Octane 91 or 93 better ?
 

What is better for the LS1. 91 or 93 octane? I have been told that lower octane burns better than a higher octane. I have noticed a slight ping, but only driving lower speeds around town. Highway and under load, never a ping. I have been using 93 octane.:flag:

Running more octane than required can definetly cause a loss of horsepower. However ping that your referring to is predetonation which is your gas exploding prior to the piston being at the top of the stroke. to low octane and just the left over heat can cause gas to ignite. your piston is trying to compress an explosion. Not a good idea. Alot more energy than usual is being converted into heat instead of kinetic energy to move your piston causing an extremely high temperature inside the cylinder, under severe enough "pinging" you can melt pistons. Also your knock sensors are detecting this ping and retarding timing in an attempt to keep the explosion off long enough for the piston to reach the top of stroke. The retarding action of your motor will cause you much more horsepower loss and potential catastrophic failure than running an octane that is too high. So i would say fail safe and pay the couple extra $ per year to run 93 vice 91.

Can you explain how "more" octane will cause a HP loss?

More "octane" means it's harder to light off.
Harder to light off means it is less likely to light off on it own under high compression.
So the higher octane will not burn as well so you lose HP if you don't have an engine with a high enough compression ratio.
Corvettes call out for 91 min.

If your motor does not have high compression (check the onwers manual) and does not ping on regular gas you are wasting money and gas mileage using a high octane fuel.
There has been a lot of stuff back and forth of the subject here.
I have run 89 octane since new.
I don't have any pinging and get over 32 MPG on the highway.
Over 100,000 miles now and counting.
Put down some pretty good HP numbers to boot!:thumbs:

Exactly, I dont know that i would run 89, But if it doesnt knock thats all that matters

Uhmmmmmm.....
No such thing as "predetonation".
There's "preignition" and "detonation" though.
Preignition is rare.
Detonation is where instead of the charge burning smoothly and progressively, enough heat and pressure is generated by the charge already burned to cause the remaining charge to ignite all at once.

Here's a pretty good article if anyone's interested. http://www.streetrodstuff.com/Articl...tion/index.php

Its to bad there are so many people like that on here who want to have a battle of wit and swear they are so much smarter than everybody else. I could go on and argue back, however I thought the idea of this post was to help Neil Baker a fellow corvette owner w/ a question that he had. im sure your response didnt help anything. Which im sure I answered his question more than he ever wanted. I could have wrote 10 pages of crap reciting definitions, Laws of Physics, Thermodynamics, Heat Transfer, Hell I could even throw in a bunch of applicable equations, Laws of conservation of energy as well as mass. But that is probably more than Neil Baker ever wanted to know, so i summed it up for him. If you would like to have a battle of wits, I have a bas in nuclear engineering and would love to see what you know, how bout you pm me and ill give you my phone number. If not then dont criticize people for trying to help others, by psycho-analyzing my sentences trying to pick out error and trying to look smarter by correcting me, especially if you have any idea what your talking about you obviously would understand what im saying. So if you really feel the need to show off how much smarter you are then me, then go ahead and pm me.

No comparision whatsoever.
Go 93, its just right.
100 is a waste, unless you are racing a setup race car and not a street car.

Now that's more than interesting!
Seems that you've inserted all kinds of implicit criticisms and meanings into my post which I never stated nor intended.

Funny how the pot calls the kettle black, and then copiously engages in the very thing he is criticizing and imagines someone else is doing.

I'm sure you're a really smart guy, and you don't need to do anything special to prove it to me. :thumbs:

Feel free to write a better article than the one I linked to, and I'll be happy to quote it next time I respond to a question about fuel octane or detonation. :thumbs:

:iagree:

That is the best write up on detonation and pre-ignition I have ever read.
Read it and learn!!!

As for running 89 octane, it won't work for me. In Cali temps get to 110F or higher. And when I put my foot in it and it rattles with Chevrons best 91, I cringe and back off. Early in the morning is best for romping the pedal. Or late Fall and all Winter. Next Summer I will try a little octane boost. I learned a lot from the article. Thanks.

The octane rating of the fuel is really nothing magic. Octane is the ability to resist detonation.

So again, how does more octane cause a loss of hp.

I'm waiting on an answer to that one too.

It's already been explained but a better question is why do people think that higher octane automatically equals more horsepower? Everyone here knows that the octane rating is not a measure of power, right?

I think it is a misunderstanding that most people make about higher octane automatically equals more horsepower, is because normally a high horsepower engine is making a lot of it's power because of a really high compression ratio or blower/supercharger/turbo/nitrous setup that requires a high octane fuel to run correctly. I believe this is where the mistake of thinking that since they use higher octane they make more horsepower starts. I have read many of articles on cheap gas wins races.

I don't see that anyone has stated that higher octane produces more power.........the question was and still is.........how does using higher octane result in a LOSS of power? I too have not seen an answer to that question.

The higher Octane only results in a loss of power if your engine does not require the higher Octane to run correctly (No ping). The higher the Octane the slower the burn rate. A slower burn rate means slower acceleration. If your engine runs fine on 87 or 89, 100+ Octane is going to actually slow it down, and if you don't have Conveters on the vehicle it will actually smell like it is running rich because it won't be burning all of the fuel off with the higher Octane fuel.

I believe octane can be independant of burn rate.

I don't think the original posters question has been answered. He asked 91 or 93, nothing to do with 89 or 100 or a pissing contest. Come on.