“On a blistering summer day, it’s unnecessary to warm up an engine excessively.”
As a Texas resident and taxpayer, I know about long, hot summers. Long before anyone on TV talked about global warming, I was enduring month-long sieges of 100-degree heat. Without the advent of air conditioning, Dallas would probably be just a sleepy gas stop on Interstate 20.
I’ll leave it to the weather experts to decide whether this summer’s heat wave is just another spike in the normal cycle or the beginning of a global meltdown. I do know that what feels bad for a person’s body is usually just as bad for a racing engine.
Race cars and racers typically don’t work well in extreme conditions, whether it’s intense cold or scorching heat. Most machines, like most human beings, are designed to function in temperate environments. Computers, CNC machines, and race cars often just don’t work properly when they’re overheated.
So why do some racers perform the same warm-up ritual in August as they do in February? I can understand warming up an engine when the weather is so frigid that jackets, sweatshirts and gloves are required race day apparel. But on a blistering summer day when T-shirts and shorts are the only defense against the heat, it’s unnecessary (and potentially harmful) to warm up an engine excessively. When it’s hot, the objective isn’t to put heat into the engine – it’s to keep it out.
A typical internal combustion engine converts only about 25 percent of the fuel’s energy into useful work. The rest is turned into waste heat or consumed by mechanical friction. Approximately 35 percent of the energy goes out the exhaust pipes, 30 percent is dissipated by the cooling system, and five percent is transferred to the air through direct contact with the engine.
The energy content of a gallon of gasoline is around 124,000 BTUs (British Thermal Unit, defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit). So if an engine burns one gallon of gas during a quarter-mile run, it will dump more than 37,000 BTUs into the cooling system. Is it any wonder that the small-capacity cooling system that are commonly used in drag race cars can’t cope? Raising the temperature of the coolant by warming up the engine and drivetrain for an extended period simply puts the system closer to its limits.
It’s not just the engine that suffers in the heat. I’ve heard racers complain that a trans brake didn’t hold and the car rolled through the staging beams when the ATF temperature is high. Heat is hard on onboard electronics, from data acquisition systems to ignition boxes. An overheated driver isn’t as sharp as one who’s cool, calm and collected.
On a 100-degree day, the engine is already warmed up as soon as the car comes out its trailer. The temperature of the pavement in the pits and staging lanes is probably 130 degrees, and that heat is radiated to the car and its components. The sun is a powerful source of radiant heat, as anyone who has laid a hand on a hot piece of roll cage tubing or picked up a ratchet that’s been sitting in direct sunlight can attest.
My recommendation for sportsman racers is to start the engine, make sure the transmission shifts and the trans brake works, and then shut it off. Just driving from the pits to the staging lanes will warm up the engine thoroughly. Going to the starting line with the engine at 110 degrees instead of 150 degrees ensures that there will be at least some reserve capacity in the cooling system to absorb the heat energy released during a run.
There are some simple ways to beat the heat on a hot day. I’ve written previously about the shortcomings of antifreeze in a racing engine’s cooling system, so I’ll simply reiterate that water is the best cooling medium for a competition engine. Put up an awning or tent to shade the driver compartment and engine – this will prevent the sun’s radiant heat from continuing to increase the temperature. A powerful portable fan can be very effective in keeping the engine temperature under control. If you stand downwind of a fan that’s blowing air over a hot engine, you can feel the direct heat loss. The bigger the fan, the better.
Keeping an engine cool can definitely improve its performance. I’ve seen the results on the race track and I’ve measured them on the dyno. That’s why most Pro Stock racers prefer to go to the starting line with the water temperature at 60 degrees if possible. When an engine is cool, its intake manifold isn’t heat soaked and it’s not as likely to encounter detonation as a hot motor.
The keys to keeping cool in summer are an abbreviated engine warm-up, shade to keep the sun’s radiant heat at bay, a big pit fan. Take it from a Texan.