You can bet on an old-versus-new debate every time a new-gen model lands in the showrooms. You’ll have your supporters of the old talking about tradition and character or how the previous car had an analog feel instead of the new car’s digitized detachment. Supporters of the new model will talk about technology, microprocessors, advanced materials and the need to keep progressing or go the way of the Neanderthal.

The two Z4s featured here could not be more different, so this isn’t so much a comparison as it is an example of how two siblings from the same branch of the family tree have gone on divergent evolutionary paths, with the newer car of the two still evolving.

Unlike some cars that start out as modest tuning projects and then snowball out of control, the owner of the first-gen E85 knew from the beginning he was going to build something specifically for the track. Having owned BMWs since the mid-’70s, including two M5s and an M6, the platform would either be based on a BMW or a Porsche. The car was built over the course of two winters by Fall-Line Motorsports in Buffalo Grove, Illinois, near Chicago. Fall-Line currently runs an M3 in the Grand-Am Koni Challenge series and build racecars for other people, so this E85 build was well within their window. Tim Stratton, the project’s point man, said the E85 chassis had similarities to both the E36 and E46 M3s he’s worked on.

Fall-Line started by gutting the interior and welding in a six-point rollcage. The stock seats were swapped with carbon Cobra race seats and a Momo steering wheel sits on a quick-release hub. Just behind the wheel there’s an AiM Sports MXL dash/data acquisition logger.

For obvious reasons, with its massive flared fenders and exposed carbon weave, the exterior gets most of the attention. The lines of the kit are similar to but not exactly the same as a Flossmann body kit from Germany. Fall-Line commissioned Prototype Composites out of Glendale, Wisconsin, to fabricate a hood, roof and rear decklid and also create different mounting points for the Flossmann kit so they’d fit better. They also left the carbon/Kevlar-reinforced panels naked to show off the weave. A Crawford Designs Grand Am-spec rear wing is mounted via custom-made wind mounts also by Prototype Composites. As it sits now, Fall-Line managed to shave roughly 400 pounds off the stock car (2,850 vs. 3,240).

The first thing you notice after you’ve climbed over the cage and into the Cobra seat is just how light the doors are. The panels can’t weigh more than a pound or two, and most of the weight of the doors comes from the metal frame. Aligning perfectly, the doors close with a secure click.

The engine fires up immediately and gets the interior vibrating to its rhythms. The characteristic metallic zing of a stock 3.2-liter straight six is replaced with a deeper rumble. It breathes through a CSL airbox and Dinan throttle bodies and cams. Spark, air and fuel are controlled by a Motec engine management system. And it exhales through a Supersprint stepped header and X-pipe, followed by a custom-built rear section utilizing Borla mufflers. A Fall-Line underdrive pulley kit helps the engine spin more freely. On a Mustang dyno, the engine made 351 whp at 8000 rpm and 255 lb-ft of wheel torque at 6600 rpm, and the rev limit was raised to 8300 rpm.

The Sachs clutch is racecar stiff but it engages with enough progression to pull away cleanly. As it gathers speed, the gummy Yokohama slicks (280/650 front, 280/680 rear) pelt the underbody with pebbles and marbles, making it sound like the car’s being sprayed by a barrage of small-caliber rounds. Onto clean tarmac and the sound of gears being meshed and the lightly muffled exhaust takes over. It’s sensory overload, and these are just the warm-up laps.

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