reach the higher top speed that you would have previously.
The fuel consumed while cruising at 50 km/h is less than the fuel needed to cruise at 70 km/h.
Also, a slower-accelerating bike takes longer to reach any given speed, so it burns fuel for longer; total fuel consumption involves both fuel burn rate and the time spent burning it.
For more information, see brake-specific fuel consumption (BSFC).
Would not need remapping because fuel injection system will compensate automatically
True. The engine hardware is the same. Adding restriction is effectively limiting the usable region of the BSFC curve.
If you reduce the incoming air, you will reduce the power output and increase the very fuel consumption you are trying to improve, ie to use more fuel instead of less for the same journey.
Make sure the bike is serviced correctly, clean filters, spark plugs adjusted corr4ectly etc.
You may find that your fuel consumption is because the route to work is arduous and not a route where you can cruise on light throttle.
Short answer: No, you're just going to make it run badly and/or quit on you.
Longer answer: Engine RPM is regulated by controlling the amount of air and fuel that goes into the engine cylinders. Airflow is regulated by a butterfly valve, when you twist the throttle or push down on the accelerator pedal you are opening that valve either directly through a mechanical linkage or the engine computer does it for you. Opening the throttle lets more air through - more air and fuel, more bangs, more RPM. Rolling off the throttle closes the valve and you get less air, less RPM.
So airflow is already being regulated, if you restrict that airflow yourself then you'll starve your engine of air at higher revs, making the air/fuel mix too rich which will ruin performance, maybe cause it to quit altogether and lower your mileage.
If you want to reduce your fuel consumption then the best thing you can do is be less aggressive on the throttle - stop caning it and you'll use less go-juice. Also, make sure the bike is well maintained and tuned well.
