NEW RELEASE: Modular Plug-in ECU for Mazda RX8 S1
The new Modular Plug-in ECU for Mazda RX8 S1 is a standalone unit offering a host of advanced features and functions.
Let’s take a look at all the built-in features.
For those familiar with our Modular ECUs, it’s basically an M2000 with the drive by wire upgrade, but with a few more inputs and outputs as required for this car. So it has 8 injector drivers (we use 6 for the injectors, and 2 for manifold flaps), 8 ignition drivers (we use 4, plus 2 for air pump control and 2 for fuel pump speed control), 4 auxiliary output drivers (we use 2 for auxiliary port control, one for the airblox flap and one for the purge valve control).
There are an additional 8 outputs on the ECU which are dedicated functions such as fuel pump on/off, 2 thermofan speeds, A/C and the 4 outputs to drive the oil metering pump. There are also dedicated digital inputs for functions like clutch, neutral, oil pressure switch, oil level switch and coolant level switch.
The Modular ECUs also have 2 internal 4-bar MAP sensors, 2 external MAP inputs (connected to the OEM airflow and baro sensors by default), 4 temperature inputs, oil and fuel pressure inputs (although these aren’t on the car, so they’re there if you want to upgrade), 2 x pedal position inputs, 2 x external 0-5V inputs which are used for alternator monitoring, 1 x spare 0-5V input which is used for APV feedback, and 2 x analogue O2 sensor inputs.
There’s no regulator in the alternator in the RX8, and the regulation is done by the factory ECU, so our ECU does this also. It feeds the alternator current into the idle control algorithm so the ECU can open the throttle pro-actively to stabilise idle speed with respect to electrical loads like the power steering, thermofans and so on.
The Modular ECU platform also supports 2 CAN ports, so one of these is connected to the vehicle CAN system, and the other is spare. So normally you would select the first CAN port to be Mazda RX8 type at 500 kbps, and then the ECU does the following on the CAN bus:
Click the learn button
The ECU also has a road speed input on an unused input pin, and a tacho output on a different unused ECU pin. The ECU also has all 3 CAS inputs available on unused pins, as the RX8 only uses a single CAS input, so you can run a JZ engine using all the CAS inputs, or run a flex fuel sensor, or a turbo speed sensor if you have a Borg Warner turbo, or a combination thereof.
Flex Fuel Sensor
This flexibility means that:
The second CAN port also means that you can connect other devices, such as an aftermarket dash or wideband lambda sensor, or both. In this setup here, I’ve run two wires into the unused pins on the factory connector for the second CAN port and connected it to our Mainline dyno. I’ve enabled the Adaptronic CAN output on the ECU on the second CAN port, so that you can watch the ECU data on the dyno screen, and it can come up in plots, logs etc – you can see the throttle position, temperatures and RPM coming from the ECU here. It’s configured in the dyno settings under External Devices – and then on the ECU end you just need to select “Enable Adaptronic Output” with the default settings.
Motec PLM (1Mbps)
What’s also cool is that the Mainline dyno can emulate a Motec PLM on the same CAN bus, so it can output the wideband data from its tailpipe probe back to the ECU. In the ECU settings we select lambda sensor as being CAN, and then select the wideband over CAN to be the Motec PLM. This means we can use an external sensor on the ECU without having to mount one in the car or have a second tailpipe probe. This means you can do the fuel map lambda error overlay in the software easily which makes mapping very fast. Of course the ideal would be to mount a 5-wire in the car permanently but not every job can afford that. In the future we’ll be able to send the data from the dyno to the ECU over serial so it can just plug into the front of the ECU.
Output wideband data
The ECU also has 4 serial ports, so you can connect wideband sensors in via those, and also drive serial based dashes through these ports.
In this installation I’m using the built-in MAP sensor on an inlet runner port. Ideally you’d use both inlet runners with a T-piece, or better still, the inlet manifold. One potential downside of using the port at the bottom of the inlet manifold after the throttle body is that if your turbocharger leaks oil then a lot of oil can flow down that port because it faces downwards, whereas the nipples on the primary runners would require the oil to run uphill to get into the ECU’s MAP sensor. Also this car still had the factory airbox so I wanted to retain the vacuum control of the airbox flap.
If you do want to connect other devices to the ECU, such as oil or fuel pressure sensors, or wire in an 8 cylinder engine, remember that you can go to the wiring page in the software and see where each of the pins on the ECU actually connects internally. The base map comes with the factory wire colours and functions but you can update these based on whatever you change in your car.
The ECU also allows up to 2 x small modules to be installed. At the moment there’s not a lot of need for this, but maybe in the future you might want to add in 4 x wheel speeds connected directly rather than via CAN, or have another 6 auxiliary outputs, or another 4 analogue inputs. These small module positions each have 6 pins that come out to unused pins on the factory ECU connector.
2 small modules upgrade positions
I’ve done plenty of other videos about fuel modelling so I won’t go into it again here, but one thing I will say is that with our staged injection model you can either let the ECU work out the amount of fuel to go to each injection stage automatically, or you can specify the percentage of each stage. This is a fuel mass percentage, so with different injector sizes between primary and secondary, if you set 50% then this will correspond to different pulse durations for each stage.
Injector Staging Menu
When I first ran up this naturally aspirated RX8, I discovered it was lower in power than I was expecting. This was using the default staging method of using up the primaries as much as you can up to a 2ms off time, then the P2 injectors which are also in the primary runners, until they no longer have 2ms of off time, and then finally the rest with the secondary injectors. Then I remembered something Paul Yaw told me at PRI one year, and I changed it so that 50% of the fuel went to the secondaries above the RPM at which the secondary runners open, 25% to the P2 injectors and 25% to the P1, which is easy to do in the injector staging map – and the power came straight up; I assume due to more homogeneous mixture in the chamber because equal amounts came in each end. It might be worthwhile putting even more to the secondaries, eg 60% or 70% because at high RPM we have the secondary ports and the auxiliary ports open but I’ll leave that as an exercise for the tuner.
Injector Staging 2
Injector staging 3
Rx8 Base vs Factory
Stage 1 does not support cruise control or traction control via CAN.