This is a rare BMW Hartge 323i RS 2.3 liter M20 inline-six cylinder engine, thanks to the Hartge tuning process it’s now considerably more powerful than the stock BMW 323i from the era.
This engine is being sold as a package deal with a matching 5-speed manual gearbox and a slew of other parts – making it potentially ideal for a 323i owner who wants to give their car a significant power transplant.
Hartge was founded in 1971 in Merzig, Germany, by Herbert Hartge (shown above), a racing driver whose family had roots in the world of BMW. The company relocated to nearby Beckingen in 1974, where it would remain headquartered for the next 45 years. Image courtesy of Hartge.
History Speedrun: Hartge
Hartge was founded in 1971 in Merzig, Germany, by Herbert Hartge, a racing driver whose family had roots in the world of BMW. The company relocated to nearby Beckingen in 1974, where it would remain headquartered for the next 45 years.
From the very beginning, Hartge’s philosophy was distinctive (and actually fairly simple) – rather than pushing a small engine beyond its limits with forced induction or exotic internals, the company transplanted larger, more powerful BMW engines into smaller, lighter cars. The signature move was fitting engines from the 5 Series and 6 Series into the compact 3 Series, creating cars that combined the agility of a smaller, lightweight sedan with the brute force of a larger engine.
Hartge’s earliest work was on the BMW E21, the first-generation 3 Series. The 323i RS had a tuned 2.3 liter six producing 180 bhp, while the more ambitious 335i shoehorned the 3.5 liter M30 engine from the 635CSi into the E21’s smaller engine bay, delivering 240 bhp, a 0 to 100 kph time of 6.4 seconds, and a top speed of 149 mph. This big-engine-in-a-small-car formula would largely define the company for the rest of its existence.
When the E30 3 Series arrived in 1982, Hartge’s model range expanded rapidly. The H23, based on the 323i, used a reworked cylinder head, forged pistons, and a raised 10:1 compression ratio to produce 170 bhp. The H26 name covered several different E30-based conversions, some earlier versions were based on the 323i with increased displacement, while later 325i-based cars produced 190 bhp from a tuned 2.5 liter M20 with a hotter cam, a reworked intake manifold, and a remapped ECU.
The H27 pushed displacement to 2.7 liters and output to approximately 205 bhp. It’s worth noting here that these weren’t crude engine swaps, they were comprehensive conversions that included suspension upgrades, limited-slip differentials, Bilstein dampers, bespoke body kits, Momo steering wheels, and Hartge-branded instrumentation.
Unlike high-end rival Alpina, Hartge was willing to sell body kits and engine packages separately, this made their parts more accessible to a wider range of enthusiasts and helped establish them as a more approachable BMW tuning house.
In 1985, the Kraftfahrt-Bundesamt (KBA), Germany’s Federal Motor Transport Authority, granted Hartge official manufacturer status – this is an extraordinarily rare distinction for an independent tuner. From that point forward, every Hartge-built car received a Hartge Motorsport VIN plate in place of the original BMW plate. Legally, these were no longer modified BMWs, they were now Hartges.
Hartge’s earliest work was on the BMW E21, the first-generation 3 Series. The 323i RS had a tuned 2.3 liter six producing 180 bhp, while the more ambitious 335i shoehorned the 3.5 liter M30 engine from the 635CSi into the E21’s smaller engine bay, delivering 240 bhp. Image courtesy of Hartge.
Perhaps the pinnacle of Hartge’s E30 work was the H35-24, sometimes referred to as the H35-24s in its E30 M3-based form, a car of almost mythical rarity. Built on the E30 M3 chassis, it used the M88/3 24-valve inline-six, an engine descended from the BMW M1 supercar, tuned from its stock 286 bhp to a fire-breathing 330 bhp.
Only six are believed to have been built at the Beckingen factory, each one a bespoke project requiring extensive re-engineering of the engine bay, relocation of ancillaries, and the addition of a secondary fuel tank. On the larger E28 5 Series platform, the model variously referred to as the H5S or H5SP used M88 individual throttle bodies to produce 254 bhp, with a production run of 46 cars built between 1985 and 1988.
One of Hartge’s most memorable models debuted in 2001 with the H50 V8, an E46 3 Series fitted with the S62 4.9 liter V8 from the E39 M5. The conversion was an engineering tour de force – the V8 was obviously quite a bit wider than the original inline-six, requiring the steering column to be routed through the left exhaust header and the oil circulation to pass through the left engine mount. The car is said to have produced close to 400 bhp in standard tune, with some sources citing up to 444 bhp.
Car and Driver magazine recorded a 0 – 60 mph time of 4.5 seconds. Production figures were never officially published, but the H50 is widely believed to number no more than 20 examples. The car’s quality was so convincing that a rival tuner, Racing Dynamics, reportedly disguised a leased H50 and controversially presented it as their own product at the Essen Motor Show. A later supercharged variant, the H50 Compressor, produced 550 bhp and a top speed of 200 mph verified at the Nardo test circuit.
By the 2010s, Hartge was facing a much harsher market for high-end independent conversions. The company ultimately entered liquidation in mid-2019 and was later removed from the German commercial register, closing out 48 years of operations. Though the company is now gone, its cars remain among the most sought-after modified BMWs ever built, and the name Hartge is spoken of with the same reverence as Alpina and M in BMW circles.
The Hartge 323i RS M20 Engine Shown Here
This is a Hartge-modified 2.3 liter BMW M20 engine that’s being sold with a parts package, the engine was originally built for a 323i RS. The seller bought the engine in 2021 with a bent valve and then undertook a comprehensive rebuild that stretched from the fall of 2025 into early 2026.
Machine work included honing the cylinders while keeping the first bore, allowing the original pistons to be reused with replacement rings. The valves, timing belt and tensioner, water pump, head bolts, gaskets, seals, and bearings were all replaced during the rebuild, with the bearings receiving a fresh coating. Photos documenting the rebuild are included in the gallery below.
This engine is being sold as a package with a matching 5-speed manual transmission, along with a Euro-spec E21 front subframe fitted with larger strut tubes, larger vented disc brake rotors, calipers, pads, front wheel hubs, brake rotor dust shields, and hoses.
It also comes with a radiator, fuel delivery system, exhaust headers, wiring harness, and some additional parts round, making this a fairly comprehensive drivetrain and front-end conversion kit rather than just an engine sale. It would likely be well-suited to a BMW 323i owner who wants to perform their own Hartge conversion.
The engine comes with Hartge dynamometer sheets, installation instructions, and TÜV certification documents, with the Hartge paperwork rating the setup at 180 PS (177 bhp). That figure does line up neatly with the known output of the Hartge 323i RS engine.
The engine comes with Hartge dynamometer sheets, installation instructions, and TÜV certification documents, with the Hartge paperwork rating the setup at 180 PS (177 bhp). That figure does line up neatly with the known output of the Hartge 323i RS engine.
The assembled engine is now mounted to a pallet for shipping, and it’s being offered for sale out of Sacramento, California on Bring a Trailer here.
Images courtesy of Bring a Trailer
Articles that Ben Branch has written have been covered on CNN, Popular Mechanics, Smithsonian Magazine, Road & Track Magazine, the official Pinterest blog, the official eBay Motors blog, BuzzFeed, Autoweek Magazine, Wired Magazine, Autoblog, Gear Patrol, Jalopnik, The Verge, and many more.
Silodrome was founded by Ben back in 2010, in the years since the site has grown to become a world leader in the alternative and vintage motoring sector, with well over a million monthly readers from around the world and many hundreds of thousands of followers on social media.
