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Honda signs E-KIZUNA project agreement with City of Saitama for EV, PHEV and electric scooter testing; new household gas cogen unit with more efficient EXlink engine

Artist’s conception of Honda Smart Home System. Click to enlarge.

Honda Motor Co., Ltd. and the city of Saitama signed an agreement to cooperate in the E-KIZUNA Project. The E-KIZUNA Project, managed by the city in collaboration with a wide variety of stakeholders, aims to help fight global warming and realize a sustainable, low-carbon society through the popularization of electric vehicles. (In Japanese, kizuna means the ties that connect people to each other.)

In this project managed by the city of Saitama, Honda and Saitama will test the urban use of electric vehicles (EVs), plug-in hybrid vehicles and electric scooters. Honda also plans to construct and test its Honda Smart Home System in Saitama in the spring of next year. This comprehensive energy management system features several Honda-developed energy production technologies, for example, a gas engine cogeneration unit and a solar power system.

Complementing the commercial grid, the Honda Smart Home System provides heat and electricity for the home, and produces power for the use of electromotive mobility. Honda will also be exploring the system’s potential to independently produce electricity for the household in the event of a disaster.

Through the E-KIZUNA Project, Honda aims to reduce household CO2 emissions to half of year 2000 levels by 2015.

Based on the E-KIZUNA Project agreement, Honda and the city of Saitama will collaborate on exploring the following items:

  • Priority items for collaboration include creating the disaster-resistant city of the future with the help of a variety of energy supplies and electric mobility: enhancing access to electric vehicles and creating EV-related business models; creating independent home communities focused on local energy production and consumption; and developing household energy systems that can operate in the event of a disaster.

  • Constructing an electric charging safety net. This includes identifying electric charging infrastructure appropriate for the unique characteristics of the city of Saitama, maintaining compatibility between current charging infrastructure and electric vehicles developed in the future, and using solar panels and fuel cells to supply energy.

  • Stimulating demand and applying incentives, including promoting the shared use of electric scooters and automobiles, promoting the use of electric scooters for commercial use, and developing a wide variety of electric vehicles to meet citizens’ needs.

  • Tailoring educational initiatives to local needs, including implementing riding safety seminars featuring electric scooters and implementing electric cart seminars for seniors.

Household cogeneration unit going on sale

Honda also announced it would begin sales this month of an all-new efficient household MCHP (micro combined heat and power) gas engine cogeneration unit through gas utilities across Japan. Building on its predecessors with a completely new design, MCHP1.0K2 serves as the core unit in the household cogeneration system ECOWILL, burning natural or liquid propane gas to generate electricity and heat water simultaneously.

Interior structure of MCHP1.0K2. Click to enlarge.

MCHP1.0K2 features Honda’s EXlink (Extended Expansion Linkage Engine). Comprising a trigonal link, swing rod and eccentric shaft, the new extended expansion linkage structure of the engine makes possible an extra-long expansion stroke (the piston stroke that produces power). By compressing a smaller volume of fuel and air and allowing the air-fuel mixture to combust and expand into a greater volume, an expansion ratio 1.4 times greater than the compression ratio is achieved, and a greater amount of combustion energy can be used to perform work.

Extended Expansion Linkage structure. Click to enlarge.

In addition, the shorter intake stroke helps reduce pumping loss, which is the energy lost from moving air into an engine’s cylinder during intake. Thanks to the higher expansion ratio, thermal efficiency is substantially higher than in an engine in which the expansion and compression ratios are equal. As a result, MCHP1.0K2 offers fuel consumption that is approximately 15% lower than that of the preceding model.

The shorter intake stroke of the high-expansion ratio engine helps make possible a smaller intake system and a more lightweight and compact overall design. The vertical engine layout featuring a vertical crankshaft, horizontal cylinder and integrated oil tank helps further minimize the weight and size of the unit. Due to the integration of parts and a variety of layout enhancements, MCHP1.0K2 has a 33% lower volume and weighs 11 kg less than the preceding model.

Extended Expansion Linkage structure working image. Click to enlarge.

An enhanced lower engine mount structure and other design enhancements help reduce pulsation and air channel noise in the intake and exhaust systems. The optimized placement of sound-proofing materials result in low vibration and noise equivalent to that of an air conditioner outdoor unit (43 dB(A)).

By integrating the heat exchanger with the catalytic converter and enhancing the cooling system design, a heat recovery rate of 65.7% has been attained. During combustion, exhaust heat and heat in the body of the unit is recovered at the high temperature of 75 °C, making possible the efficient production of hot water for bathing, heated floors and other uses.

MCHP1.0K2 offers ideal household electrical output of 1.0 kW, heat output of 2.5 kW and combined power and heat generation efficiency of 92.0%. Power generation efficiency is 26.3%, as compared to 22.5% for the preceding model.

In the alternator, the position of the rotor magnet and the position and number of the stator slots have been optimized to minimize eddy currents and prevent energy losses. The inverter features simplified circuits with highly integrated devices to reduce electrical resistance. When the electric output of the unit exceeds the electrical load usable by the household, the unit enters load optimization mode, using the excess electricity to generate additional heat.

In 2003, Honda began sales of its first compact household cogeneration unit, which combined a gas engine with Honda’s original sine wave inverter power generation technology. (Earlier post.) Under the brand name ECOWILL, cogeneration systems comprising the Honda cogeneration unit and a water heater utilizing exhaust heat have been sold by gas utilities across Japan and installed in some 108,000 households.



" expansion ratio 1.4 times greater than the compression ratio.." appears to yield 15% fuel economy improvement and retain Honda reliability - besides only a 43db operating audio level for a home energy system.

Maybe these guys haven't dropped the ball since the 51 hwy mpg of some of their 1980's autos.


I presume that this runs on natural gas and since they have none they import LNG. It might be better to produce methane from rice straw and use a fuel cell for CHP.

Nick Lyons

I'm curious to know why they went with the complex eccentric shaft/linkage approach as opposed to an Atkinson cycle design, which seems to achieve the same thing simply by modifying the intake camshaft to keep the valve open past BDC. I'm willing to believe there is some advantage to this design, but I'd like to know what it is.

Roger Pham

Agree with you, Nick.
Seems like the EXlink scheme is a bit of a gimmick in comparison to Toyota's simple delayed closure of intake valve scheme like in the Atkinson-cycle 1NZ-XFE engine. The friction reduction in reducing piston movement is made up by increase in friction in the secondary EX-linkage.
A small generator for co-generation CHP needs no speed reduction nor any complicated semi-conducting power inverter. Rotating at 3,600rpm is ideal for 60 Hz AC, or 3000 rpm for 50 Hz AC directly driving the alternator for reduction in cost and complexity. In heat-led mode, the engine can simply turn on or off when heat is no longer needed.

With Madza's SkyActive scheme permitting a compression ratio of up to 14:1, a variable valve duration and timing mechanism can allow for much more power than the 1NZ-XFE can muster right now, from 78 hp gaining to ~110 hp in a typical 1.5 liter variable intake timing engine. This reduces the necessary of electrical boost and allowing a less expensive electric drive train for HEV.


Honda and Japanese gas companies have been testing CHP for some time now. This is a good prototype. Since they are making Saitama a test community there should be whole blocks and neighborhoods utilizing these systems.

In the next phase wire 15+ homes/domiciles within a single block together to create a micro-grid supplemented by city grid. Once power levels increase to 10kW or more - these systems can provide backup and UPS services to their block residents or neighborhood.

"By integrating the heat exchanger with the catalytic converter and enhancing the cooling system design, a heat recovery rate of 65.7% has been attained."

Good use of combustion heat. And a real start on replacing home water heaters with heat and power generators. Eventually, we will find ways to make the fuel cheaper and fully renewable.


The link and eccentric system avoids pulling charge into the cylinder and then expelling it again (some of it through a partially-closed intake valve). This will reduce both pumping losses and noise compared to the common implementation of the Atkinson cycle (though not the original toggle-link Atkinson engine). The extra weight and bulk are not important for a stationary application, but explain why this hasn't been adopted for vehicles.

Roger Pham

True, E-P, but the EXlink mech. has its own share of friction as well.

Applying Mazda's SkyActiv technology to Toyota's Atkinson-cycle implementation, intake charge and compression can simultaneously be changed, allowing much more torque increase at the same rpm, allowing the generator to vary output tremendously while maintaining the same rpm, for example, at 3600 or 3000 rpm to maintain the same grid frequency of 60-50 Hz without requiring expensive power inverter, thereby reducing size, weight, and cost even more!

Nick Lyons


I see your point on reduced pumping losses. And I suppose the extra reciprocating mass is OK if you limit RPM. Still seems kinda expensive to me. I'm guessing they figure whatever efficiency gain they get will offset the extra cost for something with a much longer service life than the average car.

Roger Pham

The efficiency gain with the EXlink design is 15%, same as the gain from 33% of a conventional 1.5-liter engine, to 38% of the 1NZ-XFE running Atkinson cycle. The Prius has proven to be very liable in taxi service, with many vehicles attaining 300,000 miles on the same engine and drive train!


Single cylinder will prob. shake a bit, which I guess is not acceptable for a Japanese household (living in close quarters). Will the eccentric shaft/linkage help? Any thoughts?

@Reel, The unit is not a prototype. It's available for sale in Japan this month as announced.


The unit needs no mechanical connections (just hoses and wires), so vibration is easily isolated.


Just use a std Atkinson and shut the intake valve EARLY.
No pumping, no pumping losses (at that point).

Extra parts:
1. Redux gear
2. Eccent. shaft
3. Swing rod
4. Trigonal link

And the trigonal links can have some flopping forces due to tolerances that the crank bearing probably must carry.

I think someone at Honda is sick, buit having fun
- fine as long as it is their (well, the stockholder's) money not mine.

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