Although SUVs are all the rage in Australia nowadays, the dual-cab 4×4 utes are also chipping a large portion of the market. The Toyota HiLux and Mitsubishi Triton are the forerunners in sales, but the Nissan Navara has also become a common sight on and off the roads these past few years. The theory behind the popularity of the Navara is simple – it’s a vehicle that’s tough enough to serve tradespeople, but it’s also spacious and comfortable enough to accommodate families looking for weekend escapes in the backcountry.
But as great as the Nissan Navara is, most experienced off-roaders will tell you that it still has a lot of room for improvement, as is the case with most utes. Mileage and performance can be significantly improved with the instalment of an aftermarket Nissan Navara D40 exhaust. Stock ute exhaust systems are made with cost-cutting in mind rather than performance, in order for manufacturers to make their product more readily available for consumers. On the other hand, an aftermarket Nissan Navara D40 exhaust is made with power and mileage gains in mind. That being said, here are the key differences between stock and aftermarket exhaust systems.
The Materials They’re Made Of
The first notable difference between stock and aftermarket exhaust systems is the materials they’re made of. Stock exhaust systems are typically made using lower-grade steel, such as mild steel, which performs decently on the road, but once you take your Navara off the beaten trail, it won’t cut it. It’s not as durable, and it can’t withstand severe driving conditions. On the other hand, aftermarket exhaust systems are typically constructed of higher-grade steels like aluminised and a few variations of stainless steel, such as T304 and T409. These materials are far more durable and feature better shock-, vibration-, corrosion-, and impact-resistant properties. Aluminised steel is more lightweight when compared to stainless steel, but stainless steel is much stronger in general. In fact, stainless steel is so strong that it will likely outlast the lifespan of your Navara.
The diameter of the pipes is another notable difference between stock and aftermarket exhausts. In order to save on material, stock exhaust systems use smaller diameter size, which results in flow restrictions. Think of the exhaust pipes like a highway – while having 2 lanes might be fine for the most part, traffic would surely run smoother if there were 2 extra lanes. However, keep in mind that bigger is not always better. If the pipes are too large for your Navara, you’re going to lose on exhaust velocity, which is going to lose you some power in the low- to mid-range.
Something that most people don’t realise is that not all pipe and extractor bends are made the same. Stock exhaust systems are used using crush and wrinkle bending techniques, both of which are quite simple and affordable, whereas quality aftermarket performance exhaust systems are made with a more advanced technique known as mandrel bending.
Crush bending only employs a radius die and backing shoes, which results in functional bends that have a bend inside the radius. Wrinkle bending involves heat being applied to the pipe at the bending point until it’s red-hot. As the pipe is passed through the die, the inside throat of the bend collapses, resulting in slight diameter reduction, alongside a series of humps that impact the flow and sound.
Mandrel bending, the technique used on performance aftermarket exhausts, provides a smooth, virtually uninterrupted product that’s completely free of creases and kinks. This is due to the fact that a mandrel is employed which supports the inner walls of the pipe as it goes through the die. This results in a bend that’s free of diameter and profile changes. The mandrel is usually lubricated with lithium grease, which enables a smooth gliding action inside the pipe.
Cat-Back vs. Header-Back Exhausts
If you’re sold on the idea of getting an aftermarket D40 exhaust, you’re going to have to decide whether you want a cat-back or header-back kit. The difference between the two types is how much of your stock exhaust they replace. Header-back exhausts replace the entire stock system, and therefore, provide the most performance and mileage benefits. However, as a result, they’re the more expensive option. On the other hand, cat-back exhausts replace only the parts from the catalytic converter to the exhaust tip. According to many, cat-back exhausts are the more valuable option out of the two. However, some people claim that your system is only as good as its weakest link, so they would argue that header-back exhausts are the way to go. But what I would suggest is that you make a choice based on your budget. If you can afford a header-back exhaust, then by all means – go for it. But if you’re on a tighter budget, a cat-back exhaust would suffice.