Exhaust Heat Management is the means of lessening the negative effects of internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 exhausts by preventing heat from escaping the exhaust system

Exhaust system

An exhaust system is usually tubing used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes...

 on automobiles.

Overview

The fact that exhausts often pass near important components means that ways of protecting these components from heat soak are especially important. As a result heat management is used as a way of reflecting, dissipating or simply absorbing the heat.

Heat shield is also useful to reduce under-bonnet temperatures which therefore reduces intake temperature, subsequently increasing power.

Types

There are many different types of heat management, some more effective than others. They range from basic solid heat shield

Heat shield

A heat shield is designed to shield a substance from absorbing excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat...

 to plasma sprayed ceramics.

Heat shield

Heat shield is one of the most widely used heat management options available due to its relative low price and ease to fit. In the past it has usually been custom made out of rigid steel however heat shield is now mostly flexible aluminium.

More recently technology has become available to apply ceramic thermal barrier coatings onto flexible aluminium in order to increase the thermal insulatory properties. This same procedure is also used on composite

Composite material

Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...

 materials, which is often used on high-performance race cars, such as in Formula 1.

Ceramic Paint

This fairly low-cost solution can offer minor reductions in heat loss. It is often applied by brushing or spraying from an aerosol onto the exhaust system, followed by curing in the oven to allow the paint to adhere. This is sometimes applied to the internal surfaces of the exhaust however this often flakes prematurely due to the inability to clean the surface prior to application. It is usually necessary to reapply every 1–2 years due to it flaking and peeling.

Thermal Barrier Coating

These ceramic coatings are highly advanced coatings applied via plasma spray, and as a result, the coating is effectively welded to the surface of the exhaust system. They can offer significant performance benefits due to the low thermal conductivity of the ceramic compound. These coatings protect steel exhaust systems further by protecting from rust.

Heat wrap

This is the cheapest solution and is quite easy to apply. Heat wrap consists of a high-temperature synthetic fabric which is literally wrapped round the manifold. This however can prematurely degrade the manifold.

Heat Wrap or Thermal Barrier Coating?

There has been much debate if heat wrap is better than plasma-sprayed coatings. The far cheaper option in the short term is heat wrap but whilst being quick and easy to apply, it lacks a great deal of aesthetic appeal and is normally less effective. The fact that heat wrap degrades the manifold, means that within a couple of years, a replacement manifold is required therefore it is important to factor in this extra cost before deciding to choose heat wrap. Ceramic plasma-sprayed coatings also have far greater performance benefits and whilst being quite expensive, they last a long time and in fact protect the exhaust manifold

Exhaust manifold

In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word manifold comes from the Old English word manigfeald and refers to the folding together of multiple inputs and outputs.In contrast, an inlet manifold is the part of an engine...

.