• Sep 7th 2009 at 2:57PM
  • 53
The Lotus ethos has always been about efficient performance. "Simplicate, and add lightness" is an oft-echoed mantra coined by founder Colin Chapman. While the company is most known for its sports cars and racing endeavors, it's got a history of engineering for hire, as well. Embracing a definition of high performance that has protracted to include alternative propulsion technologies, Lotus has brought its experience to bear for series hybrids.

Bowing at Frankfurt Motor Show, the Lotus Range Extender engine has been designed for driving a generator optimally without the compromises of conventional engines. Reducing cost, parts count and emissions were all part of the design dossier. This 1.2-liter three-cylinder that produces 47 bhp at 3,500 RPM is being described by Lotus as a monoblock – the cylinder head and exhaust manifold are integral with the engine block, reducing separate parts and potential failure points. Low mass, more thermal efficiency and a low build cost are other superlatives used to describe this powerplant with a more focused purpose than traditional car engines. Lotus appears to have a keen eye on the future of autodom, involved as it is with ventures such as Tesla, and working with Jaguar, MIRA and Caparo on this engine as part of the UK Technology Strategy Board's "Limo-Green" project.

Lotus has spent its lifetime innovating with technology and making light and efficient cars. While the thrill of series hybrid sport driving may have a different soundtrack, the exhilaration will likely be the same. Press release posted after the jump.

[Source: Lotus]


Lotus Range Extender Engine Revealed

The Lotus Range Extender - designed specifically for the new breed of highly efficient series hybrid vehicles.

Lotus Engineering, the world-renowned automotive consultancy division of Lotus, unveils its Range Extender engine at the 63rd Frankfurt International Motor Show. In a series hybrid vehicle, the Range Extender engine is attached to an electricity generator and provides a highly efficient source of energy to power the electric motor directly or charge the vehicles battery. The battery can also power the electric motor which enables the design of a drivetrain that has low emissions, optimised performance and acceptable range.

The Lotus Range Extender engine features an innovative architecture comprising an aluminium monoblock construction, integrating the cylinder block, cylinder head and exhaust manifold in one casting. This results in reduced engine mass, assembly costs, package size and improved emissions and engine durability.

The three-cylinder 1.2 litre Range Extender engine is optimised between two power generation points, giving 15 kW of electrical power at 1,500 rpm and 35 kW at 3,500 rpm via the integrated electrical generator. Its low mass of 56 kg makes it ideal for the series hybrid drivetrain configurations for which it is designed. The engine uses an optimised two-valve port-fuel injection combustion system to reduce cost and mass and, in line with Lotus Engineering's extensive research into renewable fuels, can be operated on alcohol-based fuels or gasoline.

For successful market uptake of series hybrid vehicles with acceptable driving range, vehicle manufacturers must overcome the challenges of high vehicle cost. The Lotus Range Extender engine not only offers the advantage of a cost effective design, but also its high efficiency and low mass will enable the downsizing of expensive batteries whilst maintaining vehicle efficiency and range. The engine has been designed using production methodologies and the parts procured from low volume potential production suppliers, offering a fast route to market for original equipment manufacturers wanting to source a dedicated range extender for series hybrid vehicles.

Paul Newsome, Managing Director of Lotus Engineering said: "As the world changes, Lotus Engineering continues to change with it, continuously developing solutions for more sustainable transportation. The Lotus Range Extender engine is another example of Lotus Engineering developing new technologies for efficient performance, this time in the area of series hybrid vehicles. The engine concept we have created with its optimised combustion and compact, low mass, low cost construction is a clear demonstration of the expertise and progressive approach Lotus takes for its own research and for its clients."

The Lotus Range Extender engine has been developed as part of the 'Limo-Green' project funded by the UK's Technology Strategy Board, a collaboration between Lotus Engineering, Jaguar Cars Ltd, MIRA Ltd and Caparo Vehicle Technologies, demonstrating a large, lightweight, prestigious executive saloon with less than 120 g/km CO2 emissions.

Simon Wood, Technical Director of Lotus Engineering said: "Most series hybrid vehicles that are currently being developed will use adaptations of existing, conventional engines which are therefore compromised in the efficiency that they can achieve, designed as they are for a wide range of operating conditions. Designing the Lotus Range Extender purely for use in series hybrids has allowed us instead to develop an optimised engine that has high thermal efficiency, low fuel consumption, multi-fuel capability and a 35 kW peak output from a 1.2 litre, low cost architecture over the precise operating range required by a series hybrid drivetrain."

Key features of the Range Extender engine in detail:

The Range Extender features a novel engine architecture incorporating a monoblock construction that blends the cylinder head and block together eliminating the need for a cylinder head gasket, improving durability and reducing weight. Approximately 17 parts are eliminated using this approach and the water jacket is better optimised.

Integrated Exhaust Manifold
Lotus Engineering designed and developed a new advanced cylinder head design featuring an integrated exhaust manifold. The production-ready technology can significantly reduce manufacturing costs, emissions and weight. An integrated exhaust manifold has potential to:
  • Reduce parts count: 18 fewer components resulting in lower inventory, production, logistics and aftermarket costs
  • Weight reduction: total system mass reduction resulting from elimination of separate exhaust manifold
  • Improved engine durability
Attached to the engine via the crankshaft, the generator sustains vehicle operation beyond the range provided by the batteries.

Additional Benefits
The Lotus Range Extender engine generates a reduction in emissions through faster light-off of the close-coupled catalytic converter with a reduction in heat loss between the exhaust port and catalyst inlet. Engine operating range is optimised to deliver more efficient running, which also aids underhood thermal management.

Utilisation of the monoblock construction results in an assembly cost reduction, while there is also a reduced catalyst loading requirement because less heat is lost on engine start-up between the exhaust port and catalyst inlet.

Increased vehicle integration flexibility is achieved because of the reduction in mass and the reduced package size leads to reduced space requirements. Particular emphasis has also been placed on the coupling of the generator and NVH signature.

Technical details:
Technical specification of the Lotus Range Extender engine

  • 1.2 litre 3-cylinder with 2 valves per cylinder, SOHC
  • Belt driven
  • Monoblock with Integrated Exhaust Manifold
  • All aluminium
  • Balance shaft (optional)
  • Direct-coupled generator
Bore and Stroke
  • 75.0 mm x 90.0 mm
Compression ratio
  • 10:1
Maximum power
  • 35 kW (47 bhp) at 3500 rpm via integrated electrical generator
Peak torque
  • 107 Nm at 2500 rpm
Maximum BMEP
  • 11.2 bar
Maximum Engine Speed
  • 3500 rpm
Fuel System
  • Port fuel injection, Lotus EMS
Dry weight
  • 56 kg

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    • 1 Second Ago
      • 5 Years Ago
      The basic problem with most modern cars is unnecessary weight. Electric cars with batteries exacerbate this problem.

      Serial systems with limited batteries and great fuel consumption in the generator combined with a light weight vehicle is a more sensible short to mid term solution for rising fuel costs.

      BMW seem to agree with that basic philosophy. There is a heck of lot more efficiency available going down the serial route in my opinion. Mass uptake of electric vehicles is gonna take a lot longer.

      The biggest challenge is getting consumers out of big fat tanks and 4wds that they plainly don't need. Consumer are going to have to kiss some luxuries goodbye if they want to keep the freedom of personal transport. The freedom itself will be the luxury in the future.

      I think Lotus have got a market for this approach. In fact I've been looking for just such an engine for a project. Combine this with a wheel motor and a small battery/electronic control unit in a light weight vehicle and we've got something interesting.

      • 5 Years Ago
      @ Snowdog

      Thanks for jumping in.

      "There will almost certainly be power limiting moves to ensure as you state, that the battery is never completely drained. You don't get power from the electron fairy at this point. You either start really draining the battery or you cut power output to be in line with the generator capacity."

      Here we go:

      When the battery's charge drops to a certain level, the ICE kicks in and spins a generator. The generator is rated to provide more power than what the electric motor requires (on average). In this fashion, while the electric motor is discharging the battery, the ICE/generator is recharging it at a higher rate. So, there is a net surplus of charge being sent into the battery, and the electric motor driving the wheels never notices any disruption.

      The very fact that the ICE can be turned off while the ER-EV is in "charge-sustaining mode" demonstrates that it is not required at all times - meaning it is capable of recharging the battery faster than the battery is being depleted. "Stop-Start" ICEs will be used in both the Karma and the Volt.

      The Karma has specialized software to differentiate between driving modes: "Stealth" maximizes battery power by limiting acceleration and top speed and allowing the battery to reach a lower charge limit, while "Sport" allows greater acceleration and top speed while increasing the run time of the ICE/generator to keep the battery at a higher minimum charge.

      "When in HEV or charge sustaining mode the Q-Drive control system operates
      the vehicle very much the same as a normal strong hybrid. This includes
      deceleration engine shutdown, zero speed engine-off, electric launch and autostart
      capability, and charge sustaining while maintaining charge balancing
      throughout the customer drive cycle. When the driver is in Sport mode, the QDrive
      automatically transitions to the charge sustaining mode at a higher SOC
      level than when in Stealth mode. This ensures that sufficient energy is
      available to support driver demands. Should the driver transition from Stealth
      to Sport while in HEV mode; the Q-Drive will restore the higher low-energy
      threshold. This provides for a high performance, on-demand, no-compromise,
      vehicle operation."

        • 5 Years Ago
        All well and good for the Fisker with its 260HP genset.

        But a car with the 47HP lotus Genset would likely run into issues.

        Driving 80MPH with the AC and Stereo running is not uncommon and would likely be near the limit for the genset. Throw in a long uphill grade and the lack of reserve may become evident.

        I think it is good that GM didn't cut it that close and go with a smaller genset as many have suggested (often the suggestion is 25HP or less, completely untenable).

        I wouldn't be terribly surprised if some people manage to find limits in the 70HP genset. 4 big passengers driving through the Rockies?

        I will be very curious about the range extender performance of the Volt. How does it compare to the Prius for real MPG. How annoying is it with the likely stepped operation, or droning away at stop lights while it makes up for deficits.
        • 5 Years Ago
        You say the genset won't have stepped operation like this lotus genset (essentially two speed) so will it have a full continuous RPM range giving up the advantage of operating at the most efficient speed or is it just one speed?

        The question remains, about wether it will be droning away at stoplights trying to make any deficit you might have incurred.

      • 5 Years Ago
      Wow. That engine only weighs 123 lbs.
        • 5 Years Ago
        If you had an 8-speed gearbox (3500rpm limit), it seems like it'd be a good drop-in for an old VW Beetle or a Geo Metro :)
      • 5 Years Ago
      I believe Freddie Dixon, a pre-WW2 Riley driver, first coined the expression "simplicate and add lightness"
      • 5 Years Ago
      Ask a Lotus engineer anything about a chassis and they can tell you how to build the perfect chassis. Unfortunately Lotus has never been known for their engines. I think it must have been some deal with the devil Colin Chapman made that he traded the ability to build decent engines for the unholy ability to build the chassis.
        • 5 Years Ago
        I think the devil/s, were Mike Costin and Keith Duckworth of Cosworth.
      • 5 Years Ago
      Right now, Lotus doesn't even make their own engines for their street cars. They source them from Toyota. Before that they sourced them from Rover. Before that they sourced the Elan motor from Isuzu. I think the Espirit engine was theirs.

      So I'm a little bit skeptical about taking an engine design from Lotus.
        • 5 Years Ago
        I'm not convinced that this engine is the right place for Lotus to start building engines either. There already are 15kW engines (which this is) designed for specifically for electrical power generation. Atop that there are mass-produced three-cylinder kei-car engines that produce similar output, are quiet, and are very efficient that can achieve higher economies of scale then this bespoke endeavor.

        At the moment, there is still a very small market for exclusively serial-hybrid, and the system that is in cars like the Prius and Fusion Hybrid can do operate in both serial and parallel modes. In the modern automotive industry, its all about parts sharing, bulk supplier purchases, etc, there is very little room for manufacturing low-volume engines for low-volume cars.
        • 5 Years Ago
        Yeah the Esprit engines were. Also they designed the heads for the Corvette LT5.
        • 5 Years Ago
        Although the engines in the Fusion or Prius do operate in a mode where they are storing energy in the batteries, they don't really ever operating in a truly serial mode. Every time the engine is running in those cars, it is connected to the wheels, which is definitely not a serial mode.

        You're right there are lots of good Kei car engines, you'd only have to do at most some emissions work to utilize one of them, so it'd be very cost efficient. And I think if you were to create a new engine for a series hybrid, you'd likely want to use an Atkinson/Miller cycle. (are you listening, GM?)
        • 5 Years Ago
        In the typical lotus fashion of using someone else's bottom end and their own head/manifold setup: Ford, BMC or Triumph for the early Lotus 7's, Ford for the elan and Europa twin-cam, (with a few Renault blocks in the Europa for good measure), (?), the Esprit motor was actually a Vauxhall "slanted" 2.0 litre block, as also used in the Jensen Healey. This engine, (which I did some development work on, for the Lotus Talbot rally car application), was later bored out and eventually turbocharged.
        In my humble opinion, the people on the right track for reliability, performance, range and economy is BMW, with the 3cyl turbo diesel / electric setup, as shown on AB recently in the prototype Vision.
      • 5 Years Ago
      Since the engine is decoupled at the wheels, how about two of these engines and a very small battery pack (5 minutes worth of power at full discharge)? The configuration would be one engine operates at all times to power the car at its minimum capacity and the second engines is activated when the additional power is required. A full tank of gas with a secondary engine still holds more energy and weighs less than the Volt's 1000lb battery pack.
        • 5 Years Ago
        This Lotus unit is not designed to be a prime mover. It only demand is to keep a battery at optimal charge.

        Your concept would be better off if it dropped the two generators, and fused the two 3-cylinder blocks into a V-6.

        Bingo, more power and less weight than a 1000lb battery pack.

      • 5 Years Ago
      This just highlights another questionable design decision about the Chevy Volt - if the engine is used purely to recharge the batters, why didn't GM use a small 3-cylinder engine or even a 1.0 litre 4-cylinder instead of a 1.4 litre 4-cylinder that's large enough to move the whole vehicle? Especially considering Daewoo - who designed the Cruze - has 3 cylinder engines available?
        • 5 Years Ago
        I'm afraid that burning sensation was probably contracted by another method. You might want to have a doctor check that out. The whole point of ER-EV is first and foremost that it IS an electric vehicle. Both GM and Fisker are quite clear on that point. The batteries always provide the power to the electric motor, even during ER mode. At no point have I said otherwise.

        Both GM and Fisker have also made it abundantly clear that the Volt and the Karma are meant to be recharged primarily by the electric grid and that the gas engines are there to provide enough power to continue driving until you can get the car to an outlet (aka, extending the range). GM and Fisker have both also admitted that the performance will be decreased when operating in ER mode vs EV mode. Yes, when the battery gets drained to a preset level (it will never get completely depleted; sorry if you couldn't grasp that from my statements), the engine kicks in to maintain the minimum battery level. But the vehicles are not meant to be run like that as their primary method of operation. Can they run in ER mode indefinitely? Probably. But then why would you buy one of these vehicles over a regular hybrid?

        GM has plenty of other engines that they or Fisker could have used that would provide enough juice to the battery to power the car and recharge back to full capacity. But they chose not to in order to ensure people use the grid. And running the engine when at a stop does nothing to extend the range. It just wastes fuel. If the battery isn't already at the minimum ER level, it will run long enough to reach the minimum ER level and then shut off. It will then restart once the vehicle begins moving again. It will certainly never run long enough to fully recharge the battery.
        • 5 Years Ago
        "Assuming no wind and no grade, it takes 25whp to maintain a speed of 65 miles an hour for a vehicle weighing about 4200lb (fuel, passengers, cargo, and vehicle). That's about 30hp back at the flywheel. Certainly, I wouldn't want to ride in such a vehicle, but it's certainly possible. "

        yeah. just try getting up to highway speed, or passing, or doing anything.
        • 5 Years Ago
        @ Jimbo

        No disrespect intended, but you don't need to correct me.

        "The gas engine charges the battery, which powers the electric motor, which drives the vehicle just like you said."

        Yes, that is essentially what I'm saying.

        "Essentially the battery and electric motor behave like an electric transmission for the gas engine, like Jim said"

        No. Jim is assuming the Volt's ICE powers the electric motor directly. That would be an electric transmission. That never happens. The ICE in the Volt turns a generator which only supplies enough current to keep the battery at a certain charge. The ICE is never called upon to be the sole prime mover of the Volt, which is why it can be a relatively small unit with a low power output.

        In an electrical transmission of the diesel-electric hybrid type exemplified in freight trains, the ICE provides direct current to the electric motors.

        In the Volt, the ICE turns a generator which send current to a BATTERY, which then sends the current to the electric motor. The battery acts is a storage device, which is why the Volt should not be looked at as having an "Electric Transmission".

        Once again, for clarity:

        Electric transmission : ICE to Electric Motor to wheels

        Volt drivetrain: ICE to generator to battery to electric motor to wheels

        • 5 Years Ago
        @Clavius @ Jim

        The Volt's engine in no way connects its power to the road. It is simply there to recharge the battery. Think of it as a purely electric car in terms of propulsion using an engine as a means to charge itself. Therefore the question was, is it really necessary to have a 1.4 liter inline 4 to charge a battery?
        • 5 Years Ago
        Ok, now you're just arguing semantics. Submarines have diesel engines or nuclear reactors that can generate power to the electric motor (like a locomotive). Or it can recharge the batteries to power the electric motor (like the Volt). In both cases, it is referred to as an electric transmission.
        • 5 Years Ago
        @ Jimbo

        I apologize for being short, but I'm not disagreeing with you, I was disagreeing with Jim.

        Jim was the one who said:

        "...if the batteries are low/drained, the engine and generator have to move the car."


        "That's only true until the battery is drained. Then, in "range extending" mode, the car is powered by the gas engine, with what is essentially an electric transmission (a la diesel-electric locomotives.)"

        I disagree with both of those statements. You then attempted to correct me, by saying Jim and I were saying the same thing in different terms. You said I was arguing semantics. Well, there is a difference between the prime mover in a diesel-electric locomotive, which does required the ICE to supply current directly to the hub motors, and the drive train in an ER-EV such as the Volt and Karma, which use units similar to the Lotus unit to keep a battery at its optimal charge.

        You are correct about the ER-EV being primarily intended to be recharge via a wall plug. However, that is not vital to the car's functionality. Both the Volt and Karma can be driven without ever being recharged - the ICE is fully capable of keeping the batteries at an operational level. Actually, I agree (with Lotus) that a smaller ICE could also accomplish the same task - a claim that Jim denies (which is the source of another disagreement).

        It is Jim's stupidity that I meant to curse; I apologize if you think I meant you.

        Willyolio makes the point best. The generator coupled to a small ICE is fully capable of keeping a battery charged in such a fashion that the ICE can be much smaller than if it were required to power the wheels through a direct mechanical transmission.

        I agree with everything you said in your last post.

        1. ER-EVs are ALWAYS powered by the electric motor, using current stored in the battery.

        2. ER-EVs use an ICE to keep the battery charged at a sufficient level that the ER-EV can be used until the ICE runs out of fuel. The ER-EV can then be refueled, and continue to operate in a normal fashion until any point when it can be plugged back into the main grid. This is not the typical usage, but it is what makes an ER-EV an ER-EV.

        3. Other ICE choices (including smaller units like this one from Lotus) would fulfill the ER-EV's mission - the size of the ICE does not limit the performance of the ER-EV in any fashion other than battery recharge capability. A fully charged battery is not a requirement of the ICE.

        As to the "stop-start" nature of the ICE in an ER-EV, I'm not so sure. Since the ICE runs at a steady speed, it really doesn't matter if it's on or off when the car itself isn't moving. The ICE is only charging the battery, after all.

        • 5 Years Ago

        "And you fail to grasp simple physics. A 47 hp gas or diesel engine running as a range extender (aka, the battery is DRAINED) can never deliver 250 hp of power to an electric motor unless you've somehow figured out a way to create energy from nothing."

        and you fail to grasp the fact that BATTERIES STORE ENERGY. 1 minute of power generation at 25HP (sitting at a red light or something) to charge the battery will give you 6 seconds of 250HP power. or, cruising down the highway, using 20HP but generating 25HP of power will still gradually build up battery charge for you to bring on 250HP when you need it.

        do you only have solar-powered flashlights at your house or something? you seriously can't figure this out?
        • 5 Years Ago
        letstakeawalk: I think you misunderstood what Jim was saying because he essentially said the same thing you did. Jim said that the engine is MECHANICALLY decoupled from the wheels, which it is. The vehicle is always powered by the electric motor.

        But the engine not completely decoupled. Jim said that the gas engine powers the car during "range-extending mode" because it is. The gas engine charges the battery, which powers the electric motor, which drives the vehicle just like you said. Essentially the battery and electric motor behave like an electric transmission for the gas engine, like Jim said. You are both saying the same thing, just in different ways.
        • 5 Years Ago

        I wouldn't say that I4's are really a good measuring point for smoothness, but I3's are worse. The optional balance shaft probably shouldn't be considered optional, if NVH is a priority in the target vehicle.
        • 5 Years Ago
        Sadly we as Americans have a distain for the term small or underpowered. If Chevy slapped in a low displacement under powered engine it would be ripped to shreds in auto reviews and the perception would spread to the masses. I would like to believe though that once the Volt hits and several other hybrid and small cars hit that trend of bigger is better will slowly lose ground and people will realize "lighter is better".

        • 5 Years Ago
        because when the batteries are drained, you'll still need enough power to move the car. A 47 hp engine in something the size/weight of the Volt would be miserable.
        • 5 Years Ago
        willyolio: It is more fuel efficient to shut off the engine at a stop just like every other hybrid. That is a primary fuel savings measure that is even being adapted to non-hybrids. The point of extended-range EVs is to use the electrical grid as the primary method to recharge the battery. Keeping the engine running at a stop defeats the purpose on ER-EVs.

        You're incorrect about ONLY needing 20 hp or even 47 hp. That's true during steady-state cruising but not during acceleration, changing direction, non-steady-state cruising, or on non-level surfaces. In other words, driving. If 20 hp motors were adequate, all vehicles would be powered by 500cc lawnmower engines.

        And you fail to grasp simple physics. A 47 hp gas or diesel engine running as a range extender (aka, the battery is DRAINED) can never deliver 250 hp of power to an electric motor unless you've somehow figured out a way to create energy from nothing. If so, you'd better get a patent on that idea quick. Heck, even a 250 hp gas or diesel engine cannot deliver 250 hp of power to an electric motor due to conversion losses.
      • 5 Years Ago
      I'd like to see some cutaways that show how they implemented the monoblock?
      • 5 Years Ago
      This is part of the Lotus strategy. To provide off-the-shelf "hot" technology for the mainstream automotive industry.

      • 5 Years Ago
      There's a difference between a Range Extender and a Limp Home Device.

      This is closer to the latter.
        • 5 Years Ago
        A range extender doesnt need to supply peak power. It just supplies average power.

        When accelerating, this genset doesnt provide enough power by itself, but the difference is made up by the batteries.

        When decelerating or cruising, this genset provides more than enough power, and the excess power is added to the batteries.

        Unless you are climbing mount washington with your car, or cruising at 90+ mph, it should be sufficient for a reasonably sized, aerodynamic vehicle.
      • 5 Years Ago
      "Lotus has spent its lifetime innovating with technology and making light and efficient cars."

      Unfortunately, "reliable" hasn't been part of their vocabulary.

      So far, we only have a rendering. How far away is an actual engine?
        • 5 Years Ago

        There is a good reason why Lotus uses Toyota engines instead of their own.
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