A Four-Cylinder E30 Comparison

One of the defining elements of nearly every BMW from the 1980s is the legendary inline six-cylinder engine (at least for the U.S. market). The beauty of an inline six is that it is perfectly balanced; it has enough cylinders lined up along the same axis that it is inherently smooth—buttery smooth, in the case of our favorite engine-builder from Bavaria. Smooth is good when it comes to engines, for it means that they are less likely to destroy themselves, and that fewer bits are required in order to prevent such a possibility.

There were, however, some very notable exceptions to the 1980s BMW inline six. These, of course, were the iconic E30 M3 and its non-M sibling, the E30 318is. I just happened to have an example of each at my disposal recently, so a brief comparison was in order.

Four-cylinder E30s; the 318is and M3.

When viewed from a comparative perspective—and with thirty years of hindsight—the original M3 and 318is are a paradox; they are strikingly similar, yet vastly different. They are both four-cylinder versions of the E30-generation 3 Series with a focus on performance. Neither was a resounding sales success compared to the middle-of-the-market 325i, perhaps due to their original price tags of $35,900 for the M3 and $21,500 for the 318iS in 1991 dollars. This is colossal gap—but the differences don’t stop there.

The M3 was the E30 with the volume turned up to eleven. It was born for the express purpose of Group A racing, and it had all of the associated race-car kit: an aggressive front air dam, flared fenders, and a shallow, raked rear window that improved drag and channeled air onto a raised trunk lid and spoiler.

The 318is was the entry-level economy E30, built with a minimalist focus on lightness, which, thanks to a paltry option list, gave it a 300-pound weight advantage over the M3 (2,600 versus 2,900 pounds).

The M3’s legendary S14 engine.

At the M3’s heart was the 2.3-liter S14B23 engine, a combination of the M10 block and a shortened version of the M88 head—both tracing their origins back to the 1970s and prior. The S14 was a proper M engine, featuring individual throttle bodies, machined intake and exhaust ports, extra crankshaft counterweights, and a redline of 7,250 rpm. It was good for 195 horsepower, which propelled the M3 to 60 miles an hour from a standstill in 6.9 seconds. Besides its exclusive sheetmetal, the M3 also had its own gearbox, suspension, brakes, and wheels over the regular E30. Over its short racing career, the M3 dominated virtually every form of Group A motorsport.

The M42 engine of the 318is was the most advanced to find its way into the E30 platform.

Powering the 1991-model-year-only 318is was the M42B18 engine, a 1.8-liter four-cylinder—and the most evolved engine to find its way into the E30. It featured some significant technological improvements over its M10 predecessor, such as 10:1 compression (as opposed to 10.5:1 in the racing-bred S14), an aluminum head with dual overhead cams, lightened internals, a stainless-steel exhaust manifold, and coil-pack ignition. It was also rev-happy, peaking at 6,500 rpm, a few hundred shy of the S14’s max rotation, but producing roughly 60 horses fewer at 138 horsepower. In the weight-conscious 318is, this was still good enough for 60 mph in 8.7 seconds. It shared similar spring rates and the same limited-slip 4:10 final-drive ratio as the M3, but the mechanical similarities end there.

Nearly three decades on, the 318is and M3 are still a paradox of being so similar, yet so different.

Nearly three decades later, the E30 M3 and 318is paradox continues. M3 values have appreciated to a point that has only widened the price gap over the 318is despite the latter’s recent tick upward. To the general public, the E30 is almost unanimously recognizable as an iconic BMW, but even the most novice enthusiast can spot the difference between an M3 and a regular E30. That is because it is special!

Behind the wheel of the M3, you truly do feel special; there is no mistaking that you are driving a BMW Motorsport icon. You channel your inner mustached Touring Car racer as you rev that S14 to redline with your hair on fire. Ripping through first, second, and third gears with a few carved apexes mixed in, and you have become a legend in the flesh—that is, until you look in the rearview mirror and see an angry woman in a Subaru Outback who is clearly late to her yoga class thanks to your slow old car.

And therein lie both the joy and the pitfall of the M3; you have to rev the snot out of it to extract its performance.

An M3 always makes its driver feel like a legend (I once drove this example from Washington D.C. to Colorado).

The 318is is no different, except for that you can make that woman late to yoga for a fraction of the price of the M3—and you won’t care as much when she peppers your car with rock chips as she angrily passes on the double yellow (Namaste). The M42 engine is just as rev-happy as the S14, but despite having less top-end grunt, it feels smoother and more refined. The suspension feels similarly sporty, thanks to similar spring rates and a stiffer front sway bar than a regular 318i. The sport front seats and other interior bits also seem nearly identical—because they are.

The M3 will give you more options like cruise control, an overhead check panel, a thirteen-button computer, a special headliner, and a bolstered rear seat for two. But you gain something notable in the absence of those items in the 318iS, and that is lightness. It’s only a few hundred pounds lighter, but in a 2,600-pound car, that is a discernible difference, and it inspires a confidence that can only come from favorable physics (and maybe a less-precious vehicle should things go wrong). The result is one of the most undiluted BMW driving experiences possible, a plus for the 318is.

The 318iS is the lightest and most undiluted E30 of them all.

What makes the M3 and the 318iS so wonderful is that they are both E30s—the E30 is called God’s Chariot for a reason. The M3 is no doubt the better of the duo; it is an important piece of BMW history and has a prominence that just can’t be replaced. It is the original M3, and there is only one original.

But when you consider factors like price and preciousness, not to mention parts cost and availability, the 318is makes a compelling argument, even though going rates for clean examples are on the rise, just like the rest of the E30 market. It is the lightest and most advanced E30 of them all, and certainly one of the most fun to drive—and after all, isn’t that why we drive E30s?—Alex McCulloch

[Photos courtesy Alex McCulloch]

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