How much boost is too much for a Subaru FA20DIT engine? That depends on who you ask. The turbocharged engine has been used in the WRX (and other performance-focused Subarus) for over a decade, so there are likely dozens of answers.
We don’t have a definitive number for that question, but we can be certain of two things. There are few vehicles in the world subjected to all manner of amateur and professional tuning as the WRX. And the turbocharged 2.0-liter FA20 featured in this I Do Cars video—be it at the hands of amateurs or professionals—did not survive the process.
This becomes apparent from the very beginning when the engine doesn’t quite turn over as it should. Our next clue comes just a couple of minutes later when the spark plugs are removed. Three look good, but one clearly had an unexpected encounter with a piston. The intake comes off next, and bits of piston are found inside. Or at least, it’s theorized those are piston bits. Once the intake is off, a gigantic hole is discovered in the top of the engine block. Horizontally opposed engines can detonate themselves differently than inline or V blocks, but still. A big hole at the top is impressive.
Digging deeper, we find the timing system and heads are actually in great condition. One head is torn up from debris bouncing through it, but the heads and cams are impressively clean. The engine was pulled from a 2021 WRX with 95,000 miles, so it’s neither old nor blitzed with excessive mileage. Still, it looks like the oil was changed regularly and kept full.
That didn’t prevent a piston on the left side of the engine from splitting, however. And once the oil pan comes off we see the true extent of the carnage. The rod is fractured and bent, and bits of piston are everywhere. Even the wrist pin—the hunk of metal that connects the piston and rod—shows heavy damage. It appears the rod simply buckled under the strain, bending and causing the piston to fracture. It likely occurred at high RPM, sending parts flying with enough force to break the block.
What caused this failure? As mentioned in the beginning, this looks like a classic case of someone running too much boost or not managing that boost properly. There were no signs of hydrolocking or oil starvation. The cooling system was in good shape, so the engine wasn’t overheated. The video description confirmed it came from a tuned Subaru, but we don’t know how tuned it was.
In any case, the engine couldn’t handle it. So take heed, seekers of speed. Having prolific boost can be a good thing, but only if it’s done right. Otherwise, you may end up with a hole in the top of your engine.
Source:
I Do Cars / YouTube
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