The 325 series was updated to the M50TUB25 engine for 1993, featuring the same 2,494 cc displacement but with slightly higher compression and VANOS variable intake cam timing. Horsepower and max torque remained the same, but max torque now came at 4,200 rpm. This engine was in use until the end of the 325 line in North America at the close of the 1995 model year.
328i (1996–1999)
For the 1996 transition to OBD-II in America, BMW selected the M52B28 engine with 2,793 cc of displacement and changed the 325i into the 328i.
Like its predecessor, the M52B28 engine offered four valves per cylinder and DOHC with VANOS. To create the extra displacement, the new engine used the same 84-mm bore as the M50B25 engine, but extended the stroke to 84 mm as well, creating a “square” engine geometry. The 2.8-liter engine produced 190 hp at 5,300 rpm and 210 ft-lbs of torque at 3,950 rpm. This engine was used throughout the E36 328i production run, ending in 1999.
Interestingly, the 2.8-liter engine did not produce any more horsepower than the 2.5-liter, but the increased stroke added 29 ft-lbs of torque, making the 328 a much better performer at lower RPM and the best low-cost candidate for performance upgrades.
The 328i used the longer stroke of the M52 engine to produce almost 30 more ft-lbs of torque than the 325i. The M52 also supported OBD-II engine management; the previous M50 engine did not.
The M3 was BMW’s factory hot rod E36. First released in 1995, the S50 engine produced 2,990 cc of displacement, 240 hp, and 225 ft-lbs of torque. The S52 was released starting in 1996 at 3,152 cc and the same horsepower, but with 240 ft-lbs of torque.
323i (1995–1999)
With the advent of the 328i, BMW did not abandon the 2.5-liter engine but instead updated it to M52 standards, creating the M52B25. This engine was used in the new 323i 1996–1999, violating the convention of putting the displacement in the last two digits of the model code. The 323i engine still displaced 2,494 cc with a bore of 84 mm and stroke of 75 mm, but it was detuned to 168 hp, presumably to provide more of a performance difference with the 328i. Torque remained the same at 181 ft-lbs at 3,950 rpm.
M3 (1995–1999)
For serious performance enthusiasts, the best E36 variant is the M3. Introduced in 1995, the first M3 used the S50 engine based on the M50 line. This engine used the same fundamental cast-iron block and aluminum cylinder head as the M50, but with lighter pistons, upgraded connecting rods, better cams, stiffer valvesprings, an improved exhaust manifold, and an optimized cat-back exhaust system. The new engine featured a square bore and stroke at 86 mm, yielding 2,990 cc of displacement and 240 hp at 6,000 rpm and 225 ft-lbs of torque at 4,250 rpm. The S50 engine can be identified by the “BMW M Power” logo on the plastic engine cover.
But like the rest of the E36 line, major changes were in store for the 1996 model year. The S50 was upgraded to the S52, which remained in place until the end of the E36 line in America in 1999. The S52 is based on the M52 line in the 323i and 328i models. The S52 engine offered an increased displacement of 3,152 cc courtesy of an 86.4-mm bore and 89.6-mm stroke. The combination produced the same 240 hp at 6,000 rpm, but boosted torque to 240 ft-lbs at 3,800 rpm.
The M3 also included upgrades in suspension, brakes, steering, and bodywork, making it the top choice for stock performance. However, M3 models cost more to purchase at all levels of age and condition, and performance enhancements from the already high level of the M3 come at an incrementally greater cost.
S50 and S52 engines read “BMW M POWER” on the valvecovers. S52 engines carry intake-side VANOS where S50 engines do not.
It is worth noting that apart from the valve size and displacement, the M52B28 and M52B25 engines use the same head and block as the S52. M3 cams are a direct replacement on these engines, so some smart work on the valvetrain can bring a lower-cost 328i much closer to M3 engine performance.
Project: Swapping an E46 S54 M3 Engine into an E36 chassis
If you are looking for a lot more power in your E36 chassis, it is possible to swap in an S54B32 engine used 2001–2006 in the E46 series M3 and the 2001–2002 Z3 M and the 2002–2008 Z4 M. Before you set out to achieve this, however, be aware that this is a very difficult and expensive project.
You can tell the difference between an S52 and S54 visually because the S54 engine simply has an “M” logo on a plastic engine cover, whereas the S52 has a plastic cam cover that reads “BMW M POWER.”
Internally, the S54B32 used a larger 87-mm bore that results in 3,246 cc of displacement compared to the S52 series at 3,152 cc and the 1995 S50 at 2,990 cc. Both the S50 and S52 delivered 240 hp in U.S. trim, and 225 or 240 ft-lbs of torque respectively; the S54 boosts output to 333 hp and 262 ft-lbs of torque.
The S54 engine makes its power with the displacement increase and by using a new cam design with high-pressure infinitely variable double VANOS on both the intake and exhaust sides, plus increased compression to 11.5:1 (from 11.3 in the S52). With the E46 engine, you also get the European-style individual throttle bodies for each cylinder. The engine also offers other incremental efficiencies.
The S52 in this 1997 M3 was upgraded to the later S54 found in the E46 M3 series. This new engine makes 333 hp and 262 ft-lbs of torque.
The good news is that the S54 drops right in to the E36 chassis, and it saves you from extensive modifications required for other engine swaps. No modifications are required to the firewall, crossmember, or any other fixed parts of the chassis. You do need the BMW/Siemens MSS54 engine management control system, more commonly called an electronic control unit (ECU), but BMW official nomenclature is DME for “digital motor electronics.” The S54 does not run at all with an S52 or any other stock BMW DME. The engine mounts and pickup points are the same. The oil pan has a different shape in some areas, but these do not impact the crossmember or other features in the engine bay.
Looking at the front of the S54 engine, you can see the double VANOS bulge on both the intake and exhaust sides of the cam cover.
Unlike the E36 series engines, the S54 engine offers an individual throttle body for each cylinder. All of the E36 engines used in North American production offer a single throttle body leading to the intake plenum.
The project is made more difficult and expensive by the extensive modification and adaptation necessary to fit all the ancillary components and connect the older systems to the newer engine. Because the S54 engine uses an entirely different DME, that unit requires its own wiring harness and then an adapter harness as well to connect the chassis, engine, and DME.
The mechanics of this engine swap are comparatively simple, but the list of required additional parts is long. Here’s a rough shopping list to complete the swap:
• Drive-by-wire accelerator pedal
• S54 wiring adapter harness
• S54 transplant wiring harness
• Z3M engine wiring harness
• S54 DME and EWS (German abbreviation for electronic drive-away protection) and key
• S54