Mazda Demio SkyActiv tops Japan's "Eco Cars" survey, Toyota Prius #2

I don't know anything about a 12:1 engine, perhaps cyclopathic can send a link so we can learn more. Ford was going to make a 13:1 version for regular gasoline and that suposedly had 3% less fuel economy and 5% less peak torque than the same size 14:1 running premium. I would guess the drop from 13:1 to 12:1 would be even smaller percentage change since both are regular gasoline. The sky-g on intake can switch between otto and Atkinson cycles so a 14:1 engine running regular might just have to give up its otto cycle in valve timing. This would be a less than optimal engine design though.

Given the testing methods, I doubt it will get us to 56% improvement in epa highway mpg. This should come in around 40mpg highway like the cruze and focus it is competing against. Maybe 14:1 compression would add 2 mpg.

 

The higher compression ratios are do to the use of direct injection.
[ame=http://en.wikipedia.org/wiki/Gasoline_direct_injection]Gasoline direct injection - Wikipedia, the free encyclopedia[/ame]
Improving Internal Combustion with Direct Injection - TechConnect Online News Blog

Many of Toyota's V6s have recommended mid-grade. Owners probably didn't even know that. I think using it would just generate the backlash caused by premium. I suspect Mazda will go with premium. They are already have made a sporty niche for themselves, and premium for a sports car is more acceptable than in a family car. Some models already are premium fuel. Plus, it further differentiates their engines from Ford's GDI.

 

One of the flaws with E85 here is that the flex fuel engines have a native compression for regular gas. If they had the compression ratio for premium gas, they would be taking a lower reduction in fuel economy when burning E85. Designing them to run on E85 as baseline and then adjusting for gasoline would have been even better.

 

Designing a normally aspirated engine for e85 would leave it starved for power when running gasoline. With turbocharging and injection the engine can adjust to the blend in the tank. Ford even has a dual tank gasoline/e85 design that greatly improves high power efficiency by using more e85 to cool the engine when needed.

 

Why so?
If such an engine existed, wouldn't it dial back the timing down for the lower octane fuel? Is the power delta between the two fuels just to great for the engine?

There are a couple of cars capable of running on straight gas through E100 in Brazil, but it sounds like the engine is designed for E20 or E25.