We’ve spent a lot of time discussing branch manifolds and explored the factors that impact the performance of header pipes, secondary pipes, and various branch designs. However, this only scratches the surface of a much broader topic, one we’ll continue to explore in more detail: the performance free-flow silencer system!
Exploring Branch Manifold Development: Aesthetic Trends vs. Performance Gains
There are two primary approaches to developing branch manifolds for road cars.
The first method focuses on enhancing power by pairing a branch manifold with the existing stock exhaust system (silencer system). This approach is common overseas, particularly in regions where catalytic converters (cats) are mandatory. However, the research and development involved is extensive. Many newer car models are already equipped with well-designed manifolds, downpipes, and silencer systems. A growing trend overseas is to install highly polished stainless-steel branches onto the existing exhaust system, maintaining the stock setup up to the catalytic converter. Afterward, a cat-back performance silencer system is fitted, often featuring beautifully polished, TIG-welded rear silencer sections.
I’ve had the opportunity to examine a few of these systems and, upon closer inspection, concluded that their performance benefits are limited. This leads one to believe that these modifications are more about aesthetics than performance. While these polished grade 304 stainless steel systems look stunning, the steep cost of such imported systems makes them out of reach for many of us here in South Africa.
Maximizing Performance: The South African Approach to Branch Manifold and Free-Flow Silencer Development
The young (and young at heart) South African motorist is all about performance, with a passion for everything fast and exciting. Here in South Africa, the development of bolt-on branch manifolds for stock exhausts isn’t a popular option due to their limited power gains. Local enthusiasts demand maximum power and torque. But it’s not just about performance—looks and sound matter too. That’s why you often see polished cold air induction piping and air filters for that distinctive induction sound, and sleek, polished stainless steel tailpipes for a bold visual impact.
When it comes to the stock manifold, secondary link pipes, and silencer systems, especially in newer cars, manufacturers have put in significant effort to meet a range of requirements. These include:
- Minimising noise and vibration to comply with global noise abatement regulations
- Efficiently routing exhaust gases to keep them away from occupants
- Reducing vibration and resonance to meet strict standards
- Adhering to mandatory exhaust emission regulations
In other words, the stock manifold and exhaust system are designed together to optimize power and torque while also meeting these regulations. But if we open up the exhaust system with larger tubing and less restrictive silencers, we unlock more potential for branch manifold development, as the stock manifold is designed with the stock exhaust system in mind.
For this reason, the performance free-flow silencer system should be developed separately to achieve maximum power gains, paired with sporty sound levels that are enjoyable both inside and outside the vehicle. In South Africa, many branch manifolds have been developed in conjunction with free-flow systems using dynamometers. However, it’s crucial to develop these components separately to fully realize the power gains of both modifications. Without this, we can’t ensure the effectiveness of either component.
When developing a free-flow silencer system, it’s common to gradually increase the tubing and silencer bore size until the power gains level off. But sometimes, going too large can backfire. For example, on the VR6 engine, reducing the exhaust pipe diameter from 63.5mm to 57.15mm yielded better results.
That’s all for now!
Abel Dos Santos
