Anyone know how the Rainbow Box works?

[Chodan]

I have a 2022 S4.
In the stock setup, the Boost gauge was displayed, but I installed the Rainbow Box to enable the engine data and G-force meter.
Since the Rainbow Box is also compatible with the A4, it seems to have some influence on the Boost gauge, and now it displays differently from the stock behavior.

In the stock configuration, the Boost gauge only started filling up when I pressed the accelerator quite deeply. However, now, with the same level of input, the gauge already shows more than half or even full boost.

Also, right after a cold start, before the RPM stabilizes, the Boost gauge slightly rises. (Added image)

I’m considering disconnecting the pin related to the Boost gauge from the module, but I don’t know which pin is responsible for what function.

Has anyone had a similar experience or knows how to resolve this issue?




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[Smac770]

Is this going to be some issue with absolute vs gauge measurements? The data values from the ECM are in absolute terms, not gauge terms. You have to subtract ambient if you want "boost", ie gauge, numbers.

Specified can go below ambient, since specified is based on the air needed, not necessarily the air present. Actual will be the actual measured value, so it'll never be (more than a very little) below ambient.

No idea what number range the instrument cluster is expecting the data value to be at. Maybe it's getting it from the ECM direct. You should use an independent tool (VCDS) to monitor the charge air pressure actual and see how the boost display relates to the factual data.

[Chodan]

Is this going to be some issue with absolute vs gauge measurements? The data values from the ECM are in absolute terms, not gauge terms. You have to subtract ambient if you want "boost", ie gauge, numbers.

Specified can go below ambient, since specified is based on the air needed, not necessarily the air present. Actual will be the actual measured value, so it'll never be (more than a very little) below ambient.

No idea what number range the instrument cluster is expecting the data value to be at. Maybe it's getting it from the ECM direct. You should use an independent tool (VCDS) to monitor the charge air pressure actual and see how the boost display relates to the factual data.

Thank you for your valuable opinion.
One thing that is certain is that this issue is caused by the module. Depending on the situation, I will attempt recalibration while considering ambient pressure. If that doesn’t work, I will consider restoring the relevant pin on the module or removing the module altogether.


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