Headers Vs. Exhaust Manifolds: What's The Difference?

If you plan to upgrade your car on a budget, most car enthusiasts often start with the engine's air intake system and a performance exhaust. Add-ons like a cold air intake or a straight pipe will let your machine breathe more freely, allowing it to burn more fuel or run more efficiently, thus delivering more power and performance.

However, even if you open up your car's breathing with an aftermarket intake and exhaust, you might still run into an airflow bottleneck with its stock exhaust manifold. This could potentially hold you back from maximizing the performance of your upgrades. It's worth considering a replacement of your exhaust manifold with a header to get the most out of these aftermarket parts.

Why would an exhaust manifold prevent your car from going faster? How would a header resolve this issue? And what other parts do you need to ensure you get the most from a header upgrade?

An exhaust manifold is a set of iron pipes that lead from your car's cylinder bank to the initial pipe that leads to the catalytic converter. This part connects your engine to the rest of the exhaust system, allowing it to expel the waste gases produced by the combustion process.

You need one exhaust manifold per cylinder bank; meaning inline engines only have one exhaust manifold, while V or flat engines have two. Some exceptions, like the legendary W-16 Bugatti engine, uses four exhaust manifolds — one for each set of four cylinders.

Because car manufacturers balance cost, reliability, comfort, performance, and several other factors, exhaust manifolds are typically made from heavy cast iron material for strength and longevity. Furthermore, it usually also has a built-in heat shield to prevent the high temperatures of the exhaust gases from heating the engine bay and potentially damaging other parts.

This means that exhaust manifolds are heavy for their size. Furthermore, since the iron pipes most manufacturers use must withstand all kinds of situations with little to no maintenance, they usually have thick walls, thus limiting the amount of air they can carry to their dimensions.

On the other hand, headers are aftermarket parts designed to replace the exhaust manifold. Headers are usually made from mild steel, stainless steel, Inconel, or titanium, making them lighter than exhaust manifolds. Because these materials are stronger than the usual cast iron used in stock exhaust manifolds, manufacturers can make them thinner, allowing for a larger interior diameter without increasing the exterior size.

Although one of the advantages of headers over exhaust manifolds is their lighter weight, they usually have longer tubes over the latter to help manage the flow of exhaust gases, thus reducing back pressure in your exhaust system.

This reduction helps in scavenging, which according to On All Cylinders, "occurs when the rush of exhaust gas leaving the cylinder helps to pull in a fresh air/fuel mixture." By ensuring that the exhaust gases flow freely, the header helps the engine get more fresh air or fuel/air mixture into the cylinder during the intake, allowing it to operate more efficiently.

Headers will improve your engine's airflow, allowing it to breathe easier. However, it has little to no effect and could even negatively affect your engine's performance if installed on its own. That's because the header only improves flow between your engine's cylinder banks and the rest of the exhaust system.

If you don't upgrade your intake, then the header won't have any effect because its sucking power is limited by your stock parts, which are designed specifically for the stock exhaust manifold. Furthermore, you should upgrade your exhaust before getting headers, as the stock exhaust system will bottleneck the headers. It's like having a bottle with a huge opening and then using a funnel to pour water out — no matter how big the opening is, water will still flow much slower because of the small diameter of the funnel.

You should only get a header upgrade after installing the two parts we've mentioned. Also, don't forget to upgrade your ECU so that your car's engine will know you have a bigger, better-flowing exhaust system.

Performance cars or vehicles modified for speed are great recipients of this upgrade. Getting a header isn't worth it if you're looking to add just a couple of upgrades to your daily driver — you're better off installing an aftermarket intake or upgrading your suspension to make your car a bit more fun to drive.