Talk:BMW M51

Horsepower units
Hi. Thanks for your suggestion a while back regarding the horsepower units for this article. Here's a mock-up of how I think the specs table would be like, using natural numbers and the default output unit from the {convert} template. Could you please let me know if it looks ok to you? Regards, MrsSnoozyTurtle


 * The SI figures here are "correct"; (id est these are the official 80/1269/EEC-compliant figures for all iterations of the M51 engine). Best regards, --Johannes (Talk) (Contribs) (Articles) 16:42, 5 September 2021 (UTC)


 * Many thanks for checking this, I will update the article now. Regards, MrsSnoozyTurtle 22:23, 5 September 2021 (UTC)
 * Alas, these do not match the sources for these cars. The X25DT produces 130PS for instance.  Mr.choppers &#124;   ✎  03:18, 29 September 2021 (UTC)



The 85 kW version of the BMW M51 engine has no intercooler. It was offered in the 525td model which was available both for the E34 and E39. The E39 525td was neither available as an estate, nor available with a hydrodynamic trilock torque converter or automatic planetary gearbox. All 525td cars were saloons with a five-speed manual gearbox. According to 80/1269/EEC, the M51 is rated 85 kW at 4800/min, and produces 230 N·m at 1900/min. Its epsilon figure is, despite the turbocharger, 22 (because it is swirl-chamber injected). According to 80/1268/EEC, an E39 with this engine has an underwhelming fuel consumption of 6 l/100 km extra urban (which I believe is unrealistic; the testing procedure forbade to shift reasonably). The E34 525td was available both as a saloon and as an estate; both body styles were available with either a five-speed manual gearbox or a hydrodynamic trilock torque coverter mated to a four-speed automatic planetary gearbox. The five-speed autobox was only available for the E34 525tds. In the E34, the 525td engine is rated 85 kW at 4800/min, and produces 222 N·m of torque at 1900/min (both figures according to the DIN 70020 standard). Note the difference in torque; I don't know for sure, but I believe that this is because of the different standards. I doubt that BMW has significantly changed the M51 engine for the E39. Another possible explanation could be a different ECU programming, or a different turbocharger. As far as I'm concerned, all M51 engines were fitted with a two-way catalyst converter. See the manuals and brochures: page 212; page 37. Best regards, --Johannes (Talk) (Contribs) (Articles) 16:06, 29 September 2021 (UTC)


 * Hi Johannes. Thanks for all this info. I have added these references to the article, and restored the table formatting to as per the above discussion. Regards, MrsSnoozyTurtle 07:36, 30 September 2021 (UTC)
 * And as per BMW themselves, and the majority of all other sources, the output of the non-intercooled engine is 115PS/85kW. The X25DT produces 130PS/96kW according to Opel as well as Vauxhall, see page 57 here.  Mr.choppers &#124;   ✎  00:23, 1 October 2021 (UTC)

The engine is rated 85 kW according to 80/1269/EEC and the DIN 70020-6 standard. Unfortunately, this is "approximately" 115.57 PS. Car manufacturers can choose whether they use 115 or 116 PS. They could also go with something like 114 or 117 PS – this figure is rather marketing than 100 % precise. Sometimes I wish we had ГОСТ – these figures don't necessarily have to be natural numbers… best regards, --Johannes (Talk) (Contribs) (Articles) 08:48, 1 October 2021 (UTC)