B5 RS4 EGT sensor woes?

[A1QSHIP]

EGT Sensor Exposed




Photos showing the internals of the EGT sensor.

[prj]

Dmitri can you tell us how the RS4 use the EGTs?
Is it an economy / emissions strategy to keep the AFRs leaner and use the EGTs to trim fuel to cool the combustion as required on WOT rather than a "safe" rich AFR target on WOT?

Fueling strategy is:
1. Closed loop Lambda 1 through the rev range.
2. When temp hits 750C (Simulated EGT model) do some light pre-enrichment
3. When temp hits 980C (from EGT) enter closed loop PI controller, where the control variable is fuel enrichment and the feedback is EGT.
Basically it will dump fuel until the flammability limit to keep EGT's down.

This fueling strategy wrecks exhaust manifolds, turbos and so on.
If you go from a standing start you will be at Lambda 1 until end of 3rd gear where it will hit 750C and then very quickly 980C.

The reason this is done is for economy and emissions.

If you just code out the EGT's (CATR,CDATR,CDATS) it will still hit 980+ C and melt your engine if you keep flooring it.
The entire fueling strategy has to be altered to keep EGT's controlled through the simulated model.

What's so special about them that they cost £400? Can you not just splice in a standard K type thermocouple? This is what I use as an EGT sensor, cost £10 off ebay 5 years ago and still going strong!

It is a cold junction compensated controller, which outputs PWM based on Thermocouple reading.
The ECU then processes this PWM information and turns it into temperature based on a linearization map.

The 2.7TT EGT's are narrowband. They basically read from something like 950C to 1050C from memory.
The RS6 ones are wideband. they read from -40C to 1050C. Same goes for the 1.8T's that have them fitted. If buying new ones, I'd buy those and alter mapping... but that is because I can.

On my RS4 I ran no EGT's. I modified the simulated model to be correct and added fuel control based on the simulated model.

[le mans]

Dimitri great info! My RS4 runs C5 RS6 EGTs with altered mapping. The fuel strategy was also changed by the mapper to keep the EGTs down.

[Monkeymagic]

Dimitri you certainly know your stuff. I clearly need to find a uk based mapper with a little knowledge.

[prj]

Dimitri you certainly know your stuff. I clearly need to find a uk based mapper with a little knowledge.

Ring up Tim at the phirm. There is someone working with that shop that can do all this.

[Error404]

Great info thanks Dmitri

[Monkeymagic]

Cheers Dimitri, excellent advice. Steven