[Senor PuffPuff]

What I'm wondering, is why is it that the L36 with 9.4:1 compression requires 87 minimum octane, whereas the L67 with 8.6:1 compression requires 91 octane minimum?

If engines with higher compression require higher octane, then why does the L36 require a lower minimum octane?

And also, why the hell is the compression ratio of the L36 higher than the L67? That doesn't make much sense to me...

 

[playtoy_18]

Easy answer?
More heat from boost is more susceptible to preignition,octane is simply knock resistance.
At least that's my take on it.
Might google static versus dynamic compression as well.

 

[thebeewantsboost]

think about what compression is..... in this case, we're compressing air and fuel into a cylinder. the l36 has higher compression because it needs it, for naturally aspirated power. Only so much air can be sucked in. Low octane gas is ok because detonation isn't as big of a factor as it is with forced induction.

why is detonation more of a factor with forced induction? because there actually is more compression. the more air that is "compressed" by the blower into the
motor. the hotter the air is and the greater the chance of detonation. an l67 is designed for forced induction. the lower compression is complimentary to boost. it allows more boost safer.

feel free to correct me if im wrong