MotoGP » 21 August 2008
Pietro Caprara (JiR Team Scot): Q&A.
With JiR Team Scot experiencing a superb MotoGP season with Andrea Dovizioso on their Honda bike, attention now turns to who has made them such a force to be reckoned with in 2008.
Close to the top of that list if Pietro Caprara, JiR Team Scot's Chief Technician, who plied his trade in MotoGP with Yamaha and Aprilia before switching to the satellite Honda outfit.
With more than 12 years experience in MotoGP, the 41-year-old looks at the state of the championship now, compared to then…
Since the mid-seventies, two-strokes dominated the 500 class, before the four-strokes came along at the end of 2001. What are the characteristics and differences between the two technologies?
“The differences between the two types of motors have both construction implications and mechanical, environmental, how the motorcycle is driven, as well as construction and maintenance cost issues. Mechanically the two-stroke engine is simple, the piston, with its alternating motion, opens and closes the ports of the intake and exhaust from which the mixture of air/petrol and oil and exhaust gases enters and leaves.
In comparison, the four-stroke motor is complex and heavier than its two-stroke equivalent. The upper part of the engine is the 'head', which holds the intake and exhaust valves, driven by camshafts. Engine power comes from petrol shot into the engine via injectors.
The lubrication of the two-strokes engine, crankshaft and connecting rods, is entrusted to the fuel. The power is normally governed by a carburettor that has a mechanical operation typically controlled by the depression created by the movement of the piston.
The lubrication of the various mechanisms of the four-strokes is entrusted to oil and this can be collected in a reservoir, built in the lower part of the engine called a sump, which can either be a 'dry' or 'wet' sump depending on whether the oil is collected in a separate tank.”
How have these differences changed the way you work in the pit garage?
“The maintenance and alteration of a two-stroke is very different from a four-stroke and can be carried out completely in the field, given the simple nature of its construction. Historically these changes used to be made by the team, even in satellite squads.
The maintenance of the four-stroke is complex and only factory technicians are entrusted to work on the engine, while mechanics from satellite teams are only allowed to do maintenance that doesn't involve opening up the engines.”
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