It happened on the 11th quarter-mile run in the SRT-4 Extreme Lightweight. Halfway down the track the exhaust note suddenly went flat, and the three of us standing behind the radar gun all exchanged the same knowing look. The fury that is 370-hp worth of combustion just found itself a victim. The only question now was how hard the victim would be to replace.
The Lightweight rolled back to the staging area chugging the uneven three-cylinder thrum of a steroidal Geo Metro. A thin, black cloud of smoke swirled in its wake as the car rolled to a stop, sputtered and died. Everyone there had blown up cars before, so the diagnostic process was almost instinctive. With hardly a word, the engine was restarted, and Ethan Bayer, who designed the Stage 3 kit responsible for the 370 hp, and who'd spent months proving the kit's durability, anxiously pushed on plug wires to be sure they weren't loose. When he reached number three, 25,000 volts shot up his arm, down his torso, did doughnuts around every major organ, and shot down to his leg, which he had inadvertently grounded on the fender.
Between expletives, I think I heard something about the number three spark plug being bad.
Unable to fix it with our bare fingers, we hit the auto parts stores. It turns out the SRT-4 is built with Champion spark plugs that, to save a buck, are exactly the same heat range as every other four-cylinder Dodge, turbo or not. The bean counters may have won that battle, but the engineers got their revenge by creating a part number for an optional replacement NGK plug (part number LZTR5A-13) that's colder. (The Stage 3R kit is supposed to use the NGK plugs.) Our quest was for the colder plug. And a spark plug wrench. And some plug wires.
Two auto parts stores, one Dodge dealer and one Chrysler dealer later we had a fistful of Champions and two plug wires. Oh well. The last set of plugs had survived through ham-fisted maltreatment by salesmen during the car's first life as a dealer demonstration car, through countless tests and engineered floggings in Michigan, through our 370-hp dyno pulls and 10 runs down the quarter mile, so this next set should surely be enough to get us to the track tomorrow. Still, for good measure, we bought a spare set too. Assuming, of course, nothing else was broken.
Big assumption, it turns out. We were expecting that the extreme heat of combustion, combined with plugs designed for a base Neon, had overheated the electrodes on the plug, burning them back until the plug gap was too big for the spark to jump. As soon as the number three spark started thinking it would be easier to go straight through the spark plug boot rather than across the gap, it was "game over." Send a spark through a normally insulating spark plug boot a few times and it burns a nice, conductive trail of carbon-rich rubber crusties, making that shortcut even more attractive. Hence the need for a new plug wire or two.
At least we diagnosed the wire correctly.
Putting our $.99 spark plug wrench to work, the extent of the plug problem became obvious. The center electrode hadn't burned back, it had left the building. The center electrode was gone. The ceramic was gone. The plug was nothing but a hollow tube with a ground electrode probing hopelessly into space. That left a glaring question. Where did the center electrode go? That's a big, hard piece of copper and ceramic just bouncing around in the cylinder. It would take a very active imagination to conjure up a way for that to leave the cylinder without hurting something.
With the new plugs installed, the car started and ran normally. Looks of surprise and relief were exchanged. Bayer turned the car around and drove down the track. We'd dodged the bullet. Then he nailed the throttle, the turbo spooled up, and the uneven blat returned. I got on the phone to reschedule the track day.
The engineers all played Ping-Pong with panic theories. The center electrode was still bouncing around in the cylinder and had just landed so wrong it punched a hole in the piston! Rock-hard chunks of ceramic were getting pounded into the valve seats, keeping them from sealing properly and bleeding off the compression in that cylinder. Spark plug bits flew into the delicate, millimeter-thick blades of the titanium-aluminide turbine wheel when it was spinning at more than 100,000 rpm, shattering blades and throwing the whole rotating assembly off balance.
But no. With a hole in the piston, torrents of air would be pumped into the crankcase, but pulling the oil cap off at idle revealed nothing but the normal breeze of blowby. A valve that wasn't seating would make noise as the valve lash went wide and the cam lobe slapped into the rocker arm, but all was quiet. A shattered turbine wouldn't make boost, and an off-balance rotating assembly should start spewing oil out the blow-off valve, but the valve was blowing clean air.
Other than that running-on-three-cylinders thing, the Lightweight was a model of internal combustion perfection. Baffled, I pulled out my two most powerful tools-a cell phone and a AAA card. Nothing fixes a car like calling a tow truck. The last three times I locked my keys in my car (don't ask) the coat hanger only worked after I had a tow truck on the way. Even as I listed off our location and described the car, Stephan Zweidler, the mastermind behind the Lightweight, was driving up and down the parking lot slowly turning up the speed. By the time I hung up he was blasting back and forth at full boost, hitting on all four cylinders. I called AAA back and cancelled.
The number three cylinder got soaked with gas from lumbering around with a perfect fuel injector and only half a spark plug. Even with a fresh plug in place, there was so much fuel bouncing around in there, the new plug had fouled until Zweidler managed to slowly turn up the heat and clean the plug.
What happened to the old electrode? Even if it got lucky and was spit out an open exhaust valve, it should've hit the turbine wheel. But the turbo worked fine, performing flawlessly through the next day's track thrashing. Look closely, though, and the wastage is nearly in line with the number three exhaust port. The SRT-4 Lightweight had eaten its spark plug, spit it out the wastegate, and come back for more. We should all be so lucky.
Next time I'm calling AAA earlier.