Quote:
Originally Posted by Occasionally6
(about EV mode in the Insight: )
Are the valves open or are they closed? From the point of view of reducing pumping loss and air cooling the catalytic convertor, I'd say they're closed if they are being disabled.
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The intake valves are wide open during that mode. Letting the air move freely in and out the engine at low revs does not put any stress on the piston, closing all valves all the time would either create a big vacuum on the downstroke or high compression on the upstroke, which cause much more friction.
Dunno about the output valves. It seems logical if they are kept closed, but haven't actually seen it.
This mode is operated by an extra camshaft (Honda VTec). The engine actually has 3 camshafts; EV mode, efficiency mode, power mode. A bit much for a simple 8 valve 4-potter
Quote:
Originally Posted by Occasionally6
Something else: The premise behind pulse and glide is to operate the engine at high load. I expect that is also going to wear out the engine faster than operating at 'normal' loads. Against that the duty cycle is lower.
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Load need not be realliy high, just efficient.
If your engine does 3000 RPM@60mph in top gear, it will probably lose more power on pumping losses than it produces. It could produce say 3 times as much power for just twice the fuel consumption by mildly accelerating at say 40% of WOT. You'd save 33% by P&G-ing then, but stress on the engine would still be way lower than what it is designed for.
My engine does just 1900 RPM or so at 60 mph so the throttle has to open further, and pumping losses are reduced. It is hard,maybe even impossible for me to gain anything by P&G-ing at highway speeds.
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gigameter or 0.13 Megamile.
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