Saturday, Jul 02, 2005 at 09:58
During my time as a research engineer with General Motors we came across a few a such devices that could marginally improve either fuel economy, or power output but in every case the gain in one was obtained at the expense of a loss in the other.
When designing an engine one seeks to achieve a balance between power and economy that suits the majority of users.
It is readily possible to alter that balance (as after-market engine computer chips show). But to improve both parameters is usually possible by some quite major advance in technology - of which an excellent example is turbocharging for diesel engines.
I am always wary of users' reported results of fuel economy as that is extraordinarily difficult to measure accurately. Magazine tests in this area can be absurd unless very costly and specialised testing gear is used. It is not uncommon for magazine testers to work on the basis of how much fuel is needed to refill a tank - and then report consumption to three decimal
places (implying an accuracy of less than a teaspoon full of fuel in a big tank!).
Likewise standing start acceleration data - again often given to two decimal
places, yet it is not unknown for the distance over which it is measured to be paced out by the 'measurer'. Probable accuracy plus/minus 5% at very best.
Collyn Rivers
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