Tech Talk #68 – Playing With Fire

DavidTechArticlesBy David Reher, Reher-Morrison Racing Engines

“The bad fires are the ones that happen away from the race track.”

Last year I watched my neighbor’s house burn down. I don’t mean he had a barbecue fire that singed his hamburgers. No, he had a blaze that took the house right down to its foundation. A small fire that began as a short circuit under a deck quickly became an inferno when it reached the chemicals and solvents that were stored in the garage. Fortunately no one was injured, but the house was left in cinders.

We’ve all seen fires at a race track. If I had to choose a place to have a fire, I suppose that a drag strip is a good place to have one. There are trained safety crews equipped with serious fire-fighting equipment on duty. Race cars are required to have fire-suppression systems, and approved apparel is the order of the day for every driver. If there is a fire in the pits, there are always plenty of extinguishers nearby, and the crews from nearby transporters rally like an old-fashioned fire brigade.

The bad fires are the ones that happen away from the track – a fire in a home workshop, a fire in a dyno cell, or a fire in a car hauler. I’ve been told that if a fire department can’t respond to a residential fire within a few minutes, it’s unlikely that the home will survive. When your garage is ablaze, you’re really on your own. A garden hose and a two-pound extinguisher aren’t going to do the job.

As racers, I think we tend to become complacent about the risks of working with gasoline, methanol, solvents, and flammable chemicals. These materials become part of our everyday life, and consequently we forget their power. In fact, one pound of gasoline contains 19,000 btu’s – enough energy to propel a Pro Stock to 200 mph or to blast the roof off a garage. Pour 35 pounds of racing gasoline into a five-gallon jug and you’ve got enough stored energy for a potent bomb. Those cans of carburetor cleaner, acetone, and propane on the workbench shelves are what the fire investigators call “accelerants” in their incident reports.

Fortunately liquid gasoline inside a sealed container is not very volatile – but vaporized gasoline fumes are extremely flammable. A workspace filled with fumes is just like a cylinder before the spark plug fires. Who hasn’t spilled gasoline on an intake manifold or valve covers while changing carburetor jets? Maybe you wipe it off with a shop rag, or just let it evaporate. But when that fuel is in a vaporized state, one spark from a starter motor or an electric drill can ignite it. I speak from personal experience; years ago, we nearly lost our shop when a dyno cell caught fire after a gasoline spill. Only good luck and a good fire door saved it.

It only takes a moment’s inattention to start a fire. I’ve seen smart racers flood an engine, pull the spark plugs, and then hit the starter button. But if someone forgot to turn off the ignition switch, a spark from the ignition wires can turn the gasoline being pumped out of the cylinders into a flamethrower. It’s not a pretty sight.

I’ve seen static electricity start a fire when a racer was filling his fuel tank in the dry heat of Denver. That’s why we’ve now got a grounding wire attached to the metal ring around the filler neck. The caution notices on gasoline pumps about not filling plastic jugs in the bed of a pickup truck are there for a good reason: a static spark between the nozzle and the jug can light off a serious fire.

Fuel and electricity can be a dangerous combination, but electricity alone deserves a racer’s respect. Good wiring practice requires that every circuit be protected by a fuse or breaker. But if the race car’s engine is popping and banging in high gear, often the first fix is to run a wire directly from the battery to the ignition box. Now there’s a high-amperage circuit with absolutely no overload protection, and that’s a prescription for trouble if the electricity finds a path of less resistance.

An electrical fire inside an enclosed trailer or transporter is bad news. By the time the flames become visible, it’s often too late. It’s especially important to make sure that the master switch is turned off before the race car goes into its box. Back in the day when I was racing, I’d check that the master switch was turned off two or three times before we hit the road.

Drag racers depend on fuel and electricity to power our vehicles, but we must handle them with care. Even a small fire becomes a huge mess when you have to clean up the residue of extinguisher chemicals, charred paint and toasted wires. A severe burn is an extremely painful experience, and recovery is long and arduous. Please remember that every time you fill a fuel cell, change a carburetor jet, or charge a battery, you’re playing with fire.