rickscamz28

well I just dropped off my Camaro at New Era and I told mike what gas I was using and he said I should be using 93 with ethanol.he said I was losing 5-7hp.
well I'm glad he told me(wasting extra 20 cents a gallon.i was using it on my 2012 maxima and I was getting 34mpg on the highway.(no diiference in city driving though).

RPM WS6

iTrader: (3)

If you have a 93 octane tune, then you need to use 93 octane to assure no knock retard. Ethanol free fuel will get better MPG so it's not a waste in that sense, but if the octane rating of the fuel is lower, and you need the higher octane to prevent KR, then you'd definitely be losing power with the lower octane (ethanol or not.)

Having said that, some people misunderstand octane. More is not always better. Actually, you want the *lowest* possible octane that still 100% prevents detonation in a given application. So for example, if your tune and combo has 0 KR on 91 octane, then switching to 93 would not offer any benefit at all, nor lead to any gain in power. Octane is resistance to detonation, and the higher it is the harder the mixture will be to ignite. This will cost you power if it's higher octane than necessary for the application in question. If, for example, you were to run 100 octane race fuel through a stock LS1 with a stock tune, you might actually go slower as this is far more octane than needed, thus a harder-than-needed mixture to ignite. And all of this is true regardless of the ethanol content of the fuel in question.

SouthernRex

They only offer 93 where I live. Would a mechanically stock LS1 be able to be tuned to 93 without damage, and get the proper benefits?

Smokin00WS6

iTrader: (4)

Your LS1, if in a 1997-2004 Vette or 1998-2002 TA or Camaro, is already tuned for 93 in stock form. Like RPM said above, 91 wont hurt it, but you will get more knock and less HP but maybe better MPG's. If i were you, I'd just stick to 93 and you will have nothing to worry about. Hope this helps.

Mike

RPM WS6

iTrader: (3)

The factory tune requires a minimum of 91 octane for best performance. There is a low octane spark advance table in the PCM that allows for use of lower octanes (by detecting KR and reducing timing), but the engine won't perform at its best using anything less than 91.

Having said that, usually there is some power to be gained from a slightly more aggressive tune even on a stock LS1, so if you have 93 available (I do as well) then the tune could likely be a bit more aggressive than for the folks who only have 91 available.

RevGTO

iTrader: (12)

This is not only sound theory, but fact. I proved it for myself at the track. I typically get KR on 91 (all we can get around here) so I tried boosting my octane with toluene (or something like that). Went slower.

1 FMF

iTrader: (1)

going to disagree with the admin

with regards to "gasoline" the higher the octane the more you can compress that mixture and the more resistant it is to detonation without the spark from the spark plug. higher octane allows you to have higher compression, where higher compression = more heat within the cylinder prior to top dead center and before the spark plug ignites the mixture. higher compression = higher cylinder pressure = more power if the fuel can handle that compression and not self detonate. All this is not the same as igniting the gasoline mixture with a spark, and i don't believe 93 octane nor 100 octane is "harder to ignite" than a lower 87 octane gasoline. Once ignited, 87 octane vs 93 octane produces no significant difference in heat output per mass quantity of fuel. that is to say under the same conditions (cylinder pressure, spark advance, air/fuel ration) the same ignited mass quantity of 87 octane vs 93 octane gasoline will produce the same increase in cylinder pressure and yield the same power output.
where everyone goes wrong i think is not accounting for the blended fuel, ethanol at around 76k btu/gallon has a much lower heating value than gasoline at 114k btu/gallon. and with 10% ethanol in gasoline that results in 112k per gallon, along with a lower air/fuel ratio. so you can easily bump up the octane rating of your gasoline fuel by adding more ethanol which by itself is 100 octane. so higher than 10% gasoline blends with ethanol can result in a fuel around 95 octane but the real reason you lose power and go slower is because there is less energy content now in your fuel along with a lower a/f ratio. unless you increase compression with either forced induction or variable connecting rods to make up for that loss in heating value you will have less power. good example = methanol, has 1/2 the btu of gasoline but make much more power using forced induction to make up for that less btu by taking advantage of it's higher 113 octane rating. If you used methanol, it's not because of higher octane than you need as the reason you have less power and economy, it's because of a/f ratio and heating value.
how you blend the fuel is what matters most.

RPM WS6

iTrader: (3)

It's OK, we can agree to disagree.

"Harder to ignite" was the wrong way to word it, I can agree to that. However burn rate can/may be impacted by octane, among other factors, though different chemists and sources seem to disagree on just how much or little effect there is in this regard. Then there is also the matter of pump fuel vs. special "race" blends, and the different effects that changes in octane may have on burn rates for each.