Gasoline direct injection (GDI) and turbocharged GDI (GDI-T) engines are expected to capture 60 to 65% of the North American new passenger car market by 2019. GDI and GDI-T engines are headed for dominance and for good reason: better fuel economy, better torque, and better power from the same size engine versus indirect port fuel injection (PFI) engines. A turbocharged GDI engine can also be downsized and deliver the same peak power along with significantly better fuel economy.
Compared to PFI engines GDI and GDI-T engines have several unique features:
- increased production of fine carbon particulates during combustion which can enter the crankcase via blow by and cause excessive wear
- increased fuel dilution of crankcase lube oil (cylinder wall wetting by side-mounted direct fuel injectors allows fuel to contaminate the lube oil)
- increased oxidation and deposits from higher operating temperatures and pressures
- higher initial cost than PFI engines for the higher-pressure fuel injection system
The one component that suffers the most from accelerated wear in GDI and GDI-T engines is the metal timing chain, which drives the camshaft(s) off of the crankshaft. Excessive wear can cause the check engine light to illuminate and could result in very expensive internal engine hardware repairs. Excess wear is evident in chain elongation which can disturb valve timing leading to degraded performance and higher engine out emissions. Researchers are not yet sure about the exact wear mechanism—it could be abrasive wear from carbon particles suspended in the lube oil or an interaction between carbon particles and the lubricant or both. A typical timing chain connecting the crankshaft and the overhead cams is shown below.
ILSAC has proposed a timing chain wear test for their new ILSAC GF-6 passenger car engine oil specification click here to view the draft specification proposed for first API licensing in the first quarter of 2018. Ford is developing the chain wear test in a 2.0 L I-4 EcoBoost GDI-T engine. The wear test procedure is proposed to assure that ILSAC GF-6 engine oils can meet the timing chain durability requirements in GDI and GDI-T engines.
The rest of the world is faced with the same challenge. The European Automobile Manufacturers Association (ACEA) is discussing the problem with counterparts in the oil and additive industry with a view of developing a suitable test in the future.
The timing chain is constantly facing unfavorable mixed and boundary layer lubrication regimes. Click video link below to learn more about boundary layer lubrication. Mixed and boundary layer lubrication regimes are not the ideal hydrodynamic lubrication regime where metal surfaces well separated by a protective oil film. GDI and GDI-T engine field experience shows in addition to timing chain wear more aggressive oxidation, viscosity gains, and related increases in varnish deposits. None of this is good, so improvements in lubricant performance is necessary to enable the successful introduction of this new engine technology.
Lubrizol is developing high performance advanced additives packages for high performance GDI and GDI-T engine technology which will soon dominate the passenger car market. Lubricant additives can minimize wear, combat oxidation and control deposits. New lubricant chemical additives require development involving years of test results before commercialization. Given long lead times for lubricant product development, testing, and commercialization there is a growing urgency to proceed with the ILSAC and ACEA programs if the requested commercializations dates are to be met.