Fail of the Week: Engine Flips Out

A few weeks ago an incredible video of an engine exploding started making the rounds on Facebook. This particular engine was thankfully in a dyno room, rather than sitting a couple of feet away from a driver on a track. We’ve all seen engine carnage videos before, but this one stands out. This diesel engine literally rips itself apart, with the top half of the engine flipping and landing on one side of the room while the bottom half sits still spinning on the dyno frame.

Building performance engines is part science, part engineering, and part hacking. While F1 racing teams have millions of dollars of test and measurement equipment at their disposal, smaller shops have to operate on a much lower budget. In this case, the company makes their modifications, then tests things out in the dyno room. Usually, the tests work out fine. Sometimes though, things end spectacularly, as you can see with this diesel engine.

The engine in question belongs to Firepunk diesel, a racing team. It started life as a 6.7 liter Cummins diesel: the same engine you can find in Dodge Ram pickup trucks. This little engine wasn’t content to chug around town, though. The Firepunk team builds performance engines — drag racing and tractor pulling performance in this case. Little more than the engine block itself was original on this engine. Let’s take a deeper look.

A stock Cummins 6.7 produces 385 horsepower. This engine had been modified to produce over 2,212 horsepower. This kind of insane power requires changing just about every engine part. Bigger turbos for more boost — 146 psi in this case, larger pistons, and a stronger crankshaft to handle those pistons. A performance camshaft timed for power was added and an upgraded valvetrain brought in to handle the increased load.

Generally the last part someone would change would be the engine block itself. The block is the shell of the engine, which holds all the other pieces. Manufactured engines are generally cast parts. In this case, the block is made of cast iron. That’s exactly where the failure happened.

In the video, you can watch the failure happen in slow motion, from several different angles. The initial point of failure was at the rear of the engine. Maybe there was a casting defect, a microscopic crack or void. The crack quickly spread under the pressure of the running engine. The extreme pressures in the engine started rushing out, expanding the crack further. As the crack spread, the pistons began binding in the cylinders, forcing the top and bottom of the engine even further apart. The crack quickly zipped around the engine. The rear section where the failure started was launched up and over, flipping the entire top half of the engine up and away. Pistons were ripped from their wrist pins, connecting rods bent. Nearly every part of the engine was damaged or destroyed in the cascade. Somehow the head and valve train survived the carnage, but everything else went straight to the scrap heap.

Since Firepunk’s engine was on a dynamometer when it failed, plenty of data on the failure was available. Many armchair mechanics surmised that the engine was running low on oil. Not true, and Firepunk had the data to prove it. The oil pressure was steady at 66 psi when the failure occurred.

One thing to note is what you don’t see in the video: oil pouring out everywhere from the broken engine. This engine was fitted with a dry sump system. Most engines use a wet sump system where the sump (aka oil pan) catches and stores the oil to be circulated around the engine. This works, but it’s not an optimum setup. Oil pressure in the sump can vary as the vehicle experiences varying g-forces of racing. Hot oil in a hardworking engine isn’t allowed to cool before being recirculated back to the engine. A dry sump system adds an external reservoir and pump to the system. Oil is pumped from the engine sump to top of the reservoir, where it passes through several baffles. The oil cools as it drops through the reservoir. At the bottom of the sump the now cool oil is pumped back into the engine. A system like this is actually better for the engine than a wet sump, however there are more parts, which means more points of failure, and more expense. In street cars, you’ll generally only find dry sumps on sports cars like the Chevrolet Corvette.

Many an engineer will tell you that testing is all about finding the weakest point. In this case the team found it — the engine block itself. The Firepunk team says they’re currently having a billet block machined, and will be back testing in no time.

66 thoughts on “Fail of the Week: Engine Flips Out

  1. Uhm…The oil pressure in a wet sump doesn’t change at all. There is no oil pressure in the sump, to be exactly correct. It just sits there just like any other fluid. The issue with a wet sump is that oil sloshes around when the vehicle experiences acceleration in any direction, causing the oil pickup to not be immersed in oil and sucking in air instead.

    A dry sump setup has pumps which suck out the oil from the oil pan into a container that is not affected by sloshing, then other pumps push it into the engine under pressure.

    Also, in both cases, an oil cooler is required as a dry sump system can not provide adequate cooling.

    1. All diesel engines have oil coolers, either through a coolant to oil heat exchanger or through a direct air to oil heat exchanger.

      Due to the excessive pressure and heat of a compression ignition engine, its near impossible to keep oil temps low without one.

      1. No, not all, many modern high speed diesels and stationery diesels do, of the eight diesel engined machines I own 2 have oil coolers, a unimog with coolant to oil and a digger with a massive sump.
        I’m disappointed to learn that a stock 6.7 litre Cummins produces 385HP while my stock 6 litre unimog engine produces 90HP! No that’s not a typo, ninety horsepower, presumably the other 295 are in the .7 id be better off with that bit.

          1. It’s the OM 352 from the late 70s or early 80s, the lack of a turbo doesn’t help the horse power situation but does tend to add to the reliability.

        1. “6 litre unimog engine produces 90HP”

          Horsepower is a function of torque at a given RPM. That 90HP 6L engine generates insane torque. It just doesn’t spin up very high and probably redlines below 2000RPM.

          1. Yes, what it lacks in HP it makes up for in torque and an incredible amount of noise, it’s happy to spin up to nearly 3000 which is just as well because all the power comes in at 2800 and the torque peaks at 1700, I had to check the torque figure and while doing so learned that the displacement is actually 5.672L or 346.1 cu in

    2. “causing the oil pickup to not be immersed in oil and sucking in air instead.” – That would cause a change in oil pressure in the system. It’s likely that the author isn’t well versed on the topic and meant to say “pressure in a wet sump system” instead of “pressure in the sump”. I understood what they were trying to say but that’s probably because I understand the subject matter.

      1. Well, of course any car guy will get what was actually meant, but someone who’s not that much into cars will end up thinking that the sump is pressurized. And then they’ll learn about crankcase ventilation and end up scratching their heads.

    3. pressure in a wet sump system can change based on the aeration of the oil, this is another beinfit of dry sump systems as they usually send the oil through an air-oil separator to remove any trapped air caused by the crankcase whipping through the oil. Sloshing will happen in any container that the oil is placed in, just dry sump systems are usually designed in such a way to reduce that (usually by carrying a larger volume of oil to begin with). The major benifit to a dry sump system is a reduction of air trapped in the oil as this leads to better lubricity as well as a more stable oil pressure feed to the engine as air can be compressed easily while oil cannot.

      1. No not really, the only part that might end up splashing in oil is the crankshaft or its counterweights to be correct. But that only happens if you put too much oil in the system.

        The terminology is dry sump vs. wet sump. The sump being the key word here, because in a wet sump system, there’s oil in the sump aka the oil pan while in a dry sump system the oil is not kept in the engines sump but sucked into an external container, making the sump dry.

    4. Your guess is just a guess, nothing more. You do not know how a dry sump works, so I shall explain in detail. The oil is fed to the various parts of the engine; that is, the Crank; Camshaft and rockers (should rockers be used); to the pistons, via the crank and all other moving parts. A scavenge pump picks up the oil that drops into the oil-pan (sump), and, is sent back to the oil reservoir
      along with the other oil that has been circulating through the crankshaft and camshaft and this too is added to the reservoir. The reservoir then feeds the pump (via oil particle filters (3 micron or better) under pressure, to a second filter (1-micron), then fed back to the engine, clean as you like. In this case (can’t see if a chain or belt is involved) likely a chain snapped (sparks are seen at the base of the engine block where the oil pan joins) then hit the oil pan, pulling it off the engine block. The torque, being a LOT and the potential energy, released as kinetic energy, threw the
      engine block up. The pistons and connecting rods did what they do best and helped the engine block across the room. This was likely a thermal and mechanical stress that likely ceased the top bearing and cog, making the chain snap at the weakest link. The rest is how you see it, frame by frame. Nothing to do with the lack of oil, rather a cam drive problem. I accept checks, postal orders; or credit cards. Chas is preferred, in a large brown paper bag (marked SWAG) and sent via courier to the address below.

  2. This was a very predictable failure, as they no doubt knew somewhat in advance that the block probably wouldn’t handle the sort of performance they wanted to drag out of it.

    Surprised, given how much money they poured into the build, that they didn’t just go with a billet block to begin with.

    1. The description on youtube suggests that the block should be able to go up to 3000hp.

      The surprising part to me is the price of the engine components. Sweet jesus. I could pay my rent for four months for the price of the connecting rods.

    2. I think this was a “lets see what RPM it’ll do before exploding”.

      While it may have had the performance mods in the past they don’t seem recent as you can see carbon buildup on one piston and it seems to progress past the main compression ring right down to the oil rings.

      Many performance engines are only used a small number of time in competition before being retired.

      It looks like the dyno was due for an upgrade as well as it turned to jelly under load before the engine exploded.

    1. There was one angle showing a guy watching from the hallways through a window. He noped the hell out of there right fast, under cover of the expanding mushroom cloud. Probably headed right to the men’s room ;-)

  3. I hate to be another armchair mechanic but I slowed this down and am going to go with clutch explosion. The first frame (below) shows white-hot metal inside the clutch-dyno (just above the “I”) at failure, and the second shows rotation upward rotation around the forward mounts as the engine lifts from the very rear. There was a bit of smoke as the clutch was engaged on the dyno, but this is typical.

    Given the rotational energy released at that point, this sort of wild failure is pretty common – you can look up “clutch explosion” videos, including the one that injured Don Garlits.

    1. Had a clutch disc explode on a M35 deuce and a half once, at fairly low RPM (under 1000) coming down a hill. That made enough of a mess. I could totally see a clutch disc failure, or worse, reaching the burst speed of the flywheel, really wrecking the place on a high-speed, high-power dyno test.

    2. If you watch the video again and listen carefully (and there also a few small visual queues) you hear the engine failing a couple of frames before you see the sparks from the clutch/flywheel assembly. Too bad the didn’t have any high speed footage, then you’d probably be able to discern more accurately where the failur originated.

    1. Really? How do you supply said electric motor? Portable nuclear plant? At 2200hp, it putting out 1640KW or so. Even the worlds most powerful electric cars use liquid cooled motors at the wheels making x amount of power. None use a single powerplant making this kind of power.

  4. To me it looks like the bottom end separated from the top of the engine. Allot of high power diesel engines grenade this way. To me, the engine had uneven combustion pressure in the cylinders, what happened next is that the cap bolts grenades and that caused a chain reaction.

    1. A follow up video the discussed that they’ve run over 180 psig in boost and that PCPs were likely the cause. They were not sure if crank deflection was causing the irregularity or not.

  5. “Manufactured engines are generally cast parts.” Remember a trade show I went to. Should have seen the size of the machine used to bore the engine block. Not to mention a Ford plant and the tower of power that stamped out parts. Manufacturing can be a beautiful thing.

    1. Interesting read, thanks for that.

      I enjoyed this quote: “I’m OK now … except for the brain damage, which the doctors all said was a pre-existing condition, or else I wouldn’t have been going that fast, anyway!”

  6. If you want to see some serious engine explosions, go to an NHRA national event and watch the nitro funny cars and top fuel dragsters. When those engines “explode” they often really explode and not just come apart as often is the case with engine failures in other forms of motorsports. I guess one of the biggest I ever witnessed live was Tim Wlkerson in Atlanta 2014. The cam shaft sheared causing some intake valves to remain open when the cylinders fired. This caused a backfire into the supercharger. In an 11,000 Horsepower engine that’s typically not good and the result is a big kaboom! There’s video of it on youtube if you’d like to search. One lady in the grandstands was actually struck by a piece of debris and injured. Fortunately her injuries weren’t life threatening and I believe she made a full recovery. The very same weekend Jack Beckman had a similar explosion. Anyway, in these types of engines and the fuel they run, nitromethane, violent engine explosions are pretty common. It’s an experience to behold, 0 to 330 Mph in under 4 seconds and less than 1000 feet.

      1. Yes, that’s video of it. And in a later qualifying session at the same event Jack Beckman had a similar explosion as well. I didn’t get as good of view of this one from where I was seated. Here’s video of that one as well. Ironically, the car in the other lane is Tim Wilkerson, with a new engine and body of course, and the TV announcers are talking about his explosion, earlier in the weekend, right before this one happens.

    1. A top fuel event is something anyone who has any interest in big hp should experience in person, at least once. The noise, the way the bleachers (and your body) shake, and the insane acceleration are both frightening and awe-inspiring. They launch hard enough that the drivers vision starts to gray out. I can’t quite wrap my head around how they’re able to get traction with that kind of acceleration.

      1. “I can’t quite wrap my head around how they’re able to get traction with that kind of acceleration.”

        Well VHT helps a good bit with that. That’s the sticky stuff that smells kinda like bubble gum they spray the track with between sessions. The tire technology is probably a part of that also. If you watch the way the tires deform in slow motion video, it looks as if there is a sort of standing wave that develops around the tire. That creates a large contact patch between the bottom of the tire and the track surface. Apparently the wheel speed has to be just right at the hit of the throttle for this to happen. If it’s too fast, the tire just slips and spins. If it’s too slow they get oscillations in the tire that result in violent tire shake and breaks traction. Therefore I think the wheel speed must initially be at just the right amount that the flexing of the contact patch will be at a wavelength that will form this standing wave around the tire. Of course only the crew chiefs who are experts at tuning these cars know all the deep dark secrets to achieving that.

        And I totally agree that everyone should go to one of these events at least once in their life. It’s not just an awesome experience watching the cars run. It’s also interesting to be able to walk around in the pits between rounds and watch the crews tear down and rebuild the engine and clutch between rounds.

        1. Yeah, the VHT is amazingly sticky. After the last race of the last day, they let the crowd walk across the track. A number of people lost their shoes to the stuff.

          And agree with watching the pit crews rebuild between races. Talking to some of them, I got the impression they had a healthy fear of their engines when running, and had no desire to become a driver.

  7. More inf required….constant oil pressure is a good indicator, but more importantly, where was it measured? If you measure it at the main line coming into the block and not at the other side of all of the oiled parts you could have a loss of presure issue that would detonate the block before you record this. A few years of racing and a couple of lost engines taught me this.

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