Forced Induction Upgrades

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Summary of forced induction upgrades

2048kg/h MAF Sensor switch

MS43 MAF Sensor Handling in IDA

When installing a higher rated mass airflow sensor than 1024kg/h you have to modify the program code inside the ECU.

Modifiying program code is dangerous and should only be done by people who knows how to recover a bricked ECU.

Inside the MS42s and MS43s code there is a mass airflow limit of 1024kg/h because it's leftshifted four times reducing it from the real limit of 16384kg/h.

You have two options to alter the MAF limit:

  1. Do it manually with a HEX editor and change the bytes listed below according to the software version from "4E" (1024kg/h) to "3E" (2048kg/h) and double the conversion in the Tuner Pro MAF table to "0.03125*X"
  2. Download RomRaider and the matching definition file for your softwareversion, flick the switch under the "Forced Induction" section and use the special MAF table right next to it.

Either way you have to recalculate the program code checksums inside the 512kByte file even if you use files with deactivated checksums for the calibration area.

MAF reading limit offset:

  • MS430037: 0x3D719 & 0x3D73D
  • MS430055: 0x413A3 & 0x413C7
  • MS430056: 0x3D8A3 & 0x3D8C7
  • MS430064: 0x3E0E5 & 0x3E109
  • MS430066: 0x3B4C3 & 0x3B4E7
  • MS430069: 0x3B4C3 & 0x3B4E7

Exchange 0x4E with 0x3E in both locations for 2048kg/h maximum reading.

Audi RS4 MAF Sensor Conversion

A cheap alternative for the HPX PMAS MAF is the Audi RS4 B5 MAF sensor manufactured by Bosch and is able to measure upto 1800kg/h.

The MAF sensor module comes preinstalled in a 3.5 inch housing and has a 5 pin connector with the following pinout:

  • Pin 1 - IAT sensor output (not used on MS4x)
  • Pin 2 - voltage input 12V (red?)
  • Pin 3 - common ground (black)
  • Pin 4 - voltage input 5V (brown/white)
  • Pin 5 - MAF sensor output (yellow)

The IAT output on pin 1 can be connected to an aftermarket logging device to monitor the intake air temperature before compression, or in case you leave it unconnected, make sure to seal the pin in the plug, to prevent the maf from corroding.

Pins 2, 3 and 5 should be self explaining, just connect them to the OEM MAF wires, or create a new 4-wire loom and run it to the cable distribution box located under the intake manifold.

Pin 4 needs a stable 5.00v supply voltage as this is the reference for the MAF output signal. This is very important for a precise reading!

The MS43 has two integrated 5V outputs, one for the electronic accelerator pedal and one for the electronic throttlebody. You can tap into the second supply right inside the cable distribution box.

By the way, this is pin 7 at the middle ECU connector (X60003) for the voltage U_DKG (brown/white, 0.5mm²). If anybody is concerned about the MAF drawing too much current, during operation it only needs 1,1mA

Now that you have the connection from the MAF to the ECU, the next part is applying the MAF hack (512k file) and editing the sensor definition (64k file)

In addition to that, you need to set "C_MAF_KGH_R_LS_MES_MAX" to 1800kg/h and C_MAF_MAX to 1389kg/h (the highest value possible for this constant).


  • Audi RS4 MAF: Bosch partnumber 0 280 218 067 or 0 986 280 219
  • Connector: VAG part number 1J0973775A

Discussion on

Using rear lambdaprobe inputs for WBO2 or MAP

Several people removed their engines rear lambdaprobes and just left the ECU inputs unused. (Make sure you set c_conf_cat to "1".)

After taking a closer look at those two input in INPA, we see that they are rated for voltages from 0V to 5V with an accuracy of 4.8828125mV.

Why not using those otherwise wasted inputs for something handy like integrating a manifold absolute pressure (MAP) sensor or wideband lambdaprope?!

Both, the MS42 and MS43 share the same pinout at connector X60002, which is the second connector from the right looking at the ECU mounted still in car.

MS4x Rear Lambda Inputs 1.PNG

As we you see in the schematics, both lambda probes have four connections:

Lambdaprobe X60002

Bank 1 / 2

Pin 1 - U_HR Ignition switched +12V for heater element
Pin 2 Pin 07 / Pin 19 T_LHH1/2 PWMed ground for heater element
Pin 3 Pin 22 / Pin 24 M_LSH1/2 Sensor ground
Pin 4 Pin 16 / Pin 18 A_LSH1/2 Sensor inputvoltage

The minimal setup would be using only the two inputs at pins 16 and 18 and feed a sensor return voltage into them.

But there's also a +12V supply switched by ignition and a ground connection, we can use those for creating +5V to power the MAP sensor by using a LM7805.

Attention: Never use the PWM ground to ground your sensor, as the ECU uses this to control the heater element inside the lambdaprobe!

Also keep in mind, that the signal ground was never rated for high currents like a heater element. Use a seperate, solid ground when you expect a higher load than a few mA like a small 5V sensor usually takes.

The sensors can be read by INPA, RomRaider, TunerPro or any other logging program. Just make sure, that you input the matching formula to convert volts into bar, kpa, psi or lambda, afr.