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Mazda Develops New Naturally-Aspirated MZR 1.3-liter Miller-cycle Engine; 20% Improvement in Fuel Economy

The new engine will power the new Mazda2 (Demio).

Mazda Motor Corporation has developed a new, naturally aspirated MZR 1.3-liter Miller-cycle gasoline engine, which will power the all-new Demio (Mazda2 in non-Japanese markets) when it goes on sale in Japan in July 2007.

In combination with Mazda’s first continuously variable transmission (CVT), the engine enables the new Demio to offer a 10-15 mode fuel economy of 23.0 km/liter (4.3 l/100km or 54 mpg US), an improvement of approximately 20% over the 19.2 km/liter (5.2 l/100km, 45 mpg US) rating of the current 1.3-liter engine model.

Newly developed from the current MZR 1.3-liter DOHC aluminum engine, the naturally-aspirated MZR 1.3-liter Miller-cycle engine employs delayed closing of the intake valves in order to reduce pumping losses and improve thermal efficiency through a higher expansion ratio.

Intake valve timing is optimized by the Sequential Valve Timing System to provide improved fuel efficiency over the current MZR 1.3-liter engine when cruising and accelerating. In conjunction with the CVT, which transfers torque at low speeds without power loss and eliminates gear-shift shock, the setup achieves excellent fuel efficiency as well as good ride dynamics.

In addition to the new powertrain, the all-new Demio has been made approximately 100 kg lighter than its predecessor through weight reduction techniques, which have resulted in nimble handling and support for the significantly improved fuel economy.

The Demio model with the naturally aspirated MZR 1.3-liter Miller-cycle engine combined with the CVT transmission achieves a fuel economy that is rated as 20% or better than the level specified by Japan’s 2010 fuel economy standards. Exhaust emissions are also at least 75% lower than 2005 standards, which conforms to Japan’s Super Ultra-Low Emissions Vehicle (SU-LEV) standard and qualifies the Demio for Green Tax exemptions.

Separately, the day prior to the announcement of the new 1.3-liter engine, Mazda had celebrated the 40th anniversary of its first rotary engine. As of the end of April 2007, Mazda has manufactured approximately 1,970,000 rotary vehicles since production first began.



Finally, a replacement vehicle for my 99 Chevy Metro. No fancy, expensive hybrid system required. What's it cost?


Hi Keith - Yep,

Just a fancy expensive Turbo Charger, mechanical CVT and cam shaft phasor. And expensive brake jobs every 40 K miles.

The next generation Prius is rated 103 mpg in that Japanese 10-15 test, which people have calculated to mean 63 mpg combined old EPA cycle.

So that puts this car around 33 mpg combined. Its probably something like 27 City, 40 highway (55 mph prewarmed) by the old EPA cycles.

I just cannot figure out why people think Hybrids are expensive and complicated. When they are not expensive in the long term (or factoring in the higher resale) and the mechanics are simplified (at least in the Toyota HSD).

I mean, when is the last time you called a manual transmission fancy or complicated? I remember walking around Engineering Open house when I was a senior in college with a buddy. We electrical engineers went by the mechanical engineering department. They had a cut open mechanical transmission. It took the presenter 20 minutes to explain how it worked to us totally ignorant, but bright engineering students. You know Ferdinand Porshe (inventor of the synchro and hybrid car builder) was a great engineer!


Porshe's fiirst car was also electric with in-wheel motors.


Porshe's first car was also electric with in-wheel motors.


"the naturally-aspirated MZR 1.3-liter Miller-cycle engine"

Actually, this is an Atkinson-cycle engine. A Miller-cycle would be supercharged, like the Millenia S was.

Max Reid

CVT's are better than conventional 4 & 5 speed transmission. 54 MPG US mileage is great.

Someone said "next generation Prius is rated 103 mpg " , can they send the link.


@ Keith
"03 mpg in that Japanese 10-15 test"

This is in Imperial mpg, which is 83 mpg US. Also, its not accurate to do apples to apples comparison between what this car is expected to get based on the Prius' 10-15 results and back calculating it.

Also the 53 mpg is in US gallons (4.3L/100km), Japan's 10-15 mode is heavily city based driving (with a 70km "15" segment thrown in); the US CITY mpg figures should be relatively close, however not the highway or combined mpgs.


Great! I applaud Mazda for introducing a fuel-efficient powertrain. I fail to see the innovation, except in how they made the vehicle 100kg lighter while still meeting crash requirements.

Mazda finally produces an Atkinson-cycle engine- but in a feable attempt to differentiate themselves (and harken back to their Miller-cylce forray of the early 90's), they have marketed this as a "naturally aspirated Miller cycle." I suppose the marketing intent is to portray Mazda as innovative- vice the third-rung Japanese auto manufacturer that it is.

Seeing Mazda included a plug for their "40 years of rotary engines" (an engine that all other manufacturers have long abandoned for numerous reasons) is further evidence of Mazda's marketing intent. Yes, the Wankel rotary is a neat design, and Mazda has spent much time and effort greatly improving on it, but so far Mazda has not been able to match the efficiencies of reciprocating Otto designs.

Back to the Mazda2/Demio: please bring it to the US with a proper Miller cycle (supercharged). As is, I would hate to see the 0-60mph times are for this 1.3 liter Atkinson-cycle (woefully underpowered) car.

Toyota had the right mind to boost the Prius' 1.5 liter Atkinson with electric motors (thus making it a gas-electric hybrid). Still, a Prius does 0-60mph in a liesurely 10.5 seconds.



Q: How does a "naturally aspirated" engine possess a turbo?

A: It does not, silly.


Rafael Seidl


I believe an overexpansion cycle is called Atkinson if the intake valves are closed before BDC and Miller if they're closed after BDC. Each has its pros and cons.

Both cycles can be fitted with a mechanical supercharger to compensate for the power loss, but this negates most of the fuel economy gains. Turbocharging is tricky because of the reduced exhaust enthalpy in part load, which limits boost and aggravates turbo lag in acceleration transients. A pressure wavesupercharger (Hyprex) would be a better fit, but it's a rather exotic beast.


What's the point when we have the Mazda2 1.4Tdci (Ford/PSA unit) at 60.1mpg combined:

price difference between petrol and diesel is negligable 200quid


Rafael - Read the links.


MPG (L/100 km, km/L) is a decreasingly useful measurement when it comes to green cars. Not only is there the confusion between different test cycles and Imperial versus US gallons, we are more and more trying to compare gallons of fuels that don't have similar energy content per gallon- or worse, don't even translate well into gallons at all (hydrogen, compressed methane, electric, etc). Oh, and the US just completely revamped its fuel economy estimating system, so numbers for 2008 and later models will not be comparable to past models.

So one guy says the Mazda2 1.4Tdci gets 60.1 mpg combined. On whose cycle? With Imperial or US gallons? And diesel has ~15% more energy in it per gallon than gasoline anyway. Diesels are efficient, I will grant, but it's not fair to compare diesel fuel economy to gasoline fuel economy. And don't get me started on how terrible MPG numbers look when you consider ethanol as a vehicle fuel- but sucking through lots gallons of ethanol and getting low MPG does not mean the vehicle is necessarily using it inefficiently. Wow, I can plug a Prius into a coal fired power plant and get 100 mpg instead of 60- did it really use less *energy*? Probably not.

I think we need to largely move away from MPG type info and move toward CO2 g/km, and maybe a unit that relates a quantity of embodied energy (kwh?) and distance traveled.


at the end of the day its just another boring "me too " car nothing
to get excited about ,


at the end of the day its just another boring "me too " car nothing
to get excited about ,


I agree with your conclusion that we should move to g/km of CO2. But your last example was incorrect: you cannot plug a (factory version) Prius into a coal station because it is a HEV and not a PHEV.



I know (I have one!). But there is a cottage industry going now centered around converting existing hybrids into PHEVs. I'm not necessarily opposed to the concept but the advocates thereof tend to get mentally trapped in the 100 mpg they achieve without considering the big picture- source of the power, transmission losses, etc. It's not a free lunch.

Every source of energy has various characteristics- advantages, disadvantages, etc. In the end it has gotten very easy to compare apples and oranges in this field though- that was the gist of my argument above. We need to be careful when we make arguments, or read articles making claims about a technology or product, that we think carefully about the equivalency of what is being claimed.


Is it possible to make variable compression ratio with variable intake valve timing?

Tom Schaffter


Nice clearity.

A couple of comments on PHEVs:
1) Using electricity to power vehicles reduces our dependence on foreign oil;
2) As the grid gets cleaner (wind, solar, etc.), PHEVs get cleaner.


With Mazda part of Ford, I wonder if this will translate over to the NA market. Atkinson engines are already used in Escape/Mariner hybrids. A Mazda2 entry or Ford Fiesta reentry to the NA market would give Mazda/Ford competent/great contenders into the growing US subcompact market.


When can I get a PHEV powered by the solar panels on my
roof a little less expensively? that's all I want to know.
P.S. 'The Wankel has some problems'. Hasn't Mazda solved most of them? Having such a small footprint per hp, wouldn't it be a great engine to use in PHEVs, allowing more room for Li-ion batteries, giving me more trunk space? If the thing's a PHEV, who's worried about fuel economy? plugging-in to your solar would take care of most trips.
A Mazda rotary running on E-85 looks like a good idea to me.


Mazda has made some headway on Wankel durability, but they are still struggling to comply with emissions standards. A major component of that is that they burn a lot of lubricating oil. They also have dreadful fuel economy. I mean... really, really dreadful. You ask "who's worried", but keep in mind that a Mazda RX-8 gets fuel economy that would embarrass many SUV owners. Halving the space consumed by the engine isn't that advantageous if you have to double the size of the fuel tank to make up for it.

A range extender engine only needs to be big enough to keep the battery afloat on a long trip, anyway- not big enough to support acceleration like a traditional car needs- so it would be pretty darn small even if it were of a conventional ICE design.


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