Soot isn’t just for diesels anymore

Today’s gas engines can produce as much soot as yesterday’s diesels.

Matt Erickson | TECHNICAL MANAGER – PCLT PRODUCTS AND MECHANICAL R&D

I bet most of you reading this have some level of emotional attachment to traditional vehicles. The muscle-car era of the 1960s and 1970s kindled a lifelong passion for cars in millions of Americans and Canadians. And how many of you who grew up in the 1980s had a supercar poster or two on your bedroom wall? Today, based on sales, big pickup trucks seem to be everyone’s favorite vehicle.

With fuel-economy regulations slowly reshaping the industry, it’ll take more than nostalgia to maintain the viability of the internal combustion engine. They must continue to become even more efficient and clean-running.

That’s one reason for the proliferation of turbocharged gasoline-direct-injection (T-GDI) engines over the past several years. Directly injecting fuel into the combustion chamber as opposed to an intake port upstream of the cylinder, as with a port-fuel-injected engine, offers more precise control over fuel delivery. This arrangement increases fuel economy and reduces CO2. T-GDI engines are also smaller and lighter than traditional engines that make similar power, helping automakers reduce weight and boost efficiency.

It’d be great if the story ended there. We’d all drive into the sunset in our pickups that deliver the perfect combination of comfort, functionality and efficiency. But somewhere along the way engineers noticed a strange phenomenon: Some T-GDI engines were experiencing abnormally high rates of timing chain wear, and many think soot is at least partially to blame.

You’re probably thinking, “But diesels produce soot, not gasoline engines.” Wrong – at least with T-GDI engines. When engineers borrowed the practice of directly injecting fuel into the combustion chambers of diesel engines and applied it to their gasoline counterparts, soot production tagged along. In fact, on some light-colored T-GDI vehicles, you can see a ring of soot on the bumper near the exhaust.

Soot, which is made of carbon, is the result of incomplete combustion. In a port-fuel-injection engine, gas and air mix in the intake port prior to entering the combustion chamber. This arrangement allows ample time for the gas and air to mix more completely, which results in more complete combustion. In direct-injection engines, the gas doesn’t have as much time to mix with the air since it’s injected directly into the combustion chamber. Plus, it’s injected later during the operating cycle, further reducing its ability to completely mix with the air. As a result, direct-injection engines can result in less-complete combustion – and increased soot. Believe it or not, some modern T-GDI engines produce more soot than older diesels not equipped with particulate filters. That’s one reason gasoline particulate filters are in development now and could soon end up on your next T-GDI vehicle.

All that soot is bad news for the timing chain. The particles can agglomerate into larger particles that wear out timing-system components and other sensitive engine parts prior to lodging in the oil filter. If bad enough, the chain can elongate and jump the teeth on the sprocket, throwing off timing enough to kill the engine. The chain could also break, which can result in catastrophic and expensive damage if, for example, a piston strikes and breaks a valve.

Fuel dilution may also be to blame for timing chain wear since excess fuel in the oil causes the oil to lose viscosity, which reduces wear protection. Though experts are still studying the problem, they have soot in their sights and are working hard to develop a test that measures an oil’s ability to protect against soot-related wear. The current test under development uses a Ford* 2.0L Ecoboost* engine to evaluate timing chain protection. The final details of the test are still being ironed out, but it’s well on its way and slated for inclusion in the forthcoming GF-6 motor oil specification, set for introduction in 2019.

We’ve already run the test, and I’m happy to say that Signature Series Synthetic Motor Oil performed extremely well. Oil formulation, specifically additive systems, plays a huge role in how the oil handles soot. The oil needs the correct dispersant and detergent additives in the correct concentrations to hold soot particles in suspension and prevent them from agglomerating into larger, wear-causing particles. Our oils are formulated with potent additives that keep soot in suspension to protect your engine.

Good filtration is just as important in today’s engines. Our Ea® Oil Filters’ synthetic media offers improved efficiency and capacity, helping ensure agglomerated soot is safely trapped in the filter and doesn’t ruin your engine.

As engines grow more complicated, so do the challenges they present. That’s why we remain diligent about identifying problems to engine life and developing solutions. That way we can all drive off into the sunset in the vehicles we love without worrying about wear.