With the outside temperature 32 degrees and expected to get cooler before dawn, I backed our 2010 Prius down the 40 yard driveway, turned it around, and backed it to the original parking place. This took less than a minute so the catalytic converters never had a chance to 'light-off.' In the morning, I'll configure our AutoEnginuity to record all engine metrics. Then I'll start it up and record the knock event. I'll setup the cell phone to make an audio recording. Hopefully we'll have some good data in the morning. Bob Wilson
Trying a new protocol: Scangauge shows 0.64 gal/hr that drops to 0.32 gal/hr after cats light off I stopped the engine AFTER it reached 0.32 gal/hr and in a few hours I'll try again . . . with AutoEnginuity. If no knock, I'll try 0.64 gal/hr and we'll see. Bob Wilson
I've found that -in some cases- when the engine is cold, the knock can be initiated by starting the engine, turning it off immediately, and then restarting. I have *not* thoroughly tested this, since I greatly dislike the knocking... ;-)
Wash the car...let it sit at least two hours. Start the Prius..then right when the engine kicks on power it off. Next morning start it up and it should happen.
Due to an unfortunate Windows vs. hacker event, I wiped out my infected, virtual PC and AutoEnginuity. I'll eventually replace it but not right away. We're already past the window of when the intermittent engine knock occurs. But I was able to replicate something like it using E85 after a freezing weather, cold-soak. I am fairly sure the cold-weather, engine knock, is tied to an engine, 'open loop' control problem. Somehow the engine long-term trim and cold weather is leading to a short period of excessive lean operation and possibly poor spark advance. It could be E10 contributes but like a little dog, the bark is worse than the bite. Bob Wilson
Good luck proving it. Cold starts are always rich, by definition, and not lean. Like I said in the comment in the youtube video, moisture in combustion chambers and intake from a previous cold shutdown and cold soak temporarily shorts a spark plug or two.
