You're getting closer, but still no cigar. It all burns at essentially the same speed, both high and low octane. It is not supposed to be set off by pressure waves. It is supposed to be set off by the spark plug, and burn in one smooth burning front across the entire cylinder. Knocking and detonation are the same thing. What happens is that the ignition characteristics of the low octane fuel are such that once the initial burning starts from the spark plug, the pressure wave causes the fuel to start burning at many individual points within the cylinder. It is not supposed to do that, and will not do that will a fuel of proper octane rating. Since with knocking, the burning has started at so many points, the fuel in the cylinder does indeed get done burning faster. But it is not because it's burning any faster at any individual point. It is because it is burning from many starting points, instead of burning in one smooth flame front starting at the spark plug. So a low octane fuel does not burn any faster. What it does is ignite easier.

If you want yet another analogy, think about starting a grass fire in a field. If you start it at only one point, at the edge of the field, it takes a while to burn across the whole field. But if you set the field on fire at 50 different points, the field gets burned quicker. It's not because the field is burning any quicker at any individual point within the field. It is because it is burning at many different points.

 

another way to think of it is thus:

preignition (ignition before proper time hence the pre part).
detonation is a spontaneous uncontrolled explosion.

if we use a clock as an illustration for preignition. if the 'timing' was set to fire the spark at exactly 12:00, preignition would occur anytime ignition occured before 12:00. if the fuel ignited at 11:57 you would have preignition.

detonation is the uncontrolled ignition of the fuel. let's say you had a plastic bag full of water. you carried the bag of water to the sink and began to pour it out (slowly) into the sink. unbeknownst to you there was a fork sitting on the counter and as you began to pour the water it pierced the bottom and now you have an uncontrolled flow getting larger by the second........

 

Pre-ignition by that definition is very rare. It requires either an old, dirty engine, with hot spots on the deposits that act like glow plugs, or ultra high compression ratio where you actually get diesel-type ignition, or an ultra low quality or contaminated fuel. If pre-ignition by this definition was the source of most knocking, knock sensors which retard the spark would not work, because the fuel would be igniting before the spark anyway, so who cares what the spark timing is.

As far as detonation, we're starting to split hairs on definitions, but I go back to my earlier post in this thread. The stuff doesn't explode, or burn any faster, it simply self-ignites at many points from the initial pressure wave, and the fuel in the cylinder thus gets consumed faster. Not because it's burning faster or exploding at any given point within the cylinder,but because it's burning at many points within the cylinder instead of in a single, smooth, flame front like it's supposed to.

 

My spouse would have probably put in the 87 then gotten ticked when I didn't praise her for filling up the tank on her own.

 

Then you just say "Thank you dear, you did a great job and I really appreciate it." Any thing other than that will lead to a "Discussion", and you know what that means.

 

Alcohol does burn faster period...

 

Look at what it has caused here, I can only imagine if the "Discussion" was betwen my wife and I. She would probably never fill it up again. Just run it dry and leave for me

Les

 

LDB - Thanks for the in-depth description. I was on the right track, but you cleared it up for me even further. I feel like I have really learned something here.

Back on the wife topic, I think the best approach is to discuss the way you plan feed and care for the vette in the beginning, before she has the opportunity to not pick the correct fuel. After that the "Thank you dear" rule still applies, but hopefully, she will have done it correctly.