This guide provides a comprehensive overview of the steps required to perform an E30 M52 Obd2 Swap while retaining OBD2 functionality. This method focuses on simplicity and effectiveness, drawing from real-world experience.
Wiring Harness and ECU
The first step involves the engine wiring harness. Source a harness specific to your M52 engine, ideally included with the engine purchase. This harness needs modification, either through a professional service like Markert Motorworks (http://www.markertmotorworks.com/) or a DIY approach.
Next, acquire the corresponding ECU for your M52 engine. This should also be sourced with the engine. The ECU requires a tune to delete functionalities like the rear O2 sensor, Secondary Air Pump (SAP), EWS, fuel tank sensor, and muffler flap valve. DesertBMW offers a reputable and cost-effective tuning solution. (http://www.r3vlimited.com/board/member.php?u=35673). Alternative tuning options include TRM Tuning (http://www.racersmarket.net/) and Markert Motorworks.
SAP Deletion
With the SAP functionality deleted in the ECU tune, the physical SAP system can be removed. A cost-effective method involves cutting the SAP pipes at the flanges and welding the flanges shut.
Alternatively, pre-fabricated block-off plates are available from various manufacturers like ECS Tuning, Turner Motorsport, and Achilles Motorsports.
Fuel System Considerations
OBD2 M52 engines utilize a remote Fuel Pressure Regulator (FPR) and a running loss valve mounted on the frame rail. While retaining this setup is possible, using an M50 OBD1 fuel rail and FPR, coupled with an M50 intake manifold, offers a slight performance advantage. This necessitates bending the tabs on the M50 fuel rail to accommodate the S52 injector harness. To retain the fuel rail cover, source an early OBD2 fuel rail from an E36 328i or E39 528i.
M50 Intake Manifold Conversion
The M50 intake manifold swap, while not mandatory, is a popular upgrade for its performance benefits. Kits are available from vendors like M50manifold (http://m50manifold.com/), Turner Motorsport, and KO Performance. This conversion simplifies vacuum line routing, especially when deleting the SAP and OBD2 FPR. Remember to cap the unused nipple on the manifold’s vacuum source connector.
For the intake boot, utilize a long OBD1 boot with two holes: one for the Idle Control Valve (ICV) hose and the other for the OBD2 Intake Air Temperature (IAT) sensor. Shaving some plastic around the IAT sensor hole ensures a proper fit. The recommended OBD1 intake boot part number is 13541738757.
Dipstick, Coolant Lines, and Coolant Temp Sensor
If retaining the Crankcase Ventilation (CCV) system, modify an E34 M50 dipstick by welding the CCV drain pipe from the original M52 dipstick onto it.
For coolant lines, utilize the E36 S52 hoses where possible. The top radiator hose often requires no modification. For the bottom radiator hose, NAPA part number NBH 8484 provides a reliable solution. The long E36 S52 hose can be cut and used for the expansion tank and heater core lines. Ensure the heater core lines are correctly connected: back of the head to the bottom heater core port and back of the metal pipe to the top heater core port. Deleting the throttle body coolant lines simplifies the setup; weld the opening on the coolant pipe shut if choosing this route.
An E30 brown top coolant temperature sensor is required for accurate cluster readings. This sensor replaces the throttle body coolant line pipe on the cylinder head. Options include rethreading the sensor, tapping the head, or purchasing a pre-modified sensor from Markert Motorworks.
Transmission, Differential, Driveshaft, and Brake Booster
For transmission options, a ZF transmission bolts directly in, utilizing the stock 318is/325i transmission brace and E36 M3/328i shift linkage. A Getrag 260 requires a custom or aftermarket transmission brace and a modified selector rod.
Differential choices are flexible, but a medium-case LSD, such as a 3.25 LSD, is recommended for durability. Driveshaft options include a 1986-87 325e driveshaft, a 1996-99 M3/328i driveshaft, or a Revshift adapter guibo.
Brake booster options include relocating the stock booster, using an E30 325ix booster, modifying an E21 320i booster, or adapting a Porsche 944 booster. Relocating the stock booster often provides the best pedal feel.
Engine Mounts, Oil Pan, Throttle Cable, Cooling Fan and ECU Mounting
Use E36 aluminum mount arms with either E28 535i/M5 engine mounts or aftermarket 24v mounts.
The M52’s rear sump oil pan requires replacement with an E34 M50 front sump pan, pickup tube, dipstick tube, and oil level sensor. This swap involves removing the original components, cutting the S52 pickup tube bracket, and installing the E34 M50 parts with a new gasket. Secure the oil pump nut with safety wire and Loctite or tack welding.
An E34 M50 throttle cable (Part Number: 35 41 1 160 609) is necessary.
Space constraints necessitate an electric cooling fan. A SPAL 16″ pusher fan (30100401) with corresponding gasket (30130074) and mounting brackets (30130011) is a recommended solution.
Mount the ECU using brackets from an E30 318is, adjusting their position for optimal fitment. For reverse lights, splice a compatible E36 two-prong plug into the E30 wiring harness.
Finally, dropping the engine and transmission in together, using a load leveler, and having sufficient assistance simplifies the installation process. Protect the front support and other vulnerable areas during installation.
