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Nissan Unveils New 3-Cylinder 1.2L Supercharged Gasoline Direct Injection Engine; Targeting Lowest Fuel Consumption for Gasoline Engine

HR12DDR
The new 1.2-liter direct-injection supercharged engine. Click to enlarge.

Nissan Motor Co., Ltd. unveiled a newly developed 1.2-liter engine, the HR12DDR, which aims to achieve the lowest level of fuel consumption in the world for gasoline-powered cars while delivering power output equivalent to that of a 1.5L engine and CO2 emissions of 95 grams per kilometer (New European Drive Cycle).

The engine will first be mounted on the new Micra (known as March in other markets) in the European market in the first half of 2011. The engine is based on the HR12DE, the new 1.2L 3-cylinder engine mounted on the new Nissan March. High engine performance and low fuel consumption levels have been achieved through the adoption of the Miller cycle, gasoline direct injection system (GDI), and a highly efficient supercharger, in combination with an Idling Stop (stop-start) system.

By adopting the Miller cycle, in which the power stroke is enhanced by the compression stroke as a result of delaying the closing timing of the intake valve, the thermal energy of the fuel is converted to kinetic energy much more efficiently than it is with regular 4-stroke cycle engines, and pumping loss caused by intake manifold negative pressure has been reduced.

Moreover, the highly compressed and high-temperature air-fuel mixture is cooled by the latent heat of the vaporization of fuel directly injected into the cylinder, and the temperature of the combustion chamber is lowered by adopting a piston-cooling channel and sodium-filled valves to control detonation. These technologies have enabled a compression ratio of 13 for improved combustion efficiency.

The supercharger is equipped with an automatic on/off clutch, which means that both high fuel efficiency and high engine performance can be achieved by automatically switching off supercharging while driving at low speeds, such as on city roads.

Moreover, adoption of a hydrogen-free diamond-like carbon (DLC) coating for the piston rings and a variable displacement oil pump helps to reduce friction by up to 30%, compared with conventional 4-cylinder engines with similar performance levels.

These technologies are the culmination of the company’s research and development efforts based on the Nissan Green Program 2010 (NGP 2010)—Nissan’s mid-term environmental action plan that includes initiatives to reduce CO2 emissions and introduce effective technologies, products and services into the market.

The new March. Earlier this week, Nissan announced the Japan sales launch of the all-new Nissan March. The new March represents the fourth generation of the popular series. Employing a new-generation Xtronic CVT with an auxiliary transmission and the newly developed 1.2L 3-cylinder HR12DE engine, March achieves both a 25% improvement in fuel economy over 2010 standards and SU-LEV certification, emitting 75% fewer exhaust emissions than 2005 standards in every grade. Models with stop-start offer fuel economy of 26.0 km/L (61 mpg US, 3.85 L/100km).

Comments

Ziv

The typical driver covers around 1000 miles a month in the US, less in Europe. If we can get ICE vehicles that get better than 50 mpg, we would be using less than 20 gallons of fuel a month, instead of the 40-60 gallons we typically use now. Obviously the Micra isn't an SUV but I could imagine a supercharged 1.2L in an Orlando type CUV. It would be a dog, but it wouldn't be a show stopper.
My convoluted point is that even though I want an EREV ASAP, I don't think the ICE is dead, not by a long shot. Even in 10 years when gasoline is $5+ a gallon, there will be fuel sippers that offer an inexpensive MSRP and very high mileage (60+ mpg) that sell in large numbers.
One odd function of the increase in BEV's and EREV's will be that as their % of the US fleet approaches 10%, they will have a negative impact on fuel price increases. I.e. if 10% of vehicles use 90% less fuel, the supply demand equation will shift slightly lower, but more importantly, the group think will be that there are non or low petroleum alternatives and the futures market won't be nearly as volatile.

Allen

By adopting the Miller cycle...the thermal energy of the fuel is converted to kinetic energy much more efficiently than it is with regular 4-stroke cycle engines...

I think it makes about a 2% difference in the best case. If it were really MUCH MORE efficient, then every engine would be designed to use it.

ToppaTom

A very good combination of existing technology.

Even if it is a bit pricey for a micro, it could help the acceptance of such small cars in ther US.

Treehugger

Impressive development, combination of the best available trick to slash consumption, the Miller cycle can increase the efficiency by 10%, but the downside is that it reduces the power and the torque that's why it is not used in general, here it is mitigated by the turbo, and the low friction design. The compression ratio of 13 is impressive for a gazoline engine

Alain

At 95gr/km and an average lifetime driving distance of 200000 km, you are at less than 20 tons of CO2 for the car during its life. At a realistic price of 100$ to sequester CO2, it costs only 2000$ to drive completely CO2-neutral for the entire lifetime of the car. what battery-pack can do this ?

ejj

Ultimately it comes down to MPG. At idle, this engine may have lowest fuel consumption relative to other engines, but under a load & everyday driving conditions, it may not be so good. It's kind of those Best Western commercials that came out a few years back, claiming "we're the largest hotel chain". Who cares? Largest does not mean best. Lowest fuel consumption alone does not mean best - highest MPG is best.

Engineer-Poet
If it were really MUCH MORE efficient, then every engine would be designed to use it.
You're assuming efficiency has been the most important issue. Most applications for supercharged engines have been performance models, not economy. Nobody expected economy engines to have performance.

I lean toward turbos rather than blowers, but I realize that turbo lag is a driveability issue. Nissan must have priced it out, determined that the blower would only be used a small fraction of the time, and called the losses acceptable for the advantages.

Davemart

I doubt this is very expensive to build. Nissan are doing everything to take out cost, including building it in India and making many design compromises.

Treehugger

The reason why they use a blower instead than a turbo is that Miller cycle and turbo combination doesn't work well, in a Miller cycle you over-expand the gases so as a result, there is not enough pressure left in the exhaust to properly power a turbo. Asides the turbo lag problem that you mention is BS, most of diesels in Europe have a turbo and the lag is barely perceptible, they work more than well enough for everybody use.

Peter_XX

The main reason for less turbo lag on diesels is that there is no throttling. A gasoline engine uses throttling at low load, which reduces turbo speed, so when power is demanded, you have to wait. One way to overcome this problem on gasoline engines is to use lean-burn GDI, where throttling is significantly reduced. This has been practiced by some European car makers. I think Nisssan is using conventional stoichiometric combustion (lambda=1), since it makes NOx reduction so much simpler (TWC). A specific problem with Miller system and downsizing is that you cannot get high enough charge pressure. Two-stage turbocharging would be one solution to that problem. However, for this engine size, the smaller or the turbos would be very tiny and less efficient than larger turbos. Mahle has shown a prototype 3-cylinder gasoline engine with two-stage turbo but without Miller system.

Miller cycle is not a correct denotation, it should be called Miller system. An engine with Miller system is using the Atkinson cycle. Atkinson came before Miller, so the Atkinson cycle was already invented when Miller came up with his ideas on how to utilize this cycle in a better way than the original Atkinson engine. Many car manufacturers(especially Japanese) use the denotation Miller cycle.

If we strive for very low fuel consumption in the future, all engines will have to use some kind of Miller system. It is also applicable on diesels.

Engineer-Poet

There is plenty of excess energy in the engine exhaust (which is why a muffler is required to attenuate the pulses). A turbo in a Miller system would have a higher cut-in speed for the same engine displacement, but it would still work. A variable geometry turbine would ameliorate the effects of over-expansion.

3PeaceSweet

Also when you add a turbo it gets in the way of exhaust treatment and you need an intercooler which adds to the cost.

Matching one of these engines to dual clutch transmission with intergrated electric motor would give you some EV peformance

You could also use a turbo generator charging a super cap for the start / stop.

Peter_XX

Well, Trehugger is correct. There is less energy available when you overexpand. VGT cannot overcome that problem and VGT is not likely to survive in gasoline exhaust, uneless very expensive alloys are used (VGTs survive in diesel exhaust). Since we cannot get the charge pressure we need, low end torque would suffer. This is the same problem that Toyota Prius suffer from. As you might have noted, this engine has very low power density and torque. They increased engine displacement (anti-downsizing?) in the III version to get the power they wanted.

If you want to combine Miller system with aggressive downsizing, two-stage turbo or turbo+supercharger seems to be the options available. In fact, a Roots type supercharger does not fulfil the pressure requirements for aggressive downsizing. Thus, the Nissan engine "only" offers the power of a 1,5 liter naturally aspirated engine. With "proper" charge pressure you could approach the power density of a 2-liter engine. The problem is that this would increase cost and somewhere there is a limit for that. One option to increase low-end torque would be to use a mild hybrid system. Maybe that is also too expensive for this class of vehicles. However, it could be an option to the Prius drive system. Note that Honda Insigth is relatiely close to Prius in fuel consumption. With an engine like this, they would be even closer. Probably the cost would also be lower.

Treehugger

Maybe using the multi-air system of Fiat you could shut down the Miller cycle when you need torque and power, maybe but I am not too sure...

with Miller cycle and the compression ratio of 13 I am curious how much efficiency they get, should be close to 40%

HarveyD

It is amazing to see the consequences of the pending arrival of HEVs/PHEVs/BEVs on the development of traditional ICE. After decades of next to no gain (or even negative gain) in fuel economy, mid size ICE cars have gone from 20 mpg to over 60 mpg in the last 10 years. Could we expect the same for the following 10 years or is this it?

Improved HEVs and particularly PHEVs and BEVs may have to take over from 60+ (equivalent) mpg.

Treehugger

Harvey

The 60MPG is in the Japanese Cycle and is not realistic, and this engine is for a compact not for a mid size cars. So it is more like from 32MPG to 40-45MPG. The next gain will be on weight and aerodynamic, then you'll be in the 50-60MPG for a compact car and 40-45MPG for a mid-size sedan in the EPA cycle.

Engineer-Poet

The difficulty with turbos on gasoline engines is that the exhaust is too hot under WOT conditions. But this engine violates the assumptions:

  1. The exhaust is over-expanded, so it's considerably cooler than it would otherwise be.
  2. The exhaust manifold pressure is much lower, so excess compressor output can be bypassed to the exhaust to cool it.
  3. The bypass eliminates the need for WOT enrichment for cooling purposes.
The one difficulty is low-speed torque, which works better with VVT like Fiat's Multi-Air.

Treehugger

They don't report the torque on this engine. I wonder if the 3 cylinder can be used for bigger engine like 2.0 liters.

ai_vin

Check out this site; http://www.cpowert.com/

Peter_XX

If you decide for Miller system, it a decision you cannot change. When you have a compression ratio of 13:1, you cannot just "switch off" the Miller system (variable compression ratio could be an option). Severe engine knock would be the result if you did. At low load, it is an option but you also want to minize throttling losses, so there is no gain in trying to "swith off" the Miller system.

You need some kind of VVT or a rotary valve to restrict the effective induction stroke with Miller system. Whether the Fiat type of VVT is better or not to achieve this, cannot be assessed based on the information provided by Nissan. Withoud doubt, the Fiat VVT or BMW Valvetronic could do a good job to control the engine. I have for long wondered why BMW has not yet utilized the advantages of the Miller system.

Overexpansion helps to cool the exhaust but when you add a turbo to increase power density, exhaust temperature increase again, implying problems to use e.g. VGT. Possibly, you could reduce or eliminate fuel enrichment at full load. At full power - when you would like to use scavenging to let some inlet air out via the exhaust valve (called bypass by Engineer-Poet) - the pressure ratio is negative, so this is not a viable option to further reduce exhaust temperature.

VW already produces a 1.4-litre engine that surpass the power of a 2-liter engine, so clearly there is a potential for a 1.2-litre engine to approach - or surpass - the power of a 2-liter engine. The experimentl 3-cylinder Mahle engine goes even further in power density. A 3-cylinder engine is better adapted for turbocharging than a 4-cylinder engine, so there is an advantage here. My comment was referring to if you could achieve this target with Miller system. My conclusion is that the requirements for charge air pressure will be difficult to meet. I also listed some options to improve that condition. I did not discuss different "e-turbo" options but I could add that later...

Engineer-Poet
Overexpansion helps to cool the exhaust but when you add a turbo to increase power density, exhaust temperature increase again
The polytropic gas law doesn't care about the final gas density. You've got a Cp/Cv of about 1.27 and the temperature drop for a given expansion ratio is going to be about the same. If the over-expansion is about 1.5:1, the absolute temperature will drop from e.g. 900 C to about 780 C. That's not into diesel territory, but it's substantial.
At full power - when you would like to use scavenging to let some inlet air out via the exhaust valve (called bypass by Engineer-Poet) - the pressure ratio is negative
You're saying an OVER-expanded exhaust, with a much greater P*v product than the intake air (and thus far greater capacity to do work even at a lower pressure) is going to be at greater pressure than the compressor outlet? Not with decent efficiencies in the turbo.

Let's scratch up a cocktail napkin. A kilo of intake air is about 0.8 m^3 at 1 bar and 25 C; compress it to 2.5 bar and cool to 100 C and you're at about 0.4 m^3. The adiabatic reversible compression work is about 90 kJ/kg. Call it 128 kJ/kg with a 70% efficient compressor.

You can either vent air directly to the exhaust manifold or spill it through valve overlap (or just use late exhaust valve closure instead of early intake closure to reduce compression). At 780 C, your 0.8 m^3 of ambient air has expanded to about 2.9 m^3 of exhaust gas. Even if you just let backpressure push against a piston, getting 180 kJ/kg of work out of it (about 70% efficient) only needs about 64 kPa of overpressure compared to the 150 kPa of gauge pressure in the intake. A real turbo which captures the impulse energy of the fast-moving gas leaving the exhaust valve will have a lower backpressure between pulses.

So yes, you can use air to cool the turbo.

Peter_XX

Engineer-Poet, you have to re-do you many of your calculations or look at the reality. Data with pressure difference for a real engine shows that it is way too negative at high speed, where you would like to scavenge during the valve overlap. Apparently, you are not aware of that. You might get some scavenging at an "ideal" area of the load and speed range but the temperature is lower there so what is the point of doing that. You could do some tricks with valve timing to get some scavenging but it is marginal and it would increase pumping losses and fuel consumption. As you concluded, temperature will decrease due to overexpansion but I already mentioned that. Eventually, it is ulikely that a real engine could use as high overexpansion as 1.5:1. (Overexpansion is probably not the best denotation but since it was already used by others, I continued with that.)

Besides that the physics is against you, venting air into the exhaust is not a good idea. With excess oxygen you cannot use a TWC catalyst for NOx reduction. You could argue that a NOx-trap catalyst could be used but if you decide to use that, why not use lean-burn combustion instead. This would also reduce temperature and in addition, reduce fuel consumption even further.

You could also use heavy (cooled) EGR at full load to reduce the exhaust temperature. This also increases the demand on the charging system.

As noted by other researchers, one of the best ways to reduce exhaust temperature on gasoline engines is by using a water-cooled exhaust manifold. But then you also reduce enthalpy in the exhaust.

Whatever of the the mentioned strategies you use to reduce the exhaust temperature, they would put even more demand on the charging system. And, as I said before... the charging system is the main problem if you want to increase specific power.

Engineer-Poet

The reality is that turbodiesels already run much higher intake pressures than exhaust backpressures. If you know what you were talking about, you'd know that.

Peter_XX

I know what I am talking about but I can see that you do not. At high speed, when exhaust temperature is the highest, the pressure balance for passenger car diesels is negative. I can be slightly positive for heavy-duty engies, especially those that use no waste gate. The reason for the negative pressure difference is that a passenger car engine is "dumping" 50% or more of the exhaust via a waste gate, i.e. a huge waste of energy. VGT helps but the pressure difference is still negative at high speed.

I did not mention another issue before but you did probably neglect the waste gate in your calculation. Small error, ha, 50%... If you calculation does not fit reality, the reality is wrong.

I do not car to give you any more free lessons in basic engine technolgy, so this will be my final comment on this matter.

Engineer-Poet

If you were correct, the Delta Hawk aerodiesel would need its Roots blower full-time and would not be able to sustain power if it had a belt failure in flight. That is not the case.

If you thought you had a point, you'd do a calculation or cite an example. Absence of proof = proof of absence.

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