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Octane levels...??

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Old 02-01-2011, 11:15 AM
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Default Octane levels...??

I know, I know, ANOTHER question about fuel....


I was told I should run 91 octane fuel in my Procharged 454 Mag MPI. Problem is that on the water around here you can basically only get 89 octane fuel.

I usually fill up with 94 octane at the gas station and half way through the tank I top up on the water with 89 octane....question is, " If you mix 94 octane fuel with 89 octane fuel, do you get something close to 91 octane fuel...........
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Old 02-01-2011, 11:22 AM
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Originally Posted by FogduckerIII View Post
I know, I know, ANOTHER question about fuel....


I was told I should run 91 octane fuel in my Procharged 454 Mag MPI. Problem is that on the water around here you can basically only get 89 octane fuel.

I usually fill up with 94 octane at the gas station and half way through the tank I top up on the water with 89 octane....question is, " If you mix 94 octane fuel with 89 octane fuel, do you get something close to 91 octane fuel...........
add meth injection just in case knock sensor may retard it if it wasnt deleted in the tune.
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Old 02-01-2011, 11:23 AM
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Originally Posted by FogduckerIII View Post
I know, I know, ANOTHER question about fuel....


I was told I should run 91 octane fuel in my Procharged 454 Mag MPI. Problem is that on the water around here you can basically only get 89 octane fuel.

I usually fill up with 94 octane at the gas station and half way through the tank I top up on the water with 89 octane....question is, " If you mix 94 octane fuel with 89 octane fuel, do you get something close to 91 octane fuel...........
Yes.

1 gallon of 94 mixed with 1 gallon of 89, acts like 2 gallons of 91.5 in terms of compressibility. Since the ProCharger raises both the pressure and temperature of the air/fuel mix, preventing premature detonation is why you want to run the higher octanes.
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Old 02-01-2011, 11:26 AM
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sounds logical to me. Obviouisly if you are not sure on your fuel you should not run your boat hard IMO. I do know that there is a lot of misconceptions on octane boost, and there is no way that octane boost will help at all in a boat. Having to do with octane points/octane numbers. There are 10 points in 1 octane number.

So you are on the correct track by mixing higher octane fuel with the 89 on the water.
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Old 02-01-2011, 11:54 AM
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sounds logical to me. Obviouisly if you are not sure on your fuel you should not run your boat hard IMO. I do know that there is a lot of misconceptions on octane boost, and there is no way that octane boost will help at all in a boat. Having to do with octane points/octane numbers. There are 10 points in 1 octane number.

So you are on the correct track by mixing higher octane fuel with the 89 on the water.
The following is in reference to pump gas.

Octane in reference to pump gasoline, is correctly called the octane rating. This is a comparison to, "2,2,4-Trimethylpentane, also known as isooctane" which is an octane isomer and defines the 100 point on the octane rating scale. Heptane is the zero point on the octane rating scale.

Octane rating is used to reference the compressibility of the gasoline. The higher the octane rating the more compressible it is, the lower the octane rating, the less compressible it is. As an example, an octane rating of 91, says this fuel acts like is was 91% isoctane and 9% heptane.

Higher octane rating fuels do not have more stored energy in them, and do not make more HP, they just allow for higher compression rations, (before detonation occurs), and the higher compression rations produce a bigger bang, which is where the additional Hp comes from.

Running higher octane fuels in a motor designed to run on a lower octane, does absolutely nothing to improve performance, and doing so wastes your money.

Two more things:
octabe boost does help in any engine, and allows for higher compression and temperatures, before detonation occurs, if used properly

sometimes higher octane pump fuels had additional additives, which many slightly change characteristics of the fuel.
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Old 02-01-2011, 11:58 AM
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What about the bottled stuff you can get on the shelf. If some one needs to run 93 octane can an additive be used to take you from 89 to 93?
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Old 02-01-2011, 12:23 PM
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I just bought some of the Torco accelerator product to use in my engine, but have yet to run it. My boat is 10.5:1 and I try to run about 94-95 octane. Last time out I mixed some Trick Racing gas and some premium and it ran great. I will post up once I have some time with it.
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Old 02-01-2011, 12:30 PM
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What about the bottled stuff you can get on the shelf. If some one needs to run 93 octane can an additive be used to take you from 89 to 93?
Not the junk stuff at the auto parts store. Best thing to do would be to add some race fuel or tolune. Toluene is 114 octane. You need to add about 10 gallons of 114 race fuel or toluene to 50 gallons of 89 octane to make 93 octane fuel.

Real octane boosters made by people like Torco are good, but pricey also.
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Old 02-01-2011, 01:04 PM
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I have an electronic octane test machine. I have found that after testing more than 60 separate tests that gasoline sold at the pump has 1 - 1.5 more octane than is the Minimum rating suggested on the pump. Gasoline tested from 7-11 last week, I purchased 89 octane was actually 90.5 octane when tested. Out of 60 test including Exxon, Shell, Sunoco, Mom & Pops little store, Marina etc... I have never had less that 1 octane above what is written on the pump, and if your read the pump carefully it states that that is the "minimum" octane rating. I went to the auto parts store and purchased a bottle of everything they had on the shelf to increase octane. I can tell you it takes a lot of "booster" to increase a gallon 1 point and ton of "booster" to increase the octane one number. I have gasoline being tested that is more than 1 1/2 years old from the purchase date, left purposely in sealed and unsealed containers. Each test has lost no octane over the period. Understand that the fuel may have lost volatiles that make it hard to start, smell bad etc...but it has not lost octane. These fuels also contain 10% ethanol.
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Old 02-01-2011, 01:23 PM
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Originally Posted by Griff View Post
Not the junk stuff at the auto parts store. Best thing to do would be to add some race fuel or tolune. Toluene is 114 octane. You need to add about 10 gallons of 114 race fuel or toluene to 50 gallons of 89 octane to make 93 octane fuel.

Real octane boosters made by people like Torco are good, but pricey also.
OK. Didnt know. thx
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