Thread: 93 Octane?
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Old 04-04-2012, 08:10 AM   #168
old greg
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Quote:
Originally Posted by chulooz View Post
Just missing ~50hp
Quote:
Originally Posted by Enemies View Post
Like almost 20% less horsepower
The difference in HP is purely due to RPM. In terms of BMEP (the standard yardstick for pissing contests between engineers) the two engines are very evenly matched.

Quote:
Originally Posted by Baldeagle View Post
But can anyone help me understand why one engine with a 12.0:1 compression ratio is fine on 87 octane fuel and why another engine with a 12.5:1 ratio requires 93 octane.
Mazda went to great lengths to increase the knock resistance of their engines.

Quote:
Originally Posted by Baldeagle View Post
And if the concept of efficiency enters the equation, why does the heavier, larger and less aerodynamic Mazda3 get 39mpg hwy compared to the estimated 30 mpg hwy for the BRZ?
Taller 6th gear (probably) and lower bsfc at low engine speeds. The same characteristics that allow the Subaru motor to make more torque at high rpm than the Mazda make it less efficient at low rpm.
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