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Mazda is already discussing Skyactiv 3 as well

Mazda only recently started introducing its Skyactiv engines to its different vehicle models, but the automaker is already talking about the upcoming Skyactiv 2 -- and even Skyactiv 3 -- engines for the next decade and beyond. 
According to a new report from Automotive News, Mazda plans to gain 30 percent better fuel economy with its Skyactiv 2 engines, which are expected to have a 2020 release date. A 30 percent improvement in fuel economy would make the already impressive Mazda3 rise from 29/41 mpg (city/highway) in its more efficient trim to 38/53 on regular unleased gasoline.

2014 Mazda3

Mazda plans to achieve this 30 percent increase in fuel economy by improving the internal combustion of the Skyactiv 2 engines. More specifically, the Skyactiv 2 engine's compression ratio would be bumped up to 18:1 from a current level of 14:1. 
This higher compression is able to reach the same combustion temperature as the current engines, but with a leaner mix of fuel -- meaning improved fuel economy. 
The Skyactiv 2 engines will utilize homogeneous charge compression ignition (HCCI), which compresses the fuel-air mixture to a high enough pressure and temperature that it ignites by itself without needing a spark. This allows for more complete fuel combustion and lower nitrogen oxide emissions.
However, the Automotive News report indicates that HCCI won't come easy. Engineers must first expand the range of engine speeds for HCCI specifically, because the engine revving too quickly can result in a misfire due to the high number of revolutions, and if revved too slowly, it can misfire due to low temperatures.

2.0-liter Skyactiv four-cylinder engine
Aside from that, engine cooling and the engine's tendency to behave differently based on the use of different fuels need to be figured out.
The main goal with Skyactiv 2 is to meet European carbon dioxide emissions standards of 95 grams per kilometer in 2020, but Mazda is looking even further ahead at meeting Europe's standards of 65 grams per kilometer in 2025 with Skyactiv 3. 
Mazda didn't go into great detail about Skyactiv 3, but the automaker plans to make more energy available for powering the wheels by limiting the fluctuation of heat in the combustion chamber and reduce losses from exhaust and cooling. Mazda hopes to reach well-to-wheel carbon dioxide emissions with Skyactiv 3 that rival electric vehicles.
Mazda first introduced Skyactiv engines to the U.S. market in 2011, starting with the Mazda3 sedan. Since then, they've been added to the Mazda6 sedan and CX-5 crossover.
Mazda has been trying to bring the Skyactiv-D diesel engine to the U.S. via the Mazda6, and was supposed to have achieved this by the second half of 2013. However, in September of last year, it was announced that delays in emissions testing has pushed that timetable to late spring of 2014.

Source: Automotive News

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RE: Hmmm
By Samus on 1/6/2014 2:13:23 PM , Rating: 2
Mazda reduced the compression ratio of North American Skyactiv models to 13:1 in order to run 87 octane. Only the overseas models run 14:1.

I've historically owned vehicles that use premium fuel (for performance or economy) so it's mysterious to me Mazda is trading a fuel that is 10% more expensive for economy that increases over 15%.

I can't wait for a tuner to develop a ECU flash for the CX-5 that increases the compression ratio to 14:1. The vehicle has four knock sensors and some trick piston designs that would protect it quite well from detonation, so it should be relatively safe.

But Mazda knows we have the most poorly regulated gasoline in the modern world so it's safe to say they are taking this conservative approach to prevent warranty claims, especially with all the CX-5 Skyactiv-Drive transmission valve body problems. Mine was at the dealer for three weeks waiting for parts from Japan.

I love the car, but I'd recommend anybody research (ie these Skyactiv vehicles before purchasing so you know what to expect.

A few things I'd recommend avoiding in any new Mazda is AWD (because it is a joke, I couldn't even get my crossover out of a 8" snow bank because the rear wheels only get 10% power with a maximum of 50%, which never seems to happen.)

I'd also avoid the technology package. Adaptive headlights don't work properly, proximity key fails on pretty much everybody (stalling, not detecting the key, walk-away locks are intermittent) and the TomTom GPS is probably the worse unit I've ever seen. The Mazda 3/6 have adaptive cruise control that constantly deactivates (and only works up to 18mph so it's really for stop-go traffic, not highway cruising) just like city brake, which even Top Gear proved is hit or miss, no pun intended.

RE: Hmmm
By TheEquatorialSky on 1/6/2014 2:21:33 PM , Rating: 3
Efficiency only grows logarithmically with CR. Without doing the math, I'd say going from 13:1 to 14:1 is only a 1-2% boost in efficiency.

The Skyactiv engines don't really operate at 13-14:1 CR anyways, they only do so at part throttle. The engines use specially shaped pistons and a tuned exhaust to increase cylinder scavenging, reducing intake charge temperature. If they ran at 14:1 at max BMEP, the engine would detonate (even with GDI). They use a variable intake valve to limit high CR to part throttle operation only.

RE: Hmmm
By Spuke on 1/6/2014 7:09:45 PM , Rating: 2
I was wondering how they were able to get away with that high CR (even with DI). Thanks for that info.

RE: Hmmm
By Samus on 1/7/2014 1:50:21 AM , Rating: 2
You don't have to do the math. Thousands of others all over the world have already done it for you. A quick Google search shows many people in Great Britain, Australia and Japan average around 35mpg mixed driving in the 2013 CX-5 2.0 where our 2013 CX-5 2.0 averages 28. The 2.5 is said to reduce the economy only 1 mpg. Once I've owned mine long enough and it isn't -15f I will know my real-world fuel economy. But the point it, American versions of international vehicles with identical engines always get lower economy.

I had an SVT Focus, known as the ST170 in Europe, and imported an ECU, reflashed my PATS theft module, and tuned it with a builder in St. Albans, UK. I regularly achieved 35mpg mixed driving on 93 octane fuel. No other SVT in the United States could get over 32 HIGHWAY without hypermiling, even with economy tunes.

International Skyactive's run 14:1, ours run 13:1. Is there more to it? Of course. Emissions regulations (in which Japan is the world-leader, so this is irrelevant) and fuel quality play a roll. Any petrol engine ideally burns at "stoic" but running leaner and using technology to monitor the consequences will improve fuel economy. The compression ratio can be increased in a variety of ways to improve fuel efficiency; special intake and head cooling techniques, piston design, tuned headers, valve/cam timing, etc. This improves overall efficiency, but the industry PR simply calls it compression ratio, which is all I was referring too.

What you need to keep in mind, like you mention, is the purpose of direct injection is to keep peak compression ratio across the power band, which obviously isn't going to always be 13:1+ but even if you can get away burning above stoic at idle, you are going to save fuel.

RE: Hmmm
By TheEquatorialSky on 1/7/2014 12:07:53 PM , Rating: 2
The math is simple: thermal efficiency=(1-(1/CR^(specific heat-1)). I just did it and the improvement from 13:1 to 14:1 is 1.6%.

Unless you have scientific sources for those MPG numbers, the differences you cite are just anecdotal and thus suspect. I'm not saying you are wrong, but I can't assume you are right. According to the manufacturer's website, the CX-5 (2.0 manual) is rated at ~39mpg(US) combined on the British cycle and 29mpg(US) combined on the American cycle. Certainly a huge difference, but so are the drive cycles...

Mazda refers to the peak of their "dynamic" CR as though it were the static CR, as stated by nearly every car manufacturer since cars were invented. Late intake valve closure (LIVC), as pioneered by Ralph Miller with his work on industrial diesel engines, has muddied the water. As with any internal combustion engine, the value that really matters is the pressure ratio, as the CR refers to a geometric quantity.

The purpose of GDI is to increase volumetric efficiency, intake charge cooling and fuel metering. Nearly every engine in America is designed to run at stoichiometry (14.7:1) unless peak power is required (e.g. acceleration). Running lean results in high NOx and is almost always avoided. Notable exceptions include Honda hybrid vehicles, which use a NOx adsorption catalyst that it periodically flushes by running rich.

RE: Hmmm
By Samus on 1/7/2014 1:30:00 AM , Rating: 1
I love how DT'ers down-rate those who own a product, express their opinion, while providing valuable advice and experiences.

Absolutely shocking.

RE: Hmmm
By Spuke on 1/7/2014 11:53:21 AM , Rating: 2
I love how DT'ers down-rate those who own a product, express their opinion, while providing valuable advice and experiences.
That's because you were supposed to have glowing reviews of your Mazda product, the golden child of the wanna be eco-enthusiast. I appreciated your post. It's always nice to get past all the hype and hear the real story.

RE: Hmmm
By Moishe on 1/7/2014 4:21:24 PM , Rating: 2
Simplicity breeds reliability and Mazdas have not been very simple lately.

I applaud them for their history of innovation, but innovation requires quality as well or you're just building something that will be perfected by the next guy.

"Young lady, in this house we obey the laws of thermodynamics!" -- Homer Simpson

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