I'm curious, on a extended or mild street port, what octane should you be using?

 

well i always run the best that i have around here i have never put regular into my FC and dont ever plan to even on a blown motor. but i would say always stick with the highest octane

 

it depends.. its it a turbo or NA?

Turbo=94 octane pump gas or higher
NA= 86 octane pump gas or lower.

 

94 octane...good lord.

at the regular stations west coast only has 91 octane

 

Ultra94, by Sunoco... its tha hot ****. I used to run it all the time in my DSM up north... it woke the **** up... 91,92, and 93 cant compare... its crazy how much a difference 1 point will make. the stuff even SMELLS like race gas.

now, im stuck in fla... and only get 93 once in a while

 

NAs run best on low octane. However if the motor is ported (bridge, street, monster) I would be curious to know if you should up the octane.

 

Unless a ported NA is somehow running higher compression (doubt it!!) then use plain ol 87.

 

Word brotha. I'm with Josepi.

The factory race teams use to add to much premix to lower the octane rating of the fuel. They did this for two reasons. Reliability and they made more HP with the lower octane fuel. The sanctioning body finally caught on due to the nasty habit the engines had of smoking more than everyone else. Not sure what IMSA did to them.

 

i use 91 or 93 on my bridgeported fc. it seems to run good. too bad i only get like 11mpg

 

well I'm running a n/a street port. I live in california so all that's available to me is 87, 89, and 91. so should I be using 87 since it's just a n/a street port?

 

Yes the octane you use is due to the compression and boost if your a turbo car. But since you probably still have N/a rotors you don't need any higher. I remember hearing the 787B used 85 octane on a peripheral port so I wouldn't worry about upping the octane on a street port.

 

I would trust Josepi's advice.

 

i have a turbo 2 btw

 

The lower the better. You could run 80 octane without any problems, that is if you could find 80. N/A of course.

 

This 87 octane and lower thing blows my mind....how and why would you run such a LOW octane fuel in your NA? I have a mildly streetported S4 NA, basic bolt-ons, and I ALWAYS run 93, with 8oz or so of premix. Hell, I've ran 110 a few times, runs great. Whats with the lower octane, lower the octane, more chance of detonation.

 

where do you find 110 at? what you really want for performance is leaded gasoline, hell on the environment and wallet but you get more power.

 

They sell it a block from my house, no ****. I live 5 miles from an ORV park, and the guys with bikes, 4-wheelers and buggies buy it from there. They dont even have the BIG tip on the pump, just a plain jane pump. Pull up, pay at the pump and away you go.

 

forgot to mention, its 4.84 I think a gallon, not TOO bad. I've watch my turbo buddies spend 100+ bucks to fill up on 112 and 114. **** a bunch of that.

 

which part of missouri is tokyo in? jeebus. thats expensive gas. there is a station across the missouri/arkansas state line that sells 93 so if i can i usually buy that at 1.80 a gallon

 

Just posted price, and Im in Columbia Missouri. I can get BULK race fuel at pretty good prices too, buddies dad works for the distibution company.

BULK means drums...

 

im near branson. so columbia is not too far. how much for a drum?

 

You're an idiot to waste money on 110 for an N/A. My car actually felt slower on 91 than it did on 85 when I tried it once.
Lower Octane burns faster, making more power, but the detonation chance is higher.
Higher Octane Burns slower, making less power, but detonation is much less likely.
The only reason you'd need 110 in a SP N/A is if you want to run some crazy timing advance.

 

You make more power with lower octane. Higher octane is not used to gain performance, at least not directly. It is used to allow more boost to be ran. Its for safety, not power. You want to run the lowest possible octane that you do not detonate with.

 

It all depends on your mods if your a TII, I have full exhuast, intake, and a walbro with my street port, port match turbo runners, and ported the wastegate, I only boost to 7 psi with my street port and I run 87 octane all the time. I get 15-20 mpg depending on driving condition and still am running pretty rich....I believe that in the owners manual its says to use 87 for a stock TII.

 

Octane rating of gasoline is a measure of it's ability to resist detonation. The higher the compression ratio (or boost level), the higher the octane needed. 93 octane fuel ignites at a higher temperature than 87. This prevents the fuel charge from igniting at the wrong time due to combustion chamber temperatures.
I don't know exactly how changing the porting affects combustion chamber temperatures, but I suspect that since it is similar to changing camshaft lift and duration in a reciprocating engine, the purpose is to move gasses through the chamber faster.