Tech analysis of GM's new 1.4L four cylinder engine

In recent months we had been hearing that GM's new compact car to replace the Cobalt - which we now know as the Cruze - would get a new 1.4L turbo four cylinder engine. The assumption was that the engine would get direct fuel injection like the 2.0L turbo used in the Pontiac Solstice GXP, Cobalt SS and others.

Unfortunately we found out that GM has opted to stay with the less expensive sequential port fuel injection system for now. Chris Meagher, Chief Engineer for GM's Family 2 engines explained that the engineers met the fuel economy targets for the engine without using DI.

Meagher however didn't rule out the addition of DI in future years as fuel efficiency requirements get tighter and the cost comes down. In fact, as GM moves toward implementing HCCI engines down the road, more engines will get central direct injection as an enabling technology.



The 1.4L engine will initially be available in two flavors here in North America. As we learned back in July from Larry Nitz, a normally aspirated version will be used as the range extender for Volt. That variant will have an output of about 100 hp. The Cruze gets the turbo for an estimated 140 hp and 148 lb-ft of torque.

The turbocharger has been integrated with the exhaust manifold keeping the exhaust gas flow distance to the turbine short. This will help provide quick boost pressure build in response to driver demand. The combination will result in the feel of a larger displacement engine when needed while providing the light load efficiency of the small displacement base engine. The integrated installation also provides for more compact packaging, an important element in a small car.

The port injection system has been designed to accommodate ethanol capability and the normally aspirated edition for the Volt will have flex-fuel capability. Meagher wasn't able to tell us whether the turbo engine for the Cruze would be flex-fuel capable at launch in spring 2010.

The base engine consists of a cast iron cylinder block and an aluminum cylinder head. The engineers have designed the block with a hollow frame to keep the weight down while maintaining strength. Meagher couldn't give an estimate of the weight difference compared to an aluminum block because the Family 0 engines have never been done with an aluminum block architecture. The head contains dual camshafts both of which are hollow for reduced weight. The cams are driven by a chain to ensure long life and durability. Each of the cam shafts also has an independent variable phasing mechanism.

In addition to these macro-level design decisions, the GM powertrain engineers have put significant effort into the detail design elements needed to optimize efficiency and reduce parasitic losses. For example, GM has added a flow control oil pump. The pump has a variable displacement that's mechanically controlled based on the flow demand of the engine. A high pressure accumulator in the pump provides the oil to the engine and as the accumulator is depleted the pump displacement is increased. The result is that the mechanical draw on the engine is reduced under light load conditions.

The engine also has an electronically-controlled thermostat to regulate the temperature of the coolant. This can help warm up the engine faster and keep it at the optimum temperature for different load conditions. The 1.4L engines also get roller cam followers to help reduce frictional losses.

At this point GM won't provide any hard fuel efficiency numbers. However, last week at the reveal of the Cruze, Chevrolet General Manager Ed Peper implied that the Cruze should get in the vicinity of 40 mpg with the 1.4L turbo and the new 6-speed automatic that is coming up. GM will start construction of the new factory in the next few weeks with production due to start in early 2010. The Cruze starts production in Lordstown, OH in April of 2010. The factory will have a capacity of 800 engines a day or about 200,000 units a year.

Four cylinder engines will account for about 21 percent of GM's North American sales volume this year and the company expects that number to climb to one-third of all sales in just three years. This new engine will be a big part of making that happen. The turbo four will go into at least two other applications in 2010 with at least one of those likely to be the next-generation Astra which shares the Delta compact platform with the Cruze and Volt.