Let us help you with that: Lotus develops off-the-shelf range extender engine
by Dan Roth on Sep 7th 2009 at 2:57PM 
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]
PRESS RELEASE
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:
Monoblock
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
General
- 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
- 75.0 mm x 90.0 mm
- 10:1
- 35 kW (47 bhp) at 3500 rpm via integrated electrical generator
- 107 Nm at 2500 rpm
- 11.2 bar
- 3500 rpm
- Port fuel injection, Lotus EMS
- 95 RON ULG / ethanol / methanol
- 56 kg
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Reader Comments (Page 1 of 4)
BigWill 3:12PM (9/07/2009)
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?
Reply
Clavius 3:27PM (9/07/2009)
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".
Jim 3:26PM (9/07/2009)
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.
why not the LS2LS7? 3:52PM (9/07/2009)
Because they already had this engine ready to go. Being a bit larger won't be a huge problem, it'll just run for a shorter period of time when it runs.
I think perhaps GM is concerned that they never want the driver to have to restrict their speed in order to keep from using energy from the battery faster than the ICE can put it back. And in hilly areas, with a 1.0L engine it's possible that this could happen I think.
Over time maybe they can change the engine if the 1.4L turns out to be unnecessarily large in normal use.
Ricky 5:25PM (9/07/2009)
@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?
Jim 6:03PM (9/07/2009)
"The Volt's engine in no way connects its power to the road. It is simply there to recharge the battery."
No. that the engine is mechanically decoupled from the wheels doesn't mean you can ignore the laws of physics. If the battery is drained, the engine/generator has to produce enough power to move the car and try to charge the battery. A 47 hp engine would not likely be able to do this job.
you're falling into the trap of assuming that if the engine is completely decoupled from the wheels. It is not; if the batteries are low/drained, the engine and generator have to move the car. And the power that the engine has to produce is wholly dependent on what the driver is demanding. Just like a conventional drivetrain, though with somewhat lower driveline losses.
"Think of it as a purely electric car in terms of propulsion using an engine as a means to charge itself."
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.)
"Therefore the question was, is it really necessary to have a 1.4 liter inline 4 to charge a battery?"
GM seems to think so. What evidence do you have to prove otherwise?
Chris O 9:45PM (9/07/2009)
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.
If what Lotus had in mind was for this engine to feed into the CVT of a small, light PHEV, then this could work. Let's say that the max GVWR was closer to 3400lb, and that the CVT & driveline losses were on the order of 20-25%, then you could still have a workable (if pokey) vehicle.
If Lotus was thinking that this engine would be good for serial electrical range extension, then I'm not so sure. Electric motors are efficient, but not 100% - and neither is mechanical to electrical power generation. Assuming Lotus' engine is expected to run at a continuous RPM, then it probably is engineered for higher thermodynamic efficiency than a "regular" ICE. Those gains are still likely to be lower than the losses incurred from the serialized electical powertrain. It seems like you'd be looking at one of those small, urban EVs for it to be really feasible.
Regardless, I think this is a loser for Lotus. Most manufacturers already have small, efficient powerplants that they can use in a pinch, should they feel the need. Looking a bit farther forward, I would hope that manufacturers are looking at more efficient alternatives, like Atkinson or VCR engines.
Jim 9:59PM (9/07/2009)
"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.
Chris O 10:34PM (9/07/2009)
Uh... that's why I had said that it might work better with 800 fewer pounds. That's also why I said that I wouldn't want to ride in such a vehicle.
Jimbo 10:46PM (9/07/2009)
I don't know much about I3 engines. How do they compare to an I4 for smoothness?
Chris O 11:27PM (9/07/2009)
Jimbo:
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.
unni 11:46PM (9/07/2009)
One old post in GM-Volt site, may be helpful :-)
http://gm-volt.com/2008/07/26/gm-explains-why-the-14-l-ice-range-extender-was-chosen-for-the-volt/
letstakeawalk 11:46PM (9/07/2009)
@ Jim
"You're falling into the trap of assuming that if the engine is completely decoupled from the wheels."
Which it is. Which is why you are so wrong. The electric motor is the sole source of propulsion for the Volt.
"Then, in "range extending" mode, the car is powered by the gas engine"
Sorry, that is flat-out wrong.
LS2LS7? is correct. GM chose the small I4 because they had it available in mass quantities. A smaller ICE would work, but GM went with what it already had on the shelf.
http://movementbureau.blogs.com/projects/2007/01/the_chevrolet_v.html
Pay attention at point 4:
"4 - At this point, a small, petrol internal combustion engine (yellow) starts. Unlike a normal internal combustion engine car, or indeed the Prius hybrid, this petrol engine cannot drive the wheels. Instead, it drives an on board generator (green) to continue to power the electric motor (red), which continues to provide drive to the wheels."
Jimbo 12:02AM (9/08/2009)
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.
willyolio 12:30AM (9/08/2009)
Jim and Jimbo, you two are missing an important point: a car, even a non-hybrid gas car, never runs at peak power all the time.
47hp is more than enough as generator. you know why?
because it can still charge the battery when the car's sitting still. it can still generate 47hp of electricity when the car's only using 20 (i.e. cruising down the highway). a 25hp generator can still power a 250HP electric motor if you don't have the pedal on the floor all the time.
letstakeawalk 12:43AM (9/08/2009)
@ 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
zamafir 12:48AM (9/08/2009)
@willyolio, good point.
Jimbo 1:07AM (9/08/2009)
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.
Jimbo 1:23AM (9/08/2009)
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.
letstakeawalk 1:39AM (9/08/2009)
@ Jimbo
"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."
No. Stop. The stupid burns too much.
A pure EV uses the electric grid to recharge the battery. An ER-EV by definition uses an ICE to recharge the battery. (ex: GM Volt, Fisker Karma)
I hate to use Wiki, but we need a basic level of understanding here:
http://en.wikipedia.org/wiki/Range-extended_vehicle
"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."
Here's the point you missed:
The Volt, or any other ER-EV, never lets the battery below a certain charge. The battery is never "drained". The battery in an ER-EV is always able to provide electricity. The ICE never provides current directly to the electric motor, only the battery.