Skip to main content

The Art and Science of Header and Exhaust Technology

T here are a lot of misconceptions about headers and exhaust system upgrades on the market today. The general idea is that they achieve better air flow than the stock exhaust design and thus make more power. They talk about how they flow more cubic feet per minute (CFM) with their respective header and exhaust designs. Unfortunately, these ideas are simply not true. A motor is an air pump, it has a mathematically fixed volumetric cubic inch. Meaning, aside from elevation, a motor cannot flow more air through it by changing to a bigger pipe size.

To achieve more volume of air, or displacement, there are only 2 ways to do it. You can bore and/or stroke the motor to achieve more cubic inches or you must push more air in with a supercharger, turbo system or blower. A motor runs on atmospheric pressure only, meaning the amount of air (displacement) is fixed unless you go up or down in elevation, then it varies very slightly. So, if you can’t flow more air with headers, what is their purpose?


That’s all they can do is to create much more efficiency. Once you understand that headers CANNOT flow more volume of air through the motor, then we can get to the actual mathematical purpose of header technology.

The Venturi Effect

A header must have a design that can create velocity of air as opposed to volume. The FASTER the air goes through the motor, the better it atomizes the fuel into a vapor which in turn produces an exponentially bigger explosion in the cylinder. That’s where the bigger horsepower and torque are created. The industry tends to test everything like heads and headers etc. on flow benches, to try to measure how much more volume of air their respective designs flow. But there’s only one problem… a motor is NOT a flow bench – it doesn’t flow a solid column of air like a flow bench does – it produces a PUFF of air that’s exactly the cubic inch of the motor divided by the amount of the cylinders. So, the data they get from testing on a flow bench is completely useless. It presupposes that their design is flowing according to a solid column of air when it is in fact not. It is a pre-measured puff of air that is exactly the cubic inch divided by the number of cylinders. It gets far more complicated than I could get into here. If you imagine that the air is flowing in through the intake in a solid column. It’s ambient (meaning outside) air temperature is about to explode to around 1300 degrees Fahrenheit, and the dynamic of air molecules expand rapidly and create pressure literally changing the volumetric amount and so on. The trick is to get the air and fuel to explode much more efficiently in the motor – how do you do that? … the header has to work like a Venturi, the FASTER the air is going through the motor, the more it turns the fuel from a liquid into a vapor. The more the fuel turns to a vapor, the bigger the explosion. The bigger explosion in the cylinder the BIGGER the horsepower gain. The end result is more power, and the emissions are lower because you’re burning more of the fuel, and the gas mileage goes up because the power is pushing the car down the road further per explosion in the cylinder.

Let’s talk about equal length. So technically, all motors are a one cylinder sequentially firing machine. It ceases to be a V-8 or V-10 etc. because the motor is simply running or it’s not. The motor doesn’t know it has a certain number of cylinders. For instance, it doesn’t add up all 10 cylinders and calculate fuel trim and timing – it deals with this in a linear sense. Kind of like an automatic rifle. Each puff of air is shooting out of the tailpipe like a bullet out of the barrel of a gun. There’s an X-factor that is a header killer, it’s called “valve overlap” – for a split second in time, both intake and exhaust valves are open. When one is almost shut, the other one is already opening, which causes reversion. Reversion is bad because atmospheric pressure pushes some of the burnt air and fuel from the last explosion, back into the cylinder and mixes with the new fresh charge of air and fuel and dilutes it, making the explosion smaller and robbing horsepower.

So how do you fix this problem?!! The header design must create the “Venturi” effect or the street term for this is scavenging.

This is where our sophisticated, state of the art, TRI-Y designs come into play. With our invention of the TRI-Y header design way back in the early 60s, the capability to administer the Venturi effect into our collector designs was realized. Now we can eliminate the reversion back into the motor and create huge horsepower and torque gains. Today’s advanced computers love the TRI-Y design because they are highly capable of tuning forward to make such big gains but can’t if the wrong, old school header designs slow down this process. The Venturi effect is so powerful that we actually have to de-tune our header designs so we don’t over-scavenge the air/fuel mixture right out of the cylinder and lean the mixture so bad that it can blow the motor up. For this reason, we can easily stay within the confines of the tuning range for each car and have no check engine light troubles.

Last thing is materials, stainless steel made its name back when the only other alternative was mild steel. Stainless seemed like a great idea – it doesn’t rust and you can polish it up real shiny. But it has several fatal problems. First, stainless is an extremely hard metal. The higher the grade of stainless, the harder it is. This creates a terrible problem – it doesn’t have any give. It wants to hairline crack around every weld. Air leaks out of the cracks but even worse, it also leaks in. Then it mixes with the burnt mixture coming out of the cylinder, giving the O2 sensor the impression that the motor is running lean. Then the computer tries to fix the problem by adding more fuel and timing. The tune is now wrong and the computer has no way of knowing that external air is leaking in and corrupting the tune, resulting in a CEL (check engine light). On top of all that, stainless steel runs twice the temperature on the outside compared to mild steel. We were the first stainless header manufacturer in the world and we abandoned it not long after these bad traits surfaced. Fortunately, there is a far superior product compared to stainless for manufacturing headers and exhaust with. Belanger Headers exclusively uses aluminized tubing for all header and exhaust designs because it runs half the temperature on the outside and like stainless, it also doesn’t rust. Stainless has its place in our systems like flanges, brackets, mufflers and catalytic converters etc. Aluminized tubing combined with stainless parts together make a great combination. Welding soft aluminized to hard stainless creates an unbreakable bond that eliminates cracks and leaks. There are many other important characteristics like equal length tubes and D porting and overall length of the header along with other factors that combine to create the perfect header design for every application. Header back exhaust systems are less about horsepower gains and more about proper pipe size and less heat and of course, better sound and looks.


For nearly 70 years, Belanger Headers has led the industry with our invention of the TRI-Y header along with X-pipes and Y-pipes and H-pipes. As technology races into the future, we will be right there inventing and perfecting new designs for decades to come.