WHAT EXACTLY MAKES AN NHRA FUNNY CAR BLOW UP
- Autoweek asked Ron Capps' crew chief and long-time tuner Dean "Guido" Antonelli what makes an NHRA Funny Car explode.
- Turns out, the combination of gallons of nitromethane pumping through a dragster's motor that has damaged a cylinder (or multiple damaged cylinders) can lead to catastrophic failure.
- Thankfully, explosions are rare, as Antonelli says, "Even when something goes askew, you lose that balance, and still 99 out of 100 times, you don't even see engine failure."
On June 23, the Chevrolet Camaro SS Funny Car of John Force blew up at Virginia Motorsports Park, near Richmond, resulting in a serious brain injury to Force.
Four weeks later, Ron Capps' Toyota GR Supra Funny car suffered a similar demise, exploding during the early stages of a peddlefest with Gary Densham at Pacific Raceways, near Seattle. Fortunately, Capps was unhurt.
So, what gives? What causes such catastrophic failures in these finely tuned NHRA dragsters?
Autoweek asked Capps' crew chief and long-time tuner Dean "Guido" Antonelli what he tells fans who ask, "What makes an NHRA Funny Car explode?' He gave us an earful.
"I usually tell them we pour nitromethane in them," Antonelli said, matter of factly. "Nitromethane, obviously is a very reactive fuel. You don't even need flame to light it. You can light it with just pressure. I guess you could say it's semi-unstable."
Antonelli won't get any argument from Capps or Force about the semi-unstable part.
Antonelli, who got his start at John Force Racing in 1994, knows his stuff. One of the first things he'll tell you is don't blame the drivers when things go awry to the point of a car exploding, either.
Here's the anatomy of the Capps' explosion during last week's peddlefest with Densham, from a man who knows every inch of a Funny Car.
"So, in our case, I made a bad call that spun the tires. When you're in eliminations, and the other car has a similar situation, Ron, the driver, is trying to win. So both drivers are out there, beating on the throttle, peddling it, and spinning the tires.
"The motor has a fuel curve which is predetermined for a full power run with traction. While, when it spins, it's getting an increasing volume of fuel in it. It puts cylinders out because it has no load and a lot of fuel. When the cylinders go out, the boost goes up.
"On a regular run, even with traction, these things are tricky. You put a lot of fuel in them. You might miss the curve a little bit and put a cylinder out. Depending on what cylinder goes out, the boost will go up because the volume fill of the liquid isn't going to the next cycle, so there's less cubic air that it can take. The boost goes up in the other cylinders, which messes up with the fuel-to-air ratio that they would normally have, so they'll run a little hotter.
"And it depends which cylinder goes out. It has to do with the firing order and everything, how much it changes. On our car, with the double swap cam, if No. 5 goes out, at say two and a half seconds, the boost will go up three pounds. If it drops No. 1 at three seconds, the boost goes up three quarters of a pound. So, if it drops No.1 it's not as hard by the finish line on the other seven cylinders. But if it drops No. 5, it's going to beat on the other seven cylinders pretty hard because it's quite a bit more boost.
"So in our case, when it spun and Ron pedalled, it put a couple holes out. He peddelad it, trying to get it to re-hook up, put a could different holes out and re-lit some of them, and then pedalled it again, put a couple holes out. Even though it wasn't hooked up, the car was starting to gain steam and it was closing on Gary (Densham) and it had four cylinders out. Well, with four cylinders out, the boost was up eight pounds. And the four cylinders that are running are now carrying the load of what eight cylinders should do. That makes those four cylinders that are running really hot.
"Sometimes you get away with it. Sometimes you don't."
Antonelli says he's been fortunate in that very few of his cars have blown up over the years. He says he has to go back to 2009 or 2010 when he was with JFR for the last time one of the cars he worked on exploded during a run.
Just like he says not to blame the driver, it's probably not wise to blame it on a fatigued part still being used past its normal expiration date.
"It's unfortunate. It's scary," Antonelli said. "And it's not a fatigue deal with parts. The bigger teams have run counts on every part, and those counts are usually way on the safe side. There's some teams with lower budgets that might run parts a little longer. So, it's not like fatigue or the motor was a little out of skew or broke something.
"It's just when the boost goes up—it's no different than if the car was running eight cylinders and say I put 5% too much overdrive on it by mistake, say maybe the crew guys got the wrong pulleys or something. And if it just had 5% too much overdrive on it because of a pulley mistake, and it was hooked up and going down the track, it would blow up just like that by 200 or 300 feet."
Experience goes a long way in helping to make sure teams running on the edge know exactly where the edge is. It's a fine line with a Funny Car that runs on 16-gallon fuel tanks, burns maybe half of that in the pre-run staging and burnout, and then burns about four gallons of nitromethane in less than four seconds of a run.
"Over years of data and everything, you learn how to run them safe," he said. "Even when something goes askew and you lose that balance, still 99 out of 100 times you don't even see engine failure. You might see a burnt piston or burn the chambers out of the heads or something like that.
"In this case, when it's that long on four cylinders, it's not going to come back."
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