Is a secondary air injection system necessary for your car?

Does your car really need a secondary air injection system? Check out images of car engines. Stephen Chiang/Workbook Stock/Getty Images

Why do so many people assume their cars have features they might not actually need? Maybe it's the influence of the Internet and forums filled with armchair experts, who seem to think tuners know more than automakers or environmental scientists. The secondary air injection system, part of the exhaust system, is often a target for DIY tuners and amateur racers, as there's some confusion about what it really does.

Despite what automotive marketers may claim,

engines can never achieve perfect efficiency. There's always a portion of unburned fuel (hydrocarbons) that doesn't convert into engine power during combustion (which happens in the induction chamber, essentially the "primary" air injection system, though it's rarely called that). These hydrocarbons are then released with the exhaust gases. This is due to unavoidable mechanical flaws in mass-produced engine parts, variations in fuel quality, environmental conditions, driving conditions, and the car's overall state. Since hydrocarbons contribute to engine power and are also a key factor in emissions, it's crucial to burn them as efficiently as possible. Until someone figures out how to collect those tiny, almost negligible hydrocarbon particles from the exhaust and recycle them back into the engine for another go at fueling power, they simply go to waste — and as they do, they pollute more. The fact is, burned fuel causes less environmental harm than unburned fuel, even if burning it doesn't generate any power at all.

The secondary air injection system is designed to clean up the excess fuel that wasn't burned. Fuel requires pressurized air for combustion, but once it's leaving the engine, it's mostly surrounded by gases. The air injection pump pushes air into the exhaust system right after the manifold, aiding in burning any remaining unburned fuel. This system plays a crucial role in meeting government emissions standards, and thus, the law mandates the presence of a secondary air injection system.

This raises the question: Is a secondary air injection system necessary for a car to operate?

Technically, no, it's not essential.

If your car lacks a smog pump, several things could occur. If the system was improperly bypassed (say, the part rusted off or, more likely, a high school student read online that it could boost horsepower), it could end up actually decreasing the performance of the drivetrain. When there are leaks, loose components, or any type of airflow issues, the engine loses power. The air introduced by the smog pump interacts with the exhaust after it leaves the engine, so if everything works as intended, the smog pump impacts the vehicle's performance by maintaining proper pressure in the exhaust system, which is vital for optimal function.

However, it’s common in the racing and sport compact car scenes to remove so-called "unnecessary" electrical components, like air conditioning and, yes, the smog pump, because getting rid of excess weight and eliminating an electricity drain can offer a slight performance boost. There are ways to remove the smog pump and still maintain the necessary pressure, one of the easiest being to purchase a specific kit from a racing parts supplier. If the modification is done correctly (though note that 'correctly' doesn’t mean 'legally'), the engine can essentially be tricked into not noticing what’s missing.

Of course, this assumes that squeezing a few extra horsepower from the engine is more important than being a responsible member of our planet’s ecosystem.