Can I trust the knock sensors when using ethanol as fuel.

I have a Cadillac CTS-V 2017 with the E92 ECM, the LT4 engine.

Minor mods like cai, 103mm tb, 2" headers no cats, flex fuel.

Planning to put on a 15% lower for some more boost, but how do you guys tune for more boost when using ethanol, do you trust the knock sensors when adding more timing and then back off when knock occurs, for like in my case around E40-E50?

Using hptuners, what do you actually configure when adding boost?

So the detection of knock from my understanding is more about the resonance of the cylinder and should not be affected by the fuel type.

adding ethanol will lower to volatility of the combustion event. Eg, fuel is less likely to go boom unless told to by a spark plug

In many engines E85 makes many engines, fairly immune to knock. Often called not being knock limited

E40-50 though likely will still be prone to knock, more so in some engines than others. Especially if you add boost or advance timing.

So my opinion is, trust your knock sensors, however nothing beats using proper knock detection gear, to knock ears.

I have never seen enough of a variance in the knock signal amplitude when going from E0 to E85 to warrant a change in the operation of the knock system in the ECU. An induced knock event on E0 produces the same noise curve as an event induced with E85.

+1 for the above comments on knock detection itself.

That said, be cautious to avoid over advancing timing beyond where it's adding power.

Keep in mind pre-ignition is still possible and not detected via knock sensor.

Pre-Ignition is more likely with higher Ethanol content and higher combustion chamber pressures.

Pre-Ignition Characteristics of Ethanol and E85 in a Spark Ignition Engine