Quote:
Originally Posted by sierra
Interesting that the direct injection Mazda engine uses our lowest 91 octane with 13:1
Does it inject just before the plug fires so that the fuel is ignited before it can be detonated?
If that's the case then why would the 86 require 98 octane or is that because it also has the port injection?
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its because of the way mazda has designed its combustion chamber, it also uses multi-port direct injection to address higher combustion temps that result in detonation, vs from lean high compression single port direct injection that the FRS has. Because of this, the octane rating strain is loosened up, and can run higher CR, lower gas ratings, and not have to pull too much timing to compensate.
Thats why Mazda was able to test gasoline engines upwards of 16:1CR on pump gas, and still make very little NoX and emissions, although temps were reaching its limit.
From what im told, the SKY-R Rotary will use multi-port direct injection to boost fuel economy and emissions nearly 45% and raise performance upwards of 25%.
DI is the way to go for many makers, but so far Mazda's technology is ultimately winning in IRL numbers. Even if the Skyactive Branding is a silly marketing ploy.