13 February 2012

Proton CFE Engine - The Engineering Details

Note: Read first till the end before accusing a copy&paste from Lotus Mag.

Proton CFE engine has been introduced to the market at the very end of last year, under the hood of the facelifted Proton Exora MPV. The engine has been long rumoured, and has been long spied tested with the bigger-mouthed Exora for quite some times. Some called it Campro Turbo, while some referred it as Project Pheonix. Thanks to the publicity generated by the buzzy spyshots sites in Malaysia, the arrival of the CFE engine is very much eagerly awaited. 

The Brief.
CFE. It means Charged Fuel Efficiency. The engine was born out of the necessity rather than the desire to soup up the Campro engine to rival the Lamborghini. It was back in 2009, when the Exora MPV was at its final validation stage. It became clear that the Achilles heel of the much lauded Proton's first MPV would be its powertrain, where even the CPS mechanism won't be enough to mask the lack of torque, long plagued the Campro family, and the unsuitability of small capacity NA gasoline to power such as weighty people carrier.

After a series of feasible study, Proton has concluded that it would develop a turbocharged variant of the Campro engine instead of buying-in a 2.0L NA gasoline engine. In terms of the combustion concept, it was decided pretty much from the beginning to stay away from the Gasoline Direct Injection (GDI) - although that such a trend at that time and a commoner today - to accommodate the low octane rating and fuel quality of Proton's export market and its home market itself. This is essential as it could raise some durability concerns should some problem occurs later.

The baseline target was to achieve horsepower output and fuel efficiency of the modern 2.0L at that time. However, with the heavy weight application in mind, the torque delivery must be substantial even at low engine rev, something only a turbocharged engine can deliver.  

The Design.
As the CFE is Campro based, there was a necessity to carry over the cylinder block, or else, Proton might as well make an all-new engine if the cylinder block needs to be totally redesigned. Hence an intensive round of Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) were performed to assess the limit of the Campro's block without compromising its stress-endurance and jeopardizing its coolant effectiveness. 

The results of the FEA and CFD indicated that the cylinder block could be retained with the improvement to the water jacket to sustain the higher heat duty of the forced-fed engine. Another changes required was the modification to the oil gallery to include the piston cooling jet. The stroke of the crank also has been shortened to 86mm , a 2mm reduction. This is because the height of Campro's block did not provide sufficient space to increase the piston crown strength with the size limitation to withstand the compression ratio which it self is boosted by charged air from the turbo. More and more juicy details after the jump.

Perhaps, just maybe the necessity to retain the major engine components from the donor Campro was the driving factor of 'just' 138bhp and 205Nm instead of 156bhp and 240Nm of the Peugeot's engine. In its bid to make the business sense, the output has to be capped somewhat before it start needing an all-new engine design altogether.

The reduction in stroke, while retaining 76mm bore has reduced the swept capacity to 1,561cc from 1,597cc. Compression ratio was set at 8.9:1. To accommodate the higher cylinder pressure, a new piston design with 19mm floating piston pin. The turbo boost was kept between 0.6 to 0.8 bar.

For the cranktrain components, the cast iron crankshaft of the Campro has been replaced by the forged steel item. The connecting rods were beefed up too. However, based on engine loading analysis, such as bearing peak load and oil film analysis, it was decided that the crankshaft main bearing and connecting rod bearings dimensions were sufficient, but their grades were increased accordingly to sustain higher combustion pressure.

The cylinder head is an all-new item. It was redesigned to accommodate the intake cam phaser as well as to reduce the flow resistance for the coolant systems. This was achieved by adopting shallower head's jacket design, made possible by narrow thread-long reach spark plug. This in turns has enabled the modest increase in water pump flow rate.

The turbocharger unit in used is from Borg-Warner. It was selected due to its maximum low speed performance.

A host of innovation was adopted to reduce the engine internal friction. Among the changes were lower friction mechanical tappet in the place of direct-acting hydraulic tappet. Piston ring height were reduced to allow lower tangential load, piston skirt now incorporated low friction coating. A parasitic losses of 1.5kW was achieved by the addition of windage tray in the oil pan.

The Test.
Mere 7 months after the program kick-off, the first prototype of the CFE engine was already at Lotus UK's test bench. After some initial validation and design revision, the next stage of engine build was constructed at Proton's Shah R&D HQ, where a series of engineering program were run. Among them were the Torque Based EMS which allow the integration with the Punch Powertrain CVT gearbox. The calibration was also performed for the integration with Electronic Stability Control.

The CFE engine was calibrated and homologated not only for the local and Asian's hot climate but include the cold climate as well. Cold test was performed in Sweden ( perhaps under the hood of the 'Exora Penyet' we saw many times last two years). High temperature and high altitude conditions were simulated in Spain. So, rest assured, the CFE engine has been tested for many regime of temperature and altitude.

The Performance.
Proton CFE engine met its design brief to deliver the punch of a 2.0L NA engine by delivering a better full load performance and part load fuel efficiency of a 2.0L NA engine. While the engine delivers 138bhp at 5000rpm, the new powertrain kicks out 205Nm between 2000-4000rpm (which is the CVT engine rev limit). At 1500rpm, CFE engine already exceed the torque of a benchmarked 2.0L NA and produced more than the peak torque of the Campro CPS engine.

The Drive.
Proton CFE engine debuted in the Proton Exora BOLD. In this application, the CFE engine clearly delivered a superior kick compared to asthmatic CPS engine. It was quite an impressive drive in the Exora BOLD. Read MMN verdict HERE. The CFE engine also has been designated to power a range of Proton's product, starting from the forthcoming Proton P3-21A, the so-called Proton Global Car. In this application the CFE engine will be paired up with the Punch CVT again, albeit with a step up in features, i.e with 7 virtual speed and comes with the paddle shift. Roll on Proton 2012!

Source: Digested from proActive Winter 2011 Issue. Heavily condensed for masses!

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