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Infiniti M35 Hybrid Features Original 1 Motor/2 Clutch Parallel Hybrid System

Elements of the new hybrid drive. Source: Nissan. Click to enlarge.

Infiniti unveiled its first production hybrid, the M35 Hybrid, at the 2010 Geneva Motor Show. The M35 Hybrid uses an original parallel one motor/two clutch hybrid system and features a decoupling 3.5-liter V6 engine; a 50 kW, 270 N·m (199 lb-ft) electric motor integrated into the 7-speed automatic transmission (7AT); and a high-output, fast charge/discharge 1.3 kWh Li-ion battery pack.

This new hybrid system, said Owen Thunes, Senior Project Engineer, Electric, Hybrid & Fuel Cell Vehicles, Nissan Technical Center NA, at the SAE 2010 Hybrid Vehicle Technologies Symposium in February, can deliver fuel economy similar to that of a compact car, even with its 3.5-liter V6-based engine. There is also a significant improvement in fuel efficiency at highway mode, compared to conventional systems. The system delivers better response and a more direct feeling than a 3.7L V6, Thunes said.

The architecture of Nissan/Infiniti’s new parallel one motor/two clutch system. Source: Nissan. Click to enlarge.

The first clutch is installed between the naturally-aspirated 3.5-liter V6 and the electric motor. This clutch allows the full decoupling of the V6 when the systems is in either electric or power regeneration modes, thereby reducing mechanical drag and boosting the efficiency of the electric motor. The second clutch transmits the drive force.

Nissan opted for this particular design, Thunes said, after a thorough modeling comparison of a range of hybrid systems including series-parallel (power split) and parallel architectures, with a particular focus on fuel consumption and acceleration, but also drivetrain loss, packaging and cost potential.

The scope of Nissan’s study of hybrid architectures. Source: Nissan. Click to enlarge.

Nissan found that on a V8 5.6L system, two variants of the parallel system, a 7AT 1Motor-2Clutch, and a 7AT 2Motor-2Clutch, outperformed all the other systems for fuel consumption on the US combined cycle. With a 3.5L and CVT-based (continuously variable transmission) system, the 1Motor-2Clutch and 2Motor-2Clutch types bested the power split systems in terms of acceleration, and performed as well in fuel consumption.

Likewise, in a 2.5L and CVT case, the CVT + 1Motor-2Clutch and 2Motor-2Clutch systems outperformed the power split systems in terms of fuel consumption and acceleration. In a 1.5L-CVT case, the CVT+1Motor-2Clutch and 2Motor-2Clutch systems outperformed all the others in the terms of fuel consumption.

The study also concluded that the 1 motor parallel system had the most attractive cost structure.

To be able actually to implement the 1 motor/1 clutch system and achieve the performance and cost breakthroughs, Nissan needed to develop an integrated control technology to regulate battery, inverter, motor, clutches, engine and transmissions simultaneously. A high-output Li-ion battery capable of switching between charging and discharging very rapidly was required, as well as high-speed and precise motor control to allow a smooth connection between the two clutches.

The ability to connect and disconnect the engine offers a number of benefits, Thunes said.

  • At low- and mid-speed, frequent electric driving can be realized without engine friction. In a three-month US-based test program that incorporated a large range of use, the M35 Hybrid was able to drive in electric-only mode for as much as 50% of the time.

  • At mid- and high-speed, the engine can be used in the efficient operating range by generating ower with the motor and the high final gear ratio. The system is highly efficient because the clutch transmits the engine torque directly.

  • In deceleration (regeneration), disconnecting the engine eliminates engine friction.

Layout of the system components. Source: Nissan. Click to enlarge.

The M35 Hybrid’s transmission is a more sophisticated version of Infiniti’s 7-speed Adaptive Shift Control (ASC) automatic transmission. One difference over the ASC transmission used in other Infiniti models is that there is no torque converter, and therefore none of the losses that torque converters cause.

The lack of a torque converter also enhances responsiveness for a sportier-feeling drive. The throttle can be “blipped” just as in a manual transmission car, while acceleration is seamless thanks to motor-assisted gear-shifting that ensures ratio changes are completely smooth.

Apart from its fast charge/discharge response, the Li-on battery pack is built with laminated cells, enhancing its cooling performance. Temperature stability is further improved by the use of manganese cathodes. An end result of this is exceptional battery reliability, Infiniti says.

“Infiniti Direct Response Hybrid is the core of the future Infiniti performance.”
—Toru Saito, Corporate VP, Infiniti

The technology, which previewed in the Essence concept coupé at the Geneva Motor Show in 2009, has been given the name Infiniti Direct Response Hybrid.

The M35 Hybrid will be the first Nissan hybrid offered in the US, Europe and Japan markets. The vehicle is due to arrive in Western Europe from spring 2011, depending on market. Power outputs and performance data will be confirmed at a later date.



Sounds exciting! Let's see the real results when it finally come out.

Dave K.

This is what Honda should have done, by not adding the second clutch they limited their fuel economy potential and lost market share to Toyota. Nissan needs to put this in a small efficient car and show us what it can do, most hybrid buyers don't want a V6 and don't care that much about performance.


Dave K:

Agree with you. An Altima equipped the same way but with a much smaller 4 cyls could be very interesting.

A smaller ICE could liberate enough room for a second battery pack to double e-drive capability and further reduce liquid fuel consumption.


It seems like there could be a one clutch series/parallel EREV. One side of the alternator is coupled to the engine and the other side of goes to a clutch between the alternator and traction motor.

Roger Pham

Ah, but Toyota's HSD with 2-motors/generators and a planetary power split unit requires NO Clutch and NO Conventional Transmission, and offers the least battery usage, meaning that the battery will last the longest. The HSD is the best serial-parallel hybrid arrangement available. It is the lightest and offers the highest possible fuel efficiency.

Any other alternatives are used only because Toyota's HSD is patented.


@ Roger,
The fact is that Toyota uses in Camry hybrid and some Lexus hybrid SUV a version of HSD that has a 2-speed transmission somewhere in the drivetrain. I read about it, but wasn't able to find the actual layout (ie where the transmission is located, I guess between the engine and the rest of drivetrain).
Also read that there are loud clicks in a Lexus hybrid when it switches something. I guess it must be coming from some (de) clutching. There is nothing that can produce clicking in Prius HSD.

IMO HSD in Prius is not very flexible, there are too many interdependencies between MG1, MG2 and ICE RPMs. That way its not possible to optimize the system for all driving modes in terms of efficiency and performance (say for hill climbing and highway cruising).
I think that the addition of a 2-speed transmission somewhere in the driveline would greatly increase the ability to optimize the system output for variety of driving conditions. It does cost, but also offers benefits.
On the other hand GM's two-mode system has several clutches (plus many speeds) that gives them great freedom of optimization, but it's costly.

Roger Pham

The Prius' HSD is surprisingly flexible and offers impressive efficiency at all practical speeds.

The two-speed feature of larger HSD is so that one can use smaller electric motor but still get the torque multiplication at lower speeds. At higher speeds, the engine provides a lot of torque, hence less torque is demanded of the electric motor, and the motor can turn slower that won't exceed the high-end rpm limitation of the motor even thought the vehicle is running at high speeds.

High-duty-cycle vehicles like the diesel electric locomotives do not have any clutches that would introduce another weak link that can fail and requires additional maintenance.


@Dave K: Honda IMA doesn't have any clutch. Nissan is looking at 1 clutch or 2 clutch design. The upcoming Porche and Hyundai hybrids seem to have similar design. I hope they have worked out patent details.

@MG: Camry hybrid and RX450h have two planetary gearsets. One is used to split power from the ICE and another is used to multiply electric motor's torque. Both of them are single speed as they have no clutch.

You may be referring to Lexus LS600h (V8 HSD) with two speed eCVT with a clutch. It may have been needed to unleash all the V8 power at both low speed and high speed. For a 4 or 6 cylinder HSD, it is not needed

Account Deleted

i wonder what happened after this.. been wanting to get some ideas about having some Infiniti Parts get "crossed" other cars. really sounds exciting.

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