[alf]

An update on testing low octane fuel

Before I share my initial 87 results, I need to mention that I realized having occasional knock with 91 itself. When I bought the car, I had a bad habit of accelerating on 6th gear from very low 2000-3000 RPM range on highway. A distinct "knocking" noise was coming from the engine, very brief though. Now I know it was a real knock, as I was able to correlate it with OFT realtime data. The condition is very easy to reproduce. BTW, I abandoned that habit early on.


Now real 87
Filled up a gas can 2 gallons of low quality 87, I took my BRZ to the highway to almost run out of gas, which is about 30miles after computer shows "--" or 56 miles after low gas warning kicks. I perfectly caught the moment when the car gave a first warning, like a slight engine interruption, pulled over and added precisely 2 gallons of 87. Hooked up OFT and started recording and monitoring real time data.


First observations is that there is no knock if engine works at steady RPM between 3000-4000. Works very smooth. However, the knock occurs, not always, occasionally when pushing an accelerator abruptly. The knock somewhat more pronounced, but not nearly as bad as pushing engine from 2500RPM with a decisive WOT input on 91 octane.

I also took a car to lower speed, more dynamic street driving - 30-50MPH with a few harder accelerations but delivered in a very smooth manner and never exceeded 5500RPM. There were not a single sign of knocking in the logs.


So the initial conclusion is, the knock is there, but by driving carefully and knowing how to prevent it, maybe I can get by.


The next test will be diving into why it knock even on 91. I need a better monitoring took though. OFT is very limiting. Thinking about building my own PICAN2 based devise.