How Volkswagen Pioneered The Diesel Compact Car With A Converted Gas Engine

The concept of the diesel commuter car is almost alien to the American automotive market these days. Diesel is a fuel for trucks, while little cars get around with tiny gas engines and electric motors. It’s all the more strange given Americans had the opportunity to get in on the ground floor when Volkswagen invented this very concept five long decades ago.

The 1970s and 1980s were a tumultuous time for the US. As superpowers bickered and bit players fought for scraps of trade and power, one energy crisis raged after another. Gas prices spiked, inflation raged, and households looked to tighten their belts as cars were thrust into the center of the political arena. Fuel had been cheap enough that consumers could simply select the biggest engine they could afford, but now running costs were front of mind for the average American on the street.

Amidst this challenging backdrop, diesel gleamed on the horizon. The humble, greasy fuel held promise of greater efficiency and lower costs, tantalizing every automaker to flirt with bringing it into the mainstream. While International put it in off-roaders and Chevy put it in land yachts, Volkswagen had a better idea. The German automaker was about to invent the compact diesel commuter car.

Gettin’ Gassy With It

These days, diesel cars are widely popular around the world. While there are few on American roads, they’re a big deal in places like Europe, even in the smallest city cars. Every automaker from Peugeot to Porsche will sell you a diesel, with displacements from 1.1 liters and up. However, it wasn’t always thus. Go back 50 years, and diesel cars were obscure everywhere.

In the early 1970s, diesel was almost solely seen as a fuel for trucking and other heavy-duty applications, like tractors or other farm machinery. While a handful of automakers had built some diesel-powered cars for on-road use, they remained an obscure curiosity more than anything else. Gasoline was cheap and made for easy-to-run, high-revving engines. There was little reason to bother with an alternative fuel that generally offered less power, poor cold-starting performance, and was seldom readily available at gas stations for the general public.

The oil crisis of 1973 would come to change all that. A number of major oil producers had banded together under the banner of the Organization of Arab Petroleum Exporting Countries. In October of that year, they announced a total oil embargo against several countries, which instantly skyrocketed oil prices worldwide. The price per barrel quadrupled in just six months, and across the world, drivers were left reeling at the pump. The embargo soon ended, but prices failed to return to previous lows. With gas now an expensive commodity, there was suddenly a huge demand for cars that used as little fuel as possible.

World governments saw disaster, but Volkswagen saw opportunity. The market was seemingly primed for a compact car with an ultra-efficient engine that could offer untold gains to fuel economy. The automaker had already successfully launched the Golf as a replacement for the Beetle. Sold as the Rabbit in the US, it was already finding its place in the market. It combined light weight with great practicality, and was quite the fuel sipper in its existing gasoline guise. All it needed was a decent diesel engine to get those mileage numbers to the moon.

You might think Volkswagen would have started with a clean sheet of paper when it came time to design a diesel engine fit for a small economy car. Instead, engineers elected to start with a pre-existing gasoline engine, an inline-four known as the EA827. It had previously found use in various Audi and Volkswagen applications; it featured in the Rabbit in displacements from 1.3 to 1.8 liters.

As Road & Track reported in 1977, converting the gas engine to diesel operation proved quite the wise move from an economy standpoint. Volkswagen was able to reuse the same crankshaft, connecting rods, flywheel, and bearings, providing great economies of scale. The same basic block was used too, albeit machined differently and with a thicker deck to better handle diesel cylinder pressures. The diesel engine got its own aluminum head, which provided a high compression ratio of 23.5:1. It had the same basic external dimensions as the gas engine head to enable the castings to be machined on the same line. Pistons and wrist pins were upgraded for the extra strain of diesel operation, and VW fitted glow plugs for cold weather starting. With the high number of shared parts, the diesel engine option was just $170 more expensive than the gasoline-powered Rabbit—much cheaper than diesel offerings from some rival automakers.

Both gas and diesel engines were assembled on the same production line. The first diesel version of the EA827 had a displacement of 1.5 liters, and put out a humble 48 horsepower and 58 pound-feet of torque. It wasn’t much, but the 1.5-liter EA827 variants were only putting out 70 hp and 81 pound-feet by comparison. It relied on the contemporary technology of mechanical injection with a distributor injection pump, and used swirl pre-combustion chambers in the head to improve fuel mixing and thus efficiency and performance.

The magic of the diesel Rabbit was readily apparent from the outset. “It’s no secret by now that we think very highly of the Rabbit Diesel,” noted Road & Track in its initial review. “This diesel drives like a car!” The model was naturally praised for its fuel economy—52 mpg highway and 37 mpg city as per the EPA, with Road & Track recording 43 mpg on its own fuel test loop. The low power wasn’t such a problem, either, given the 1978 Rabbit had a curb weight of just 1980 pounds. Road & Track recorded a quarter-mile time of 20.4 seconds and a zero-to-60 mph sprint of 15.8 seconds. Not quick, but the Rabbit Diesel certainly not the slowest new car on the roads back in 1977.

Car & Driver was more reluctant to believe when it road tested the car in its June 1977 issue. “Substituting a Diesel motor for such an outstanding 78-horsepower gasoline engine seemed cruel and unusual punishment—like sending a kid sister to work the coal mines,” read the review. And yet, the converted gas engine won them over all the same. “Right here and now we’d like to confess we judged too soon,” read the review. “The Diesel Rabbit works, it is a success and you don’t have to sacrifice your enthusiasm to like it.” The engine was credited for its easy cold starting and great economy, which weirdly came in at 39.5 mpg city and 35.0 mpg highway during the magazine’s testing. “Speed, however, is at the top of the list in the sacrifice column… you lose fifteen mph in top speed, and a quarter-mile takes almost three seconds longer,” noted the reviewer. ” The other negatives pale by comparison… granted, there is more noise, but it’s not intimidating, and the classic Diesel vices of odor and smoke just don’t apply.”

The contemporary reviews also note a rather amusing problem that diesel faced, which draws a sharp parallel to modern EVs. Back in the 1970s and early 1980s, most gas stations didn’t have diesel pumps, because they were for commuters, not truckers. Diesel cars just weren’t a thing, so there was little infrastructure to support them. As Road & Track explained:

The “worsts” cannot be summed up so neatly, especially because the worst of the worsts isn’t really the fault of the vehicle itself. Undoubtedly, however, the least appreciated feature is the inconvenience of the fuel supply. Although it has a per-tank range of 400-plus miles, there’s always the specter hovering that suggests that, sooner or later, you’re going to need fuel and there isn’t going to be a station. In the first 24,000 miles none of our drivers actually ran out before reaching the next source but there was hardly a driver who wandered beyond the local, familiar area who didn’t experience the “will I find one?” pangs as the needle descended toward the bottom of the gauge.

Diesel For All

The diesel wasn’t just for the Rabbit, either. The Rabbit pickup would also get the diesel option, too. Soon to follow was the very first Volkswagen Jetta, which hit the US market in 1979 for the 1980 model year. It would also appear in everything from the Santana, Polo, Quantum, and Type 2 depending on markets, and the Audi 80 as well.

The initial engine was winning fans, but Volkswagen wasn’t resting on its laurels. By 1980, it was offering an ever-so-slightly larger version of the EA827 diesel, now with a 1.6-liter capacity. It offered more power and torque, too, with a subtle bump up to 53 hp and 72 pound-feet of torque.

Things would get yet more advanced by 1982, with the introduction of the new turbodiesel models. This addition of forced induction saw power boosted by 25%, hitting 68 horsepower and 98 pound-feet of torque. The single turbocharger mounted to the exhaust manifold also had the benefit of reducing some of the classic diesel exhaust noise to more pleasant levels.

Come 1983, Road & Track had plenty of praise to heap upon Volkswagen’s more powerful effort. In a review of the turbodiesel-powered Quantum, it noted the engine was “spry, quick, [and] smooth,” with one driver noting they “almost forgot it is a diesel.” The luxurious sedan was somewhat heavier than a Rabbit at 2660 pounds, but recorded a much healthier zero-to-60 mph sprint of 12.6 seconds nonetheless. The heftier four-door was able to hit great economy figures, too, achieving 41 mpg city and 50 mpg highway according to contemporary EPA figures. Overall, the reviewers were big fans of the upgrade. “With the extra boost available from its turbocharger, the diesel is an economical, enjoyable power source for the Quantum,” noted reviewer Dave Black.

Volkswagen was winning reviewers over because it was doing diesel right. Unlike some other automakers, its diesel engines weren’t just good on fuel. They were also reliable. As a bonus, in many applications, they didn’t suffer as much from a lack of power. Volkswagen was primarily putting its diesels in lightweight compacts, where drivers weren’t suffering so much for losing 10-20 horsepower compared to their gasoline counterparts. Furthermore, it was dropping diesels into what were, fundamentally, well-built compact cars.

By the mid-1980s, many automakers in the US were calling time on their diesel experiments. Toyota had given up trying to get Americans keen on the idea, and GM had killed the Oldsmobile diesel V8 after its own attempt to convert a gas engine had blown up in its face, and many owner’s faces to boot. That alone gave the diesel name a bad rap with consumers, economy be damned. References to diesel models started to dwindle in brochures, and subsequent low sales saw the options culled from lineups in short order.

And yet, somehow, Volkswagen persisted. As the generations changed, the Rabbit became the Golf and the Jetta shifted to a new design, too. VW of America kept diesel options coming, on and off, skipping a few model years here and there as they catered to what was ultimately limited demand.

The “TDI” name would start to gather steam from the mid-1990s onwards, blossoming into popularity in the 2000s with great efficiency and incredibly satisfying performance. Volkswagen became the king of commuter diesels in the US, only for the whole tower of cards to come cascading down when the Dieselgate scandal broke. After being caught cheating on emissions, the German automaker decided to stop selling diesel models in the US once and for all in 2016.

Diesel commuter cars are a well-established market today, with all manner of automakers competing in the space. However, few took to the technology as early as Volkswagen. Even fewer made as many headlines, too, though that’s perhaps something the German automaker regrets. Regardless, it serves as a great example of an automaker picking up a useful technology and sticking with it, to the point that they establish a new category of car in the process. That’s precisely what Volkswagen did when it invented the compact commuter diesel.

Image credits: Volkswagen