Exhaust system flanges and gaskets are possibly the most misunderstood components in any car or truck’s exhaust system. And while they don’t command the awe or attention that polished headers or tunable mufflers would, make no mistake: without them, exhaust systems simply couldn’t function.
Flanges and gaskets perform the critical job of equalising pressure inside an exhaust system. What this otherwise unimpressive equalisation actually equates to, however, are increases in both engine output and fuel economy – two especially enticing benefits for 4WD and ute owners. They’re an unlikely combination of bonuses stemming from a singularly unexpected source though, making now the perfect time for an intro into just how important flanges and gaskets are for exhaust systems.
Premium Flanges and Gaskets Help Smooth Exhaust Gas Movement
From the small diameter exhaust plumbing found on 1.5l Suzuki Jimnys, to the cathedral-sized tubing used on 6.2l V8 Maloos, flexible, high grade exhaust flanges and gaskets are the essential system sealers designed to prevent unwanted exhaust gas movement. By providing a precise, pressure-tight seal that’s sized to prevent spent exhaust gases from escaping the system, flanges and gaskets are the silent keys to successful exhaust performance. And given the stresses and amount of chassis flex that 4WDs routinely incur, flanges and gaskets are as integral to engine efficiency and reliability as the air-fuel mixture itself.
Engine-specific contours and unique diameters and thicknesses are what allow flanges and gaskets to fit the mating surfaces between exhaust tubes and exhaust tubes and ports. Exhaust scavenging – the process of spent exhaust gases drawing fresh air-fuel mixtures into the engine – wouldn’t be possible without these strong, leak-proof seals. This is how their flexibility, and built-in ability to conform to irregular surfaces when compressed makes them ideal for:
- Increasing engine performance. Flanges and gaskets ensure a smooth flow of spent gases away from the engine and through the system, resulting in a huge improvement in scavenging, power output and fuel economy.
- Reducing exhaust system damages. More than any other style of exhaust system, 4WD and ute pipes have to be able to flex with chassis movement. Flanges and gaskets allow exhaust component to work freely, but without any destructive friction or vibration.
- Decreasing exhaust noise. As flanges and gaskets are engineered to flexibly fill the spaces between exhaust tubes and components, they’re ideal for eliminating unwanted cabin noise and exhaust resonance, as well as reducing tailpipe noise.
- Safeguarding engine electronics. The heat and corrosive gases that are allowed to escape from a leaking exhaust system can damage everything from sensitive engine sensors to cats and turbos. High temperature exhaust flange and gasket sets are engineered to reduce the risk of exhaust gas damages.
- Cutting emissions releases. Australian Design Rule (ADR) guidance on emissions release is strict, and high grade exhaust flanges and gaskets help prevent the release of unburned pollutants like carbon monoxide and hydrocarbons into the environment.
The fact is, while optimally sized and mandrel bent tubes are the main talking points when it comes to premium exhaust systems, it’s the flanges and gaskets used to seal them that make the difference. They guarantee smooth transitions within the system between high and low pressure, while also promoting the best possible exhaust flow and acceleration regardless of the type or size of engine.
Super Strong Composites Make the Longest Lasting Exhaust Gaskets
While the terms “flange” and “gasket” are often used interchangeably to describe the various types of exhaust gaskets that are available, they’re technically very different items. Flange-type gaskets are stamped with bolt holes and are used on exhaust components with flat surfaces. On the other hand, standard-type exhaust gaskets don’t have bolt holes, and are typically used to fill the gaps between flared and irregular-shaped surfaces.
Depending on their application, the biggest difference between flanges and gaskets often comes down to the materials they’re constructed from. Flanges are usually manufactured from metallic amalgamations, while standard gaskets can be produced from metals, as well as a full range of heat resistant fibre and ceramic composites. In either case though, their compositions are engineered to offer the highest heat resistance and tensile strength for the most difficult conditions:
- High pressure multi-layer steel (MLS) gaskets. MLS gaskets are designed to provide a sealed surface between flanged and flat exhaust surfaces, and are constructed from multiple layers of steel encased in high temperature nitrile butadiene (NBR) or fluoroelastomer (FKM) outer layers.
- MLS gaskets with molybdenum disulphide (MoS2) coatings. MLS gaskets with MoS2 coatings are desirable for their reduced wear qualities, and are regularly used on flanged surfaces with high tensile and highly compressed loads.
- Sandwiched metal gaskets. Sandwich-style gaskets are the preference for the high temperature/high pressure plumbing on engines with forced induction, and are manufactured from layers of steel, aluminium and copper sandwiched between high pressure outer layers.
- Compressed fibre and graphite composite flanges and gaskets. Graphite composite flanges and gaskets are reinforced with wire mesh or metal laminate, and are regularly used for sealing all types of exhaust tubes.
- Ceramic coated gaskets. Ceramic gaskets are engineered to withstand the severest exhaust operating temperatures and are highly preferred for their durability and superior heat and corrosion resistance.
Being able to distinguish between the various flange and exhaust gasket types is an important part of being able to recognise which types of gaskets are best suited for specific applications. Higher performance engines and driving conditions require the most durable sealing consumables available. That’s why when it comes to 4WDs, anytime an exhaust system component needs to be replaced or the system has been upgraded, it also makes sense to install the most capable flanges and gaskets available for the job.
Recognising the Signs of Impending Exhaust Flange Failure
Regardless of their durability, severe heat resistance and virtually unlimited ability to fill the imperfections between exhaust system components, flanges and gaskets aren’t designed to last forever. 4WD exhaust systems are especially prone to the kinds of excessively high temperatures, crushing impacts and atypical stresses that can cause flanges and gaskets to fail. That means owners need to know how to recognise when a flange or gasket has failed, or is on the verge of failure.
- Excessive exhaust system and engine noise. The roar of escaping exhaust gas or the rattle of loose exhaust components are a likely indicator of a failed flange or gasket.
- Unexpected engine surging. Unexplainable engine surging, vibration, or irregular RPM under load are signs of reduced scavenging that have possibly been brought on by exhaust gasket difficulties.
- An intense smell of exhaust fumes. The smell of spent exhaust gases escaping the system is unmistakable, especially if it’s the result of an exhaust gasket failure.
The quicker a possible exhaust flange or gasket failure can be recognised, the better. It’s the key to preventing a simple exhaust problem from escalating into a costly and complex engine problem.
The Final Word
At the end of the day, it’s important to remember that even though flanges and gaskets aren’t the main components in an exhaust system, they shouldn’t be overlooked. And on utes and 4WDs that are likely to see thousands of kilometres of prolonged exposure to moisture, extreme heat cycling and high tensile stresses, continuing to drive if they’re faulty or missing can be catastrophic.
With high grade flanges and gaskets, owners can be sure that their exhaust systems are have the consumables they need to deliver years of trouble-free performance. They’re one of the best investments that a ute or 4WD owner can make in their vehicle’s reliability.