OMG controls emissions

According to OMG, its HPT-X5 emissions-control-catalyst technology reduces precious metal requirements by approximately 20% and raises efficiency by up to 50% compared to other state-of-the-art catalysts. The emissions-control catalysts contain two separate washcoat layers that are tailored to the catalytic function of the specific precious metals, in this case, platinum and rhodium. The first, lower layer is optimized with respect to the oxidation of hydrocarbons (HC) and carbon monoxide (CO). The top, second layer takes on the task of NOx reduction, but also contributes towards the conversion of HC and CO, particularly in the cold-start phase.

Conventional three-way catalysts are less efficient during acceleration and deceleration testing, causing either too little or too much oxygen in the exhaust mix. HPT-X5 enables the rapid adsorption of excess oxygen under oxidizing exhaust-gas conditions. Accompanied by the simultaneous oxidation of CO and HC (and reversible release of oxygen under decreasing exhaust-gas conditions), HPT-X5 enables catalysts to operate close to their optimum in extreme driving situations.

The HPT-X5 catalysts have proven during lab tests to have a high temperature resistance. This feature allows them to be installed close to the engine and contributes to obtaining a quicker light-off temperature. The high temperature resistance also improves the aging characteristics of the catalyst through the use of high-temperature-resistant carrier oxides coupled with a reduction of the sintering behavior of precious metals on the catalyst surface.

The migration of the precious metals is significantly reduced by optimizing the carrier oxide/precious metal interaction, controlling the size and dispersion of the precious metal particles through the manufacturing process, and by modifying the carrier oxide surfaces and the related adhesion of the precious metals to the surface. Doping the carrier oxide with foreign atoms improves the lean stability of the catalyst at high temperatures, particularly in the case of rhodium.

- Jean L. Broge

Test chambers from Cincinnati Sub-Zero

Cincinnati Sub-Zero is releasing its Z-Plus test chamber at the SAE 2002 World Congress. It is shown with the hinged control section in the up position.

The SAE 2002 World Congress occurring next month in Detroit's Cobo Center is the venue that Cincinnati Sub-Zero has chosen to unveil its new Z-Plus test chamber. The new line of chambers was designed to test products under various temperature and humidity conditions, as well as for extended performance and faster ramp rates.

The construction of the chamber allows customers to incorporate both left- and right-sided ports/slots and offers the ability for the chamber to be positioned against a wall. A hinged control platform with either a standard or touch screen chamber controller is available. Access is provided to all systems through easily removable side panels.

Standard sizes range from 0.22 to 0.91 m³ (8 to 32 ft³) of workspace volume with a temperature range of -73 to +190°C (-99 to +374°F) and a humidity range of 10-98% RH. Standard features include a one-handed latch, high-volume airflow, quiet operation, leveling legs, shelf, viewing window, interior chamber light, a 76-mm (3-in) port, and top vented exhaust. Options include a stainless-steel exterior, a reversible door, LN2 boost, and dry-air purge. The chambers meet CSA 1010.1-92 and UL 3101-1 requirements and are available with CE approval.

- Jean L. Broge

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Toyota throttle-by-wire system

In Toyota's throttle-by-wire system, dual accelerator position sensors, each calibrated with a different scale, send data to the engine control module (ECM), which compares the signals to check for errors. Click to enlarge

Toyota developed an all-electric throttle-by-wire system for its Lexus LS430 luxury flagship that it has also deployed in its near-luxury ES300 and mainstream Camry family sedan. The benefits of eliminating the throttle cable include improved NVH because there is no cable penetrating the firewall. The system also allows for simplified traction-, stability-, and cruise-control systems.

"Consumers don't always do (what's) best with the throttle," said Paul Williamsen, Curriculum Development Manager at Toyota Motor Sales, U.S.A. Toyota's throttle-by-wire system analyzes the driver's actions and interprets intentions to produce better driveability and stability, while reducing emissions, especially when the engine is cold.

"We gain better overall control," Williamsen added.

It also simplifies "shift-shock" control by letting the computer ease off the throttle for smooth automatic upshifts.

An obstacle to fielding throttle-by-wire has been the need for a backup system. Earlier Toyota systems used a conventional cable as the backup, but under normal conditions throttle position was handled electronically. Several years of experience with that system on the Toyota Supra, V8-equipped Tundra, Land Cruiser, and LX430 models emboldened Toyota to eliminate the cable. "After a number of years of offering this, we've got the data on what the failure rate is," said Williamsen. "It is pretty low."

In the event of an error in the signal from one of the position sensors, the ECM can switch off the throttle-control servomotor and modulate power through the fuel-injection and ignition systems. The ECM also considers input from the traction-, stability-, and anti-theft-control systems when directing the throttle, ignition, and fuel-injection systems. Click to enlarge

That doesn't mean that a backup system isn't needed, but it did show that a physical cable wouldn't be required. The new system uses a pair of accelerator position sensors, each with a different scale, so that the signals from the two can be compared for their differences and checked for accuracy, not just for a loss of signal from one sensor.

A servomotor moves the throttle to the desired position, and redundant throttle position sensors report the results. If one of the pedal position sensors fails, the car can still be driven, and the check engine warning light is illuminated. If both sensors fail, engine control is lost, and the engine will only idle.

Toyota has designed an interesting failure mode that lets the car be driven to safety if the throttle position sensors fail. The throttle assembly has two return springs, one of which holds the throttle open slightly in the absence of control by the servo. "You get a gap of about 0.5 mm (0.02 in) on each side of the butterfly," said Williamsen. That doesn't sound like much, but the area is actually reasonably large, so the engine can produce about one-quarter its maximum power.

Having a run-away engine is no better than having an idle engine, but the engine-management computer can control engine output through other means. By altering the fuel-injection duration and the ignition timing in response to input on the gas pedal, the car responds to the driver's demand for power.

"It gives an amazing impression of throttle response, even as the throttle doesn't move," Williamsen said. "At speeds below 48 km/h (30 mph), you might not even notice it much."

This failure mode is adequate for getting home from across town, but isn't well suited to highway driving, and should be used only to get off a highway at the earliest opportunity. "In town it will limp home pretty effectively, but it would have a hard time maintaining highway speeds," he said.

- Dan Carney