FORCED

INDUCTION

TECHNICAL

MANUAL

 

 

 

 

 

 

 

 

Copyright Thunderhawk Performance, Inc., 2007

 

 

Avon Lake, Ohio

Phone: (216) 965-4800

www.thunderhawkperformance.com

 

 

 

 

 

 

 

 

 

 

 

 

FORCED INDUCTION TODAY

 

 

 

            Forced induction has become increasingly popular over the past 20 years, and is the top choice among hot-rodders and racers to significantly increase the horsepower output for today’s high-performance cars.  Factory stock Mustangs, Camaros and Corvettes continuously get faster year after year, but the addition of an intercooled turbocharger system can catapult these cars into the “supercar” category.  The advent of computer controlled fuel injection on automobiles in the late 1980’s and early 1990’s was primarily responsible for bringing turbocharging and supercharging into practical use on daily-driven vehicles.  By comparison, anyone who has experienced a carbureted turbo car can testify that the results were….well, less than spectacular. 

 

With fuel injection now coming as standard equipment on newer ATV’s and utility vehicles (UTV’s), forced induction is now positioned to become the top choice to reliably increase horsepower for UTV’s while retaining the drivability required for everyday use.  The days of temperamental carburetors, engine tear-downs to replace internal parts and constantly making trips to buy race fuel at $7-$8 per gallon are over.

 

All turbochargers and superchargers function in the same manner to increase horsepower.   By compressing the air entering the engine, more oxygen molecules are supplied to the engine without the need to increase displacement with big-bore kits or strokers.  When the corresponding correct proportion of fuel is delivered to the forced induction engine, a significant horsepower improvement will be realized which cannot be accomplished by any other means.  In purpose-built turbocharged race engines, a 150 to 300% horsepower increase can be accomplished.  For daily-use vehicles, engines are typically tuned to achieve a 50 to 100% horsepower increase.

 

            There are different types of compressors currently being used in mass produced forced induction kits.  Each compressor has its advantages and disadvantages, and each will increase horsepower to varying degrees.  There are also parasitic losses to consider when deciding on a type of compressor.  Other major components in a forced induction kit are also necessary, such as intercooler, fuel systems and engine management, and should be carefully considered as well. The primary factors which should be taken into consideration when deciding on a forced induction system are:

1.      Compressor Type – boost curve and airflow capacity

2.      Intercooler – type and efficiency

3.      Fuel System – adequate fuel flow and proper fuel management

 

Thunderhawk Performance has published this FORCED INDUCTION TECH MANUAL in order to provide a basic overview of the technical aspects involved in the design of a properly engineered forced induction system.  Just as we witnessed in the 1990's in the high-performance automotive market, you are going to find many poorly designed turbo and supercharger systems being rushed into the UTV market simply to fill consumer demand.  Many of these systems will feature major design flaws that the customer ends up paying for in poor performance, drivability and reliability.  Since we've been involved in the design and manufacturing of forced induction systems for over 15 years, we've seen this whole episode play out before.  This is why we've updated our FORCED INDUCTION TECH MANUAL and published it - for a whole new generation of horsepower junkies, and their UTV's.

 

 

 

 

 

 

 

 

 

 

 

 

TURBOCHARGER AND SUPERCHARGER COMPRESSORS

           

 

 

EFFICIENCY

 

The centrifugal supercharger and the turbocharger are the most common types of compressors currently available in forced induction kits designed for installation on high-performance engines.

           

Any time air is compressed, the temperature of the air will be increased.  This phenomenon can be described by Boyle’s Law, and is a basic part of every physics course.  By using Boyle’s Law, the theoretical temperature increase can be calculated for a perfect situation (100% efficiency).  Since no man-made compressor is 100% efficient, an adjustment must be made to reflect the actual conditions.  This is known as adiabatic efficiency, and typically runs between 50% and 80% for these compressors.  In addition, the actual “real world” efficiency varies with outside air temperature, flow and pressure, meaning that some averaging is required.  The efficiency of the compressor directly affects the temperature of the air charge (boost), which can affect net horsepower by 10 to 50%. 

 

 

 

 

BOOST CURVES

 

One consideration for any daily-use vehicle is the fact that any type of compressor you choose will spend a majority of the time working against partially or even fully closed throttle plates (cruising or decelerating) and operating at relatively low engine RPM’s. 

 

Centrifugal superchargers are driven by a belt in direct proportion to engine RPM.  Therefore, these superchargers tend to have a rather poor boost curve, with advertised boost being produced only at peak RPM.  If a supercharger manufacturer selects pulleys that produce 10 PSI boost at 7000 RPM’s, then this supercharger will produce only 5 PSI boost at 3500 RPM’s and approximately 7 PSI boost at 5000 RPM’s.  This centrifugal boost curve (supercharger lag) leaves the average driver without the full benefit of forced induction in many daily-use circumstances. 

           

Turbochargers can produce a very desirable boost curve, where full boost is available at lower RPM’s.  Since the turbocharger’s output (boost) is not directly related to engine RPM’s, a turbocharger can be selected to produce full boost (for example, 10 PSI) at 2500-3500 RPM’s.  Once full boost is achieved, the turbochargers wastegate bypasses exhaust energy past the turbine wheel, thereby limiting boost to the pre-set 10 PSI all the way up to the engines redline.  This low RPM boost produces much greater torque and horsepower in normal daily-driving situations, which is the useable power and torque that you feel when you “punch it”. 

 

 

 

 

PARASITIC LOSSES

 

Many factors affect the final horsepower output available to drive the wheels.  The method used to drive the compressor has a significant effect on the horsepower delivered to the ground.  Superchargers are driven by the engine’s crankshaft via a V-rib or cogged belt.  The horsepower required to actually turn the supercharger is therefore produced by the engine and then lost to this parasitic horsepower draw.  Most automotive street-type superchargers (Vortech, Paxton, etc.) require 30 to 50 horsepower to drive at peak boost.  The smaller superchargers used on UTV’s require 12 to 20 horsepower to drive at peak boost. 

 

This parasitic horsepower loss with superchargers has a “domino effect” on the vehicle set-up and tuning.  The fuel system must supply sufficient fuel to support the total horsepower produced by the engine, which includes the parasitic drive losses, in addition to the horsepower which is actually delivered to the wheels.  This taxes the fuel system and aggravates drivability issues as larger fuel pumps and injectors are required.  The production of horsepower lost to the parasitic drive of the supercharger also places additional demand on the engine, including increased load on the pistons, crankshaft and rods, thereby shortening engine life. 

 

Turbochargers are driven by the engine’s exhaust gas via a turbine wheel placed in the exhaust tract.  Although it would appear that the exhaust gas movement drives the turbine like a fan, the turbine is actually driven by the heat energy in the exhaust.  Even though the exhaust temperature at the engine is the same as any forced induction engine, a well designed turbo installation will result in a 300 degree temperature drop across the turbine wheel as this heat energy is used to drive the turbo.  This heat energy would otherwise be wasted to the atmosphere through the exhaust system.  With properly engineered turbine sizing, engine pumping losses (exhaust back pressure) at wide-open throttle are insignificant.

 

 

 

 

SUPERCHARGER DRIVE BELTS

 

The belt drive used on a supercharger is susceptible to slippage and failure.  Supercharger belt slippage is common, as illustrated by the use of extra wide V-rib belts on high-boost street applications and cog tooth belts on high performance racing applications.  Unfortunately, cog tooth belts are not practical for daily, extended use.  The most common causes of belt slippage for a standard V-rib supercharger drive belt are small diameter pulleys, higher boost levels and improper belt adjustment & maintenance.  Belts and pulleys can also be damaged by small debris that causes abrasive wear on the contact surfaces between the belt and pulleys.  This abrasive wear causes belt slippage rather quickly and can also lead to thrown belts.  If large debris manages to contact the belt or get lodged between the belt and pulley, this will cause immediate belt failure, pulley damage and could possibly damage the supercharger shaft and bearings.  

 

Supercharger drive belt performance and reliability is a major concern for UTV’s, due to the exposed supercharger drive belt in the off-road environment.  Although dust does not contribute significantly to abrasive belt and pulley wear, small particle contamination (such as sand) does cause significant abrasive damage.  Without a sealed belt enclosure to protect the supercharger drive belt, a UTV should be restricted from traveling anywhere that the belt may be exposed to water, sand or mud, or where sticks, rocks or any other large debris may come in contact with the belt. 

 

 

    

 

TURBO HEAT

 

A common misconception surrounding turbochargers is that they “build” or “create” heat.  Turbochargers do not “create” heat, they use the exhaust heat which is created by the engine, through the combustion process.  Exhaust gas temperatures from a gasoline engine exceed 1000 degrees, and this heat is directed away from the vehicle through the exhaust system.  For a naturally aspirated or supercharged engine, this exhaust heat travels from the cylinder head exhaust port, through the header and is then discharged to the atmosphere through the muffler.  For turbocharged engines, this same exhaust heat travels from the cylinder head exhaust port, through the header, then passes through the turbocharger turbine housing before it exits through the muffler. 

 

Despite the fact that turbos do not create heat, the problems associated with turbocharger heat are very real.  Although this reputation is not justified, turbo systems have all been branded as having heat problems.  This reputation is based on the fact that there have been many turbo kits over the years which were not properly designed to address exhaust heat issues, causing major turbo heat problems for their owners. 

 

On stock vehicles, the manufacturer has designed the exhaust system so that exhaust heat is routed away from heat sensitive components and has provided heat shielding to protect any items that are located near the exhaust heat.  Modified naturally aspirated engines and supercharged engines benefit from these factory designs, since they retain the stock exhaust system.  Aftermarket headers and exhaust systems frequently re-route the exhaust system to improve flow, which is known to cause heat issues in many cases.  With a turbocharger system, the exhaust system must also be re-routed.  Correct turbo placement, proper exhaust routing and adequate heat shielding are proven to eliminate turbo-related heat problems.

 

 

 

 

AIRFLOW CAPACITY

 

The airflow capacity of each compressor is another issue altogether.  Airflow capacity is the measurement of the maximum amount of air that a certain compressor is capable of flowing at a given efficiency.  This number is usually measured in lbs/min (mass), but certain companies use CFM (volume).  When airflow is measured in CFM, an adjustment must be made for air temperature.  The same mass (lbs/min) will increase in volume (CFM) due to the temperature increase created by compressing the air (Boyle’s Law, see Appendix).  This causes the advertised CFM to increase, although no additional air is available for the engine to consume.  In order to calculate this temperature increase, the compressor efficiency must be known.

           

Today’s centrifugal automotive street-type superchargers have adequate airflow capacity to produce up to 650 horsepower at between 60 and 70% efficiency with the typical centrifugal boost curve.  Race-type automotive centrifugal superchargers can exceed 1500 horsepower at 60% efficiency, although their boost curve is much poorer.  Today’s single turbo automotive kits have adequate airflow to produce up to 1000 horsepower; however, turbo lag is still a significant problem with these big turbos. 

 

The centrifugal supercharger, which is commonly used for UTV applications has adequate airflow capacity to deliver up to 110-115 horsepower at 71% efficiency with the typical centrifugal boost curve.  The turbocharger used by Thunderhawk Performance in our UTV turbo systems can deliver up to 130 horsepower at 76% efficiency, without significant turbo lag.

 

The choice of a particular type of compressor comes down to two basic questions:

1.                            What is the lowest engine RPM at which the compressor develops maximum boost?

2.                            Does the compressor have sufficient airflow capacity to supply the maximum horsepower level you require?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INTERCOOLING

 

 

 

INTERCOOLER FUNCTION

 

Intercoolers have only recently been getting the attention they deserve.  Whether called an intercooler or aftercooler, their function is the same.  The air charge (boost) exiting the compressor is cooled (and condensed) and it passes through the intercooler core.  This increases horsepower directly through the decrease in air charge temperature, and also allows your engine to be tuned for a further increase in horsepower due to the decreased temperature and lowered chance of detonation.  Intercoolers eliminate the need to run expensive race fuel in most applications.

 

 

 

 

IS INTERCOOLING REQUIRED?

 

The most common question about intercoolers is “Do I need an intercooler?”  An intercooler is strongly recommended for all forced induction systems (supercharger and turbo), but is not absolutely required below 5 PSI boost.  Above 5 PSI boost, an intercooler should be considered a requirement.  Even the mildest forced induction kits will experience a significant increase in air charge temperature at the boost levels at which they are sold.  Using Boyle’s Law (see Appendix), we can calculate that 7.5 PSI boost will increase the air charge temperature by 90 to 100 degrees (at 70% compressor efficiency).  By utilizing an 80% efficient intercooler, we can reduce this elevated air charge temperature by 72 to 80 degrees, delivering air to the engine that is only 18 to 20 degrees above the ambient outside air temperature.  The reduction in the air charge temperature from intercooling can produce a 10 to 20% increase in horsepower over a non-intercooled engine and significantly reduce the risk of detonation. 

 

Although any intercooler will provide some level of improvement, a properly designed and manufactured intercooler must be correctly sized with respect to the engine’s inlet airflow and compressor efficiency.  Obviously, as the boost levels rise, an intercooler changes from a useful option to an essential component.

 

 

 

 

TYPES AND DESIGN OF INTERCOOLERS

 

            There are two basic types of intercoolers available: air-to-water and air-to-air.  Each type is described below.  As with most aspects of mechanical engineering, both styles have advantages and disadvantages; but the final decision is usually made by vehicle application & usage and by weight & reliability considerations.

           

To properly design and manufacture an intercooler system, many factors must be considered:  the intercooler core dimensions, flow characteristics, internal and external fin specifications, intercooler core construction and end tank design.  This is not a simple exercise.  Intercoolers are rated by their efficiency.  A well-designed intercooler will approach 90% efficiency.  When a system is designed with a proper intercooler, a 10 to 20% increase in horsepower is possible at boost levels as low as 7.5 PSI.  In racing applications with boost levels exceeding 25+ PSI, an efficient intercooler can provide a 30 to 35% increase in horsepower.

 

 

 

 

COMMON INTERCOOLER MISCONCEPTIONS

 

People commonly confuse air charge (boost) temperature with engine coolant temperature.  I guess this is understandable, as we are all trained from age 16 to watch the “engine temp” gauge in our cars.  Of course, this gauge is measuring engine coolant temperature, and we all know it’s bad news if this gauge is pegged.  When discussing a forced induction system and intercoolers, we are not concerned with engine coolant temperature.  Our discussions revolve around air charge (boost) temperature.  This is the temperature of the air entering your engine.  On the station wagon you drove at age 16, the air charge temperature was whatever the outside temperature was on any give day.  With forced induction, the air charge temperature is increased during compression and this elevated air charge (boost) temperature is what an intercooler reduces.  Keep in mind that engine coolant and air charge (boost) temperatures are independent of each other.  I cringe whenever I hear the owner of a non-intercooled supercharger or turbo say “I don’t need an intercooler, I never overheat”.  This is the guy that inevitably turns up his boost and blows the engine; all the time blaming the turbocharger and not the poor design of the turbo system and lack of intercooling. 

 

 

 

 

AIR-TO-WATER INTERCOOLERS

 

            Air-to-water intercoolers utilize water as the medium to remove heat from the charge air.  The intercooler core must be placed in a custom housing located between the compressor outlet and the engine.  For daily-use, a second heat exchanger, located in the vehicles airstream, is required to transfer the heat accumulated by the intercooler water to the outside air.  Air-to-water intercoolers require an intercooler core with properly designed end tanks and a second heat exchanger, plus coolant reservoirs, water pump and fluid transfer hoses which are required to circulate water through the system.  Following are the advantages and disadvantages of choosing an air-to-water intercooler:

 

ADVANTAGES

·        Easier to design – Intercooler location is not dictated by outside airflow.  The heat exchanger installs easily in available space near the engine, with only small fluid transfer hose connections required.

·        Lower charge temperature – When using ice water, in a pure race environment, the air charge temperature can be lowered below outside air temperature (with a large enough intercooler).  However, this is true ONLY when ice water is used.

 

DISADVANTAGES

·        Expensive – Due to the large number of components required.

·        Heavy – Due to the large number of components and the large volume of water that must be carried (typically 2 to 5 gallons, at 8 pounds per gallon).

·        Less efficient – Heat must be transferred twice.  If both intercooler and heat exchanger are 80% efficient, system efficiency is only 64% (.80 x .80 = .64).  The heat exchanger commonly used in production kits resembles a standard oil cooler, and this design is nowhere near 80% efficient.

·        Core rupture – Damage or corrosion to the core may cause a leak, which can fill the engines combustion chamber with water and cause severe engine damage.

·        Ice Melts – Ice water is only practical for use in drag racing and the ice must be replaced after every run to maintain consistent air charge temperatures.  For extended periods of operation, such as in daily-use, the intercooler water temperature stabilizes at a relatively high temperature, due to the poor intercooler system efficiency.  This heat-soak provides less air charge temperature reduction.

·        Fluid System Failure – If for any reason (e.g., hose or pump failure) your air-to-water intercooler runs dry, or water circulation stops, practically no cooling effect will take place.  An engine which is tuned and optimized for use with an intercooler will detonate and may be damaged without intercooling.

 

Air-to-water intercoolers are high-maintenance race components.  Their use is limited primarily to automotive drag racing.  Air-to water intercoolers are not suitable for use in a rough environment, such as found in off-road UTV applications.

 

 

 

 

AIR-TO-AIR INTERCOOLERS

 

            There are two types of air-to-air intercooler cores in use today.  Bar-and-plate cores feature heavy-duty construction and are highly efficient.  Tube-and-fin cores are constructed similar to a car’s radiator; they are rather fragile and are far less efficient than a similar sized bar-and-plate intercooler core.  Bar-and-plate intercooler cores are used almost exclusively in any automotive application, even low boost vehicles.  Tube-and-fin cores are used primarily in industrial cooling systems and should be avoided.

 

Air-to-air intercoolers utilize outside air as the medium to remove heat from the charge air (boost) and therefore require that the intercooler be placed in the path of unrestricted outside air.  An air-to-air intercooler installation requires a properly sized and designed intercooler, as well as properly sized ducting from the compressor to the intercooler, and from the intercooler to the engine.  Outside air must also be directed to the intercooler to enable the system to effectively transfer heat.  Following are the advantages and disadvantages of choosing an air-to-air intercooler:

 

ADVANTAGES

·        Highest Efficiency – Results in lowest possible stabilized air charge temperature (assuming properly sized/designed intercooler).

·        Less Weight – No additional components or water to carry.

·        Will not cause engine damage – No water to leak into engine.

·        System failure eliminated – No additional components to fail, causing high air charge temperatures and detonation.

 

DISADVANTAGES

·        Sufficient outside airflow necessary for proper cooling – Intercooler mounting position can cause design difficulties, many variables must be considered when choosing intercooler location.  Fan assistance beneficial in situations with reduced outside air movement.

·        Difficult to design – Sound engineering knowledge is required to design and manufacture a low restriction, high-efficiency air-to-air intercooler.  Properly sized air ducting, to provide adequate airflow for the engine’s horsepower, must be designed to fit properly and clear all components.

 

Air-to-air intercoolers provide the greatest efficiency under a wide range of circumstances, the highest level of reliability and the lowest weight.

 

 

 

 

AIR CHARGE TEMPERATURE TABLES

 

For quick reference, air charge temperatures have been calculated below at various efficiencies and boost levels.  These tables have been prepared for both non-intercooled and intercooled applications to illustrate the dramatic differences in air charge (boost) temperature.  These two tables can also be used to compare air charge (boost) temperatures before and after the intercooler.

 

Non-Intercooled Air Charge (Boost) Temperature

85° (F) Ambient Air

 

 

 

Boost Pressure

 

 

2.5 PSI

5.0 PSI

7.5 PSI

10.0 PSI

12.5 PSI

15.0 PSI

17.5 PSI

20.0 PSI

Compressor Efficiency

100%

110°

132°

152°

171°

189°

205°

220°

235°

90%

113°

137°

161°

181°

201°

218°

235°

252°

80%

116°

144°

170°

193°

215°

235°

254°

273°

70%

121°

152°

181°

208°

234°

256°

278°

299°

60%

127°

163°

198°

228°

258°

285°

310°

335°

50%

135°

179°

221°

257°

293°

325°

355°

385°

 

 

 

Intercooled Air Charge (Boost) Temperature

85° (F) Ambient Air

80% Efficient Intercooler

 

 

 

Boost Pressure

 

 

2.5 PSI

5.0 PSI

7.5 PSI

10.0 PSI

12.5 PSI

15.0 PSI

17.5 PSI

20.0 PSI

Compressor Efficiency

100%

90°

94°

98°

102°

106°

109°

112°

115°

90%

91°

95°

100°

104°

108°

111°

115°

118°

80%

91°

97°

102°

107°

111°

115°

118°

122°

70%

92°

98°

104°

110°

115°

119°

123°

127°

60%

93°

100°

107°

114°

119°

125°

130°

135°

50%

95°

104°

112°

119°

126°

133°

139°

145°

 

 

 

 

 

 

 

 

 

 

 

FUEL SYSTEMS

           

 

 

It should be common knowledge that the increased horsepower produced by any engine will require an increase in fuel delivery to the engine.  This increased fuel delivery may require upgrading just one or literally all of the fuel system components in the stock fuel system.  There are various methods of achieving the necessary increase in fuel flow through each fuel system component; these methods are discussed below.  The only way to determine which fuel system components are sufficient and which will require upgrades, is to test all components in the system.  Manufacturer design and flow data is necessary, with a fuel system flow bench commonly used to generate flow data for the complete fuel system.

 

Stock

Component                                                  Methods of Improvement

______________________________________________________________________

 

Fuel Filter                                                       Larger filter element

                                                                                                Improved connector design

                                               

Fuel Pump                                                     Increase volume (new pump)

                                                Increase voltage to pump

                                                Decrease fuel pressure (reduces injector flow)

                                               

Fuel Lines                                                      Larger diameter fuel line

                                                                                               

Fuel Rails                                                       Larger diameter fuel rails

                                                Improved connector design

                                                                                                                       

Fuel Injectors                                                 Increase fuel pressure (reduces pump flow)

                                                Install larger injectors

                                                Install auxiliary injectors

                                               

Fuel Pressure Regulator                              Install larger regulator

                                   

 

 

 

FUEL FILTER

 

            The filtration of an EFI fuel system is particularly important.  Unfortunately, the more effective the filter is, the more it restricts fuel flow.  The only practical way to exceed a fuel filter flow limitation is to install a larger filter or multiple filters (in parallel).  If appropriate care is taken with regard to the quality of the filter element employed, and the proper installation plumbing is used, either approach is acceptable.

 

 

 

 

FUEL PUMP

 

            In order to supply a specific horsepower requirement, a sufficient volume of fuel must be delivered by the fuel pump.  The electric fuel pumps used in fuel injection systems all have a number of design characteristics in common.

1.                             The fuel pump’s rated output volume capacity applies only at the stated design pressure.

2.                             If the fuel pressure is increased, the fuel pump output volume will decrease.

3.                             If the electric supply voltage is increased, fuel pump output volume will increase.  However, beyond a certain voltage (usually 13.5 volts), pump life rapidly decreases.

 

 

 

 

FUEL LINES

 

            Fuel lines are only capable of supplying a certain limited volume of fuel, due to their diameter.  To exceed this limit, larger diameter fuel lines are required.  The following recommendations are conservative, but can be used with confidence.  The reason for the apparent contradiction of AN- sizing correlating to tubing I.D. is that the fittings used with the AN- hose assemblies have a smaller I.D. than the actual AN- hose, which restricts flow.

 

                        HP @ 40 PSI                        Pipe O.D.                   Pipe I.D.                     AN-size

                        __________________________________________________________________

                         500 HP                                  5/16”                           ¼”                                AN-5

                         750 HP                                  3/8”                             5/16”                           AN-6

                        1350 HP                                 ½”                                7/16”                           AN-8

 

 

 

 

FUEL RAILS

 

            Similar to the fuel line situation, the fuel injector rails must be sized according to the horsepower to be produced.  Fuel rails are capable of supplying a certain limited volume of fuel, due to their volume or to a restrictive supply orifice.  There must always be sufficient fuel volume in the fuel rail at each injector inlet to ensure that the injector will not run dry (be exposed to vacuum/vapor in the rail).  In racing applications, the fuel rails should be plumbed in a circular fashion, so that all injectors receive fuel from both sides.  Extra caution should be taken when two adjacent injectors are required to fire in succession.  For reference, a fuel rail with at least 7/16” I.D. and a dual AN-8 feeds should support 1350 horsepower safely. 

 

 

 

 

 
FUEL INJECTORS

 

Increased fuel injector flow can be achieved by increasing fuel pressure, installing a larger set of injectors, or by adding auxiliary injectors.

           

There are numerous methods available to increase fuel pressure.  A fuel management unit (FMU) is used by many supercharger manufacturers on applications where a return-type fuel system is used.  These FMU’s block off the fuel return line, thereby increasing fuel pressure.  For non-return type fuel systems, an FMU cannot be used, but there are a number of ways to increase fuel pressure to the injectors with these systems as well.  If fuel pressure is controlled through the ECU with a pressure transducer, fuel pressure may be able to be increased through ECU re-programming.  For a mechanical in-tank pressure regulator system, you may be able to replace or modify the regulator to provide additional pressure.  In some cases, a second fuel pump may be added after the in-tank pump and regulator which will increase fuel pressure. 

 

When fuel pressure is increased, fuel volume (through the injector) increases by the square root of the increase in fuel pressure.  Doubling fuel pressure (example: 40 PSI to 80 PSI) only increases fuel volume by 41% (√2 = 0.41).  Increased fuel pressure places an additional load on the fuel injector, since the injector must open against the higher fuel pressure.  Fuel pump output volume and fuel pump life are both significantly decreased when operating at pressures which are greater than the system design pressure.  At excessive pressures, only the most expensive, race-quality fuel pumps can operate reliably.

 

If a larger set of injectors is installed, the engine control computer (ECU) must be recalibrated.  The injector’s pulse width signal from the ECU must be reduced to deliver the correct amount of fuel to the larger injectors under all circumstances.  To accomplish this properly, the appropriate sections of the computer’s internal programming must be accessed and reprogrammed.  If significantly larger injectors are used, the reprogramming may call for excessively small injector pulse widths at idle, which causes unstable injector operation and creates fuel delivery issues at idle.

 

If auxiliary injectors are installed, they must be correctly positioned and properly controlled.  The injectors must be positioned to ensure satisfactory fuel distribution into each intake port.  These auxiliary injectors will also require a properly programmed control unit to guarantee that the correct air/fuel ratio is maintained under all operating conditions.  A properly designed auxiliary injector system allows the fuel pump and all injectors to operate at their design pressure.

 

 

 

 

 

 

 

 

 

 

 

 

COMMON QUESTIONS ABOUT  THUNDERHAWK UTV TURBO SYSTEMS

 

 

 

Q.  Will the Thunderhawk Performance turbo system produce more horsepower than other UTV turbos or superchargers?

 

A.  That depends.  Compressor flow (airflow capacity) and compressor efficiency will determine the maximum horsepower capability of any system.  For UTV applications, the maximum airflow and horsepower capacity of the turbo used by Thunderhawk Performance is greater than that of the typical UTV supercharger, by approximately 15%.  Any UTV turbo kits that use larger automotive-type turbochargers will operate very inefficiently and may experience compressor surge which causes turbocharger bearing failure when these large turbos are installed on a small displacement engine, as used in UTV’s.  Extensive engineering and R&D have allowed Thunderhawk Performance to produce a true daily-use turbo system for UTV’s, which produces maximum horsepower without significant turbo lag.  Our UTV turbo systems produce superior performance for max-horsepower, wide-open operation as well as producing greater torque for real-world trail use.  

 

 

 

Q.  What other parts will I need to purchase when installing the Thunderhawk Performance turbo system?

 

A.  None.  The Thunderhawk Performance turbo system is a complete engineered system.  Thunderhawk Performance does recommend that a high quality boost gauge and a fuel pressure gauge be mounted in plain sight of the driver to monitor these important systems.  If you wish to increase horsepower above the level at which Thunderhawk delivers our turbo kits, we can advise the best way to accomplish your goal and recommend what components may need to be upgraded to match your increased level of performance.  We will continue to run our turbo systems on the dyno and develop upgrades to accommodate your need for speed.  

 

 

 

Q.  How long does it take to install the Thunderhawk Performance turbo system?

 

A.  Typically, one day in a well-equipped garage for someone who has not installed one previously.  The fact that Thunderhawk Performance provides a complete and comprehensive system is the primary reason that this is more than just an “afternoon and a 6-pack” job.  Thunderhawk Performance includes a complete installation guide with full installation instructions, diagrams, photos, recommended tool list and helpful installation tips with every turbo system.

 

 

 

Q.  What type of maintenance does the Thunderhawk Performance turbo system require?

 

A.  No special maintenance specific to the turbo system is required.  Synthetic engine oil should be used and changed regularly, along with the oil filter.  The recommended spark plugs should be changed at recommended intervals for optimum performance.  Air filter maintenance should be performed frequently, as any forced induction system or modified race engine will draw significantly more air than a stock engine.  Thunderhawk Performance has redesigned the complete air inlet system on the RZR to eliminate the dust ingestion problems common to this vehicle.  These air filter upgrades will be available for stock, naturally aspirated RZR’s in early 2008 as well.

 

 

 

Q.  What about turbo bearing failures and “coking”?

 

A.  Turbo “coking” is not a design problem, it is a maintenance problem.  Water cooled turbochargers significantly reduce this potential problem; however proper maintenance should not be neglected.  Regular oil changes and idling the engine for approximately 60 seconds before shut down will practically eliminate “coking” problems.

 

 

 

Q.  How will the Thunderhawk turbo system affect drivability?

 

A.  With the Thunderhawk Performance turbo system, drivability will remain virtually identical to that of stock.  Since a turbocharger does not produce any boost, or create any load on the engine under light throttle, a properly designed turbo system is “invisible” to the engine under normal driving conditions.  However, system design is important, as we have seen many improperly designed or incomplete turbo systems create numerous drivability problems, incorrect fueling, decreased cooling system efficiency, header failures and many other issues.  With 15 years experience designing and manufacturing turbocharger systems, Thunderhawk Performance offers the only UTV turbo system capable of reliable, extended use, under all operating conditions from WOT desert runs to slow, technical trails.

 

 

 

Q.  Does a turbo system increase vehicle noise?

 

A.  No.  The exhaust energy used to drive the turbochargers actually causes a reduction in noise levels. 

 

 

 

Q.  Is an intercooler necessary?

 

A.  Absolutely!  Any properly engineered forced induction system producing over 5 PSI boost will include an intercooler.  Practically every O.E.M. supercharged or turbocharged vehicle manufactured includes an intercooler.  The only companies who have claimed that intercooling is unnecessary, are aftermarket manufacturers and retailers attempting to market artificially cheap packages by providing only half of the necessary components.

 

 

 

Q.  How will an intercooler assist the engine?

 

A.  By reducing the air charge (boost) temperature, engine power is increased, the chance of detonation is decreased, and head gasket, piston and valve life are improved.

 

 

 

Q.  So, any intercooler will help?

 

A.  Yes and no.  There is much expertise required in designing an efficient intercooler system, just as there is in designing any other engine or drivetrain system.  Intercooler size and design are critical.  With a correctly designed intercooler, the boost pressure drop across the intercooler will be approximately 1 PSI or less, and the air charge temperature at the manifold will typically be within 30 degrees of the ambient outside air temperature.  A low-efficiency or undersized intercooler (or one with poor airflow design) may offer some limited improvement; but the improvement will fall far short of that achieved with a properly designed intercooler system.

 

 

 

Q.  Do I need to change my camshaft before I install a turbo system?

 

A.  No.  At lower boost levels, a stock camshaft can be retained with excellent results.  Engines operating at elevated boost levels (high-boost race engines) will usually benefit from a high-performance turbo-grind camshaft, although a stock camshaft still works exceptionally well even at higher boost levels.  Please be aware that most aftermarket high-performance ATV/UTV camshafts have been designed specifically for use on naturally aspirated engines, and may be a very poor choice for use on a turbo engine.  Even the so-called “torque” cams should be carefully evaluated before changing cams.  If you feel that it is necessary to change the camshaft, a custom-ground camshaft designed for the turbocharged engine combination is recommended.

 

 

 

Q.  What is the maximum compression ratio I can use with a turbo system?

 

A.  Modern engines equipped with aluminum cylinder heads can typically operate reliably on premium pump gas at moderate boost levels (7-9 PSI) with compression ratios as high as 10:1.  This will vary by engine.  If more boost is going to be employed, lower compression ratios may be required, depending upon the octane rating of the fuel to be used. 

 

 

 

Q.  How much horsepower will the Thunderhawk Performance RZR turbo system add to my engine?

 

A.  We have not yet finalized the production specs for this system.  Once we have our pre-production systems thoroughly tested and the all engine calibrations are finalized, we will announce this information.  Rest assured, we will deliver a turbo system that is both reliable and fast.

 

 

 

 

 

 

 

 

 

 

 

 

APPENDIX

 

CALCULATING AIR CHARGE TEMPERATURE

 

 

 

 

BOYLE’S LAW

 

q       Boyle’s Law, also known as the Universal Gas Law, is a basic part of every physics course.  This formula allows the effects of pressure, volume or temperature to be calculated for any gaseous material.

 

(P1 x V1) / T1  =  (P2 x V2) / T2    

                

P  =  Pressure

V  =  Volume

T  =  Temperature

 

            As this formula illustrates, any increase in pressure (P) will always result in an increase in temperature (T) or a decrease in volume (V).

 

 

           

q       To calculate the air charge (boost) temperature discharged from a 100% efficient compressor, use the following formula:

 

T2  =  T1 x (P2 / P1)0.283

 

T1  =  Inlet temperature (degrees Rankin); ambient temperature

T2  =  Outlet temperature (degrees Rankin); air charge (boost) temperature

P1  =  Inlet pressure (PSIG); atmospheric

P2  =  Outlet pressure (PSIG); atmospheric + boost

 

 

 

q       To convert between degrees Rankin (R) and degrees Fahrenheit (F), use the following formulas:

 

F  =  R – 460

R  =  F + 460

 

 

 

q       To calculate the ideal temperature increase (100% efficient compressor) caused by the above pressures increase (in degrees Fahrenheit), use this formula:

                                               

T3  =  T2 – T1

 

T1  =  Inlet temperature (degrees F); ambient temperature

T2  =  Outlet temperature (degrees F); air charge temperature

T3  =  Ideal temperature increase (degrees F); at 100% efficiency

 

 

EXAMPLE 1:  85° F inlet temperature, 100% efficient compressor, 7.5 PSI boost

 

Outlet temperature                T2  =  (85 + 460) x ((7.5 + 14.7) / 14.7)0.283

Outlet temperature                T2  =  (545) x(22.2 / 14.7)0.283

Outlet temperature                T2  =  (545) x (1.5102)0.283

Outlet temperature                T2  =  (545) x (1.1237)

Outlet temperature                T2  =  612 (degress Rankin)

Outlet temperature                T2  =  612 - 460

Outlet temperature                T2  =  152° F

                                   

Ideal temperature increase  T3  =  152 – 85

Ideal temperature increase  T3  =  67° F

 

 

 

 

ADIABATIC EFFICIENCY

 

            Boyle’s Law allows for the calculation of air charge temperatures created by a 100% efficient compressor.  However, we cannot apply this directly to our forced induction systems since no man-made compressor is 100% efficient.  To calculate the actual air charge temperature discharged from any given compressor, that particular compressor’s measured efficiency (adiabatic efficiency) must be known.  Adiabatic efficiency varies from 50% to 80% for the compressors currently available in today’s turbo and supercharger systems.

 

q       To calculate the actual temperature increase created by a particular compressor, use the following formula:

 

T4  =  T3 / AE

 

T3  =  Ideal temperature increase (degrees F); at 100% efficiency

AE  =  Adiabatic efficiency

T4  =  Actual temperature increase (degrees F); at adiabatic efficiency

 

 

 

q       To calculate the actual air charge (boost) temperature discharged from a particular compressor with a known adiabatic efficiency, use the following formula:

 

T5  =  T4 + T1

 

T1  =  Inlet temperature (degrees F); ambient temperature

T4  =  Actual temperature increase (degrees F); at adiabatic efficiency

T5  =  Actual air charge temperature (degrees F); at adiabatic efficiency

 

 

EXAMPLE 2:  85° F inlet temperature, 70% adiabatic efficiency (typical supercharger, not intercooled), 7.5 PSIG boost

 

Actual temperature increase           T4  =  67° F / 0.70

Actual temperature increase           T4  =  96° F

 

Actual air charge temperature         T5  =  96 + 85

Actual air charge temperature         T5  =  181° F

 

 

EXAMPLE 3:  85° F inlet temperature, 76% adiabatic efficiency (typical performance turbocharger, not intercooled), 7.5 PSIG boost

 

Actual temperature increase           T4  =  67° F / 0.76

Actual temperature increase           T4  =  88° F

 

 

Actual air charge temperature         T5  =  88 + 85

Actual air charge temperature         T5  =  173° F
 

 

 

 

 

INTERCOOLER EFFICIENCY

 

An intercooler (or aftercooler) is a device designed to remove as much heat as possible from the air charge (boost) before it enters the engine.  As is the case with compressor efficiency, no man-made heat exchanger (intercooler) is 100% efficient.

           

Intercooler efficiency is the measure of the amount of the temperature increase (caused by the compressor) which is removed from the air charge (boost) before it enters the engine.  For example, an intercooler which can reduce the air charge temperature by 80° F, in a system which increased the air charge temperature by 100° F over ambient (due to the compressor), would be considered 80% efficient.

           

A properly designed air-to-air intercooler of sufficient size can achieve efficiencies approaching 90%.  With an air-to-water intercooler system, two heat exchangers are required as explained in the text.  Therefore, the total system efficiency is the multiple of both heat exchangers’ individual efficiencies. 

 

 

q       To calculate the final air charge temperature entering the engine with an intercooled forced induction system, use the following formulas:

                                                           

T6  =  T4 x IE

 

T4  =  Actual temperature increase (degrees F); at adiabatic efficiency

IE   =  Intercooler efficiency

T6  =  Temperature decrease (degrees F); due to intercooling

 

 

 

T7  =  T5 – T6

 

T5  =  Actual air charge temperature (degrees F); at adiabatic efficiency

T6  =  Temperature decrease (degrees F); due to intercooling

T7  =  Final intercooled air charge temperature (degrees F)

 

 

EXAMPLE 4:  85° F inlet temperature, 70% adiabatic efficiency, 65% efficient air-to water intercooler (typical supercharger with liquid intercooler), 7.5 PSIG boost

 

Temperature decrease                                            T6  =  96° F x 0.65

Temperature decrease                                            T6  =  62° F

 

Final intercooled air charge temperature               T7  =  181 – 62

Final intercooled air charge temperature               T7  =  119° F

 

 

EXAMPLE 5:  85° F inlet temperature, 76% adiabatic efficiency, 88% efficient air-to-air intercooler (Thunderhawk Performance intercooled turbo system), 7.5 PSIG boost

 

Temperature decrease                                            T6  =  88° F x 0.88

Temperature decrease                                            T6  =  77° F

 

Final intercooled air charge temperature               T7  =  173 – 77

Final intercooled air charge temperature               T7  =  96° F

 

 

 

 

CONVERTING CFM TO LBS/MIN AIRFLOW

 

q       At 85° F and 28.4 in. Hg., CFM can be converted to lbs/min by using this simple formula:

 

Lbs/min  =  CFM x 0.069

 

            By referring back to Boyle’s Law, it is obvious that the volume (CFM) will increase with a corresponding increase in air charge temperature.  However, this increase in CFM provides NO additional air mass.  Therefore, there are no additional oxygen molecules made available to the engine for combustion, although the volume (CFM) is significantly higher.

           

Using CFM as a measure of airflow confuses the calculation due to the wide variations in temperature, both before and after the compressor, as well as after the intercooler.  All calculations in this technical manual assume the above conversion standards.  However, to accurately compare compressors, the compressor efficiencies as specified in the compressor flow maps must be known in order to calculate density and bring all compressors back to this standard.

 

 

 

 

 

 

 

 

 

 

Copyright Thunderhawk Performance, Inc., 2007

 

 

Avon Lake, Ohio

Phone: (216) 965-4800

http://www.thunderhawkperformance.com/