Technical

Although based on the existing engine family, retaining many of the key features like bore size, block height, cam positions etc, the vast majority of the components were replaced or modified in some way.


Views of the Campro engine
One fundamental change was a reduction in stroke from 88 mm to 86 mm.  With the retained 76 mm bore, the swept volume reduced from 1,597 cc to 1,561 cc.  This was brought about by the very compact height of the existing iron cylinder block which did not provide enough space to increase the required piston strength or lower the piston crown to achieve the desired compression ratio

The compression ratio was set at 8.9:1, which although relatively low for a modern downsized engine, allows the same hardware to be used for all the target markets including those with 88 RON fuel and very hot climates without excessive retardation.

The cylinder block was based on the original Campro cast iron block. Extensive finite element analysis (FEA) showed no requirement to strengthen the casting to withstand the increased cylinder pressures. Small changes to the block were made to incorporate piston cooling jets into the oil gallery, and computational fluid dynamics (CFD) driven flow improvements into the water jacket to improve the engine cooling required for the performance increase.

A forged steel crankshaft replaced the original cast iron unit in the engine. FEA indicated that it would be possible to maintain the existing main bearing and rod bearing dimensions; however it was necessary to improve the bearing material to withstand the projected loadings.

A new piston design with a 19 mm floating piston pin to withstand the higher cylinder pressures was implemented. The cast piston incorporated an anodised top ring groove to prevent micro-welding damage with the expected high temperatures, and a scuff resistant coating applied to the piston skirts.

The changes to the piston and the increased gas pressure loading necessitated a change in connecting rod and connecting rod length. A new forged steel fracture cap design replaced the original powder metal design.

The aluminium 4 valve per cylinder DOHC Campro cylinder head was re-engineered to accept an intake cam phaser for the CFE application. This was achieved maintaining the existing cambelt location and now permits 40 crank degrees of intake cam phasing for improved performance, fuel economy and emissions.  An improved cambelt material was implemented along with an
auto-tensioner for improved serviceability.

During the cylinder head redesign, the spark plug was changed to a narrow thread, long reach design so that the spark plug boss would allow better cooling as well as a lower coolant back pressure in the cylinder head water jacket. In the same way as the cylinder block, the water jacket design actions were led by extensive up-front CFD analysis.  Through the reductions in coolant restriction developed through CFD, only a modest increase in water pump flow rate was required.

A new multiple layers steel (MLS) cylinder head gasket was developed to withstand the higher cylinder pressures.

To withstand the expected higher exhaust gas temperatures, sodium filled exhaust valves maintaining the original 5 mm stem diameter were selected.

An upgraded oil pump was also implemented to compensate for the higher demand of piston cooling jets, turbocharger bearing oil supply, and to maintain good oil pressure at low engine speed so that the intake variable valve timing (VVT) system could be operated. A water-cooled oil cooler is fitted as standard.

A Borg Warner turbocharger’s compressor and turbine were selected for maximum low speed performance. It uses a pressure regulated wastegate to control plenum pressure, and incorporated an electric integrated compressor bypass. Air from the compressor is ducted to an air to air charge-cooler mounted in the front left hand side bumper aperture.  An electrical pump which is actuated on key-off to provide coolant to the turbocharger bearing housing after engine shutdown.  This pump also circulates coolant around the rest of the coolant circuit to prevent boiling, an important feature in the high ambient temperature of Malaysia and Proton’s export markets