Exhaust Manifold Buyer's Guide

An exhaust manifold is an integral part of any internal combustion engine. It has the simple but critical task of evacuating exhaust gasses from your combustion chamber into your exhaust system. The exhaust manifold consists of a flange that is bolted onto your cylinder head. The flange is connected to runners which are aligned with the exhaust ports on your engine. The number of runners always equals the number of cylinders on your engine. The runners most often merge into a collector and from there are connected to the rest of your exhaust system which often includes more exhaust pipes, mufflers, catalytic converters and possibly other elements, ending with your vehicle's tailpipe There are three main types of exhaust manifolds you can find on a car.

  • MaXpeedingRods has been engaged in the research and development of high-quality turbochargers for decades. We offer turbochargers at affordable prices, made from high-quality materials and components to ensure desired performance and durability. All our turbocharger housings are accurately cast and all cartridges are fully balanced to ensure a perfect fit and long-lasting boost. All our turbochargers also come with bolting hardware and gaskets needed to bolt them onto your exhaust manifold.
  • Our street performance turbochargers feature a high nickel alloy shell with a temperature resistance of up to 850 degrees C. They feature high-quality journal bearings and benefit from high precision dynamic balancing. High precision cast aluminum compressor and turbine wheels ensure optimized spool-up and ensure reliable performance in the 200-600 horsepower range.
  • Our sport performance turbochargers take things a step further with a stainless steel volute that increases temperature resistance to 1050 degrees C. CNC machined aluminum compressor and turbine wheels ensure greater durability and are able to cope with extremely high boost pressures and RPMs. A stronger bearing structure with improved thrust bearings ensures that our sport performance turbos can support boost pressures of up to 3.0 bar and horsepower ranges of 300-850 hp.

As we have already said, exhaust manifolds have the task of evacuating exhaust gasses from your combustion chamber, but perhaps more importantly than that, they also have the task of promoting the scavenging effect. What is exhaust scavenging? To understand what it is, and how it works we must recall what happens inside the engine during its exhaust stroke. At this point in the combustion cycle the piston is moving upward in the bore and is compressing what remains of the combusted air-fuel mixture. However, the exhaust valves have not yet opened and the gasses are being compressed in the chamber which increases their pressure.

Once the exhaust valve opens the difference between the pressure inside the combustion chamber and the exhaust manifold is high, the pressure is much lower in the manifold. This helps the exhaust gasses quickly enter the exhaust manifolds as all gasses flow from high to low-pressure areas. The exhaust gasses entering the exhaust manifold are called an exhaust pulse and the exhaust pulse itself has three different pressure areas. The head of the pulse has the highest pressure, the middle part of the pulse has lower pressure, and the tail of the pulse has the lowest pressure. The pressure of the tail is often even lower than atmospheric because the large speed and momentum of the exhaust pulse head rapidly existing the chamber drags the tail with it thus reducing the pressure in the combustion chamber. This reduced pressure in the chamber means that the intake charge now has a higher pressure than the chamber and this promotes a more rapid entry of the intake.

This process, whereby the departure of exhaust gasses promotes the entry of the intake charge is called scavenging. The design of the exhaust manifold, most notably the length of the runners, their cross-sectional area and shape are detrimental to improving the scavenging effect, and a good exhaust manifold design can significantly improve the performance of an engine.

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Choosing an exhaust manifold for a stock, unmodified vehicle is simple as you can purchase the correct part based on your make, model, year of manufacture and engine. You can get the correct part using your vehicle's VIN or the part number of the manifold itself. Choosing a performance exhaust manifold can be more difficult and will depend on many factors such as desired power output and power curve, engine bay space, engine layout and configuration, budget, other modifications and so on. Choosing a performance turbo exhaust manifold is dependant on turbo size and flange type and wastegate configuration.

  • All our exhaust manifolds are made from high-quality materials to ensure a long service life and provide the expected engine performance.
  • All our exhaust manifolds are checked for any sort of cracks or other manufacturer defects and come with a warranty against manufacturer defects.
  • All MaXpeedingRods exhaust manifolds are made to exacting manufacturer standards and meet or exceed OEM standards.
  • Our exhaust manifolds are carefully and accurately shaped and machined to ensure perfect, hassle-free fitment and come with the required hardware.
  • All our catalytic converter equipped exhaust manifolds use the appropriate materials and have a high-quality catalytic converter construction to ensure your vehicle meets all required emissions tests and standards.

A cracked exhaust manifold can exhibit many different symptoms, some of which are easier to diagnose than others, but some will not be unique to the ehxaust manfiold and can point to other defects. If you are unsure, it's best to have a professional examine the engine to make sure the exhaust manifold is indeed the offending part.

  • Increased noise.A cracked or leaking exhaust manifold can create all sorts of weird and unwanted noises. The noises are usually in the form of tapping or muffled knocking in the case of cracks. If the exhaust manifold is leaking, it will often produce hissing sounds. The sounds may or may not get louder as you accelerate, but they are often more pronounced when the engine is colder. In some cases, when the crack is very small, the noise can even completely disappear as the engine heats up and the exhaust manifold expands, closing the gap. But the crack will get worse if ignored.
  • Loss of power, poor fuel economy.A manifold that is sufficiently cracked will cause loss of power and decreased performance, especially at higher engine rpm. This occurs because when cracked, the exhaust manifold becomes unable to fully perform its exhaust scavenging role robbing your engine of its power potential. This also negatively impacts fuel economy as the engine starts working harder and struggling to evacuate exhaust gasses.
  • Smells from the engine bay.An exhaust manifold crack will let out extremely hot gasses into the engine bay, where they don't belong. These extremely hot gasses can wreak all sorts of havoc on different components in your engine bay. They can melt gaskets, wire insulation, and any plastic parts nearby. They are also a fire hazard so it's important to replace a cracked or damaged exhaust manifold as soon as possible.

Depending on the type of your engine and the space in your engine bay replacing an exhaust manifold can be easy or it can be more time-consuming. However, the task is straightforward and can be in most cases performed with relatively basic tools. That being said, do not attempt to replace an exhaust manifold if you are not 100% confident in your abilities or don't have the right tools. In these cases it's always best to leave the job to a professional. In general the steps to replace an exhaust manifold are as follows:

  • Wait for the engine to cool down. An exhaust manifold can get extremely hot and can be a fire hazard if it touches flammable materials while it's hot. It can also cause high-degree burns if you accidentally touch it.
  • Removing the exhaust manifold from a naturally aspirated engine is always more simple than removing it from a turbocharged one. In the case of a turbocharged engine, the exhaust manifold removal requires that all turbo oil and water lines (if present), intercooler piping (if present), downpipes, and turbo air intake ducts be disconnected.
  • On a naturally aspirated engine removing the exhaust manifold in most cases starts by disconnecting the exhaust manifold from the rest of the exhaust system. The remainder of the exhaust system can be left on the vehicle as is, or it must be further supported by jacks and/or hangers. In some cases, especially on newer, FWD vehicles the exhaust manifold will not clear various suspension elements, oil filters, coolant lines, etc. which can require the removal of these parts and make the job much more time-consuming.
  • Once the exhaust manifold is separated from the exhaust system and any other parts in its way are removed from the vehicle the exhaust manifold needs to be unbolted from the cylinder head and then removed from the vehicle. The install is always the opposite of the removal.