Isuzu Dmax Exhaust Upgrade: The Facts on Aftermarket Systems

The exhaust system of your Isuzu Dmax plays a simple, yet important role in your vehicle’s performance as well as in preserving the environment. And while your stock exhaust system is capable of doing both these things just fine, sometimes, you want more than just fine – you want to unleash the extra power that your engine is capable of.

Dmax exhaust upgrade

Source: Facebook

And the best way to unearth this power is by shopping for a Dmax exhaust upgrade. You can find a variety of Aftermarket Dmax exhaust systems that can be a cost-effective way to get more out of your Isuzu.

Exhaust systems are made up of three sections. The header/manifold section is directly connected to the engine and usually merges the cylinder banks into a single stream. This section can also include a small catalytic converter known as pre-cat. The second section is called the mid/cat section, and it usually runs the entire length of the vehicle, further merging the exhaust streams. This is where the catalytic converter is located, as well as the resonators or an H/X pipe if it’s a dual exhaust system.

muffler section

Source: Parkmuffler

Lastly, there’s the muffler section, where the exhaust gases leave your Dmax. At the end of this section, you’ll find a muffler whose purpose is to reduce engine noise.

Turbocharged vehicles feature a few extra components, simply because the turbocharger is spun by the gasses that pass through the system, so the turbocharger itself needs to be somewhere in the stream. Generally, turbochargers are installed right after the manifold, and they’re accompanied by downpipes.

The downpipe is what connects the turbocharger to the mid/cat section, and it can contain a pre-cat. Also, the downpipe can feature a secondary exhaust pipe from the turbocharger’s wastegate in order to separate the two streams so that turbulences are reduced.

For most older vehicles, replacing the exhaust system is an affordable and easy way to improve not only the performance, but also the mileage and sound. However, many OEM manufacturers have caught up to this and newer vehicles are now made with better exhaust systems.

stock exhausts

Source: Hotrod

The main reason why stock exhausts don’t perform as well as aftermarket systems is backpressure. Reducing the amount of backpressure is one of the easiest ways to improve your Isuzu Dmax’s engine efficiency. There’s a myth saying back pressure is necessary to some point for the vehicle to run properly, but that’s not really true.

By replacing your existing exhaust with an aftermarket system that has a larger diameter, you can reduce the backpressure occurring in the exhaust system significantly.

However, bigger is not always better, as having an exhaust that’s too big can cause the gasses to cool more, which makes them denser. And this, in turn, forces your engine to work harder to push them out of the system. There are several ways aftermarket exhausts can reduce the back pressure of your Dmax, including mandrel bends, reducing the overall number of bends and reducing the overall length of the exhaust.

That being said, when buying a Dmax exhaust upgrade, make sure you select one with mandrel bends instead of pressure bends. Mandrel bending is more expensive, but it keeps a consistent radius throughout the bends. Pressure bends, on the other hand, are crushed at the bends, resulting in a smaller radius and thus, unnecessary backpressure.

exhaust upgrade

Source: Schearers

Another way aftermarket exhaust systems improve your exhaust systems is by exhaust scavenging. Exhaust fumes don’t come out in a steady steam from the engine, but as a series of pulses that occur every time cylinders go through the exhaust stroke. These pulses create a vacuum as they move through the system. The manifold merges the streams so that the vacuum of a single cylinder’s pulse helps pull the pulse from other cylinders.

This process is difficult to execute effectively, as there are quite a few variables to account for, including pipe length, size, bend radius, and the engine’s RPM, which is constantly changing. The manifolds (or headers) route the exhaust from every cylinder and combine the streams together.

Most exhaust scavenging gains come from high-end, well-designed manifolds. The two most popular types of manifolds are tubular and log. But keep in mind that the scavenging effects are almost non-existent if you have a turbocharged vehicle, simply because the turbo is mounted very close to the head, and the flow of gasses through the turbo is restrictive, and the pulses are crammed together, eliminating the low-pressure areas.