How Subaru’s New Ignition Technology Could Keep The Combustion Engine Alive

With the automotive landscape shifting toward clean energy and less waste, combustion engines are edging closer and closer to the chopping block. Hybrids and EVs offer more benefits with regard to reduced emissions, reduced fuel costs, and less demanding internal power operations. Simply put, clean energy is becoming a larger part of society, it’s revolutionizing more industries besides the automotive world, and it will ultimately force manufacturers to explore advanced methods of modern energy.

Subaru, a well-known, well-respected brand, has a rich history in manufacturing and strives to remain on the pulse of modern engineering. This sentiment is observed in their current and past models, with their engineering often preceding their automotive exploits. Because of this skill and passion, Subaru is experienced in such engineering advancements, and they’re not one to let a good idea go to waste.

This brings us to their current eyebrow-raising venture, an innovative patent filled by the brand that details an ingenious take on the already unique pre-combustion system. This patent, filled with the United States Patent and Trademark Office, explains a more efficient pre-combustion system that could achieve a great many things in the current automotive landscape, including reducing emissions, reducing waste, and most importantly, making the combustion engine viable in today’s environmentally conscious market.

In order to give you the most up-to-date and accurate information possible, the data used to compile this article was sourced from various manufacturer websites and other authoritative sources, including Subaru and the U.S. Patent and Trademark Office.

Pre-Combustion Is A Step In The Right Direction, But Subaru Takes A Leap

To start, the pre-combustion system isn’t a new technology, as Porsche is currently exploring such systems to maximize power. Subaru, however, doesn’t set their sights on power, per se, but efficiency. And more importantly, cleaner energy, though the patent does leave open the possibility of performance boosts. For the sake of explaining this detailed document, we’ll discuss Subaru’s intended use of this particular setup.

The patent first shines light on the rather primitive and inefficient cold-start process of combustion engines, called stratified charge combustion control, wherein the ignition cycle is lagged to allow the catalytic converter to reach a desired temperature before assuming a regular stroke compression cycle. To lower the Nitrous Oxide (NOx) in the exhaust, this process uses more fuel, which is often wasted during the retarding period and can adhere to the walls of the combustion chamber.

This build-up can increase fuel density and lead to the combustion process of said engine releasing more harmful hydrocarbons. Subaru sees this innovative step to pre-combustion as a way to combat both the fuel waste and increased emissions of the traditional cold-start process.

The Pre-Combustion System Utilized Both A Fuel Injector And An Air Injector

The patent begins by listing various engine components and processes that make up the example given. These include traditional engine components like a spark plug, a piston, and the combustion chamber. But the patent soon describes a sub-chamber inside the main combustion chamber and an integrated air injector.

As mentioned before, pre-combustion isn’t a new technology, but it is rather unused in mainstream models. Thus, its use may be largely unknown to the public. Think of the pre-combustion chamber as a small reservoir space around the spark plug at the top of the valve.

In the example given, the pre-combustion chamber is a hemispherical enclosure that surrounds the spark plug, forming a separate chamber within the valve where pre-combustion can take place. In a traditional combustion engine, the air-fuel mixture achieved by the fuel injectors and air intake valves is ignited in the main combustion chamber via a spark plug.

A pre-combustion system employs a smaller ignition in a separate chamber that expels flames which ignites the fuel in the main combustion chamber. This alternate ignition system can optimize the overall quality of burn, making for a thorough engine stroke cycle with minimized waste, especially during a cold-start process where more fuel is burned off at a slower rate.

The pre-combustion chamber detailed in Subaru’s patent describes the hemispherical chamber as having a center/main opening and two smaller through holes on either side of it. The placement of the opening and through holes is to direct the air coming from the pre-combustion chamber’s designated high-pressure air valve, as well as direct the spark that ignites the fuel.

The air pressure valve supplying air to the pre-combustion chamber acts as a shield when activated, encasing the pre-combustion chamber with a layer of air that discourages the fuel mixture from sticking to the exterior of the chamber, while also facilitating a fuel/air mixture that can be ignited more efficiently within the pre-combustion chamber.

How The Air-Injected Process Works

Now that we’ve established the basic actions taken during the patent’s unique pre-combustion cycle, we can elaborate on the process and explanation. The patent details the engine’s powerstroke, whose compression activates the air injector first, then the fuel injector, starting a sort of “swirl” effect within the combustion chamber, with both injection timing overlapping. This process essentially utilized a stratified air injection to manipulate the fuel-air mix’s quality and flow in the combustion chamber, making the process of internal combustion more versatile.

The air expelled from the pre-combustion chamber, as mentioned before, encases the pre-combustion chamber’s exterior with a protective layer and lasts briefly longer than the fuel injection period, discouraging any build-up that may form during the compression period. This air layer also interacts with the surrounding fuel to maintain a lean fuel mixture in and around the pre-combustion chamber that will eventually be ignited.

The additional air used to encase the pre-combustion chamber will ultimately make it harder to achieve a strong ignition, considering the fuel mixture is very lean at this point. The patent counteracts this problem with a smaller injection of fuel just after the piston reaches top dead center and before the stratified air injection ends. This extra bump of fuel allows the pre-combustion chamber’s mix to ignite more reliably and thoroughly.

Key Benefits Of Air-Injected Pre-Combustion Engine

• Less harmful hydrocarbon emissions
• Reduced build-up on engine components
• Increased engine performance opportunities
• Reduced fuel usage during the cold-start process

This entire process takes place in an instant and, thanks to memory programs and various types of data inputs, can be tuned to achieve various levels of performance, though Subaru is focusing on decreasing harmful emissions; at least for now. It’s important to note that the patent focuses on making the cold-start process more efficient and cleaner, so the air-injected pre-combustion system we’ve discussed deactivates and reverts to a standard pre-combustion cycle once the cold-start process concludes.

Could Pre-Combustion Ignition Save Combustion Engines?

The main problem with combustion in today’s world is the harmful pollutants produced by the incalculable number of vehicles in use. While this has sparked a renaissance in the world of electric power, “clean combustion” may not be a thing of fiction. This system won’t put combustion engines at the level of efficiency as a hybrid or EV, but it will make the argument to experiment with dated machinery more viable, which could lead to some ground-breaking innovations.

For instance, the patent clearly wants readers to know that, though a vehicle burning fossil fuel was used as an example, this technology is by no means a gas-powered car-only application. This could mean cleaner burning combustion machines industry-wide, including airplanes, trains, and combustion units that run on alternate fuel. At this point, it’s hard to conclude the future of the combustion engine, as most vehicles on the road today employ one. Though hybrids and EVs are becoming cheaper, more accessible, and more trendy.

Possible Uses Of The Air-Injected Pre-Combustion System

Of course, performance comes to mind when discussing innovative engineering and futuristic automotive ideas, especially pre-combustion, as Maserati already puts it to use in the sports car field. In this case, cleaner-burning combustion can benefit just about every facet of the automotive industry. From trade to transportation -from passenger cars to performance cars, a cleaner future is on the cards for everyone. Subaru, in particular, could benefit from cleaner combustion in both the passenger car and the performance vehicle arena.

Supercars and big-engine vehicles could also greatly benefit from this system, as their combustion units consume more fuel than the average vehicle. We’ve already established that the patent states this technology could be used with alternate fuel sources. This opens up the possibility of motorsport applications, as many race cars run on special fuel mixes and grades. To put it plainly, there is no limit to the situations in which a cleaner-burning engine wouldn’t benefit the automotive world. The question is: Who’s going to put the time, effort, and capital toward changing the status quo?

Could We See This Technology Put To Use?

While this system is untested, pre-combustion is tested and is currently employed to advance the combustion engine’s capability and efficiency. Knowing that as well as taking into account the current industry-wide push toward clean energy, it’s not far off to speculate that, at the very least, Subaru will experiment with this technology further, as it could possibly prolong the existence of their combustion efforts one day. At this point, however, it is unknown what will come of this patent. Sometimes, manufacturers file patents to protect related technologies they employ or simply to protect an idea that may apply to them one day.