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FJR Motorcycle Forums
Technical & Mechanical Problems
Fuel Economy and Smoothness without Compromise
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<blockquote data-quote="ionbeam" data-source="post: 860852" data-attributes="member: 277"><p>If you can manage it, a third data channel that monitors intake vacuum would be a powerful tool to determine how hard the engine is working.</p><p></p><p>I have ridden my FJR with a vacuum gauge monitoring the intake vacuum, DMM Velcroed to the handlebar monitoring the TPS voltage and my eye on the tach and it was highly educational. One thing that I learned right away about my fuel economy was that my running low rpms was actually harmful to economy. The engine was loaded by low rpm and high gearing, forcing me to hold the throttle open wider to maintain speed. By going to a lower gear the engine moved into a better power band resulting in a significantly smaller throttle openings. When I had low rpms and wider throttle openings the vacuum gauge would show low vacuum (closer to atmosphere) and by snicking down one gear the vacuum would noticeably increase (indicator of economy) and the throttle was less open so there was less fuel being used. The dynamic range of vacuum is ~10-12 in/Hg at idle at sea level and ~1-2 in/Hg at WOT.</p></blockquote><p></p>
[QUOTE="ionbeam, post: 860852, member: 277"] If you can manage it, a third data channel that monitors intake vacuum would be a powerful tool to determine how hard the engine is working. I have ridden my FJR with a vacuum gauge monitoring the intake vacuum, DMM Velcroed to the handlebar monitoring the TPS voltage and my eye on the tach and it was highly educational. One thing that I learned right away about my fuel economy was that my running low rpms was actually harmful to economy. The engine was loaded by low rpm and high gearing, forcing me to hold the throttle open wider to maintain speed. By going to a lower gear the engine moved into a better power band resulting in a significantly smaller throttle openings. When I had low rpms and wider throttle openings the vacuum gauge would show low vacuum (closer to atmosphere) and by snicking down one gear the vacuum would noticeably increase (indicator of economy) and the throttle was less open so there was less fuel being used. The dynamic range of vacuum is ~10-12 in/Hg at idle at sea level and ~1-2 in/Hg at WOT. [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
Fuel Economy and Smoothness without Compromise
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