Quote:
Originally Posted by 2023_ZL1-AUTO
through out all my mods, and all my tunes, from E60 to straight E85, with over +785rwhp, I've never record knock !!!
|
This brings up a good Point.
You can have a fuel that is detonation resistant enough, where knock sensors do not pick it up, but still have cylinder pressure peak at wrong crank degrees in the cycle.
Ideally and this can vary a couple degrees based on engine design, Peak Cylinder pressure should occur around 15 Degrees after top dead center to produce MBT.
What is MBT, Mean Best Torque.
At each RPM and Load, you can Locate MBT by holding the engine at any rpm and load then doing a Hook test to see where highest torque is produced.
This is what the OEMs do when building calibrations.
In testing I have pushed Ethanol fuels way beyond MBT and did not record knock from the sensors but I see different signs that is for a much deeper conversation.
Direct injection engines on good fuel are hard to make knock, if you do you could be 6 to 7 degrees too far from MBT.
One of the good practices are to back timing down until you measure a significant loss in torque.
It is always safer to operate on the lower side of the hook than the higher side.
I hope this helps this conversation.