abyss

Ok, call me a tard and what not.. but how does the Octane come into play with the higher boosted cars? Where I live (bumfawkegypt) the highest there is available (and sadly very few gas stations these days) is 91 Octane, so my question would be, with 91 octane is it feasable/safe to attempt to build a 550-600whp car with a fully built block? and those of you who run higher octane..do you get it from the pump or elsewhere? All the shops around here say they have to get barrels shipped in to run higher octane.

redman333

iTrader: (8)

Hey I'm in southern california and all I have for the most part is 91 octane. As far as I know most people buy it in barrels.

IIQuickSilverII

iTrader: (13)

yes you can run a build car higer than 550whp on 91 octane... you jsut gotta stay more conservative on your a:f ratio

Sean

if you live near a marina, see what they have.

abyss

Thats actually a great idea. I never thought about that, I'm sure alot of those heavily modded race boats out on Table Rock Lake run some higher Octane. Kimberling City Marina is full of them.

Sean

you may need to use gas cans, they may not pump it into your car directly

joe645733

iTrader: (3)

damn, no one has 91 over here...its all 93.

Dynosty

iTrader: (27)

There is only so much you can do on pumpgas... 91 or 93. Give VP or Klotz a call to see about delivery - I know Klotz offers free shipping if you buy 2+ drums.

VP Midwest
Terre Haute, Indiana
Phone: 812-466-1175
E-Mail: vpmidwest@aol.com

Klotz Synthetic Lubricants
Fort Wayne, IN
Phone: 800-242-0489

abyss

^goodstuff. thanks.

IIQuickSilverII

iTrader: (13)

hahaha
funny
i wish i could find 93 here

Nealoc187

550-600 wheel is pushing it but it's possible on 91. You have to be more conservative on timing moreso than AFR as opposed to what someone mentioned.

Around here, of the hundreds of gas stations in my city, there are probably 5 that carry race gas. you either need to call around to find it (like, open up the phone book and actually call station after station) or if you are lucky you might have a local car message board you could ask on. Or perhaps your local track has a message board on their website as many do, and you could ask there. If neither of those works out and you truly don't have any race gas in your area, you'll have to order it by the drum.

A good option for those who don't want to run race gas is water/methanol/alcohol injection - there is tons of information on this all over the internet, this board has a bit on it. check it out.

IIQuickSilverII

iTrader: (13)

i run methanol injecton to be safe

atlsupdawg#2

You can always mix toulene with a pint of 2 stroke motor oil (or Marvels Mystery Oil) to boost octane to about 98 using a 70/30 mix. If you can get a hold of xylene the same mix will bump it up to about 100. And yes, I've ran it before with no issues what so ever in my Supra TT..

Sharif@Forged

iTrader: (92)

The CA shops frequently tune cars to 91 octane on built engines, so it wont be an issue. You will trade a couple degrees of timing when using the 91, so max boost, and overall power will be reduced slightly. But 500-550whp is very doable.

jpc350z

High octane prevents detonation (Knocking) which if occurs could cause serious damage to rings\pistons etc...The octane reduces the potential to ignite the unburned gases in the cylinder after the powerstroke...

Nealoc187

Close. Detonation happens after ignition and is the uncontrolled explosion of fuel/air mixture away from the flame front. It can happen either in the very last stages of the compression stroke (but after ignition has occurred, this is one of the reasons that timing advance comes into play) or during the power stroke. During the compression stroke or the early stages of the power stroke is where it is most likely to occur. As the flame front burns there is less and less unburned fuel/air mixture left to detonate. After the power stroke is the exhaust stroke - the exhaust valves are open and the cylinder is being evacuated - thus cylinder pressures are low and the risk of detonation is basically non-existent.

Q45tech

The imaginary numbers posted on pumps are a marketing statement in most states.
Few states measure the octane directly relying on the refiners to sell regular or premium and the pipelines to not mix it up and the tank farms to not let it sit too long, etc.etc.

Premium gasoline is usually define as anything greater than 90 [90.5000001] the final number is ADJUSTED based on the altitude. In otherwords a premium can be legally labeled anything 91 or greater at the whim of marketeers.

A 91 at sealevel can magically become a 93 at a city like Atlanta, KC, Utah, etc where the local altitude is above 1000 feet since the air density is 3% minimum lower.

jpc350z

To clarify the difference between detonation and pre-ignition which are both abnormal combustion, From Engine Basics: Detonation and Pre-Ignition by Allen W. Cline

Definition of Detonation:

Detonation is the spontaneous combustion of end gases(remaining in the fuel/air mixture). It always occurs after normal combustion. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point herr is that detonation occurs after the normal combustion with the spark plug

Definition of pre-ignition:

Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mix in the chamber to ignite (heat/pressure) prior to the spark plug firing it is classified as pre-ignition. Hope this helps..

rocks

iTrader: (1)

I only have 90 octane here in mexico.

350Zzzz

Absolutely, there are distinct differences between pre-ignition and detonation, as they are not the same as many might think.

In a nutshell the octane rating measures the boiling point of fuel and end gases to spontaneously ignite under the specified test conditions. The chemical/molecular structure of the fuel is the ability to withstand pre-flame conditions without decomposing into gases that will auto ignite before the flame front arrives.

Typically, an 87 octane rating is gasoline that contains 87-percent octane and 13-percent heptane; or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane. Iso octane has a higher melting & boiling point than Normal heptane.

Running the a/f mixture on the richer spectrum, helps cool down the chambers to protect against spontaneous combustion, pre or post flame front.

The Octane rating should not have a direct effect to performance and/or mpg of the vehicle.

G
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