Dave’s 1987 BMW 325is - Old School Cool with a Motorsport Heart

Posted by BC, NP, ND, DD on 10th Mar 2017

Dave’s 1987 BMW 325is - Old School Cool with a Motorsport Heart

Dave’s E30 has seen various configurations over the years including a few different powertrains. His current install, a BMW S54 engine from an E46 M3, required precise engine control along with the use of advanced motorsport functions. For this, the Emtron ECU system was a perfect choice.

We retained every single component of the original engine, including VANOS, electric throttle, idle speed valve and all OEM sensors. We also upgraded the O2 sensors to high performance, wide-range versions that the Emtron system can control with the overall result being a significantly modernized and perfectly tuned powertrain.

In the end there is no comparing the tuning possibilities of the factory ECU to the dynamic control afforded by the Emtron system, and this is without taking Emtron’s numerous motorsport functions into account

Below is a list of calibration functions and strategies employed on this build. Each section has used nearly all of the Emtron”s comprehensive flexibilities:

Speed Density Fuel Modeling:

This uses MAP as the input to the Emtron fuel model with no dependency on problematic factory BMW MAF sensors.

Closed Loop Wide Range Lambda Sensors:

One per bank with comprehensive trimming limits, lockouts, STFT/LTFT functions as only a few of its functions.

Closed Loop Idle Speed Valve Control:

Based on the idle speed target, the ECU actively adapts and adjusts the idle valve position to match the target.

Closed Loop Idle Ignition Control:

On top of the idle air control above, the idle speed engine torque is regulated using high-speed ignition angle adjustments.

The S54 throttles are controlled with an electric motor and drive by wire pedal, which was retrofitted to ensure proper, factory-like operation of the S54 allowing for full drive by wire control with perfect function. The throttle tracks within 0.2% of target regardless of varying mechanical geometry and has full use of 3D tables for closed loop control.

This is critical and allowed us to adjust the drive by wire pedal to make power delivery smooth and not too abrupt, which is a common issue when converting to a mechanical linkage. In fact, the system works in combination with the idle air system to “blend” air delivery precisely into the engine at all times. This mimics - and actually improves upon - the factory method and Emtron’s deep flexibility allows for a perfected configuration given the E30’s much lighter weight than the E46 M3.

Also retained was full VANOS control and perfect closed loop function. VVT targets faster and more accurately than the factory ECU. While the Motorsport VANOS system uses high side outputs to actuate, and requires two outputs per camshaft, these are non-issues since the Emtron can drive low or high side from auxiliary outputs, and the high I/O count of the ECU is unrestrictive with 16 additional outputs on top of any unused fuel and ignition channels.

The Emtron system also has a special solution to properly control the solenoids using the OE strategy.

Closed Loop Windowed Knock Detection:

Employs individual cylinder feedback using short term and long term gain functions (individual cylinder knock count).

Transient Ignition Function:

For acceleration and deceleration and for quick changes to the engine load.

Overrunning Fuel Cut:

With advanced re-application of fuel based on RPM rate of change.

Closed Loop Map Blending:

Using Z-axis and based on various engine parameters such as camshaft position.

Cold Start Function:

With specific warm up strategy for better-than-stock performance.

Hardware Integration:

Integration within the original E30 wiring to ensure all gauges and warning lights (including check engine light) remain fully functional.

Sensor Configuration:

All sensors configured for error detection, with pre-programmed limp modes for major sensors and active substitute value tables (see Engine Protection below).

Rear Axle Speed Input:

This allows the ECU to calculate the drive gear, with features such as

  • Gear-dependant rev limiter
    • Prevents the engine from over-revving in lower gears during hard acceleration by slightly lowering the RPM limiter.
  • Automatic launch control activation
  • Map switching based on gear

Launch Control with Comprehensive Arming/Disarming Function

EFI relay control:

Controls its own power supply like a modern system

  • Allows ECU to stay online to keep the cooling fan on

ECU-Controlled Cooling Fans:

The E30 has no cooling fan control from the factory and is instead a separate mechanical system. Now the ECU can turn the cooling fan on and off and also keep it on with the engine off (with the above EFI relay control).

Fuel Pump Control with Key on Prime

Engine Protection Functions:

In general, every sensor can be configured with its own fault criteria. Each fault can also then trip a limp mode.

  • Oil pressure limit
  • Looks at oil pressure switch (can be configured for pressure sensor) and enables a limp function (engine stall). The configuration is comprehensive and has timers for post-start lockout (will ignore low oil pressure on startup).
  • Engine temp failure mode
  • Emtron can also enable protection functions for oil temperature, fuel pressure, and EGT temperature if enabled.

Comprehensive ECU Data Logging Set:

“Black box” data that can be reviewed at any time with simple log file download.

The result of all of these features is a powertrain that has totally open live mapping, responds like a purpose built race engine when needed, starts cold, runs clean, gets good fuel economy and generally runs as an upgraded version of the factory setup!

This is the true definition of a zero-compromise electronics and engine management solution.

Questions and Answers

Thoughts from the car owner on the build and final state

  • What is the car’s final purpose? Track? A drift car? A clean daily driver? A clean drifting daily driver track car?

The car is constantly evolving and, as with most beloved project cars, it’s impossible to conceive of it ever truly being “finished.”

The car is currently in a state of extreme versatility. I can do whatever I like, whether it’s a track or drift day, a cruise through the mountains, or simply enjoying it as a daily driver for motoring around town in the summer months.

When it is done, it will be more of exactly what it is right now: A clean, refined driver’s car that is just as pleasurable to drive as it is to look at.

  • What are the future project plans?

The future plan is to improve on the drivetrain and chassis, and ultimately maximize everything. Whatever can be upgraded and revised will be. This includes more power, a better braking setup and the right suspension configuration that yields a perfect balance between street and track functions.

  • Pros and cons of choosing the S54

The S54 is a true BMW Motorsport straight six. Before the S54 I had swapped two different M50 based engines into my car. The first was a 2.8L with upgraded camshafts that fell short of my expectations. Next was a fully built high compression S52 with a power level that kept me entertained until I realized how much the engine lacked. A great engine to be sure, but ultimately not a motorsport engine and this distinction became apparent over time.

Even a built S52 lacks the features of a true race engine like the S54. The S52’s oiling system, valve train, VANOS, and overall design are simply not that of the s54 or even the S50B32 found in the European E36 M3. While the engine did make a similar power level, being driven hard uncovered its weaknesses.

I essentially worked my way up to an S54. I needed a naturally aspirated engine that was nearly perfect right out of the box and the only real cons of an S54 would be the delay in torque and requiring a bit more maintenance than other BMW engines of its time.

  • What are the challenges of a new engine in an old car?

The S54 is nearly 15 years newer than my car. It came in a car that weighed more and had a chassis that was very well suited for its power. An e46 is home for an S54, and the factory engine management and electronics all play their part together to ensure sure the engine runs perfectly under all conditions.

The rest of the E46 drivetrain and chassis are paired with the engine. It fits perfectly under the bonnet of an E46. The biggest challenge of the swap into an older BMW is the separation of the factory ECU from the rest of the E46 electronics. It is an intricate system that is dependent upon the other components and this is a constant concern along with the limitations of the factory computer that offers little flexibility and tuning ability.

Another challenge faced during the swap was the rear sump oil pan. E30s came with front sump but there is little room behind the front subframe to accommodate the large dual pickup rear sump oil pan of the S54. Oftentimes, when this swap is performed, the rear sump is lost and changed to a single pickup front sump.

This was a compromise that I was not willing to accept.

  • Solutions

The solution was to develop a package that would retain as much of the factory components as possible and offer perfect drivability under all conditions. An aftermarket engine management package was carefully selected that would retain all factory S54 features, including the drive by wire and variable valve timing, for the flexibility and precise tuning that is critical for a successful swap into an older BMW chassis.

A rear sump oil pan was retained with modifications to both the oil pan and E30 subframe, the transmission was upgraded to a ZF unit from an E36 to better suit the S54 as well as a upgraded rear differential with an improved gear ratio for the new engine. The chassis and suspension was also upgraded to better accommodate the increase in power and weight, coilovers with higher spring rates fortified the suspension along with bigger front brakes, and all factory rubber bushings were changed to polyurethane to ensure there was no loss in the drivetrain.

  • Conclusion

The final result is a classic car that has been improved with modern BMW power and the versatility to excel both on and off the track. This car proves that modern motorsport technology is not just for a purpose-built racecar but can also be applied to allow advanced engine swaps with factory refinement.

There is no longer any need to compromise features that allow for great drivability and fuel economy under normal driving conditions.