C5/C6 Octane Usage?

[Patman]

Sunoco has reduced its super to 93 octane in NJ NY and Conn. Where are you finding 94?

All the Sunocos here in Toronto, Ontario that I go to still have 94. I'm in trouble once they get rid of it, as my car definitely can't run without detonation on 91. When I had my car dyno tuned I had them add 3 degrees of timing at lower rpms (for better throttle response off idle), so it pings too much on anything less than 94 (and even with 94 it'll ping at low rpms on very hot days in 4th gear) So when they get rid of 94 I'll need to get my tuning redone, and I'll lose the nice throttle response I've got.

 

[Evolution1980]

There are a lot of myths about gasoline, one of which was posted earlier:
Unfortunately, that is not correct. Octane has nothing to do with flash point or the temperature of combustion. Octane is a measure of the fuel's resistance to detonation. Generally, higher octane gasolines have a slower burn-rate but that's not universally true.

Isn't the flash point (more or less) directly related to "resistence to detonation"? Detonation of the fuel takes place at a certain temperature, i.e. "Flash Point". If octane is increased to lower that flash point, the resistence to detonation is decreased. Thus it burns at a cooler, albeit ever so slightly cooler temp.
No?

 

[Evolution1980]

So when they get rid of 94 I'll need to get my tuning redone, and I'll lose the nice throttle response I've got.

Are the so-called Octane Boosters effective?

 

[Patman]

Are the so-called Octane Boosters effective?

Not enough to make the octane jump from 91 to 94. I'd be lucky if any off the shelf octane booster even made a 0.5 point jump. The only way to get that much of an octane boost would be to mix in some unleaded race fuel, but that's not a cost effective solution on a daily driver like mine.

 

[hub_cap]

(brand doesn't matter, except no Citgo in my vehicles). Hub Cap why no Citgo???
He's probably POed at Hugo Chavez

Right on, my money will not support the communist dictator.

 

[Evolution1980]

my money will not support the communist dictator.

...you mean "socialist"... :cool :L

 

[Gry Ghst]

The best the sell!!!

 

[Gorgon]

Isn't the flash point (more or less) directly related to "resistence to detonation"? Detonation of the fuel takes place at a certain temperature, i.e. "Flash Point". If octane is increased to lower that flash point, the resistence to detonation is decreased. Thus it burns at a cooler, albeit ever so slightly cooler temp.
No?

Octane is added to resist self detonation with the increase in pressure in high performance engines. Remember PV=nRT? For a given fuel/air mixture as you increase the pressure the temperature will increase as well. I guess the proper method of looking at it is that you increase the flash point of the mixture with added octane and thus the mixture actually burns hotter than in an engine designed for 87 octane. If the mixture ignites prematurely under pressure then it is likely detonating on the upstroke of the piston and the energy from the blast will be absorbed by the engine as heat instead of being fed into the piston as kinetic energy pushing the piston stroke.

Making sense?

Leon

 

[Patrick]

Okay- for all this conversation about 94-Octane, I have a question: where do you find it? I've done local searches on the internet for gas stations that offer octane ratings above the 91 "limit" you see everywhere. I've asked members of my local Corvette club. I've even enquired of service tech pros at my local Chevy dealers... no one knows!

So where can you even find it anymore?

...you mean "socialist"... :cool :L

Technically, Andre, Chavez is a "Marxist" leading an authoritian regime content to shut down media outlets which disagree with him. And before this line of thought goes any further, it may become necessary to prune this thread an move these posts over the Edge.

-Patrick

 

[Remo]

Chavez is a "Marxist" leading an authoritian regime content to shut down media outlets which disagree with him.
-Patrick

So he's got a few issues. But does he have any 94 octane fuel?:L
Remo:cool

 

[Evolution1980]

I'm pretty sure that some of the Sunoco's around here still have 94. Some of the stations around here have 5 different grades versus the usual 3.

 

[Hib Halverson]

Are the so-called Octane Boosters effective?

Great question.
The answer is, in a practical sense, no.

For decades, up until the early 80s, tetraethylead, was the most common and effective antidetonant in gasolines. It is still used in some aviation gasolines (AVGAS). Many pour-in octane boosters claim to contain lead and they do but the amount of lead is restricted by Federal statute and is so small that it's not capable of a useful improvement in octane. Boosters that claim a lead component or other active ingredients (such as alcohols) are generally only capable of raising the octane a few tenths of an octane number.

The only effective octane boosters marketed in the U.S. use "MMT" as their active ingrediant and they may be capible of raising octane a point or so. The problem with MMT is that 1) it creates hard metallic deposits in the combustion chamber, piston top and spark plugs that are detrimental to durability and 2) it destroys the reactant in catylitic convertors after only a short time. I tested some MMT booster in one of my Corvettes a few years ago and, it did improve octane but I also ended up buying new cats for the car. Just a couple of tankfuls of MMT-laced pump gas killed the existing cats. Lastly, if we're talking about raising the octane of, say, 91-oct gas to 94.5 or 95 (to get maximum performance in how weather) the economics of using MMT to enhance pump gas vs. using 100-octane unleaded racing gasoline is, often, not favorable and is really unfavorable when you have to buy cats.

Lastly, most makers of octane boosters test their products for marketing purposes on 87-oct gas. That is because the chemistry of gasoline and combustion is such that antidetonants are more effective on low octane gasolines than on higher octane gas, ie: you might raise an 87 to 90 with a booster but the same product might only be able to take a 91 to 91.5.

 

[Patman]

Great question.



Lastly, most makers of octane boosters test their products for marketing purposes on 87-oct gas. That is because the chemistry of gasoline and combustion is such that antidetonants are more effective on low octane gasolines than on higher octane gas, ie: you might raise an 87 to 90 with a booster but the same product might only be able to take a 91 to 91.5.

This is an excellent point! I remember an article in Road & Track in 1989 that did a test on the various octane boosters and one of the things they mentioned was that you get diminishing returns with larger doses. So if for example you got one octane point by adding the required dose of octane boost, and you decided to double up the dosage, you would not end up with an additional point on top of that, you might only get another quarter or half point. So this same theory probably applies here as well, in such that the chemicals used in the octane boost are probably the same as the ones already present in the premium fuels. So adding more of those chemicals is going to do very little, but adding those chemicals to 87 octane will have a bigger impact.

On the subject of MMT, they still add this chemical to some of our fuels here in Canada. Sunoco's 94 has a lot of it here actually, as I get a lot of manganese that shows up in my oil analysis reports in my Corvette (which uses Sunoco 94 exclusively) In my wife's Honda, which never runs Sunoco gas, I don't see any manganese at all in it's oil analysis reports.

 

[Vettepirate]

Sunoco and Shell i believe are the only ones here that still sell the 94. I havent seen Petro Canada or Esso(Exxon) carry any, ever.

I dont even know how to hear ping if there is any at all. I hear the chatter of the valves and the rumble of the exhaust but never any kind of pinging. Im not sure if humidity factors into the equation; its usually quite humid here and i would assume it might affect performance.

 

[TODD L GRIFFITH]

My recommendation is for 91 octane minimum. At 10.5:1 compression, this is the minimum you should be using to prevent any chance of detonation. Also, ethynol lowers the octane content. Around here they use 10% ethynol, not as much as the midwest, but it does not help in the octane department.

 

[Victory Red C6]

My recommendation is for 91 octane minimum. At 10.5:1 compression, this is the minimum you should be using to prevent any chance of detonation. Also, ethynol lowers the octane content. Around here they use 10% ethynol, not as much as the midwest, but it does not help in the octane department.

I think that you are wrong in your statement about ethanol lowering the octane rating when blended with gasoline. During the Indianapolis 500 the cars ran 100% enthanol this year. I am sure that they are running compression ratios around 16:1, which greater than any stock Corvette has ever had.


[SIZE=+1]IndyCar Makes Switch to Ethanol[/SIZE]
Washington Post ^| March 21, 2007 | Liz Clarke

Posted on 03/20/2007 10:34:56 PM PDT by thackney

When Ray Harroun won the inaugural Indianapolis 500, he roared across the finish line in a 1911 Marmon Wasp that was believed to have been the first car with a rear-view mirror.
On Saturday, Indy-style racecars once again will attempt to point the way for mass-produced passenger cars, staging the first automobile race run on 100 percent field-grade ethanol. The IndyCar series plans to run its entire 17-race 2007 season, which kicks off at Homestead-Miami Speedway, using ethanol, making it the first series in motorsports to compete on a renewable fuel.
To mark the milestone, Indy Racing League President Tony George and driver Jeff Simmons (who pilots the No. 17 racecar sponsored by Team Ethanol) will join Indiana senators Evan Bayh (D) and Richard G. Lugar (R) at the Capitol today for a round of handshakes, photographs and interviews.
"This shows average Americans what they can do to help meet the energy challenge our country faces, and it makes the point in a way a politician never could," Bayh said in a telephone interview yesterday. "If a racecar going 220 miles an hour can be powered by 100 percent ethanol, the family car can be, too."
The open-wheel Indy cars have run on methanol since the late 1960s. The two fuels share many qualities; both are alcohol-based and have a higher octane rating than unleaded gasoline. But methanol is made from natural gas, a nonrenewable fossil fuel, while ethanol is a renewable fuel made from agricultural products such as corn. Moreover, there's no performance drop-off with ethanol, according to Simmons, who used the fuel in his racecar last season, as well. Simmons says that his racecar, powered by a Honda V-8 engine, actually accelerates better with ethanol. It also gets better fuel mileage, which has enabled the Indy Racing League...

(Excerpt) Read more at washingtonpost.com ...

Advantages of Ethanol Over Petrol-
1. Ethanol has a much higher latent heat of vaporisation (855 MJ/kg) than petrol (293 kJ/kg). As a result, the fuel mixture entering the cylinder is much cooler and hence denser in case of ethanol than in the case of petrol.
2. Ethanol has a higher octane number (99) than petrol (80-100). As a result, 'pre ignition' does not occur when ethanol is used.
3. Higher octane rating of ethanol allows the compression ratio of the engines to be increased; this results in increased production of power.
4. Ethanol is burnt more completely so that hydrocarbon emission is drastically lower as compared to that in case of petrol.

Negative of Alcohol Based Fules
In the case of alcohol fuels, like Methanol and Ethanol, since they are partially oxidized fuels they need to be run at much richer mixtures than gasoline. As a consequence the total volume of fuel burned per cycle counter balances the lower energy per unit volume, and the net energy released per cycle is higher.


I have read reports that indicate 100% ethanol has an octane rating of 113.

[FONT=Times New Roman,Georgia,Times]How does it work?[/FONT]

[FONT=Times New Roman,Georgia,Times]Ethanol is a very high octane fuel, replacing lead as an octane enhancer in gasoline.

Fuels that burn too quickly make the engine "knock". The higher the octane rating, the slower the fuel burns, and the less likely the engine will knock.

When ethanol is blended with gasoline, the octane rating of the petrol goes up by three full points, without using harmful additives.

Adding ethanol to gasoline "oxygenates" the fuel, adding oxygen to the fuel mixture so that it burns more completely and reduces polluting emissions such as carbon monoxide.

Ethanol and ETBE oxygenator, made from ethanol, are much safer than the toxic and polluting MTBE fossil-fuel-derived oxygenator used by oil companies. [/FONT]

I have foiund more information on the net to support theinformation above. So, your claim that ethanol lowers the octane rating is simply false. Also in the Midwest the standard ethanol blend is 10% ethanol nothing more. However, there is E85 (85% ethanol) for those vehicles that are equipped to run the higher percentage.

 

[Patman]

Sunoco and Shell i believe are the only ones here that still sell the 94. I havent seen Petro Canada or Esso(Exxon) carry any, ever.

I know that Petro Canada's in Quebec used to carry 94 octane but I'm not sure if they still do. I'm surprised you didn't know this considering Ottawa is so close to Quebec.

 

[TODD L GRIFFITH]

I think that you are wrong in your statement about ethanol lowering the octane rating when blended with gasoline. During the Indianapolis 500 the cars ran 100% enthanol this year. I am sure that they are running compression ratios around 16:1, which greater than any stock Corvette has ever had.

Here is what is happening to ethanol currently. Depending on where you live, the fuel content is going to change lowering the octane content of E-10, because the environmenmtalists are crying it is harmful to the environment. The effect is an overall lowering of the octane content of E-10. Ethanol has been used in the past as an octane booster, but that is changing as we speak. Ethanol doesn't give you any additional power it just resists pre-ignition.
The environmentalists are running the show here.

 

[motorman]

on a road trip from PA to the NCM in BG i ran high test,93 octane and my friend with the idenical car ran regular,87 octane and he averaged 3 MPG less for the trip than i did,25 vs 28. taking out timing does kill the fuel mileage

 

[85_02_Corvette]

I Live out West 91 is Premium & 100 Racing octane

I have noticed an occasional spark knock ping here and there under acceleration when I bought the 02 in LA, and when I got home like I do in my 85, I put 60% 100 Octane and 40% premium which gives me about 96 octane and the car runs smoother and no knocks period, I also can say for some reason my mileage does go up just a bit, no routes are the same but it is almost 1mpg better, could be pure luck or I drove easier? I can say a little more power, smoother running, and it keeps the fuel injectors clean and less carbon, I grew up in michigan and south east and 93 is the standard, I guess since most of the west is higher elevation they say less octane is required? not sure about that theory as never had ping in Michigan in any of my vettes, just sold a 87 so back to 2 vettes again, looking for a 68 perfect, so I have started saving, funny the l88 requires 103 octane, a sticker on the center box in yellow, high compression there. out here jabu's gas and shells gas is the same, as it is pipelined in, so brand name means nothing except some additives they put in at the station, which if you add chevron techron with each tank, 1/3 bottle everytime, really is no difference..:W