“Blow Up” is a commonly used euphemism among performance sledders to describe a seized piston—stuck in the bore because it temporarily grew bigger than the hole due to lean operation or deto. That euphemism annoys me because a stuck piston is not a “blowup”—it’s very non-destructive, non terrifying like a “blowup” would imply. I have always thought that the term “blow up” should be reserved for something more serious than a crankshaft that no longer turns, with something awry, but easily fixable inside the engine that is preventing normal rotation.
When funnycar racer John Force says he “blew up”, you know something way more violent than a stuck piston occurred.
In November I had my first real, true sled “BlowUp” on the dyno.
Terry and Mike Queenan had the Queenan Brothers Racing Hayabusa powered asphalt sled here to tune. This was to be a fun session—the fellow who provides parts and tuning for the Motec EFI system for Queenans (as well as the Al Anabi drag cars and bikes) was remotely monitoring the DTR tuning session from his home office in California, making fuel/ timing tweaks after each run via internet and observing the dynocams.
Creeping up on revs and boost (I think we were only running 11 psi boost and 410 HP) this fellow noted, watching data during each dyno test, that oil pressure had dropped a bit—perhaps due to rising oil temp? We cooled the crankcase for a few minutes before the next run. But what we did not realize was that a rod bearing on the big end of one of the engine’s aftermarket connecting rods was beginning to seize on the crank journal—perhaps smearing rod bearing material into the crank oil journals preventing total loss of oil pressure. This friction would eventually create heat that would in the next six seconds of boosted operation cause the rod to try to friction- weld itself to the crankshaft, then turn blue and eventually grab and snap sending parts flying.
On dyno test 10, we ran the engine up to 11,500 RPM and a sudden, loud snap accompanied a 7’ diameter ball of fire that enveloped the expensive area of the sled all the way to the ceiling tiles in the equally expensive dyno room!
This fire was accelerated by the 80mph air from the dyno air supply ducts—making it look exactly like one of John Force’s Funny Car “blowups” where headgaskets squeeze out and spew oil onto the headers creating one of those nasty, terrifying oil fires and an out of control funnycar. But in this case it was the rod cap blowing out the front of the Hayabusa crankcase, showering the cherry red header/ turbo with engine oil and creating the first DTR fireball.
I bolted from the control console, grabbing one of the 25 year old, but previously unused Halon fire extinguishers, and ran into the dyno room and with two pounds of Halon completely extinguished the fire. Terry and Mike Queenan were duly impressed with the speed at which Jr. Fire Marshal Jim was able to run from the control console, grab the the extinguisher and reach and address their burning sled. Halon is great stuff—today banned by the greenies but still said to be available, at a premium, from suppliers who have a stash of this stuff.
But with the fire extinguished, there was still a substantial amount of oil left on the dyno table beneath the sled….what if this sled was running down the dragstrip at 180mph instead of sitting on my diamond plate steel table?
That unburned oil, instead would surely have been spewed and drizzled in front of the smooth rubber track with instant loss of traction and directional control! It’s one thing to have an engine explode (truly “blow up”) and shut a sled down, but the prospect of dumping oil directly in front of the smooth rubber track is terrifying considering what we all know might happen should a high speed sled/ rider encounter a guardrail or concrete barrier at 180 mph plus!
Fortunately, Queenan’s sled features a high tech multi-stage dry sump oiling system which minimizes unnecessary oil volume within the crank case and the sled also has a solid pan beneath the motor which trapped some of the oil from spilling out under the chassis. Without these features, the fire on the dyno table and the potential real-world scenario could have been much, much worse.
Why not add some sort of diaper-like oil catcher like the top fuel racers use? For them, dropping oil mostly between the two rear tires is not a huge control issue, but NHRA is mostly concerned with downtime necessitated by cleaning up the mess. But sled racers with boosted four stroke engines approaching 10 HP per cubic inch will surely occasionally “blow up” engines, inevitably dropping oil directly in front of the tracks. It would be wise to deal with the inevitable spewing oil ahead of time.
From now on, people bringing heavily boosted engines to DTR must endure a pre-test fire drill.
