If you thought that a bigger exhaust system meant bigger power, you’d be mistaken. Here’s everything you need to know about exhaust systems and how to increase performance .
There’s nothing wrong with choosing an exhaust based on the way it sounds or looks, if of course your goal is to make it sound/look better. If your goal is to increase performance, however, it’s a different story. Let’s break this down into three sections :
- What are the parts of an exhaust?
- Why should an exhaust be upgraded?
- Test results from upgrading a stock car’s exhaust: Is it worth it?
If you’re unfamiliar with exhausts, this post will break down the basics:
1. What Are The Parts Of An Exhaust?
Exhaust Manifold/Header
This is the first point of contact for the exhaust gases after they exit the cylinder head. It’s also a commonly upgraded item where heavy cast manifolds are swapped out for tubular headers. The idea behind upgrading to an exhaust header typically comes down to increasing the exhaust piping diameter as well as increasing exhaust scavenging by aligning the exhaust pulses in a favorable fashion.
Catalytic converter
This is the device which allows you to still breathe the air while you’re visiting Los Angeles. It takes the incoming NOx, CO, and unburnt hydrocarbons from the exhaust and “converts” it into much less harmful N2, O2, CO2, and H2O.
Piping
It’s ideal not to have your exhaust gases pump directly underneath your car, filling your cabin with fumes. You’ll need some pipes to route the air elsewhere.
Resonator
Though it’s not a necessary portion of an exhaust, it’s often included as it helps to eliminate noise. Resonators work by rejecting sound waves and canceling each other out, and they’re typically tuned for a specific frequency in which the engine noise is loud or undesirable.
Muffler
There are many types of mufflers, but the goal is pretty much the same: eliminate noise. One of the most common ways they work is by redirecting the airflow. Along the way, the exhaust passes through porous pipes which allow the exhaust gases to expand into sound deadening material, minimizing the noise that finally exits the tailpipe.
2. Why Should An Exhaust Be Upgraded?
When I looked into upgrading the exhaust on my car, my original goal was simply to see if it made any difference. Would performance increase or decrease? It’s important to understand that the velocity at which your exhaust exits is one of the key elements to its performance. When your engine is at low RPM, the amount of exhaust gases leaving is low, so the velocity it exits the exhaust is low. You can increase this velocity by using a smaller pipe, but this will create a restriction for higher RPM.
Exhaust scavenging makes an exhaust system more efficient because as your exhaust gases pulse out of the engine (from each exhaust stroke of the engine), you have a high pressure area leading the exhaust pulse, followed by a low pressure area (with a transition). This low pressure area helps to pull the next exhaust pulse out, meaning the piston has less work to do when it’s forcing out the exhaust gases. Ultimately the goal is to have the fastest exhaust velocity with the least amount of restriction (which of course isn’t as simple as writing that sentence).
The whole idea is to increase your exhaust diameter as the amount of exhaust your engine creates increases. This reduces restriction and allows for more flow. If you have modified your engine, you’ll need to modify the exhaust as well to allow for more airflow.
3. Test Result from Upgrading Perodua Myvi 1.5L NA. (AKA: Daihatsu Sirion 1.5 Sport.)