STROM B46 / B48 Motec DI Engine Management FAQ

Why the B48?

The B48 and B58 family of engines are proving to be some of the best engines ever created and manufactured at volume. We selected the B48 as a base engine to use in class limited racing such as the NASA ST and GTS, WRL, or BMW Club displacement based classes (DM and CM). Our goal was to replace the BMW S54 with a powerful, reliable and inexpensive powerplant that most importantly did not need to be changed internally to be a great race motor.

The upfront cost of the systems to support the engine (electronics, cooling, wiring) might be considered expensive but when you are able to get a common replacement engine from a junkyard for less than $4k, not have to open it up at all and can make over 400whp reliable it becomes a long term money saver.

What kits are available?

We intend to have well sorted kits in the following formats and then you can buy the lowest level kit you need and add on individual parts as desired:

The “Dev Kit” - ECU and software with a wiring diagram and some documentation. You do most of the sorting out of the install yourself (wiring, plumbing, display integration) or can buy other parts from us a la Carte.
The Base Kit - The ECU hardware, various parts and software, no display or interior bits. Meant to fit in any car that you can stuff a B48 into.
The Integrated Kit - The base kit with one ECUMaster ADU7 or Motec C127 Display. You are still handling the chassis power system.
The B48 Super Kit - The same basic kit as our B46 but not for a E46 chassis. Two displays and every part we can think of that will work in any chassis.
The B46 Super Kit (B48 in an E46 with everything).

Can I buy the parts individually if a kit doesn’t fit my needs?

Yes - the kits are meant to align with blocks of already completed “plug and play” programming and also to allow people to see what a complete setup could look like. You can buy nearly everything individually.

So is it really that good?

We initially started with the B48B engine (2017–2020 330i and similar) and then switched to the updated and improved B48D (2020+ 330i). This engine has completely exceeded our expectations. With only a larger turbo we consistently and easily run at 340whp and rev it to over 7300rpm on an engine that, as released from BMW, made 230whp and revved to 6500rpm. With recent modifications and for different race classes (BMW C-Mod) we are now running at over 400whp reliably with more available as we modify the charge cooling system. On the dyno we have tuned it up to over 450whp and 460lbft.

The engine has proven to be strong in every way compared to its N20 predecessor. The crankshaft, rods and pistons are light and strong and the bearings are huge. The timing chain is simple and well designed and the block and head are built to take a beating. We have also consistently raced this engine at water temps of over 240F and it has no issue with making incredible power, reliably at these levels. We haven’t broken one yet so we honestly don’t know what the limit is with the stock internals.

Why Motec and not the stock ECU or a different Stand Alone ECU?

The main reasons are control and reliability.

The stock ECU is an amazing piece of hardware but the layers of code in it and base firmware are meant for an integrated street car that has the correct emissions under all conditions and will always play it safe when it comes to its various limp modes.

The Motec M1 hardware is robust and is used at all levels of Pro Motorsport. Just the name “Motec” invokes a certain heightened intensity and makes the back of your neck tingle a bit - at least if you are a special subset of race nerd.. In particular the Motec M1 Tune software is amazing in both its ability to control systems correctly but also a level of simple sophistication that allows one person to calibrate an engine well instead of a team of 20 engineers.

First you must understand Motecs system of Hardware and Firmware which are two separate things. With the M1 line of ECUs Motec created a Firmware Package System that optimizes the hardware for different use scenarios and adds layers of complexity only when necessary. On the B48 we use the Motec M142 ECU which is the hardware to run Direct Injection Systems of up to 8 cylinder but we pair it with their GPRP-DI PRO firmware which is the most advanced and feature rich available from Motec. While that firmware title seems like a mouthful, all those letters mean something. It does things no other stand alone system on the market can do outside of insanely expensive Bosch and Cosworth Systems that operate on factory level race cars and require teams of engineers to optimize.

Here are a few of the engine systems it operates with the proper background code which are more complicated than a normal engine like a BMW S54.

DI Pump
DI Injectors
Dual H-Bridge Controlled Thermostat
Servo Controlled Wastegate
Complete Torque Control System (vs just boost target).
Oil Pressure Solenoid control
Advanced Traction Control settings accounting for downforce, tire coefficients and g-forces as well as a launch control system
Advanced Anti-lag tuning and settings
Auto Blip rev-matched downshifts as well as complete paddle shift sequential transmission control
Complete Flex Fuel System
Chassis Integration through CAN Bus and advanced engine diagnostics for driver warnings and torque reduction modes.
This goes on for a while so better to look at the Features Page

What other Turbos work with this package?

You can use any turbo but the wastegate feed forward values have to be calibrated to track boost correctly. Ideally this is done on a dyno. The feed forward value for the wastegate is the assumed position of the wastegate at a given RPM and load to make a specific amount of boost. The Motec firmware can then adapt that position in closed loop control but if it is way off then it will struggle to target your boost aim. The wastegates on the BMW Hybrid turbos tend to be very small so just a couple percent of wastegate change can make a big difference.

Most of our packages are using a TD04L hybrid turbo. We have also run the Pure Stage 2 and stock.

How much power can I make?

We are circuit racers which means our engines need to last more than a dyno run or a drag strip pull. We need to keep combustion stable around the banking of Daytona or running for 25+ seconds of full throttle down the long straights of WGI, VIR, Road America etc in the draft of another car when temps are already elevated. All of our tuning is conservative and is meant to be able to run endurance races and not cause excessive wear on the engine. The biggest hurdle on higher sustained power for circuit racing is managing piston and valve heating, engine coolant and intake temps.

The second problem is Motec uses the MAP sensor in the manifold to measure load. The stock BMW engine management uses the charge pipe pressure sensor pre throttle to measure load at high boost levels and those sensors can usually read higher (4 bar absolute in the case of the B48). The stock BMW MAP sensor is 2.5 bar absolute. We provide a 3 bar absolute manifold pressure sensor but that means 2 bar above atmosphere is the current highest we have tuned to which resulted in 450whp and 460lb ft of torque. We are working on integrating higher pressure load sensors into the stock manifold but it has not been a priority yet. We have not used this system on a built motor so have not pushed our low end torque higher than 420lbft in race track use and 460 on the dyno. Everything we have done is on stock junkyard engines.

The engine power level does depend on fuel as well. So far we can make about

280whp on 91 octane
310whp on 93
350whp on 98+
420whp on E45

These numbers do depend on engine and intake temps. It can technically make more on each fuel on a cold day (60F or lower).

Which of the B48 variants does this system work on?

We have successfully run both the B48B (2017-2020 230i/330i etc) and B48D (2020+ G20 330i and similar) although more time has been spent optimizing the B48D and there are a surprising number of differences. We have calibrated engines from 250whp to 450whp with many different fuel types. It is impossible to have a perfectly calibrated package for every scenario but we will do our best to give you a base package that matches your setup if you aren’t buying the “complete” kit from us.

In theory this system would also work on the B48E found in the X2M35i and similar. We have made no effort to set this system up on the B48A found in the 330e or other transverse versions like in the Mini. It may work with no issues, it may not.

How is the turbo lag?

Lag is dependent on RPM (higher RPM, less lag) and overall power level. The more boost you run the longer it takes the system to build to that higher pressure. With a stock turbo which is extremely tiny there is minimal lag compared to other engines with single throttle bodies. Owners of S54s or other individual throttled engines will find there to be noticeable lag but it is easily adapted for in driving. With the larger turbo and running over 400whp the lag is as mentioned RPM dependent but at 4k RPM there is about ½ a second of lag to achieve full power. If the car is driven correctly this usually works out in the drivers favor as it acts as a passive traction control. Usually you want power to come on smoothly as you open up your steering wheel out of a tight corner. It is a rare scenario where the car could immediately handle 400lbft of torque to the ground instantly. In this case you just jump on the throttle as soon as the car is rotated, the boost comes on smoothly and the traction control takes care of the rest.

We also have two electronic systems to help with normal turbo lag. The Anti lag system has 3 selectable stages that will continue to produce boost after you left off the throttle. In particular this is meant for shifts on the manual car. The highest level will maintain 30psi of boost between shifts so there is no power dip waiting for boost to come back on. It does however create additional heat in the exhaust and turbo which is why we make it an on the fly selectable option.

We also use an advanced overrun system on the race cars. When you go below a certain pedal position (RPM dependent and torque based) the throttle on the motor will stay open and further driver requested torque reduction is achieved by retarding ignition timing. This allows the manifold to hold pressure in it making the engine more responsive when you get back on the throttle. This also allows us to not run a blow off valve.

What do I need to provide if I do the minimum package?

We are just providing an ECU and the basic programming to run the engine. You need the following:

Transmission and clutch
Driveshaft
Engine Coolant Plumbing
Intercooler Water System Plumbing
Wiring
Power for the electric coolant pumps for turbo and intercooler
Integration to the ECU for CAN bus messaging to a Display as well as selectable modes like traction control, auto blip downshift, anti-lag etc (not necessary though). We provide info for what channels the Motec is transmitting.

What is the reason for two displays?

Because we think its cool and more screens is fun and techy.
The Driver display is meant to tell the driver everything related to what they are doing. Speed, RPM, Brake bias,Predictive time, last lap time, fastest lap time, session time, clock and various settings like Traction Aim, Antilag mode, throttle sensitivity.
The Center display is meant to be all diagnostic data and is useful on the track if you are in an endurance race for example and something is going wrong that you are trying to diagnose on the fly and still drive to stay in the race. Or even in a sprint race for that matter. You need to know if whatever is going wrong is going to terminally hurt the engine or allow you to finish and take you podium spot. It gives a ton of engine data as well as electrical power system data like what might have shorted out or is open circuit. It is also useful for diagnosing issues once you are back in the pits without having to connect a laptop. There is so much info on this display that we could not possibly fit all the driver info and screens as well as diagnostic info into one display. No brand of display on the market has enough memory to fit it all into one.

Engine Fault Codes Explained!

The most useful diagnostic feature on our packages is the engine and chassis fault codes. Currently the Motec ECU can set and display 48 different fault codes that will tell you on the fly exactly what might be going on with your car if there is an issue. In particular it will differentiate if a problem is a reading outside of the specified range (like high intake temp or low oil pressure) or if the sensor has actually failed in some way and is open circuit for example. That way if your oil pressure goes to zero it will tell you if its the sensor causing a problem instead or your engine has actually lost oil pressure.

Each fault will often be set with a sub fault by the systems diagnostic channel and this will be stored in the data log if needed.

You will also be given a spreadsheet that describes in detail what sets a specific fault code and the process for checking how to fix it.

Some examples picked at random include:

#9 Exhaust Lambda Warning - Lambda has either been too rich or too lean for too long and the allowed lambda trim is outside the range.

#17 Coolant Temperature Sensor Diagnostic - Coolant sensor is either open circuit or shorted - coolant temp will set to a default value.

#39 Throttle Servo Diagnostic - Throttle can not achieve its desired position. Either the throttle is sticking or the gear or motor has a problem. This is defined separately from #28 Throttle Servo Position Sensor Diagnostic which means one of the two sensors in the throttle is not tracking correctly or is broken.

#44 Boost Control Diagnostic - Boost pressure is higher than its target by a margin for too long

#57 Fuel Cylinder 1 Secondary Diagnostic Pin - Can mean many things from Open Circuit or Shorted to a “Peak Warning” meaning the injector did not fully open in time and did not deliver its correct fuel quantity.

This is an extensive topic and will be elaborated on more in the cars user manual.