The Type of octane to use?

[Kevin Pedrosa]

i was reading through ome threads and guy said he need 85 oct to run his wr sti.. i run 93-95 what's the difference i thought the high the better unless i misunderstood. help if you can..thanks

[EJ257]

You need 91+ fuel

[MainFrame]

91 minimum, 93 is better.

[Kevin Pedrosa]

would there be purpose to running a lower octane? isnt the higher octance better for your car in most areas?

[Mf645]

higher or lower octane is not better or worse, it's different. High octane fuel is hard to ignite. The key is to use the proper to slightly higher octane required for your engine.

[Kevin Pedrosa]

i thought the higher octane is the greater power when ignated therefore better perfomance in the higher torque/hp area

higher or lower octane is not better or worse, it's different. High octane fuel is hard to ignite. The key is to use the proper to slightly higher octane required for your engine.

[Kevin Pedrosa]

ignited**

[MainFrame]

The higher the better in turbo charged cars. The lower ignition point of lower octane fuel makes it much more prone to knock, which is probably the number one killer of these engines.

[Kevin Pedrosa]

we wouldnt want that now would we

The higher the better in turbo charged cars. The lower ignition point of lower octane fuel makes it much more prone to knock, which is probably the number one killer of these engines.

[MainFrame]

i thought the higher octane is the greater power when ignated therefore better perfomance in the higher torque/hp area

Nope.. but with the higher ignition point the car can be tuned more aggressively before it starts knocking. Increases in timing and boost made possible by running higher octane are what produce more power.




It's also possible to run a leaner mixture with more knock resistant fuel, which also produces more power.

[Kevin Pedrosa]

leaner mixture? such as racing fuel?

Nope.. but with the higher ignition point the car can be tuned more aggressively before it starts knocking. Increases in timing and boost made possible by running higher octane are what produce more power.




It's also possible to run a leaner mixture with more knock resistant fuel, which also produces more power.

[MainFrame]

leaner mixture? such as racing fuel?

No, leaner AFR.. less fuel, more air. The leaner the mix the hotter the combustion temps get and the more power it makes.. until it knocks, or melts something.

[Kevin Pedrosa]

what you mean by knock... like engines actually start knocking?

No, leaner AFR.. less fuel, more air. The leaner the mix the hotter the combustion temps get and the more power it makes.. until it knocks, or melts something.

[MainFrame]

what you mean by knock... like engines actually start knocking?

Kind of. Knock is when the fuel mixture in the cylinder isn't igniting at the correct time. The factory knock sensor is basically a microphone installed in the block that listens for a particular frequency of sound associated with combustion. If the gasses in the chamber aren't combusting at the right time it can cause all kinds of damage.



Engine knocking - Wikipedia, the free encyclopedia

[jeremydingeman]

Ill bet the guy was referring to using E85.