February 02 2007   Story: Bryan Joslin

Until now, most of our attention has focused on making our E30 a more solid and reliable project platform. So far we've addressed oil leaks, loose oil pan bolts, worn brakes, a cracked dashboard and broken foglights. We're also underway with a total interior overhaul. But let's face it; what really gets us excited is the addition of power.

After a six-year absence, the 318 returned to the BMW line-up in 1991. But instead of the 101-horsepower, 8-valve M10 engine that powered 1984-85 318 models, BMW dropped in the 16-valve M42 engine with 136 horsepower. At 127 lb-ft, it wasn't exactly a torque factory; instead this high-revving mill relied on revolutions to make its power. Understandably, the 318is was offered only with a manual transmission and low 4.10:1 rear end. Anyone who’s driven an M42-equipped Bimmer can tell you it's more about keeping momentum than winning the holeshot.

Performance upgrades for the M42 are few and precious. The only way to get real power out of this engine is with forced induction, adding either a turbo or supercharger. It's a pricey option to say the least, and certainly not the right choice for a budget project like ours. Instead, we decided to stick with natural aspiration and make breathing and fueling improvements with off-the-shelf hardware. Our plan focuses on three main areas: front side breathing, back side breathing, and ECU tuning.

BMP Design set us up with their intake system and a SuperSprint exhaust. The intake is a simple kit consisting of a K&N cone filter, a proprietary mounting bracket and a MAF adapter plate. Installation of this setup takes only 15 minutes or so and reuses factory hardware for mounting.

SuperSprint has offered a cat-back exhaust system for the M42 for more than 15 years, but until recently it was offered only as a single-piece design. Shipping the old one-piece system was expensive- in fact, at around $150, shipping was a deal-killer for many would-be buyers. The new two-piece setup is not only easier to ship, but it's also a bit easier on the installer. Incredibly, the slip-joint fitment of the two pipes does without a conventional exhaust clamp; instead, a pair of built-in threaded closures draws the pipes together for a snug (and very clean) fitment.

Numerous companies developed software for the M42; we went with Racing Dynamics for our chip upgrade. Swapping out the performance chip in these old cars is a blessedly simply operation, as the ECU itself is readily accessible in the glove box, and the EPROM is simply pressed into its socket on the circuit board. No soldering, no laptops, no cables- just good old-fashioned hand tools make this surgery elementary.

To help us determine what each of these upgrades was doing for the car, we returned to GRD Performance in Naperville and bolted the E30 to their Dynapak dynometer. Unlike the factory's stated horsepower, which is measured at the flywheel, the figures generated by the Dynapak represent the actual torque being delivered to the hub-mounted equipment. They don't take into account the frictional and rotational driveline losses between the flywheel and the rear wheels, which can range from around 15 to upwards of 20 percent.

Even though we had run this same car on the same equipment about a year ago, we needed to establish a new baseline on which to judge the relative increases in performance offered by the upgrades. Therefore, our first dyno run was with none of the performance enhancements installed. This revealed a peak output of 100 horsepower using 91-octane gasoline. When we first dynoed the car in December of 2005, it produced a peak of 104.7 horsepower, but was running 93-octance fuel. The loss of roughly 5 horsepower might partially be due to differences in fuel, but could also be affected by temperature and other atmospheric differences between the two runs.

For the second run on the dyno, we swapped out the factory airbox with BMP's intake kit. The effect of cold air intake systems has been debated to death over the years, but in this case there was a tangible difference. Some vehicles respond better to these systems than others, and of course under-hood heat also plays a factor in their effectiveness. Regardless of power gains, they almost always inject a bit of soul into otherwise boring-sounding cars.

Our car remained connected to the dyno while the swap was performed, and within 20 minutes of the last pull we were off again. A series of four pulls resulted in a peak output of right at 105 horsepower with just the filter, a gain of 5 horses over the new baseline, a 5% increase. Even more importantly, the huge torque valley at 3000 rpm got significantly shallower with the open filter. And of course the car now possesses a more aggressive roar on acceleration.

The next step was to pump some testosterone into the engine ECU. This was once again performed with the car still connected to the dyno rig. Yet again, barely 20 minutes lapsed between pulls. Four more pulls were done with our car sporting the Racing Dynamics chip and BMP intake system. The results this time were even more impressive, as one would expect. Peak power was up to around 112, with more power being made everywhere under the curve. The chip also took torque from104 lb-ft with just the filter to 109.

The final stage of our testing was changing out the exhaust system. The dynos were disconnected from the hubs so the car could be lifted for this work. Thankfully, the 318's cat-back section mounts entirely under the rear axle and subframe. Removal was as simple as removing the two bolts that connect the rear section at the catalytic converter and unbolting the rear muffler mounting straps. The old exhaust just dropped out of place from there. Fitting the new one was essentially the reverse, and the whole procedure took just a half hour.

Back on the dyno, we let the new exhaust settle in a little before attempting another pull. Several successive attempts netted a peak figure of 114 horsepower at 5827 rpm, with maximum torque of 109.5 lb-ft at 4689 rpm.

In the course of our day, we had added nearly 15 horsepower with three simple upgrades. While that may seem modest on the surface, the character of the car is noticeably improved. It is not only considerably more athletic in the mid-range (from about 3400 rpm up), but also decidedly more eager to rev to its redline. Part-throttle response is much sharper as well.

A point that can't be overlooked is the fact that the intake and exhaust upgrades not only delivered measurable performance gains, they also improved the feel-good factor of driving the little 318. The engine no longer sounds like a wimpy little appliance; instead, it now snarls a bit from under the hood when the gas pedal is dropped. Likewise, the heartless "putt-putt" emanating from a rusty steel pipe has been replaced with a mellow baritone purr, topped off with just a hint of rasp when worked hard, all flowing through a beautiful chrome oval outlet. These improvements may be mostly intangible, but they allow the classic Bimmer to hold its head high on the street.

Once the Chicago winter surrenders its cold grip, we'll mount some serious rubber in search of a different type of grip so we can get some 0-60, 0-100 and quarter-mile times with our new DriftBox performance meter. In the meantime, we're making some real progress with the interior remodel and will have some results to show in the near future.