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Lotus and Continental Developing 1.5L Direct Injection Gasoline Engine for Low CO2 Output
14 April 2008
Lotus Engineering and Continental Automotive are developing a 1.5-liter 3-cylinder direct injection gasoline engine with a number of synergistic technologies to realize low CO2 emissions while still providing similar performance to a typical 2.2-liter naturally aspirated engine. (Earlier post.)
When applied in place of a 1.8-liter naturally aspirated engine in a GM Opel Astra (a C-class vehicle), the 1.5-liter Sabre (Spark-ignition Advanced Baselined Research Engine) engine is projected to reduce CO2 emissions by 25% (from 175 to 140 g/km), while also delivering a 1.1 second reduction in 0-100 kph acceleration time.
The Sabre project, described in a paper presented at the SAE 2008 World Congress, set out to achieve three primary objectives: demonstrate low CO2 emissions; improve driving pleasure; and use cost-effective, affordable technology.
The Sabre team made six principle design decisions in tackling the project:
Mild downsizing from a 2.2-liter, 4-cylinder engine to a 1.5-liter direct-injection, turbocharged unit.
Adopt direct injection in a centrally-mounted, close-spaced configuration using new multi-stream solenoid injectors rather than a pressure swirl type. Adopt twin cam phasers for improved control of gas exchange.
Adopt a 3-cylinder configuration for adequate packaging, lower BOM and knock limit extension. Adopt of roller-bearing shaft for NVH purposes.
Adopt a switchable valvetrain system to afford Miller cycle operation. Deactivate one intake valve, switch the other to a low lift/short duration profile to generate increased turbulence.
Use a mild hybrid system: a crankshaft-mounted starter/alternator for start/stop, regeneration and torque assist functions.
Adopt a water-cooled exhaust manifold integrated into the cylinder head (IEM). Use an advanced cooling system to tailor the characteristics of the heat rejection from the engine to vehicle operation. Specify a water-oil heat exchange to assist in friction reduction.
The resulting engine produces in excess of 240 Nm peak torque and 117 kW (157 hp) @ 5000 rpm. Lambda = 1 operation up to an engine speed approaching 5000 rpm is possible, with only moderate enrichment necessary above this with a turbine inlet temperature limit of 980°C.
Thew well-documented synergies between direct injection, turbocharging and cam phasing have been combined with the packaging, firing interval and friction benefits of a 3-cylinder configuration. The adoption of a swtichable valvetrain, an integrated exhaust manifold and a mild hybrid system compliment the engine design concept in a manner that enables low fuel consumption to be achieved from mild downsizing with a relatively large swept volume.
...It is hoped that future versions of the engine will include such technologies as spray-guided direct injection (because the degree of downsizing means that dethrottling is still attractive) or two-stage charging systems (because of the benefits of 3-cylinder banks in turbocharged engines.
Project Sabre was partly funded by the UK Energy Savings Trust. Some of the initial development of the system was carried out as part of the HOTFIRE consortium project.
Resources
Project Sabre: A Close-Spaced Direct Injection 3-Cylinder Engine with Synergistic Technologies to Achieve Low CO2 Output (SAE 2008-01-0138)
April 14, 2008 in Engines, Fuel Efficiency, Hybrids | Permalink | Comments (14) | TrackBack (0)
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Comments
Very promising work. I wonder what the first applications will be in: GM?
A Saturn Astra sub-8 second 1.5 DI TC promising +40mpg would be a welcome vehicle.
Bring it on here in the US!
Posted by: DieselHybrid | Apr 14, 2008 3:21:10 PM
Another possible change would be to have a ceramic coating on the inside of the cylinder head and exhaust main. This would allow for more efficient heat rejection which would allow the radiator to be downsized and possibly allow for improvement in aerodynamics.
Other small improvements include a light-weight nylon exhaust, a smooth underbody, aerodynamic wheels, and a CRP trunk. Ceramic additives could be used in the vehicle paint to reduce heat gain during the summer. An absorption cooler could be used to cool the car using waste heat further reducing the vehicle's electrical load.
I would also like an Astra with a 6spd manual. Ideally it would have a 6spd DSG.
Posted by: GreenPlease | Apr 14, 2008 7:47:53 PM
Is it really worthwhile to go from 4 to 3 cylinders in a 1.5L engine? Don't you have to compensate for the extra 3-cyl vibrations, etc? I'd love to hear from the experts on this.
Posted by: Nick | Apr 14, 2008 8:48:30 PM
what about the cost of this engine?
will a car equipped with this engine still be competitively priced. A Citroen C5 was unveiled a couple of weeks ago with 149 g CO2/km. I found this very interesting not only because 149 is a very low footprint for a car of this size, but also because the C5 costs a good 7000 euros less than some competitors.
Or is this going to be something like a bluemotion vehicle, something nice for carshows and magazines but way too expensive too justify buying it?
Posted by: Karl-Uwe | Apr 14, 2008 9:49:11 PM
@Nick: It's right in the text: "adopt a roller-bearing shaft for NVH purposes" Otherwise known as a balance shaft.
Posted by: pauln | Apr 14, 2008 10:07:48 PM
The Volt used the 1l 3 cylinder Geo engine with turbo at 70 hp. I guess they figured it was a good engine for a series hybrid.
Posted by: sjc | Apr 14, 2008 10:17:12 PM
The idea of the adaptable atkinson is very smart indeed. But still they propose nothing to reduce the throttle losses in this design. Also the problem in a super Atkison design is that the increase in friction tend to outweigth the gain in efficiency, unless you opt for a desin like http://www.mce-5.com/ where the friction can be greatly reduced and the throttle losses can be avoided too.
http://www.mce-5.com/
Posted by: Treehugger | Apr 14, 2008 11:25:10 PM
"But still they propose nothing to reduce the throttle losses in this design."
yes they did:
"It is hoped that future versions of the engine will include such technologies as spray-guided direct injection (because the degree of downsizing means that dethrottling is still attractive)"
Posted by: eric | Apr 15, 2008 1:53:46 AM
Basically, none of these measures is groundbreaking by itself or even in combination. Many European and Japanese car makers already have engines with similar features either in production or in development. What could make the Lotus-Continental solution interesting is if the cost is lower than anything the car makers can come up with by themselves. The supply chain would love to produce inexpensive, good quality, standardized small engines for multiple customers but brand managers are reluctant to outsource what has long been the most profitable single subsystem in their vehicles.
Really, the only bold step here is proposing a three-cylinder block as a replacement for an inline four in a mid-sized car. This permits a per-cylinder displacement of 500cc, i.e. limited cooling losses and internal friction, as well as a cheap single-scroll turbo. Water cooling an exhaust manifold integrated into the cylinder head means the turbo doesn't need a water jacket, though you'd want to minimize the coolant mass flow along that path in part load.
However, there's a catch to all this: since inline threes suffer from free inertial moments of both first and second order, a single balance shaft will only be able to compensated for the first. The shaft is generally mounted in the oil carter where it causes foaming unless there are special additives in the engine oil. The need for a balancing shaft also eliminates much of the cost advantage of lopping off a cylinder.
Normally, at low RPM, the second engine order free inertial moment cannot be damped out well by the engine mounts. In addition, the torque ripple on the crankshaft becomes more pronounced with each cylinder you remove. A two-mass flywheel can compensate for the first order ripple, but the second is transmitted to the wheels and causes longitudinal vibrations of the whole vehicle. Both effects tend to generate low droning sounds in the passenger compartment, especially in the vicinity of a natural frequency of the auto body. Of course, unbalanced inline fours also generate second-order vibrations but their direction is constant rather than rotating, so they're easier to deal with.
Turbocharging and gear ratios tuned for fuel economy means the engine spends more time at high torque and relatively low speed, e.g. around 1800 RPM = 30Hz. With three four-stroke pots, the first order is at 45Hz, the second at just 90Hz at that speed. The silver lining is that the human ear is less sensitive to low frequencies than to those of the spoken word (300-1000Hz).
In other words, customers have to trade off some comfort against higher fuel economy when choosing an inline three engine over an inline four. That, in a nutshell, is why car makers have long preferred inline fours for everything except the smallest cars.
Posted by: Rafael Seidl | Apr 15, 2008 6:13:56 AM
How is this any more efficient than the petrol Daihatsu YRV (130hp) from 2002?
http://www.carpages.co.uk/daihatsu/daihatsu_new_high_performance_yrv_turbo_part_1_07_05_03.asp
or
http://www.carkeys.co.uk/features/product/1575.asp
Posted by: fin | Apr 15, 2008 8:03:35 AM
I have thought a V4 configuration would be interesting. Ford made one for Saab may years ago, but it was not in production long. Honda had one on their motorcycles and it was very smooth and compact.
It you look at the Honda Civic hybrid and Camry hybrid, you will see the engine moved over to make room for the motor. A V4 would be compact enough to fit a motor easily.
Posted by: sjc | Apr 17, 2008 8:35:40 AM
It would seem that L&C are trying to re-invent the VW 1.4 TSI engine - minus one cylinder. VW uses, I believe, wall-guided direct injection. If that would be changed to spray guided injection, it should probably even exceed the envisioned specs for the 1.5l 3 cyl. The Mercedes 1.8l DiesOtto engine (introduced last year) appears to be the one to emulate and, according to some Mercedes data I found some months ago, they are using spray-guided di.
Posted by: hansb | Apr 17, 2008 3:11:20 PM
If Lotus and Continental can do this to an I-4 engine of maybe 1.3-1.4 liters in size, they'll have a winner right there! Imagine 150 bhp with only 1.4 liters of displacement, less vibration problems than an I-3 engine, and low fuel consumption, too.
The only downside is that the engine may need under 10 ppm sulfur compound gasoline, which is still expensive to refine, and a pretty expensive deNOx catalytic converter.
Posted by: Raymond | Apr 19, 2008 10:13:51 AM
Having read the paper I believe the idea behind this engine was to adopt stoichiometric direct injection fuelling and address the parasitic pumping loop through the application of a low-lift, early closing, camshaft profile - actuating only one intake-valve. The benefit of this being that recourse to stratified charge operation is negated as the throttling loss is addressed by Miller/Atkinson cycle operation and conventional three-way catalysis may still be retained thus removing the requirement of a de-NOx catalyst. This also means that the technology does not rely on sulphur free fuel. While it may not bring the ultimate thermodynamic and fuel consumption benefits of stratified charge operation it's a pretty good start; combining the positives of direct-injection fuelling and variable valve trains.
Posted by: Rish | Apr 28, 2008 2:22:18 PM
