Honeywell has introduced a parallel sequential dual-stage turbo system for diesel engines. The system makes its debut on the 4-cylinder engines of PSA group’s Peugeot 407 and 607, and the Citroen C5 and C6—the first such application on a four-cylinder diesel.
Unlike a serial sequential turbocharging configuration, where a smaller high-pressure turbo works in advance of a much larger turbo, the new parallel sequential system uses two small turbos working side by side at higher engine speeds of more than 2,700 rpm, but only one at lower rpm.
A specially-designed and patented progressive control valve accelerates the second turbo even when it is idling during the first engine phase. This transient phase, during which the second turbocharger starts spinning but is not yet hooked up to the air intake, ensures a smooth start-up.
Pressurized air from the first turbo is used to avoid any likelihood of oil leakage. The system also includes a position feedback sensor which is controlled by the Engine Control Unit.
This new two-stage turbo system delivers up to 30% more torque over PSA’s 2.2-liter baseline diesel engine and improves third gear acceleration in the 30 kph - 60 kph range by up to 50%.
The 2.2-liter Peugeot HDi diesel engine now delivers full torque of 330 Nm (243 lb-ft) at 1,300 rpm and 370 Nm (273 lb-ft) at 1,500 rpm, unprecedented in an engine of this size at such low rpm.
The development of the new dual-stage turbo system with PSA began in 2003.
Honeywell is also developing serial sequential dual-stage turbo system expected to be introduced around 2007, and is thus able to provide both parallel sequential and serial sequential solutions.