Avoiding Pinging with 91 Octane California Gas

[jhirasak]

I originally built my SBF 331 cu in engine to run on 93 octane pump gas with 10 to 1 compression ratio aluminum heads and .041 quench clearance. My best engine performance was obtained with 16 degrees initial ignition advance and 36 degrees total advance by 3000 rpm. After I moved to California, I could only obtain 91 octane Shell premium pump gas on a regular basis so I first retarded my timing to avoid spark knock. This led to a noticeable loss in power, lack of crispness in throttle response, and slightly elevated engine running temperature. To regain performance and return to my original ignition timing with 91 octane pump gas, I have resorted to using octane booster additive with each refueling as well as slightly increasing the richness of my air/fuel ratio.

Without changing my compression ratio, I would like ask the forum questions regarding my options for regaining the performance that I had while using 93 octane gas.

1) Is there another brand of readily available California pump gas that is better than Shell premium?
2) What brand of Octane Booster provides the best increase in the octane rating of pump gas?
3) Other options?

Comments?

John

[Bernica]

I am fortunate enough to live near a 76 station that has 100 octane race gas and I use it usually mix it half/half with premium, although many times just run it straight. The 100 is not cheap, but I am running 10.9:1 cr and once I started using the 100, I was able to go back to optimal timing. There are websites that you can use to locate high octane fuel suppliers near you, like Sunoco or 76.
Good luck!

[4pipes]

Octane Supreme, google it.......stunning results.

[Ron61]

I too use the racing gas in one of my cars. I had the compression lowered from 12.5 to 10 but it still pinged. I live in Northern Calif. and we can't get the Sunoco gas up here at all, but Union 76, Shell, and Chevron seem to be the best.

Ron

[jhv48]

I ran 18/38 degrees advance on my 302ci engine with California 91 octane gas with no problems. Compression was also 10-1.

My last 427 sbf ran 16-36 degrees with 10.5-1 compression on 91 octane California pump gas. No problems there either.

Does your original setup ping when you use 91? If not, don't change anything and run it.

[jhirasak]

JHV48

My engine ran without pinging while using 93 octane gas but now that I live in California, I am having trouble with pinging while using the available 91 octane Shell premium gas. As per comments to my questions, I will try some of the other recommended brands of premium pump gas to see if they will perform satisfactorly without the need of octane booster addition.

Thanks to all of you who responded to my questions.

Cheers,

John

[DWRAT]

In Arizona my 408 pings under heavy load using Cheveron 91 but does very well with Shell 91.
So I would recommend not bothering with tying Cheveron.

[undy]

Octane booster = snake oil. When they say it raises octane a full point, they really mean 1 point = .1. So... if your octane booster says it raises octane 3 points and you started with 91 octane you now have 91.3 octane.

As Bernica said, mix some 100/104/110 race fuel in. You'll more than likely only need 2 or 3 gallons per tankful.

[Bernica]

I know for a fact that there is a Sunoco station right by Autoclub Raceway. You can get some real potent juice there!

[jhirasak]

Unfortunately, I searched for Sunoco locations that have 100 octane gas available at the pump and the closest such station is approximately 30 miles from my home address. This leaves me with trying Union 76 premium pump gas locally or continuing to add octane booster to Shell premium pump gas. Since I use my car on a regular basis, driving to a Sunoco location that has 100 octane pump gas when my fuel level drops below 1/2 of a tank does not appear to be a practical solution.

By the way, the octane booster that I currently use is marketed by Royal Purple and it appears to be sufficient to avoid pinging when mixed with 91 octane pump gas with my ignition timing set for maximum performance.

I looked into the Octane Supreme product and found that the primary active ingredient to raise the octane number was tetraethyl lead. Because I use a wideband O2 sensor for tuning, I would prefer to stay away from this product which could contaminate the sensor.

John

[Bernica]

Look for a 76 near you with race gas

[jhirasak]

Bernica,

I searched for 76 and other brand stations that have 100 octane pump gas and unfortunately there were none sufficiently close to my home to make blending of 91 octane and 100 octane gas a practical long term solution. For the time being, I will stick with an octane booster additive mixed with 91 octane pump gas since I can always carry the octane booster with me.

I guess the next order of business for me would be to determine which brand of octane booster is the most effective one to use. I would be interested to know if anyone on this forum has useful information regarding the relative performance of the various snake oil formulations that are available on the market. It is hard to compare these product by reading the labels on the bottles or from their advertising material.

John

[ERA2076]

We have had good results running Race Gas.

RACE GAS | Racing Fuel Concentrate

[Dominik]

Is you car pinging under acceleration, or at the top end?

I had a 12.5:1 454 LS7 in one of my cars in the 90s and ran it with Euro 98 RON (US 93 MON). I slowed down the ignition advance curve using harder springs for the mechanical advance. Also, the car was very light and geared 3.54:1. So I spent little time under WOT, mid-range rpm (up to 3.500 rpm).

An "old-school" turbo mechanic, from the 70s (in Scottsdale) suggested water injection.
Probably not practical for daily use, but worth considering.

Do you have access to a chassis dyno?

[*13*]

I know of a few stations that had it, a few years ago. Probably a good 30 miles from you, as well. There is always the WEBERs option

[Ron61]

If you want to take the time, they have several videos on You Tube where they tested various fuel additives and show the results. I will stay with the racing gas in my car as I tried a few additives and none of them helped.

Ron

[Bryan Wilson]

In Australia where I am all Mobil stations have 91 and 98. My car runs like a dog on the 91 so I use exclusively the 98 which I can get at any Mobil station.

[olddog]

E-85 is a fairly high octane fuel. Its biggest problem in my area, Ohio, is that it is blended anywhere from 50% gasoline to 15% gasoline. It is my understanding that 15% gasoline (85% ethanol) is difficult to start in cold weather. So from one tank to the next you never know what the blend is.

I have heard of dirt track racers running E-85 with a carb. I have also talked with people who set up 1989-1995 5.0 Mustang to run E-85 with the old EEC4 EFI. The biggest issue is the variability in the mixture, which is why the new flex fuel cars have a sensor that measures the mixture.

That all said, California may have a more stable mixture. So this may be an option, but you will have to check into that. Get the facts first.

Your fuel lines would have to be the correct material. If your running a carb, you may have to get an alcohol rated carb to be able to meter the extra fuel.

Wish I could give more knowledgeable useful information, but I have no hands on experience.

[jhirasak]

Thanks to all of you that have responded to my questions. After reviewing material available on the web, it appears that gas additives that contain MMT provide the best improvement in raising the octane rating of straight 91 octane pump gas. Now comes the problem of separating advertising hype from actual results. However, mixing 100 octane gas with 91 octane normally available in California seems to be the preferred solution to my situation by many on this forum.

Since I would like to keep my existing ignition advance curve for best performance, I think that I will purchase a few gallons of 100 octane gas whenever I happen to be near a source of such gas and keep a can of octane booster with me to add to the tank when I can only obtain 91 octane pump gas. Since I have a MSD Knock Alert detonation sensor installed on my engine, it is easy to to determine if the current tank of gas has a sufficient octane rating.

Cheers,

John

[twobjshelbys]

Originally Posted by olddog

E-85 is a fairly high octane fuel. Its biggest problem in my area, Ohio, is that it is blended anywhere from 50% gasoline to 15% gasoline. It is my understanding that 15% gasoline (85% ethanol) is difficult to start in cold weather. So from one tank to the next you never know what the blend is.

I have heard of dirt track racers running E-85 with a carb. I have also talked with people who set up 1989-1995 5.0 Mustang to run E-85 with the old EEC4 EFI. The biggest issue is the variability in the mixture, which is why the new flex fuel cars have a sensor that measures the mixture.

That all said, California may have a more stable mixture. So this may be an option, but you will have to check into that. Get the facts first.

Your fuel lines would have to be the correct material. If your running a carb, you may have to get an alcohol rated carb to be able to meter the extra fuel.

Wish I could give more knowledgeable useful information, but I have no hands on experience.

It's much more than this. E85 is not a substitute for "octane". You cannot simply take an engine not designed for E85 and run E85. Besides the corrosive component on fuel pump, lines, etc, all of the fuel delivery system will be wrong. Since the energy content (per unit volume) of E85 is much lower you will need at least higher rate of fuel delivery to compensate. (Either a carb or higher flow injectors). If fuel injected you would also need a correct "tune". Flex Fuel (Ford's name for E85 vehicles) detect the use of E85 automatically and make engine adjustments accordingly.