Tech Talk #83 – Engines Are Engines

DavidTechArticlesBy David Reher, Reher-Morrison Racing Engines

“I’ve learned that engines with pistons and valves are fundamentally alike.”

I count myself among the fortunate people who enjoy going to work every day. The fact is that I love working on engines – all kinds of engines. After nearly 40 years of messing around with motors, I’ve learned that there are more similarities than differences in various types of engines.

As we’ve expanded our customer base at Reher-Morrison Racing Engines over the last few years, I’ve had the opportunity to work on a wide variety of powerplants. Big-block drag racing engines are still the foundation of our business, of course, and I don’t foresee that will ever change. But in addition to engines for fast bracket racing, Top Sportsman, and Top Dragster competition, we’re also building engines for truck and tractor pulls, land speed record cars, Pro Mods, turbocharged sport compacts, Comp eliminator cars, and seriously fast street machines – in short, just about any application that relies on internal combustion. We haven’t built any turbines or jets – yet.

The principles of internal combustion are the same whether an engine propels a Top Fuel dragster, a D/Stock Pontiac, a NASCAR race car, or a minivan. The familiar sequence of four cycles – intake, compression, power, and exhaust – doesn’t change. What does vary, of course, are the intricacies of each application. A nitro-burning drag race engine makes very different demands than a NASCAR Cup engine or an everyday commuter motor – and while the nitro engine is built for 1,000 feet of maximum power, a NASCAR powerplant will run for hundreds of miles, and the engine in almost any econobox will deliver 100,000 miles of reliable service.

When friends who are casual motorsports fans ask me about the difference between the Top Fuel and NASCAR engines they see racing on TV, I reply that it comes down to two key points: lubrication and cooling. If an engine is kept cool and lubricated, it will run. If an engine is overheated or lacks adequate lubrication, it will fail. It’s really as simple as that.

I’ll give an example of an engine we built that had to withstand extreme stress. One of our customers, Charles Nearburg, set a wheel-driven land speed record at the Bonneville Salt Flats at 414.316 mph. While Bonneville legends like Mickey Thompson and the Summers Brothers used multiple engines to exceed 400 mph, Nearing did it with a single 526 cubic-inch big-block and clutchless 5-speed transmission in his Spirit of Rett streamliner – essentially a Pro Stock combination with a nitrous oxide injection system.

The Bonneville Speedway course is miles long, and average speed is measured in a one-mile speed trap. The vehicle has to run this course in both directions within a specified time to set an official record, so the engine must be reliable. We knew that this engine would have to withstand 50 seconds at maximum power with its nitrous system activated, so we tested the engine on the dyno for nearly a minute with the nitrous flowing. With the engine roaring in the cell, it seemed like an eternity as I watched the clock on the wall. The seconds seemed to crawl by, but the motor survived its ordeal. A few weeks later it set the record for the world’s fastest piston-engined automobile.

We knew from our experience with nitrous-injected Pro Mod engines that we needed to reduce the compression ratio, back off on the nitrous, and run the fuel/air ratio much richer than the same engine would use in a quick 4-second quarter-mile run. In effect, we used the additional fuel to cool the engine. I see a similar effect when I’m flying my twin-engined Cessna airplane: under full power at takeoff, its air-cooled engines need nearly 35 gallons per hour of fuel to stay within a safe operating temperature, but at a cruise, they use about half as much fuel while remaining cool.

A Top Fuel dragster is essentially an oil-cooled engine that has virtually no cooling reserve; there’s simply no way to carry off the tremendous heat produced in its cylinders. In comparison, a typical passenger car – even a high-performance model – is rated for about 70-80 horsepower of continuous power. Sure, the engine might make 500 horsepower at its peak, but maximum power can be used only for relatively short intervals before the waste heat overwhelms the ability of the cooling system to dissipate it. Compare the radiator in a ZR1 Corvette to the radiator in an over-the-road diesel truck; both vehicle’s engines can produce more than 500 horsepower, but the 18-wheeler has a cooling system with enough capacity to allow the engine to produce that power continuously.

The strength of the engine’s components also determines its reliability. A Top Fuel dragster obviously needs stronger components than a Stock eliminator car to withstand the higher loads and stresses produced by nitromethane and supercharging. Regardless of the class of competition, the parts have to match the intended horsepower range. Using pieces that are heavier than the application requires is a detriment to performance.

I’m blessed to have a job that allows me to learn about a variety of engines and applications. I’ve discovered that what works in one kind of racing often transfers to a completely different type of competition – the techniques we’ve developed with nitrous oxide injection in Pro Mod can be applied to a land speed record car at Bonneville, for example. I’m certainly no expert on nitro-burning Funny Cars, Formula One, or the 24 Hours of Le Mans, but at the end of the day, I’ve learned that engines with pistons and valves are fundamentally alike.