SEVILLE, Spain — Talk about timing: Mere days before this city was virtually shut down by truckers protesting a rise in diesel prices, Mercedes-Benz showcased an impressive array of green technologies here late last week. While the company's breakthrough DiesOtto concept (pictured above and at left) was the star of tech day, Benz will go a long way as a manufacturer of luxury cars—many of them heavy and extremely powerful—toward addressing environmental concerns and long-term global fuel-efficiency requirements with this latest suite of innovation. —Barry Winfield
More Efficient Packaging
First on the list is the BlueEfficiency package, which Mercedes will apply to the entire range of its models. A combination of reduced weight, smaller engine size (optimized for comparable power by the use of turbocharging), reduced rolling resistance and improved energy management results in substantial fuel savings and reduced emissions.
Smarter, Road-Ready Hybrids
Vehicles labeled BlueHybrid will reach the U.S. next year in the form of the ML450 SUV and S400 luxury sedan, the latter said to be the most fuel-efficient vehicle in its class. The ML450 will be capable of brief electric-only operation. Like other hybrids on the market, the hybrid technology employs a coaxial electric motor to assist the gasoline engine, and features the familiar stop/restart feature that will shut down the engine in traffic.
Non-Hybrid Stop 'n' Go Tech
In an unusual move, Mercedes has fitted the stop/start system on nonhybrid European models to further improve operating efficiencies. Gains of up to 9 percent are believed possible with this system. The technology requires fitting a larger electric starter motor to provide the necessary fast starts in city stop-and-go conditions.
Fuel-Sipping Diesel Hybrids
Bluetec Hybrid, as the name suggests, describes diesel-hybrid powertrains like that featured in the company’s Vision GLK Bluetec Hybrid concept vehicle. The diesel/electric drive assembly has a combined power output of 224 hp and a combined torque of 413 lb.-ft., yet provides fuel consumption figures around 40 mpg.
DiesOtto Concept
Like every manufacturer, Mercedes-Benz is working on experimental electric and fuel-cell vehicles, too. But the big deal, as far as advanced internal combustion goes, is the DiesOtto sparkless gasoline concept. The idea, as project engineer Günter Karl cheerfully admits, is based on an auto-ignition two-stroke engine produced by Honda over 10 years ago. But DiesOtto has been refined for conventional four-stroke operation.
The principle behind sparkless ignition is that gasoline/air mixtures will spontaneously combust—like diesel— at the right temperature and pressure. We’re not talking preignition (or detonation, as it is also known) here. That’s an instantaneous explosion of the mixture and is very damaging to engine parts. Most people are familiar with that syndrome, having heard engines “ping” under load or run on after being shut off.
The beauty of controlled auto ignition is its lower burn temperature, which results in lower NOx emissions. Nitrogen oxides help produce photochemical smog when in the presence of atmospheric hydrocarbons, so it’s important to reduce them as much as possible.
The auto-ignition process also produces uniform burning within a perfectly homogeneous fuel-and-air mixture, resulting in fairly complete combustion. And, helpfully, it burns comparatively lean mixtures. Karl says the DiesOtto engine in the F700 design-study vehicle operates at a 23:1 air-to-fuel mixture, compared to the 14.7:1 stoichiometric ratio used in conventional fuel-injected, catalyst-controlled, spark-ignition gas engines.
Sounds great, but making an engine run sparklessly is no mean feat. It requires a warm fuel charge, achieved here—as in the pioneering Honda motorcycle engine—by recirculating specific amounts of hot exhaust gas. To reduce the dependence purely on EGR, Mercedes opted to increase the compression ratio on demand, and has come up with a variable-crankshaft-position mechanism to dynamically alter the relationship of the piston to the cylinder head. That task is as technically challenging as it sounds, and Mercedes is not yet revealing exactly how it’s done on the DiesOtto engine.
The other thing to remember about DiesOtto is that an engine can only run in this mode part of the time. Constant speeds at a moderate load is apparently what it likes best. The rest of the time it runs as a conventional spark-ignition engine. Only when the conditions become favorable for auto-ignition does the high-tension ignition system switch out.
The basis of the DiesOtto concept is a four-cylinder, 1.8-liter engine with some important modifications. Two-phase turbocharging is used to energize this comparatively small engine to power levels comparable, according to Karl, to a 3.5-liter V-6. He quotes 258 hp and 295 lb.-ft. of torque, with a Euro fuel cycle of 44 mpg. Adding 20 hp to the driveline is a small electric hybrid module that also acts as a high-speed starter for that obligatory stop/restart function. We were driven around in the concept car, and it does indeed feel sprightly.
The DiesOtto engine is fed by a common-rail direct-injection system pressurized to 29,000 psi. There are two injection processes; a pre-injection cycle and the main injection event. This enables complete mixture preparation for optimal homogeneity. When running normally in spark-ignition mode, the DiesOtto’s throttles work normally. Once in auto-ignition mode, the throttles go wide open, mimicking a regular diesel engine, which is unthrottled.
Other unusual aspects of the DiesOtto engine include a selectable water pump and an adjustable oil pump. There are four separate control modules handling the various functions right now, and these need to be integrated before mass production is possible.
Also showcased on the F700 experimental car is a laser surface-scanning system—known as the active Pre-Scan suspension—that checks for bumps and irregularities in the road ahead, and instructs a hydraulic spring preload mechanism to stiffen the spring at exactly the right time to absorb the bump. Like the rest of the DiesOtto concept, this device seems hugely complex and futuristic, but if the demonstration we had was anything to go by, all of this technology will make it onto the public roads sometime fairly soon.
As Mercedes-Benz’s vice president of vehicle and powertrain group research, Herbert Kohler, pointed out, there isn’t just one technology to answer the challenges of sustainable mobility. It will require a multidisciplinary approach, with various types of vehicles and propulsion systems to keep us moving as the pressing needs of diminishing fuel supplies and environmental health increase.
More Efficient Packaging
First on the list is the BlueEfficiency package, which Mercedes will apply to the entire range of its models. A combination of reduced weight, smaller engine size (optimized for comparable power by the use of turbocharging), reduced rolling resistance and improved energy management results in substantial fuel savings and reduced emissions.
Smarter, Road-Ready Hybrids
Vehicles labeled BlueHybrid will reach the U.S. next year in the form of the ML450 SUV and S400 luxury sedan, the latter said to be the most fuel-efficient vehicle in its class. The ML450 will be capable of brief electric-only operation. Like other hybrids on the market, the hybrid technology employs a coaxial electric motor to assist the gasoline engine, and features the familiar stop/restart feature that will shut down the engine in traffic.
Non-Hybrid Stop 'n' Go Tech
In an unusual move, Mercedes has fitted the stop/start system on nonhybrid European models to further improve operating efficiencies. Gains of up to 9 percent are believed possible with this system. The technology requires fitting a larger electric starter motor to provide the necessary fast starts in city stop-and-go conditions.
Fuel-Sipping Diesel Hybrids
Bluetec Hybrid, as the name suggests, describes diesel-hybrid powertrains like that featured in the company’s Vision GLK Bluetec Hybrid concept vehicle. The diesel/electric drive assembly has a combined power output of 224 hp and a combined torque of 413 lb.-ft., yet provides fuel consumption figures around 40 mpg.
DiesOtto Concept
Like every manufacturer, Mercedes-Benz is working on experimental electric and fuel-cell vehicles, too. But the big deal, as far as advanced internal combustion goes, is the DiesOtto sparkless gasoline concept. The idea, as project engineer Günter Karl cheerfully admits, is based on an auto-ignition two-stroke engine produced by Honda over 10 years ago. But DiesOtto has been refined for conventional four-stroke operation.
The principle behind sparkless ignition is that gasoline/air mixtures will spontaneously combust—like diesel— at the right temperature and pressure. We’re not talking preignition (or detonation, as it is also known) here. That’s an instantaneous explosion of the mixture and is very damaging to engine parts. Most people are familiar with that syndrome, having heard engines “ping” under load or run on after being shut off.
The beauty of controlled auto ignition is its lower burn temperature, which results in lower NOx emissions. Nitrogen oxides help produce photochemical smog when in the presence of atmospheric hydrocarbons, so it’s important to reduce them as much as possible.
The auto-ignition process also produces uniform burning within a perfectly homogeneous fuel-and-air mixture, resulting in fairly complete combustion. And, helpfully, it burns comparatively lean mixtures. Karl says the DiesOtto engine in the F700 design-study vehicle operates at a 23:1 air-to-fuel mixture, compared to the 14.7:1 stoichiometric ratio used in conventional fuel-injected, catalyst-controlled, spark-ignition gas engines.
Sounds great, but making an engine run sparklessly is no mean feat. It requires a warm fuel charge, achieved here—as in the pioneering Honda motorcycle engine—by recirculating specific amounts of hot exhaust gas. To reduce the dependence purely on EGR, Mercedes opted to increase the compression ratio on demand, and has come up with a variable-crankshaft-position mechanism to dynamically alter the relationship of the piston to the cylinder head. That task is as technically challenging as it sounds, and Mercedes is not yet revealing exactly how it’s done on the DiesOtto engine.
The other thing to remember about DiesOtto is that an engine can only run in this mode part of the time. Constant speeds at a moderate load is apparently what it likes best. The rest of the time it runs as a conventional spark-ignition engine. Only when the conditions become favorable for auto-ignition does the high-tension ignition system switch out.
The basis of the DiesOtto concept is a four-cylinder, 1.8-liter engine with some important modifications. Two-phase turbocharging is used to energize this comparatively small engine to power levels comparable, according to Karl, to a 3.5-liter V-6. He quotes 258 hp and 295 lb.-ft. of torque, with a Euro fuel cycle of 44 mpg. Adding 20 hp to the driveline is a small electric hybrid module that also acts as a high-speed starter for that obligatory stop/restart function. We were driven around in the concept car, and it does indeed feel sprightly.
The DiesOtto engine is fed by a common-rail direct-injection system pressurized to 29,000 psi. There are two injection processes; a pre-injection cycle and the main injection event. This enables complete mixture preparation for optimal homogeneity. When running normally in spark-ignition mode, the DiesOtto’s throttles work normally. Once in auto-ignition mode, the throttles go wide open, mimicking a regular diesel engine, which is unthrottled.
Other unusual aspects of the DiesOtto engine include a selectable water pump and an adjustable oil pump. There are four separate control modules handling the various functions right now, and these need to be integrated before mass production is possible.
Also showcased on the F700 experimental car is a laser surface-scanning system—known as the active Pre-Scan suspension—that checks for bumps and irregularities in the road ahead, and instructs a hydraulic spring preload mechanism to stiffen the spring at exactly the right time to absorb the bump. Like the rest of the DiesOtto concept, this device seems hugely complex and futuristic, but if the demonstration we had was anything to go by, all of this technology will make it onto the public roads sometime fairly soon.
As Mercedes-Benz’s vice president of vehicle and powertrain group research, Herbert Kohler, pointed out, there isn’t just one technology to answer the challenges of sustainable mobility. It will require a multidisciplinary approach, with various types of vehicles and propulsion systems to keep us moving as the pressing needs of diminishing fuel supplies and environmental health increase.
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