Bruce
Combustion dymanics is a very tricky subject.
ALL other things being equal, a TS head should produce more torque than a single plug head for the reason you describe.
The problem is that ALL things will never be equal...
As we've all pointed out, the problem with combustion chamber is that it is a very large surface area, and has relatively low combustion speeds. One could have sped up the combustion by adding some turbulance in the intake, but at the detriment of power.
Modern 4V heads can burn quite a bit faster than the TS heads- that meaning flame front speed and NOT time. Most 4V heads have a lot of turbulance built into them, so the flame fronts move quickly. Add in the smaller combustion chamber space, well, a lot of things get better- with the smaller space, one can run a higher compression, even with the fast burn....
Lets just say that the Alfa past it's prime a while ago, even the TS head.
alfatwincam- it's not that the Nord engine isn't good- it is one of the best of the 20th century, I believe. But, it peaked in design concept in the mid-60's. To be passed in the racing world in the late 60's, and in the production car world in the mid-80's.
Talking with a Technical Specialist Alfisti here at F, he also mentioned one other problem with the engines base design- the free wet liner design would limit single plant production to about 100k/yr. Which is not nearly enough for a mass production engine.
Swede- don't throw away the low end performance! I need it! The autocrossing I do occasionally runs down to 3000rpm. And don't tell me to shift- I hate 2-1 shifts.
Eric
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