Larry Widmer "Softhead" and economy
Has anyone used this theory for improved mileage before? It's not really 'his' concept (Chev used it in the 50's) but he describes it best and has adapted it for other engines.
The idea is that you run as much squish as you can, focussing the combustion chamber around the exhaust valves and spark plug, to the point of altering cam timing so that you can bring the piston crown close enough to the intake valve to get even more squish. This both necessitates and allows super-high compression ratios (as in, above 13:1 on pump fuel, 16:1 on race gas).
The theory is that:
A: Because tiny combustion chamber with minimum distance to the edges and very high squish velocity the burn happens a lot faster. As in, 15-20 degrees advance at peak power fast.
B: Because it's focussed over the exhaust valves, that bit burns first, and doesn't get the chance to absorb heat from the rest of the chamber burning, and avoids detonation
C: Because it burns so completely, so quickly, and with a higher expansion ratio you get higher average cylinder pressures, cooler egt, and more efficiency
D: Because some magic involving high compression ratios (haven't quite figured this bit out yet) ultra-lean air fuel ratios still ignite at high loads.
It's more or less adaptable to most types of cylinder heads, provided you can machine piston crowns to suit
It *sounds* like a neat theory (and most of it makes sense) but I don't know of anyone except Larry having used it. Has anyone here heard of it being used?
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Originally Posted by Crazyrabbit
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