I vividly remember reading in Auto Motor und Sport the first time about BMW’s plans to build a diesel. Oh no! How can they sully their reputation for their engines, which invariably get described as being “turbine smooth” in every magazine review? What’s the world coming to?
But then after BMW unleashed their low-rev, high-efficiency eta gas engine, in the form of the 528e in 1982, which contradicted all of their efforts so far in building the ultimate engines, the writing was on the wall. And sure enough, just one year later, the 524td arrived, and it turned out to be, well, the BMW of diesels. It had the highest specific output (47.5 hp/L) of any diesel at the time, it revved cleanly to 5000rpm, it had a top speed of 112mph and clicked off the 0-60 run in 11.0 seconds, and was remarkably quiet to boot.
There was only one problem.
Which is the fact that by the time it arrived, 1983, the diesel boom had peaked and was quickly heading downhill. Gas prices had moderated, and performance was in again, thanks to turbos, fuel injection and better technology. It was all about timing, and BMW’s was a bit late, in the US anyway. But in Europe, the diesel boom was really just getting under way, so it’s not like its investment in a new engine plant in the Steyr area of Austria was for naught. Within a couple of decades, the majority of BMWs in Europe would be diesel powered.
As to the actual methods to achieve such a remarkable level of performance and efficiency, BMW started with its well proven M20 smaller six family, but kept the bore down to 80mm in order to provide full water jackets to each cylinder. The cylinder head was of course totally new, still a SOHC, but the hemi head configuration does not work in a diesel given the need for a very small combustion chamber with its 22:1 compression ratio. A Garrett turbo provides up to 11.6 psi of boost, resulting in 114 hp @ 4800 rpm, and 155 lb.ft. @ 2400 rpm.
Interestingly, the 528e’s eta gas six had its power peak at a significantly lower 4250 rpm, and made 121 hp. Somewhat surprisingly, the 528e made more torque, at 177 lb.ft. Diesels do inherently make less torque, but that’s easily compensated by boost. But apparently the boost wasn’t yet enough at this time to make up the difference. That would change over time, as induction pressures grew ever higher in the late ’90s and 00’s, resulting in phenomenal torque ratings.
But at the time, the 528e and 524td had quite similar results, but different approaches. Performance was also roughly similar. But the 528e vastly outsold the 542td, in the US.
That 0-60 time of 11.0 seconds I quoted earlier came from R&T’s test, but that was a manual. Undoubtedly the automatic as installed in this very nicely kept survivor would be a bit slower.
Such a clean example, although there does seem to be a bit of an issue with the seat back card. And that seat must be just about all the way pushed forward, as the leg room in these E28 sedans was anything but stellar.
BMW was in a very conservative stage at the time, in terms of its styling, which really was getting old in the case of the 5 series, as well as the 3 series. The E28, which arrived in 1981, was really nothing more than a refreshed E12, which dated back to 1972. And the E28 soldiered on until 1987, by which time it was rather embarrassingly outdated, especially in comparison to the Mercedes W124.
BMW was willing to share its new diesel, and did so most notably with Lincoln, where both the Mark VII and the Fox-based Continental could be had with the little diesel six in 1984 and 1985. Take rates were very low.
And the Vixen 21 compact motor home also used the same engine out back, making for a very efficient rig.
The 524td may have had a modest impact in the US, but it signaled the beginning of an era of ever-more refined and powerful diesel engines. That alone makes it a pioneer.