New Hardware New Challenges GDI Engines and LSPI

New Hardware New Challenges GDI Engines and LSPI

Dec 3, 2015

Topics: Passenger Cars

Just five years from now, it’s estimated that a quarter of all cars on the road in North America and 39% of global production will utilize engine hardware that was mostly unfamiliar just a few years ago. Why? It’s all in pursuit of producing more power and torque from smaller engines, thus achieving greater fuel economy.

Greater fuel economy, along with greenhouse gas reduction, has been the biggest driver in the automotive industry in recent years due to increasingly strict demands at the regulatory levels. Automakers have been challenged to meet these goals with innovative new hardware technologies, and the industry is on the cusp of new realities. New hardware, including gasoline direct injection (GDI) engines, will require advanced lubricants to reach full potential. GDI engines, and the potential challenges that can arise with a major technology shift, must be fully understood. As automakers have increasingly moved to GDI, challenges have indeed arisen, and it’s taken the industry’s best experts to help overcome them.

More power, more pressure, at lower speeds

GDI engines offer higher power density in comparison to traditional port fuel injected (PFI) engines—this means GDI engines can be made smaller and can operate at higher loads and lower speeds in order to achieve maximum fuel efficiency. And GDI isn’t the only new technology making its mark on the industry: Automakers have further utilized turbocharger technology in order to recoup energy that would, absent a turbocharger, be lost with engine exhaust. GDI and turbochargers (together, TGDI) complement each other well, and automakers have taken advantage of the pairing.

In both GDI and TGDI engines, hotter temperatures and higher pressures are created. This environment, while great for fuel efficiency, is harsh and can lead to a phenomenon known as low speed pre-ignition (LSPI).

LSPI is a form of uncontrolled, abnormal combustion that left unchecked can potentially lead to engine failure. It is believed that LSPI is caused by droplets or particles in the combustion chamber—combinations of fuel and oil—that ignite prior to spark, resulting in uncontrolled combustion. This creates spikes in engine pressure, ultimately causing the damage.

Experts believe that the right additive technology can help mitigate this issue, and as such, a crucial new test is currently under development for inclusion within the proposed GF-6 specification.

The lubricant’s role and developing a reliable test

Critical to remember is that a given lubricant does not cause LSPI—a lubricant can, however, effectively reduce the likelihood that LSPI will occur.

So far, automakers have been successful in reducing the occurrence of LSPI by spraying additional fuel into the engine at those low RPMs—conditions where the engine both operates at its most efficient, and where LSPI is most likely to occur. Over fueling at this point in operation helps cool the engine, and reduces the risk of LSPI. But this over fueling is also counterproductive, decreasing the overall fuel efficiency of the engine.

Extensive testing, including in-depth analysis performed by Lubrizol Additives, has shown that differing additive technology can lessen the chances of LSPI occurring—highlighting the importance of additives that can help stop the phenomenon. Lubricants that can successfully help stop LSPI effectively increase the fuel efficiency of GDI engines by eliminating the need for over fueling. This has resulted in the need for a robust, reliable test within the proposed GF-6 specification that can evaluate a lubricant’s ability to help prevent LSPI, better enabling engine technology to reach fuel economy peaks.

Lubrizol understands the importance of this challenge. With its unmatched testing capabilities, Lubrizol has been an active participant in developing a reliable LSPI test for inclusion in the proposed GF-6 specification, and is concurrently working with multiple testing laboratories and OEMs to better understand LSPI.

Developing the LSPI test hasn’t been simple. By its nature, LSPI is a random occurrence, and as such, developing a test that consistently and reliably recreates the conditions under which LSPI is most likely to occur has been challenging. An engine must be operated long enough to provide a statistically significant number of LSPI occurrences, and because LSPI is a destructive phenomenon, the test engine and sensors must be robust enough to routinely survive extremely high, instantaneous cylinder pressures. It’s a challenge that needs a solution, and Lubrizol is working hard to offer meaningful contributions.

To a more fuel efficient future

Additive chemistry is critical to these formulations. In absence of a “magic bullet” fix to LSPI, Lubrizol’s work has shown that certain additive technology can help mitigate the phenomenon. But a balanced approach is required, from the base oil, to viscosity modifiers, and more—all can affect the likelihood of LSPI.

Working together, Lubrizol and its partners will continue efforts to develop solutions for the challenges of new, advanced engine hardware as the industry reaches toward higher and higher goals, from fuel economy and reduced emissions to robust and reliable protection, and beyond.

For more information, contact your Lubrizol representative.



Get Lubrizol360 updates in your inbox.

Sign Up Today