24 Hours Of LeMons: Junkyard Supercharger Somehow Improves BMW Reliability

The judges at the 24 Hours of LeMons has traditionally looked down on cars that push the “easy” button among those available for $500. Typically, this has included Mazda Miatas (Spec Miata take-offs are a dime a dozen), many Hondas, Porsche 944s (despite their powderkeg nature), and BMW 3-Series cars, of course. They are frequently treated derisively not so much to give the teams themselves a hard time as much as to say, “If you’d brought a Sterling 827, you wouldn’t be getting grilled during BS Inspections.” However, some BMWs like the Knights of the Roundel supercharged E30 have won over the anti-bimmer bias.

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The Knights have been around the East Coast for a few years and their 3-Series from the 1980s has in the past been a relatively unremarkable example. The car isn’t super lowered or on Kony adjustable dampers or anything egregious. Similarly, under the hood has traditionally been the standard M20 straight-six engine that left Bavaria in a similar car.

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However, they have entertained the LeMons Supreme Court, in some small way, with their “Brave Sir Robin” theme from Monty Python and the Quest for the Holy Grail. LeMons judges aren’t always the most savvy on modern pop-culture, but classic geek culture usually rings true with the LeMons Supreme Court.

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This particular E30 has climbed through the standings over their races to be a halfway decent competitor, cracking the Top 10 on more than one occasion. The Knights, however, wanted to win and they figured that to do that, they’d need to go faster. In late 2015, they emailed Judge Phil to ask for a residual value on their heap with the intention of using any money left in their budget after Phil’s assessment to add forced induction.

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Phil was indeed hip to the idea of more horsepower and less reliability on the stock M20, something that multiple race winners Bucksnort Racing had briefly attempted on their E30 with a junkyard supercharger. That resulted in near-catastrophic fire on a Test Day that prompted them to abandon the idea immediately. With a precedent like that, Phil figured that the supercharger belt was just enough rope with which to hang Brave Sir Robin and gave them the budgetary leeway to blow up their blown M20 faster, provided that whatever turbo or supercharger setup they used poked conspicuously out of the hood.

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The Knights’ original plan had been a twin-turbo setup accomplished by simply flipping the stock exhaust manifold upside down and bolting turbos on each manifold’s three-cylinder banks. However, when an Eaton M90 supercharger from a Buick popped up locally on CraigsList for $50, the Knights knew they’d hit paydirt. Naturally, the first move was to cut into the stock intake manifold because most LeMons teams’ first instinct to any problem is to grab the reciprocating saw.

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Guided by the team’s “old guy,” they then used a mill to shape the rest of the intake manifold. They capped the manifold with a flat piece of aluminum to form the intake plenum onto which the supercharger would sit.

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Fits like a glove!

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From there, it was a simple matter of grafting on a five-groove air-conditioner pulley from a later (E36) BMW 3-Series, adding Ford Mustang fuel injectors to give enough fuel at high RPM, and—after some free dyno tuning on an available dyno—throwing in the mass air flow (MAF) sensor from a bigger-displacement 3.5-liter BMW straight six engine. We’re sure it wasn’t a nightmare at all and when they were “done” (a relative term for all LeMons cars), they were pushing between five and six pounds of boost into the 2.5-liter engine.

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Most importantly, the blower stuck through the hood, as requested by Judge Phil.

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Slightly confident that the whole contraption wouldn’t toss connecting rods halfway back to Bavaria, the team loaded up last May for New Jersey Motorsports Park and the Real Hoopties of New Jersey race. Since its previous run, the team had replaced the engine, transmission, and differential all in one go, which left them feeling a bit nervous about the longevity of everything else. Upon unloading Thursday night, the team promptly snapped a headbolt on the engine, requiring a late night to swap a new head gasket and bolts on.

 

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During race weekend, the team strictly imposed a 5000 RPM redline for this race to make sure they weren’t taxing the blower or engine too much (Factory redline is 6500 RPM). Even with short-shifting, they noticed the car was already quicker on Test Day. But would it last?

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As it turned out, the BMW engine ran strong all weekend and just about everything except the supercharger failed. The Test Day found their newly installed transmission leaking substantially, so the team then spent most of Friday throwing a backup in it. Just for kicks, the car’s radiator developed a leak, which the team only noticed minutes before Saturday’s green flag. A quick thrash with a replacement got them back on the track in time to see the green flag and run all day Saturday without issue.

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On Sunday, the car felt funny to the regular drivers and the team eventually figured out that something was hugely wrong with the differential, which they’d later discover had mostly welded itself together. They loaded E30 on the trailer oddly enough, with confidence in the supercharger setup.

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With some bugs worked out, they returned to Thompson Speedway Motorsports Park in Connecticut on a muggy August weekend to finish a tepid 63rd of 105 cars. After that came a much more successful weekend at Halloween Hooptiefest at New Hampshire Motor Speedway in October. At that race, the supercharged E30 completed 448 laps to finish 21st of 117 entries.

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That leaves a high ceiling and while the car is still not in the quickest 25 cars at a given race, the Knights of the Roundel may just have proven the naysayers—the LeMons Supreme Court, mostly—wrong by keeping it all together so far.

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