Pontiac Fiero Hot Air Engine Setup - Engine

It showcases not only the spirit of innovation of the great Smokey Yunick but gives some insight into how non-conventional thinking can lead to significant technical innovation.

For decades, hot rodders and for that matter Detroit engineers have been locked into the idea that the only way to make more power in an engine was to cram more air and fuel into the cylinders. Traditional methods of doing that have included long camshaft event cycles, pressurizing the induction system, and cooling the incoming air/fuel charge. Those methods have produced success within limits but there has also been a heavy price to pay for power achieved with those methods in terms of efficiency. What has been consistently overlooked is the quality of the mixture that enters the cylinders in terms of its ability to react or oxidize. In everyday terms that means how well and how completely it will burn. When the reaction takes place, chemical energy is converted to heat energy. How much heat is generated and how well that heat energy is used to produce work is efficiency and quite frankly most internal combustion engines are pathetically inefficient, using only about 25 percent of the heat available. The rest is wasted-lost out the tailpipe, into the cooling system and into the air.

Now all of this business of efficiency is nothing new, but most people seem to have shrugged their shoulders and accepted it as a fact of life without really questioning if it has to be that way. Instead, in their quest for power they have been willing to accept even less efficiency if they could cram enough extra air and fuel into the cylinders to result in more net power at the wheels. Obviously, an approach that could improve efficiency has the potential of releasing even greater amounts of power from the same amount of fuel or equal power from a smaller amount of fuel. By the same token, extracting and using as much heat as possible from a given amount of fuel means better economy of operation. The bottom line is, if efficiency could be increased, we could have our cake and eat it too.

This is where Henry "Smokey" Yunick enters the picture. Smokey's mastery with racing and high-performance engines is legendary. Over the years many Hot Rod readers have learned a great deal from his insightful engine building procedures which have appeared in numerous articles and Smokey still writes a racing oriented questions and answer column in Hot Rod's sister publication, Petersen's Circle Track. Smokey has always been one to take the common sense approach to evaluating all aspects of engine operation, accepting nothing as fact until it was proven to be so, and applying the basic laws of physics and chemistry to problem solving. As he has often said, "It's all right there in any good high school physics and chemistry text books." What is less well known is that for the past 32 years, the same Smokey Yunick, who has become a recognized authority in racing and high performance has been developing and refining what may very well be the most significant advance in engine technology since the original concept of the Otto-cycle internal combustion engine.

If the above statement seems a bit farfetched, consider the Pontiac Fiero shown here. Equipped with Smokey's "expander cycle" exhaust and induction system and requiring only a cam change inside the production 151 cubic inch (2.5-liter) Iron Duke four-cylinder, the car now gets more than 50 miles to the gallon, develops 250 hp and 230 lb-ft and cleanly, has no computer controls, passes federal emissions standards, and oh yes, it'll accelerate from 0-60 mph in as little as 6 seconds flat! Here's how it works.