The E92 BMW M3 holds a special place in the halls of M. It's the only 3-er to get a V8, and with a redline well north of 8,000 rpm, it's a humdinger to wring out. When everything is just right, the naturally aspirated mill generates 414 horsepower (309 kilowatts) in stock trim. The 2010 M3 featured here is indeed stock, but at 152,000 miles, it's not exactly new.
How will that mileage affect the V8's powerband? Such things always depend on maintenance, and judging by what we see in this dyno video from Evolve Automotive, it looks well-kept. However, the group has considerable experience with the V8 M3, and it felt a little flat on a test drive. A few dyno runs confirmed that the BMW was a bit down on power. Not detrimentally so, but with a healthy engine making 414 ponies at the crankshaft, this one only managed 398 once the calculations were done.
But wait, there's more.
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This time around, we aren't just bearing witness to a high-mileage, high-performance car getting power-tested on a dyno. Evolve Automotive takes a deeper dive into the engine parameters, showing just how clever modern systems and diagnostic equipment can be. For all intents and purposes, the engine was running fine. But data from those runs showed the M3's computer was pulling ignition timing at the higher end of the rev range. Retarding the ignition timing causes the spark plugs to fire later, which can be safer for the engine but also reduces power.
Apparently on the V8 M3, frequent spark plug changes are required to keep the car at max power. The plugs on this engine only had around 30,000 miles of use according to the video, but sure enough, after changing them out the missing power returned. A series of dyno pulls with new spark plugs showed the ignition timing was almost back to factory spec at high rpm, and power increased to 411 hp (306 kW) at the crankshaft. That's close enough to call this high-mileage engine good as new.
Changing spark plugs every 30,000 miles might be a pain, but on high-performance engines, such maintenance can indeed make a big difference.
Source: Evolve Automotive via YouTube