93 octane not available. HELP

[DaleRider]

Originally Posted by Astro14
Originally Posted by DaleRider
Originally Posted by mattwithcats
I have been buying Sunoco Race Fuel 260 GTX from Richmond Raceway...

98 Octane, no lead, no ethanol, no metallic additives...

One quart in 5 gallons 87, cheapest octane booster I can find...

https://www.sunocoracefuels.com/fuel/260-gtx



Just curious, but what do you think you're really accomplishing with that mixture? From doing the math, 1 qt of 98 octane plus 19 qts of 87 octane to create a 20 qt (5 gal) mixture gives a final octane rating of 87.55. Since you're not raising the octane much at all, what's the point?





Is the relationship between octane and chemical composition strictly linear?

I suspect it's not...



What do you mean by that question? Are you talking about the chemical composition of the fuel or the way I figured out the true octane of his mix?

If it's the latter, I used a formula given by Sunoco themselves and is why I made a 20 qt mixture (5 gal) with a 1 + 19 mixture.

https://www.sunocoracefuels.com/tech-article/mixing-fuels-calculating-octane

The formula reads:

( [ % Fuel A ] x [ Octane of Fuel A ] ) + ( [ % Fuel B ] x [ Octane of Fuel B ] ) = Octane of Mixture


Since he's putting 1 qt into a 20 qt mixture, the 1 qt of the 98 octane gas represents 5% of the total mixture, right? The other 19 qts. of 87 octane gas represents the other 95% of the final mixture.

So, using the equation, 5% x 98 (octane) + 95% x 87 (octane) = (0.05 x 98) + (0.95 x 87) = 4.9 + 82.65 = 87.55 octane of his final mixture. Easy peasy math.

 

[Olas]

if you really need a particular AKI then ideally order proper racing fuel from Shell/VP/Penta etc etc. 100LL could be an option if you dont have cats and are close to an airfield

VP Octanium can be mail ordered and provides significant AKI boost

Chemical suppliers have Toluene, Xylene, Acetone etc

there's nothing to stop you using a 5% mix of e85 in your 95% full tank of 91

significanlty improve cooling and the octane requirement will fall slightly (diminishing returns here)

water/meth injection sucks LOTS of heat out of its surrounding environment

change pulleys for less boost is less than ideal ut would reduce knock

lots of choices

 

[y_p_w]

Originally Posted by Astro14
Originally Posted by DaleRider
Originally Posted by mattwithcats
I have been buying Sunoco Race Fuel 260 GTX from Richmond Raceway...

98 Octane, no lead, no ethanol, no metallic additives...

One quart in 5 gallons 87, cheapest octane booster I can find...

https://www.sunocoracefuels.com/fuel/260-gtx



Just curious, but what do you think you're really accomplishing with that mixture? From doing the math, 1 qt of 98 octane plus 19 qts of 87 octane to create a 20 qt (5 gal) mixture gives a final octane rating of 87.55. Since you're not raising the octane much at all, what's the point?





Is the relationship between octane and chemical composition strictly linear?

I suspect it's not...

The linear math is pretty close to how it ends up.

 

[y_p_w]

Originally Posted by ammolab
Originally Posted by Marco620
You don't need that high of an octane at that high of an elevation


On a normally aspirated engine? Absolutely....... But his Zl1 is supercharged. Under max boost he may want 93 octane. No big risk as knock sensing is very protective these days.

Use the 91 and accept a bit of power loss at WOT.

California only has 91 octane at every elevation, sea level even. Those guys run 91 in their supercharged GM V-8s, Your tune may not need 93 octane or benefit from it.

About the only way to get anything higher than 91 AKI in California is to use something with a blend of 100 AKI street legal race gas. There's this one place that has it, although I've been there when they were out of it and all their 94/96/98/100 selections were covered up/disabled. The sign said "out of race gas". This place is hilarious too as they repurposed an 86 octane label and use it upside down to make 98.

 

[dave1251]

91 will work good especially at 4500 feet.

 

[y_p_w]

Originally Posted by dave1251
91 will work good especially at 4500 feet.

Forced induction is different though. The blower should be able to go up the specified pressure regardless of atmospheric pressure. However, that's just boost. I think there might still be slightly lower pressure, but much higher than without a turbo.

Turbos were extremely common with aircraft engines that needed to operate at high altitude.

 

[red7404]

years ago i read in a motor cycle magazine how this guy would raise the compression ratio to compensate for the altitude.