Minimum Octane Required-Is There A Formula?

[Mustang 1]

Good Morning!Thanks in advance for all replies!Is there a formula to figure minimum octane for a given situation?As an example,with 23 degrees of timing and 20psi of boost?How about 26 degrees with 24psi of boost?I do not have a scanner to monitor knock yet.Would like to be safe.Thanks

 

[Nojug]

Just go with C-16 and you wont have to worry about it.

 

[MSDGN]

Have to disagree...you can over octane these cars which will degrade performance...not on all cars but many I've seen including mine...you need to try different octanes and mixes of octanes to see what your car likes...I use a mix of 116 and 110...also use 112 when I can find it...this is with a 26 degree chip at 26 PSI boost...if I run straight 116 car doesn't perform as good...without a scan tool you're just asking for trouble running any type of high boost...

 

[Brian Mc]

Originally posted by MSDGN
Have to disagree...you can over octane these cars which will degrade performance...not on all cars but many I've seen including mine...you need to try different octanes and mixes of octanes to see what your car likes...I use a mix of 116 and 110...also use 112 when I can find it...this is with a 26 degree chip at 26 PSI boost...if I run straight 116 car doesn't perform as good...without a scan tool you're just asking for trouble running any type of high boost...

I agree, you should tune for whatever octane you are running. I am using 100 unleaded 76 now because it's close to the house. Not C16 but 100X better than 93.

 

[Mustang 1]

I usually mix 110 leaded with 93 unleaded. Most of the time I run right at 98 octane as an average.When I got the chips burned it was specifically for 98 octane but with the boost programed into the chip at 17psi at base. It runs better if I adjust the wastegate at 20psi.This chip is termed a street high performance and it was done by Joe Lubrant. I just wondered if the addittionl boost of 3 psi required more octane. Also I would like to know the cost of the c16 if anyone here knows.The 110 octane leaded gas here is 3.59 a gallon.When mixed 2 to 1 the average cost is about 2.25 a gallon.I get anywhere from 15-20 mpg.I just got an OTC Scanner and will start reading the directions and learn to use.Thanks again!

 

[MSDGN]

The additional 3 PSI may not necessarily require more octane but will most likely need more fuel so you will have to up the fuel pressure...if O2's or whatever you're using to monitor look good but you're getting knock at a specific boost level then you probably need more octane...I run a JL 110 chip and can run straight 110 up to a certain boost level...about 24 PSI...over that I get a degree or two of knock and need a little more octane so I mix in some 116...friend of mine can 26 PSI on the same chip with pure 110 and no knock...all cars are different...just have to experiment...but take it slow...don't crank the boost up too much between runs...several friends did that and got familiar with pulling engines/replacing head gaskets...