Keep in mind I am discussing my motorcycle engine which is an FI single and has the throttle body in the middle of the runner as pictured in the earlier post so a plenum isn't really present as the air box is running with the dirty side lid off right now so it should pretty much always stay at atmospheric regardless of any pulsing.
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Quote:
Originally Posted by ERTW
your engine peaks not only at 8700 rpm, and also at 6450 rpm.
tuning also depends on valve area, and hence port area. waves happen at all rpm, at all throttle positions.
6000 rpm wants a 380 mm intake runner, as measured from the valve to the plenum. the plenum can be as large as 2L, but slightly smaller (~1.5L) will help throttle response.
increasing flow by porting, in other words reducing pumping loss, will boost economy.
imo the biggest thing is the large cam overlap designed for 8700 rpm power. you want minimal overlap so you're not sucking raw fuel out the tail pipe. roughly in the 200* @ 0.050", 112* LSA.
hth
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