Interfacing Ignitron ECU to turbocharged 24V VR6 engines

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Ignitron ECU is a plug and play solution for the 1.8L 20VT engines, however, above hardware version 1.94 it can be used on the 2.8L/3.2L VR6 engines (with Drive-By-Wire throttle and 4 valves per cylinder), too. These engines came as naturally aspirated (without a turbo or supercharger) and use a different version of the motronic engine management system (ME7.1 instead of ME7.5). There are subtle differences between the two and their pinout is not exactly the same either!

Functional differences

• VR6 uses a dual cylinder bank layout with two oxygen sensors (one for cyls. 1-3 and one for cyls. 4-6).
• VR6 has no MAP (manifold absolute pressure) sensor at all, load is calculated by the MAF (mass airflow) sensor.
• VR6 has its IAT (intake air temperature) sensor in the MAF (mass airflow) sensor (right after the air filer).
• VR6 has a variable length intake manifold.
• Late VR6 can adjust camshaft timing on both the intake and exhaust cams.

Looking at the above list it is easy to recognize that the OEM VR6 engine management is not optimized for using a turbocharger at all. Although it has a more advanced variable valve timing (only on later variants), all other features are beneficial on a naturally aspirated engine only.

- Having two oxygen sensors on a single turbo setup is completely unnecessary, since all six exhaust runners merge into the same collector (this is not a real V engine), therefore the two cylinder banks cannot be analyzed separately. Placing the oxygen sensors before the turbo is not a viable solution either, because the increased exhaust gas pressures make the sensor readings off when on boost (also can damage the sensor if the pressure is too high). Ignitron ECU has a single wideband lambda (oxygen) sensor driver built-in, which is designated as lambda probe 1 (for cyls. 1-3) on the VR6 engines. That can be used as the one and only oxygen sensor after the turbocharger in the downpipe. The Ignitron ECU above hardware version 1.94 can drive both LSU 4.2 and LSU 4.9 oxygen sensors. LSU 4.9 are fitted to late 3.2L R32 engines. Make sure you do not mismatch oxygen sensor types in the settings/basemap, because the settings for LSU 4.2 can damage LSU 4.9 probes!

- Having no MAP sensor on a turbocharged engine is unforgivable! Even if you have an external boost controller (or no boost controller at all), the engine ECU needs to monitor the pressure in the intake manifold so at least it can enter into limp mode to prevent catastrophic engine failures upon dangerous overboost conditions. Furthermore, using a MAF sensor on a heavily modified (race) engine is unwanted! Without going deeply into this topic (it is not the objective of this article), the OEM MAF sensor is *NOT* capable of measuring multiple times the airflow of the unmodified, naturally aspirated engine! There may be workarounds for this (different MAF housings, different sensors, ...) which are used with (budget) OEM ECU builds, but the proper way is to install a MAP sensor in the intake manifold (where the sensor can see both vacuum and boost) and wire it into the ECU. This way the MAF sensor can be omitted (it will not restrict turbo intake either) and the ECU can be set up to run on "Speed Density" load/fueling calculation method. It is a far more reliable way of operating a modified engine.

- The OEM IAT sensor cannot measure the temperature of the compressed air, because it is located in the MAF sensor (which will be deleted anyways). An IAT sensor has to be mounted into the intake manifold (or into the cooler pipe after intercooler), so the ECU can see the actual temperature of the air entering the engine. Intake air temperature is a vital information for the engine management in load/fueling calculation!

- Using the OEM, plastic variable air duct length intake manifold on a turbo setup is a bad idea. It is bulky, weak and fragile, cannot withstand any serious boost. When using a turbocharger its purpose is rendered useless. Replace it with a proper metal intake manifold designed for turbocharged applications. Mount the MAP and IAT sensors into the intake manifold.

Pinout differences (to-dos)

Ignitron ECU was developed on/for the 1.8L 20VT engines. Most of our users (as of today) are coming from the 1.8T platform. Since there are some pinout differences between the 1.8T ME7.5 and VR6 ME7.1 systems (number of cylinders doesn't matter now), we would have to manufacture two different ECU versions for both platforms. We do not want to do that (for obvious reasons), but optimized the pinout of Ignitron ECU (above hardware version 1.94) so it can work on both platforms with very few modifications needed for the VR6. Since the MAP sensor, IAT sensor, optional turbocharger wastegate regulator solenoid, etc... would have to be added to the wiring for the VR6 any way, it is not a big deal to move 1 additional pin around.

- Relocate PIN 21 to PIN 20. Thats all! The biggest difference between the two platforms is the switched 12V supply (Terminal 15) to the ECU. 1.8T (ME7.5) gets switched 12V on PIN 3, but VR6 (ME7.1) gets it on PIN 21. Problem is that PIN 21 functions do conflict on the two platforms, on 1.8T this is an output (main relay drive), but on VR6 this is an input (ignition switch status). To have a workaround for this, we assigned the VR6 ignition switch signal to PIN 20 on Ignitron ECU (V1.94+). PIN 20 is not used on either platforms so it will not conflict with anything.

- PIN 121 is not available for use. This is again a conflicting pin between the two platforms. On 1.8T (ME7.5) this is a high current 12V power input for Drive-By-Wire throttle on the later wideband ECUs. On VR6 (ME7.1) this is a solenoid driver output which is used for the variable intake switchover. Ignitron ECU does not use PIN 121 at all (not even on the 1.8T platform), so you will not be able to drive the variable intake switchover on your VR6 at this pin. Luckily a turbo build does not need the variable intake at all, so not a big loss. A watchful builder can re use the wiring in the OEM loom lets say for turbocharger wastegate regulator (N75 solenoid) and relocate PIN 121 to PIN 119 or 116 (115 and 120 are reserved for VVT).

- Add a MAP sensor and an IAT sensor. As previously discussed you have to add a MAP sensor and an IAT sensor (both mounted in or fed from the intake manifold)! Any MAP sensor will work which outputs a 0-5V analog signal and any thermistor type IAT sensor is fine. MAP and IAT sensors from other VW/Audi can be used (just as the 1.8T or diesel ones). Make sure you use the lowest range MAP sensor you will need (as it will have the best accuracy and resolution). It is always a good idea to leave at least 20-30kpa safety margin above the maximum boost level. MAP sensor signal should be routed to ECU PIN 101, IAT sensor signal to ECU PIN 85. MAP sensor will need +5V and GND, IAT sensor will need a GND. Please refer to Ignitron ECU pinout for possible 5V and sensor GND pins. The pinout is available in the windows software, Help menu, Users manual, Appendix, Pinout.

- Add optional solenoid(s) or sensors. You can add additional sensors (f.eg exhaust gas temperature, oil pressure, etc...) to the Ignitron ECU. Adding an N75 (turbocharger wastegate regulator) solenoid is very good idea. This way the Ignitron will be able to regulate turbo boost, which is essential for cars with a DSG gearbox. Please refer to Ignitron ECU pinout for extra analog input pins and possible 5V and sensor grounds.