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Old 11-05-2012, 09:54 AM   #260 (permalink)
JohnAh
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Join Date: May 2012
Location: Vallentuna, Sweden
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Phantom Blot (Sp÷kplumpen in swedish) - '75 Saab 96 V4
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To put it short: I think the Honda C90 project can do well despite heavy weight but those fat tyres must be inflated to high pressure (increasing wear in the center) and the gearing ratios may be the most critical of all.

12hp┤s are always 12hp┤s regardless of engine displacement but a smaller engine have a shorter power band, increasing the need for exact gear ratio in every situation. When I halved my Fiat engine from 1050cc to 525 I definitely needed at least one extra gear between 3:rd and 4:th to keep the speed up and I had to work hard with the stick during a lot of the 40.000 km I drove that car. The perfect transmission for a small displacement engine is a CVT but they unfortunately have higher losses. Perhaps a rubber belt CVT (like a snowmobile) can help squeezing out a lot more performance from the 90cc Honda engine but that will come with increased fuel consumption.

The ideal transmission for an under-powered combustion engine would perhaps be a CVT with one (or two closely spaced) additional fixed gears that can be engaged at highway while the CVT is disengaged. The fixed gear(-s) should be calculated for de normal cruising speed.
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