Octane Observations
- Thread starter Minimichael
- Start date
Now that's certainly food for thought as well. And the more we talk about this the more I'm learning that there's always more to learn. Like just last night I got to reading about PCV on race car engines and man did I get an eyeful - and brain full. I was surprised to learn the usefulness of PCV is still so debatable, and that's because the gases being recirculated are "long strand hydrocarbons" and an octane reducer. I guess "long strand" is kinda like a half-baked combustion charge leftover, and way less combustible than a fresh gasoline charge, which has "globular" and way more combustible hydrocarbon ...things (molecules?). To make matters more precarious, the question of how much of this stubborn "long" hydroC is being circulated depends on how much blow-by your piston and rings are allowing to escape into your crankcase, and that depends not only on the quality of your seal, but also on the amount of vacuum pressure in your case -- which of course depends on how you're venting the engine in the first place...like can the case freely breathe in and out, or is it restricted in a way that creates a negative or positive pressure in the case ...that could be pushing or pulling against the backside of the piston/ring seal and allowing more or less blowby. One of the race forum messages then made a comment that made me laugh. They said something like "So there's just so many variables at work here that there's no way to account or compensate for the anti-octane quality of PCV long hydroC's, unless of course we were only talking about a single piston engine."
Hah! Man, I got a lot to learn...
Hah! Man, I got a lot to learn...
Would love to see a video shot of your "juicing the tank" with a shot of octane booster, the results of that, plus testing of different octane levels in your engines. Your first post doesn't sound like the octane did anything good since you say it slowed down the idle--I personally think it was something else that happened that was coincidental to you juicing the tank.
Most of us "feel" that we can notice a difference in performance just by the seat of our pants but for real gains we have to make drastic engine changes.
Best rule of thumb is to buy the cheapest and lowest octane gasoline (usually synonymous) you can find that is also ethanol free. These "lawnmower" engines have too low of a compression ratio for high octane gasoline to make an impact.
Most of us "feel" that we can notice a difference in performance just by the seat of our pants but for real gains we have to make drastic engine changes.
Best rule of thumb is to buy the cheapest and lowest octane gasoline (usually synonymous) you can find that is also ethanol free. These "lawnmower" engines have too low of a compression ratio for high octane gasoline to make an impact.
I don't have a video of the slowing idle upon octane booster juicing, unfortunately... But at the time I equated the idle drop (and combustion sound) with a good thing because I've been trying to figure out and tame a pre-ignition issue (knocking) I was also having in one of my other engines. Juicing made the engine sound more stable -- to this greenhorn anyway. But yeah, I'm going to find ethanol free when I get a chance, and maybe then I'll run basic performance tests and post about them. I say "basic" as a disclaimer here because we're a long way from dealing with a high performance machine. (See pic)
Yes but in a hi performance car when you go full throttle manifold vacuum should be 1” or under meaning your not pulling the PVC open any longer. Now your blown bye / crankcase
Psi is going out the valve cover breather. If the breather is vented into the air cleaner it will get reburned but many vent it into the under hood area or into the exhaust draw tube.
Psi is going out the valve cover breather. If the breather is vented into the air cleaner it will get reburned but many vent it into the under hood area or into the exhaust draw tube.
Here's some of my observations on fuel and octane. In my part of the country regulator leaded fuel was 89 octane. Gasoline is nasty stuff. Whether it has ethanol in it or not gas has always been hard on rubber and plastics and its not nice to aluminum if it's left sitting. Today's gas if not as volatile as gas was 40 years ago. Fuel is made to be atomized with a fuel injector not a venturi. The fine mist from a fuel injector ignites easily. Unless a manufacturer specifically calls for premium fuel you are probably not helping yourself much by running it. Fuel injected, computer controlled engines are continuously adjusting mixture and timing for best efficiency. I have always run the 87 octane gas in all my vehicles and equipment. I don't see any more fuel related problems than I did before ethanol. With my 4 stroke snowmobile I do the last ride with no ethanol fuel. I add a little 2 stroke oil to everything else to prevent corrosion in the off season. My final observation is old gas is old gas whether it has ethanol in it or not, and it's nasty.
