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The Wizardry of Bruce Crower

Those of us with a few years under our belts will recall that the most recent issues dealing with rising pump fuel prices are simply links in a chain of events that first occurred back in the 1970s when gasoline “shortages” plagued the country for a time.  I remember seeing lengthy lines of cars backed up at gas pumps and dozens of loaded tankers anchored in the Long Beach and San Pedro harbors of California, waiting out the “shortage.”

So as all this was playing out, I was involved in developing some Edelbrock intake manifold concepts more focused on fuel economy benefits than outright performance, and began contemplating another approach to boosting mileage.  Since the company was also engaged in designing and marketing street-performance camshafts, this was an area that appeared worth investigating.

Here was the deal, and give this a little time to soak in.  By creating certain valve events relative to an engine’s piston position, it’s possible to delay the intake closing point such that some of the already-ingested air/fuel charges can be displaced back out into the intake manifold’s cavity.  In a sense, this is an extreme condition of a phenomenon called “reversion” whereby by combustion residue (exhaust gas) gets displaced back into the intake tract during early stages of the intake event.  Actually, this occurs during low intake opening lift when cylinder pressure is higher than atmospheric, as the exhaust cycle is being completed.

So the notion was to further delay intake valve closing to the point some of the air/fuel charge normally delivered to the cylinders would be forced back into the intake manifold for other cylinders during their respective intake cycles.  The end result of all this was a net reduction in total engine air flow and a corresponding decrease in fuel flow.  It made carburetors “look smaller” to the engine.  Remember, the objective was to improve fuel economy.

But there was a problem.  By reducing the sum of air and fuel available for combustion, the density of delivered air/fuel charges was also reduced.  In simple terms, this meant there was less available fuel to combust, and the resulting reduction in power would cause a driver to go deeper into the throttle and defeat the goal of increased fuel economy.  The solution was to raise the mechanical compression ratio to “super squeeze” the smaller amounts of air and fuel, thereby extracting as much power as possible, particularly at part-throttle road speeds where fuel economy was intended.

 

Frankly, I figured this was a pretty slick way to boost mileage and began assembling a “proof of concept” small-block Chevy V8 to demonstrate how clever the idea really was, but I had difficulty finding a cam grinder who wanted to play.  And then I saw an ad from Crower Cams.  But before I go there, let me tell you when I first became aware of Bruce Crower.

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