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FJR Motorcycle Forums
Technical & Mechanical Problems
Carb Sync Pressure
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<blockquote data-quote="Fred W" data-source="post: 952098" data-attributes="member: 3828"><p>Well... The spec* for throttle vacuum at idle is 33.3 kPa (250mm Hg, 9,8 in Hg) which translates to negative .333 bar or 4.8 psi. But that is just at idle.</p><p></p><p>If you want to use the vacuum gauges "real time" as Pepperell mentioned, you'd need to know the maximum vacuum that will be seen0. The highest vacuum the engine will produce is when you get it spun up to redline and then chop the throttle closed. That is likely to be considerably higher vacuum than the idle pressures.</p><p></p><p>As a point of reference, the Morgan Carbtune scale goes from 10 to 40 cm Hg (1.9 to 7.7 psi) and I've never seen mine max out no matter what I did to the throttle. That would probably be a good estimated working range for a real time vacuum gauge.</p><p></p><p>* that most people rightfully ignore</p></blockquote><p></p>
[QUOTE="Fred W, post: 952098, member: 3828"] Well... The spec* for throttle vacuum at idle is 33.3 kPa (250mm Hg, 9,8 in Hg) which translates to negative .333 bar or 4.8 psi. But that is just at idle. If you want to use the vacuum gauges "real time" as Pepperell mentioned, you'd need to know the maximum vacuum that will be seen0. The highest vacuum the engine will produce is when you get it spun up to redline and then chop the throttle closed. That is likely to be considerably higher vacuum than the idle pressures. As a point of reference, the Morgan Carbtune scale goes from 10 to 40 cm Hg (1.9 to 7.7 psi) and I've never seen mine max out no matter what I did to the throttle. That would probably be a good estimated working range for a real time vacuum gauge. * that most people rightfully ignore [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
Carb Sync Pressure
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