Do KN Filters Increase Horsepower and Fuel Economy?

As the owner of a 2001 Acura NSX-T and a 2017 NSX, I have tried various air filters, including KN filters, and have found that they do not contribute to improved performance in modern vehicles equipped with sophisticated engine management systems. In this article, we will explore the effectiveness of KN filters in terms of horsepower and fuel economy, and debunk common myths about aftermarket air filters.

Personal Experience with KN Filters

Having installed KN air filters in three different vehicles, I can confidently state that there was no noticeable difference between using a KN filter and a replaceable paper Hastings filter. The engine can only use so much air! This observation is supported by the findings of many vehicle owners and tuners in the automotive community.

Engine Performance Fundamentals

A car engine is a machine that combines fuel and air, which contains oxygen, and burns it to generate rotational force. The fuel and air must burn at a fixed ratio, which is determined by the chemical equation: fuel plus oxygen CO2 plus water. In modern engines, which are highly refined compared to engines from 50 years ago, the only way to gain more power is by burning more fuel with more oxygen. This principle holds true even for simple engines from a bygone era, where a few tweaks could increase power, not fuel efficiency.

MYTH: KN Filters Boost Horsepower and Fuel Economy

It's often claimed that aftermarket air filters, including KN filters, can increase both horsepower and fuel economy simultaneously. However, this is a common misconception. Any modification that allows 'more air' into the engine will likely require more fuel, which generally does not result in better fuel economy. Here's why:

Air Filters and Fuel Efficiency: A KN filter, like any other aftermarket air filter, might allow for a slight increase in air flow, but this increase is negligible and does not significantly impact the fuel efficiency. When the engine management system is in control, it ensures that the correct amount of fuel is injected for optimal performance. Dyno Testing: When dyno testing a vehicle with different air filters, the results will typically show no significant difference. This is because the engine management system regulates the engine's performance, and any slight air flow increase is immediately matched with a corresponding increase in fuel flow. Induction Noise: KN filters allow for a little more induction noise to escape, which is a nice feature, but it doesn't contribute to performance or fuel efficiency in a meaningful way.

Alternative Solutions: Turbochargers and Computer Control

The only modification that can potentially increase both horsepower and fuel economy is a turbocharger. However, this requires carefully swapping a larger engine for a smaller one. Adding a turbocharger to an existing engine will increase power at higher RPM, predominantly leading to higher fuel consumption.

Modern engines, particularly those with turbochargers, are designed to maintain a balance between performance and efficiency. Turbochargers work by compressing air to increase its density, allowing more fuel to be burned and more power to be generated. However, this is only truly beneficial at higher RPM, where the engine would naturally benefit from the additional power and fuel efficiency.

The introduction of computer-controlled engines has made a significant impact on modern vehicle performance and fuel economy. These engines can be set to operate in different modes, such as economy or performance, allowing for a compromise between the two. This capability means that a vehicle can be optimized for fuel efficiency at lower speeds and power at higher speeds, or vice versa, depending on the driving conditions.

Technological Advancements: Diesel VWs and Emissions Testing

It's worth noting that the ability to switch between different modes in modern engines is a sophisticated technology. In some cases, vehicles like the diesel Volkswagen (VW) cheated emissions tests by switching to a low power, high economy mode during testing. This is an extreme example, but it highlights the importance of computer control in managing engine performance and efficiency.

Modern engines are equipped with advanced control systems that can adapt to driving conditions and optimize performance accordingly. These systems work in the background to ensure that the vehicle operates in the most efficient manner, taking into account factors such as speed, load, and even the driver's behavior.

For car enthusiasts and owners of performance vehicles, it's crucial to understand the limitations of aftermarket modifications and the true capabilities of modern engine management systems. A KN filter, while it may offer some aesthetic or minimal airflow benefits, is unlikely to significantly impact horsepower and fuel economy. Instead, focusing on more advanced modifications, such as a turbocharger or adapting to the latest computer-controlled engine technology, is more likely to yield the desired results.