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n unfortunate side-effect of the internal combustion

engine is the generation of waste heat and combustion

by-products. While originally just a convenient method

of disposing of this waste, the exhaust system of a racing

powertrain now also serves to significantly enhance the engine’s

performance and tune its performance characteristics, as well as

reduce noise – or, as seen in Formula One, improve aerodynamics.

However, the high temperatures and sometimes corrosive gases

make this one of the harsher environments to be found on a racecar,

requiring a significant application of technology to provide a system

that can withstand the conditions yet deliver performance for the

minimum weight possible. And the demands on exhaust systems are

growing, particularly as stricter noise and emissions rules are enforced

on the roads as well as in motorsport.

DesignThe fundamental purpose of a racing exhaust goes far beyond the

mere removal of exhaust gases to a convenient location. The design

of an exhaust system can benefit a racecar in two distinct ways –

by improving the performance of the engine and improving the

aerodynamic performance of the vehicle. The benefit to aerodynamic

performance can be considerable, as seen during the recent

technology ‘arms race’ of Formula One’s exhaust-blown diffusers. For

most racing applications though, the primary objective is to provide

the best increase in engine power, torque and driveability for the best

balance of weight, service life and packaging space available.

The design of an exhaust starts with the selection of an appropriate

diameter and lengths for each section of the system. A smaller

diameter pipe increases back-pressure (that is, flow losses) against

which the engine must pump the exhaust gases, so why not simply use

the largest diameter possible? The counter-argument centres on the

effects of pressure-wave tuning on the engine, which operates well in

smaller diameter pipes. As always, there is a compromise.

When the exhaust valves open, a pressure wave is generated in

the exhaust, which travels to its end and out into the atmosphere.

Whenever the wave encounters a significant change in exhaust section

– such as a larger diameter pipe, box collector or the end of the

tailpipe – a rarefaction wave is reflected back in the opposite direction

(a smaller section change simply reflects some portion of the original

positive pressure wave). If this rarefaction wave reaches the exhaust

ports just prior to their closing, it can aid in scavenging exhaust gases

from the combustion chamber. It may also result in a lower cylinder

pressure as the inlet valves open, aiding in drawing in the fresh charge.

However, if mis-timed then the effect of a positive pressure wave could

have a detrimental effect.

To optimise the pressure-wave tuning of the engine, the lengths of

the primary exhaust pipes are crucial in determining the frequencies

at which these wave-tuning effects operate at their best. Correctly

52

David Cooper reports on the technologies underpinning the design and implementation of exhaust systems to enhance engine performance

Exit strategies

Exhaust heat: this is the Audi Le Mans turbodiesel V6, with its exhaust

primaries feeding a single turbo within the vee (Courtesy of Audi Motorsport)

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53

FOCUS : EXHAUSTS

of equal length, and as close to optimum as possible, while bends will

have the largest radius possible to reduce flow losses. The inevitable

battle with packaging space and the proximity of other temperature-

sensitive components usually means that some form of compromise on

minimum bend radius or tube lengths will eventually be reached.

designing the primary lengths

can enable the exhaust designer

or engine builder to increase

engine power and torque at a

chosen engine speed. The exhaust

collector can contribute to this

effect, as can any other significant

change in section area or the

overall length of the exhaust

system (waves reflected back from

atmospheric pressure).

Focusing for a moment on the

design of the collector, this can

follow two schools of thought

– a dramatic change in section

to promote wave-tuning effects,

or a smooth merged collector

to minimise flow losses. Which

design provides the greatest

performance gain is debatable, as

the end results depend completely

on the individual engine and

overall design philosophy adopted.

Exhaust layouts can be optimised

in many ways, the most common

approach being the four-into-one

configuration, where four primaries

are merged simultaneously into a

single pipe. This can also be done

in stages, with some NASCAR systems following a four into two into

one layout, or in the case of some dragster exhausts maintaining each

cylinder’s exhaust as a separate one-to-one pipe. As cylinders fire

at different times, the use of link pipes can promote pressure-wave

interactions between the exhaust pipes of each cylinder.

The optimum design can be determined through experience, or

where possible an extensive dynamometer test programme using

prototype exhausts with variable configurations and telescopic

sections. This enables real-world, back-to-back testing of various

layouts and primary lengths to establish the best design before

committing to manufacture. The use of computational fluid dynamics

(CFD) can be helpful in determining initial lengths, using one-

dimensional simulations of the pressure-wave effects or full 3D CFD

simulations of gas flow through particular exhaust geometries.

The use of CAD software to design exhaust systems within the

packaging envelope available is increasingly common, ensuring

that the system fits first time, and also allowing some consideration

as to how it will fit before the design of the vehicle is completed.

Historically, exhaust manufacturers were often presented with a car

space and asked to manufacture an exhaust, an increasingly complex

task as packaging spaces grew smaller through the decades.

Once the primary lengths and other critical dimensions such as

overall length and tube diameters have been decided, the next trick is

to fit them all into the space available. Ideally, all the primaries will be t

Four-into-one smoothly merged collector with bellmouth exit

to provide a venturi effect (Courtesy of Hytech Exhausts)

SolidWorks CAD design of a WTC exhaust

system and image of the manufactured

exhaust (Courtesy of SS Tube Technology)

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FOCUS : EXHAUSTS

ManufactureThe fundamental processes in exhaust manufacture

have varied only minimally, if at all, in recent history.

Almost unanimously, the companies queried during

research for this article say the fabrication processes

are by and large still the same.

Stock tubing is mandrel bent to form the various

bends required, then manually welded with the use

of jigs and fixtures to ensure maximum accuracy. The

use of an internal mandrel during the bending process

permits the use of thinner walls without the tube wall

collapsing during bending, although different materials

have different limits in this regard.

Inconel (a nickel alloy which we will discuss later) is

one of the more difficult materials to bend successfully;

however, Inconel tubing as thin as 0.5 mm has been

seen in Formula One in the past, while current systems

have moved to thicknesses in the 0.7-1.2 mm range to increase their

reliable service life, so the limits of the mandrel bending process are

not currently limiting the design and manufacture of exhaust systems.

The use of CNC bending to form multiple bends is rarely practical

for the tortuous shapes required of most systems, as there is insufficient

straight length between bends that can be gripped, so systems are

usually manufactured in a series of smaller sections that are then

welded together. TIG welding is the near-universal process of choice

for joining exhaust sections, with shield gas purged on both sides of

the tube to ensure a high-quality weld without oxidation on the back

face. Each weld is dressed inside and out before the next section is

welded and becomes inaccessible.

Where more complex shapes such as collectors are desired,

these can still be fabricated from tube stock, although naturally the

complexity, time and cost is greater. An alternative is to form any

complex shape from a pressing; for example, two halves of a four-

into-one collector may be stamped in a hydraulic press and then

welded together. Pressings are particularly useful where dramatic

changes in section away from a circular tube are desired, and so

can be achieved so long as a press tool can be machined to give the

shape required.

While these processes may sound relatively simple, there is an

impressive amount and range of accumulated knowledge, techniques

and indeed the variety of physical tooling required to offer any

appreciable range of bends, shapes and thicknesses in several

materials, as well as in the understanding of the limits to which

each material can be pushed in terms of minimum thicknesses and

bend radii without distorting or reducing the cross-sectional area

throughout the bend.

Some larger exhaust manufacturers also make their own tubing

from stock sheet material where particular thicknesses or diameters

are not readily available off the shelf, rolling sheet material and then

using automated seam welders to achieve the tube form desired. This

is particularly true of the more exotic materials such as Inconel or

titanium, with very few sizes of tube available at a reasonable cost.

Complex exhaust systems are rarely fabricated in a single piece;

more often, several sub-assemblies are fabricated and then joined

together to allow sections to be removed, replaced or altered to suit

development or in case of damage.

Several fastening methods are also used throughout racing,

depending on the application. Bolted flanges are commonplace

on the average roadcar, but they are a weighty solution for a race

54

t

Press tools and fabricated bends for section changes

in Inconel 625 (Courtesy of Good Fabrications)

Formula Three exhaust system; note the sheet metal

tabs and links (Courtesy of Prototechnik)

Four-into-one collector showing swaged slip joints that allow

for some movement of the system, and a clamp ring on the

exit side (Courtesy of Burns Stainless)

RET_ADTEMP.indd 1 06/02/2013 20:31

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exhaust, although they are often necessary to provide

sufficient mechanical strength when mounting a

turbocharger. For most systems, a joint which has

a degree of movement is typically preferred as

the higher temperatures cause significant thermal

expansion of the materials used, so any joint

must make allowance for this. Sheet metal tabs

and fastenings are popular as they provide a very

solid connection, but allow sufficient movement.

In applications with significant vibration, such as

dragster engines or motorcycles, a spring clamp

solution is often used, which is also very quick

to remove and replace. For some more solid

connections, a Jubilee clamp-type arrangement is

adopted, with two rings welded to the tube on either

side of the joint, the clamp then mating the two.

MaterialsA wide range of materials are used for exhaust manufacture,

depending on the application and budget available. Mild steel is often

used for its low cost and ready availability in a wide range of tube

diameters and thicknesses. However, it can be a high-maintenance

choice, as it readily oxidises at high temperatures and may need

repeated application of paints or coatings. On the other hand it is low

cost, and is a particular favourite in off-road racing or rallying, where

exhausts are likely to be frequently damaged.

Most widely used are the austenitic grades of stainless steel, typically

300 series alloys. The chromium content of stainless steel enhances

its high-temperature oxidation resistance and mechanical strength,

permitting thinner sections to be used at higher temperatures than mild

steel, yet it is still widely available at moderate cost. 304 stainless is

Comparison of potential exhaust materials according to mechanical properties with increasing temperature

(Source: References 1 and 2)

RS Fabrications, Thorpe House, Thorpe Way, Banbury, OX16 4SPtel +44 [0] 1295 266655 fax +44 [0] 1295 266695

e-mail russell@rsfabrications.com

Visit us at www.rsfabrications.com

RS Fabrications specialise in all aspects of Vehicle Performance Engineering & Fabrication, from Design Concept, CAD Design, Manufacture, Inspection and Installation.

Technical, passion & artPietro FASOLI –

Creating Racing Exhaust Systems by hand since 1990

 – Calculation, project management, build & tuning

– We cater for exhaust systems of all diameters and lengths with optimized volumes

– Pipes are calculated to the specific technical characteristics of the engine

www.lamarmitta.it | fasolipietro@gmail.comTel: +39 045 8200 435

Mobile: +39 338 1467 777La Marmitta s.n.c., Verona, Italy

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FOCUS : EXHAUSTS

for improved mechanical properties, above about 4wt% the alloys

rapidly become unweldable, suffering significant cracking problems

and limiting their potential use in exhausts.

An alternative alloy is Inconel 718, which is strengthened with γ’’

(gamma double prime) precipitates based on niobium additions that

precipitate more slowly than γ’ to achieve better mechanical properties

than a solid solution strengthened alloy, but without cracking during

welding. Other advantages of the Inconel alloys are their low thermal

expansion at high temperatures, which aids in keeping exhausts

geometrically stable as well as reducing the propensity to crack after

repeated thermal cycling compared to stainless steel. Inconel’s low

thermal conductivity can also be beneficial in controlling heat transfer

out of the exhaust and into the engine bay.

The use of titanium is quite limited in exhaust systems. Although its

low density is in its favour, its mechanical properties decrease rapidly

above 500 C, making it suitable only in low-temperature exhausts or

for tail pipes, rather than primaries or collectors. It is most commonly

found in motorcycle applications, as airflow is easily available to keep

the material within its operating limits. Rather than using exotic (and

correspondingly expensive) alloys, it is actually more common to find

titanium used in its commercially pure form.

The move to turbochargers in Formula One in 2014 is expected

to see exhaust gas temperatures rise beyond 1050 C, with higher

typically used for exhaust gas temperatures (EGTs) below 760 C

(1400 F), with 321 stainless preferred above this temperature in

turbocharged applications or for rotary engines. Where the EGT exceeds

980 C (1800 F) then nickel-based superalloys such as Inconel are the

only realistic choice for a lightweight exhaust that can still endure the

mechanical loads and resist oxidation at these high temperatures.

Inconel is a notoriously difficult material to work with, being hard to

bend or machine as it rapidly work-hardens. The most common version

in use is Inconel 625, a solid solution strengthened alloy (where the

dissolution of a strengthening element within a single-phase alloy

prevents the movement of dislocations, so strengthening the alloy)

based on nickel and chromium with additions of molybdenum, iron

and niobium among other elements. This particular alloy is relatively

weldable in comparison to some of the other nickel-based alloys

available, although its mechanical properties at high temperatures are

lower than some of the more troublesome nickel alloys.

Most very high performance superalloys are based on a precipitation

hardening mechanism, (where a second metallurgical phase is formed

or precipitated to strengthen the alloy) using additives of titanium

or aluminium to provide high-temperature mechanical strength and

creep resistance (known among nickel alloys as γ’ or gamma prime

strengthened alloys). The problem with γ’ strengthened alloys is that

although increasing concentrations of titanium and aluminium provide t

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58

FOCUS : EXHAUSTS

working with Inconel or titanium. Its use could dramatically simplify

the development and manufacturing cycle of high-end exhausts, where

rapid design iterations are required. Indeed, one supplier queried for

this article manufactured 16 different exhaust designs for one Formula

One team over last year’s 20-race season, as the team attempted to

regain the aerodynamic benefits lost with the ban on blown diffusers.

ALM is proving itself as a technology for manufacturing high-

performance components, and is now a serious contender for the

manufacture of high-performance exhaust components when used

sensibly. For example, it would be folly to produce a complete exhaust

system using the technology, but its use for the manufacture of the

more complex components such as collectors and flanges/headers

makes a great deal of sense, particularly as several headers of differing

geometries could be made simultaneously to reduce the unit cost.

The manufacture of headers – that is, the flange and first inch or so

of exhaust – cuts out a lot of complex fabrication time, while also

permitting a greater range of geometry to be explored in this critical

section. A gain of a few millimetres or degrees in the shapes possible

here can dictate the position of the rest of the exhaust quite significantly.

It is worth noting that ALM processes are essentially small-scale

repetitive welding operations, so similar limits of weldability apply to

the materials that can be processed in this manner. Currently though,

stainless steel, titanium and Inconel 625 & 718 are all readily available.

Post-processing and inspectionThe manufacture of an exhaust system does not stop once the

components are welded together; various post-processing steps often

take place depending on the delivery requirements. These can take the

form of a simple visual inspection of all welds for cracks or defects,

and a test fitting of the exhaust onto the vehicle. As the margin for

error decreases in the search for greater performance, other processes

are turned to, to ensure the system is capable of withstanding the loads

involved or that it will fit into an exceptionally tight space.

For some materials such as titanium or Inconel, a post-weld heat

treatment regime may be defined to relieve any residual stresses in

the weld area, as well as to normalise the microstructure and improve

ductility in the welded material. Shot-peening surface

treatments may also be specified, which induce a

compressive stress in the surface of the weld zone –

again, combating any residual tensile stresses from the

weld process.

According to one surface treatment supplier, the

shot-peening process has recently been given an added

layer of sophistication, in the form of a completely

automated process, based on an eight-axis robotic

system. The benefit of this system is in its dexterity, as it

can provide greater fluidity of movement and so a more

continuous and controllable process. This also provides

the ability to vary the parameters of the process, rather

than treating the whole exhaust system in the same

manner, so reducing or increasing the compressive

stresses imparted to the material for different areas of

the welds/tubes as required. The peening process can

mechanical loadings both from internal gas pressure and the turbo

unit itself, increasing the demands on exhaust materials. This could

potentially raise the game in terms of the materials used. If Nimonic

alloys can be successfully fabricated – remember they are classed

as unweldable – or otherwise manufactured then they could be a

potential candidate to keep the system weight down.

Additive layer manufacturingThe use of additive layer manufacturing (ALM), where metallic

powders are melted with a laser beam to form fully dense

components, is a possible alternative route to fabricating complex

exhaust components. The geometric freedom available to designers

when manufacturing components in this manner allows exhaust

shapes to be made that would otherwise be incredibly difficult or

time-consuming to fabricate.

The usual cost barriers to the use of ALM are reduced in the field

of exhaust manufacture, where material costs are high anyway when t

Titanium exhaust system for the Ducati Panigale; note the

spring clamps and lightweight carbon fibre heat shields

(Courtesy of Akrapovic)

ALM exhaust primary in Inconel 718 (Courtesy of EOS)

HyTech Exhaust IncDeveloping & manufacturing racing exhaust since 1984

Anti-reversion technologyStainless-Inconel-Titanium

Custom bending & fabrication

HyTech introduces the Nozzle Merge CollectorState of the art design using CFD technology

Increased velocity & scavengingAvailable in 2, 3, 4, 5 into 1 designs

Patent # US20100146956A1

HyTech Exhaust Inc12 Hammond Dr. Suite 203, Irvine, CA 92618

949-581-2181hitechexhst@earthlink.net • www.hytechexhaust.com

RET_ADTEMP.indd 1 06/02/2013 20:36

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60

solution may be used to keep the external surface

temperatures down. Where possible, cooling airflow

can be encouraged over the exhaust as well, although

in formulae where aerodynamics are important, this can

come at a penalty to drag, so is preferably minimised.

Perhaps the lightest insulating solution is a ceramic

thermal barrier coating. Typically, such coatings are

based on a zirconia-type material and applied via

proprietary plasma spraying techniques, the aim of

which is to increase the porosity of the coating to

enhance its function as a thermal insulator. While

high-quality exhaust wrapping can reduce the

temperature by a similar degree, its performance can

decline with use, requiring renewal, while ceramic

coatings last the lifetime of the exhaust.

One manufacturer of ceramic coatings quotes a

33% reduction in surface temperatures, a significant reduction in heat

being transferred to the engine bay or sidepods. However, possibly

the greatest benefit of a ceramic coating is its minimal volume and

weight, requiring no additional space for packaging. Ceramic coatings

can be applied to any exhaust material, although differing sub-layer

treatments are used to ensure the coating adheres correctly, providing

a highly durable solution. Also, and while perhaps not a particularly

functional benefit, coloured coatings are becoming increasingly

popular to add some extra ‘bling’ to the style-conscious racer’s engine

bay!

Possibly the ultimate in surface temperature reduction is achieved

through the use of exhaust lagging, typically a sandwich construction

using two thin sheets of stainless steel or titanium encapsulating

an insulating core. The thermal performance of this system is quite

exceptional, with a 3 mm thick lagging reducing exhaust surface

temperatures from 750 C to less than 120 C, or for maximum effect,

a 6 mm lagging resulting in a surface temperature of a mere 65 C – a

reduction of more than 90%.

Due to its metallic outer layers, this lagging is pressed into shape

and is relatively rigid. As such, it can be manufactured as a removable

shell around components, or indeed a simple bag around the entire

exhaust system that can then be vented to the car’s exterior in a

serve to improve surface finish around the weld area as well, reducing

the number of potential crack initiators, while the resulting clean

surface also aids in visual crack detection.

Depending on the geometric tolerances demanded by the

application, several high-end exhaust manufacturers use coordinate

measuring machines to validate the geometry of the manufactured

system before delivery to the customer. More recently, laser

scanning systems have been developed to provide a faster method

of validating the geometry, generating a ‘point cloud’ that can

be compared to the original CAD surface. As laser scanning is a

relatively quick and easy process, it can be performed between

manufacturing steps (such as before heat treatment and then again

afterwards) to aid in understanding the effect each process has on

the geometry of the exhaust.

Non-destructive testing may also be used to ensure that welds are

free of cracks and porosity before delivery. Typically this may include

the use of fluorescent penetrant inspection (‘dye pen’) or eddy current

detection methods.

Coatings and thermal managementExhaust systems are often packaged in very tight and enclosed spaces,

particularly in single-seater or Prototype racing. This creates problems

not only for the physical packaging of the exhaust but also its thermal

packaging, raising underbody temperatures and preventing sensitive

components from being located too close to the hot exhaust.

In reality, thermal management of the exhaust is a double-edged

sword. Insulating the exhaust reduces temperatures for the surrounding

components and allows tighter packaging, but it also retains heat

in the exhaust, raising the demands on the material to survive yet

higher temperatures. This is one reason motorcycles can often happily

implement an all-titanium exhaust, as cooling airflow is readily

available to keep exhaust temperatures low and still enjoy very tight

packaging solutions.

Traditional heat shielding solutions can include simple metal shields

to prevent accidental contact and the transmission of radiant heat, or

exhaust wraps/tapes that insulate some of the heat within the exhaust.

For high-temperature turbocharger applications a double-walled tubing

Validation of critical exhaust geometry by laser

scanning (Courtesy of Good Fabrications)

Thermal lagging reduces exhaust surface temperature

to 65 C (Courtesy of SS Tube Technology)

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61

particularly rally cars. Catalysts promote the reduction of harmful

emissions by converting exhaust products in a controlled reaction on

the surface of a catalyst, (typically a ceramic matrix or monolith) once

a certain ‘light off’ temperature is reached. Most modern catalysts

are termed ‘three way’, converting three harmful exhaust products –

carbon monoxide, unburnt fuel (hydrocarbons) and nitrogen oxides

– into less harmful carbon dioxide, nitrogen and water vapour.

Emissions are therefore not reduced until the catalyst reaches a certain

temperature after starting the engine and conditions are correct for the

reactions to take place (for petrol catalysts this is typically 280 C), so

ideally a close-coupled catalyst will have the best emissions efficiency

but will be most detrimental to exhaust back-pressure. While this is

true in conventional automotive scenarios, the much higher exhaust

temperatures of race engines usually mean the catalyst can be placed

further downstream without too much concern.

The catalyst’s monolith typically has a construction much like a

bundle of drinking straws, aligned with the exhaust gas flow. The

number of cells per square inch (CPSI) is used as a measure of the

density of the catalyst monolith, with a smaller number of cells

indicating a less dense construction that will reduce exhaust back-

pressure but at the cost of available surface area for the catalytic

reaction to occur. Racing catalysts typically use monoliths with

between 100 and 200 CPSI, compared to OEM catalysts which are

between 400 and 600 CPSI; FIA rules require only that the catalyst

reduces the engine’s emissions by half compared to the same engine

without the device fitted.

The material used for the catalyst substrate also differs. While OEM

units use a ceramic material, racing catalysts use stainless steel, which is

better at withstanding the extreme vibration of a race engine installation.

One manufacturer queried provides an additional system, a

divergent section of exhaust that creates a ‘vortex’ or low-pressure

effect to ‘vacuum’ exhaust gases out of the exhaust or any emissions

treatment system, and so increase performance or minimise the impact

of installing a DPF or catalyst – or indeed help to reduce turbo lag.

ConclusionsWhile the fundamental methods of exhaust design and manufacture

have undergone few changes in the past 10 years or so, it is in the

manner that is either convenient or indeed

beneficial to aerodynamic performance.

While the weight of the system is a disadvantage

when compared to some other solutions (estimated

to add perhaps 700 g to a full V8 exhaust system)

its potential to reduce underbody temperatures and

so provide packaging or cooling benefits is worthy

of serious consideration. Indeed, the potential

for aerodynamic benefit is quite exciting if the

sidepods of a single-seater car can be reduced in

size without increasing the underbody temperature.

Insulating the exhaust so effectively also means

that more energy remains available in the exhaust

gas itself for the purposes of aerodynamic use, or

indeed to power a turbocharger, if fitted.

Such complete insulation does bring its own problems though.

While exhaust gas temperatures are very high, typically the exhaust

material itself does not attain the same temperature, working at

some point below peak EGT thanks to heat lost to the surrounding

environment. If the exhaust is insulated, however, this raises the

demand on the exhaust material, as less heat is radiated to the

environment and the working temperature of the exhaust material

is likely to be raised closer to the actual temperature of the exhaust

gases. For some applications this may not be a particular issue, but

it is worth considering if for example the system is turbocharged and

exhaust temperatures are already very high.

EmissionsEmission control systems are a relatively rare sight within the racing

powertrain world, but that is unlikely to remain the case in an

increasingly environmentally conscious society if motorsport wishes to

maintain roadcar relevance.

Possibly the best known emissions devices to be found in racing

are the diesel particulate filters (DPFs) used in the exhaust systems of

the diesel Le Mans Prototype cars. These have a filter material to trap

the soot particulates from diesel combustion that would otherwise

exit the exhaust in an unsightly cloud of smoke. Once trapped, the

soot particles are periodically burnt off, in a process usually termed

‘regeneration’, at a temperature of about 700 C, which can be

achieved by using fuel additives to trigger a burn in the filter or by

directly injecting an additive or fuel into the filter. Two pressure sensors

monitor the exhaust gas pressure drop across the filter unit, providing

information on when a regeneration cycle is becoming necessary.

Implementing such devices in the exhaust system can have a

significant impact on its design and layout. For example, the Audi R18

moved the exhausts for its diesel V6 to sit between the vee banks, rather

than outside, moving to a ‘hot side inside’ configuration, as seen on

some Formula One turbo cars of the 1980s. This is not only beneficial

to a car’s overall aerodynamics, it also allows for a single larger

turbocharger, meaning that the downstream exhaust requires half the

components, and particularly only one DPF, rather than the two needed

when keeping the two banks separate, so reducing weight for the system.

Catalytic converters are used in many national racing series,

FOCUS : EXHAUSTS

t

Complex V12 exhaust system with 6-3-2-1 layout and

mechanical fastenings (Image courtesy of RS Fabrications)

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62

SOME EXAMPLES OF EXHAUST SYSTEM MANUFACTURERS & SUPPLIERS

UK Alunox Exhaust +44 1978 851100 www.alunox.co.uk

Ashley Competition Exhausts +44 1922 720767 www.ashleycompetitionexhausts.com

BTB Exhausts +44 1327 261 797 www.btbexhausts.co.uk

Chris Tullett Exhausts +44 1296 483777 www.christullettexhausts.com

Good Fabrications +44 1844 202 850 www.goodfabs.com

Jetex Exhausts +44 1789 298989 www.jetex.co.uk

JP Exhausts +44 1625 619916 www.jpexhausts.co.uk

Milltek Exhausts +44 1332 227 280 www.millteksport.com

OJZ Engineering +44 1777 248844 www.ojzengineering.co.uk

Primary Designs +44 1844 216057 www.primarydesigns.co.uk

RS Fabrication +44 1295 266655 www.rsfabrications.com

Scorpion Exhausts +44 1773 513730 www.scorpion-exhausts.com

Simpson Race Exhausts +44 1753 532222 www.simpsonraceexhausts.com

SS Tube Technology +44 1865 731 018 www.sstubetechnology.com

Vortex Exhaust Technology +44 1708 861078 www.vortex-performance-exhausts.co.uk

USBeyea Custom Headers +1 315 497 1215 www.beyeaheaders.com

Borla +1 805 986 8600 www.borla.com

Brocks Performance Products +1 937 912 0054 www.brocksperformance.com

Burns Stainless +1 949 631 5120 www.burnsstainless.com

Coast Fabrication +1 714 842 2603 www.coastfab.com

Dynatech +1 812 897 3600 www.DynatechHeaders.com

HyTech Exhaust +1 949 581 2181 www.hytechexhaust.com

PRO-FABrication +1 704 795 7563 www.profabrication.com

Pypes Performance Exhaust +1 215 712 9982 www.pypesexhaust.com

Reid Washbon Racing Exhausts +1 949 548 9783 www.reidwashbonracing.com

Specialty Products Design +1 916 635 8108 www.spdexhaust.com

ARGENTINAConforma +54 3462 429604 www.conformainox.com.ar

FRANCEAtelier Chabord +33 450 221402 www.echappement-chabord.fr Devil +33 4 75 84 74 90 www.devil-exhaust.com

GERMANYHJS Fahrzeugtechnik +49 2373 9870 www.hjs.com MHG Fahrzeugtechnik +49 71739 27330 www.mhg-fahrzeugtechnik.de Prototechnik +49 7171 8748 100 www.prototechnik.de

ITALYArrow Special Parts +39 075 861811 www.arrow.it La Marmitta +39 045 8200435 www.lamarmitta.it ZARD +39 0141 659239 www.zardexhaust.com

SLOVENIAAkrapovic +386 1787 8404 www.akrapovic.si

FOCUS : EXHAUSTS

refinement of the process and the use of new validation and design

tools where recent progress has been made.

The global trend towards turbocharged engines for higher efficiency

is pushing the limits of exhaust materials, providing an interesting

future for novel exhaust manufacture in the near term. The potential for

waste heat or energy recovery from exhaust gases is also likely to be

an arena of interesting development.

AcknowledgementsThe author would like to thank Mike Dewhirst of SS Tube Technology,

Neil Morgan of Good Fabrications, Colin McGrory of Sandwell UK,

Chris Tullett of Chris Tullett Exhausts, Pietro Fasoli of La Marmitta, John

Bowers of JP Exhausts, Vince Roman of Burns Stainless, Christoph

Abele of Prototechnik, Gary Donahoe of Coast Fabrication, John Vella

of AM Group Redback, Mijta Reven of Akrapovic, John Grudynski of

Hytech Exhaust, Barry Mead at Vortex Exhausts, Grant Cameron and

Steve Sousley at PRO-FABrication, Stuart Jackson of EOS and Raffaele

Rosi of Arrow Exhausts for their invaluable assistance and insight in

writing this article.

References1. “Springer Handbook of Condenser Matter and Materials Data”,

2005, Springer Berlin Heidelberg

2. “High Temperature Characteristics of Stainless Steels”, no 9004,

American Iron and Steel Institute

n

RET_ADTEMP.indd 1 07/02/2013 15:10

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