01/24/02

 

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4.0       Turbochargers

 

In Chapters 2 & 3 we addressed the first part of the CPP Performance Recipe "FUEL".

A turbocharger provides large amounts (if done properly) of pressurized to the engine by utilizing exhaust gas energy to drive an exhaust wheel that is mechanically coupled to the turbocharger compressor wheel.  Just like a big fan blowing air into the motor.

This chapter will provide an overview of turbo fundamentals, applications and principles that, hopefully, will provide you with enough information to make an educated turbo selection for your performance and driving needs.

1.         What is a turbo?  How does it work?

2.         Turbo fundamentals and generalities.

3.         How to select your turbocharger.

4.         Turbo options & peripherals.          

 

4.1       What is a turbocharger and how does it work?

Figure 4.1 denotes the components that make up a turbocharger.  The turbine wheel is mechanically connected to the compressor wheel via the turbine shaft.  Exhaust gases pass over the turbine wheel and causes it to spin.  This rotation spins the compressor wheel at a very high rate of speed and provides a high volume, high pressure source of air to force feed the engine.  Essentially, we get something for nothing by harnessing the energy of the exhaust to do all the work.

The following is a generalized compilation of information that I refer to as …

I use it to describe the cause and effects of different turbo trims and components and can be applied to all turbochargers.

 

1.                  COKING of turbo bearings

Coking does happen but can be easily avoided.  Idling the engine a few minutes before turning it off reduces turbo housing temperature which in-turn reduces oil temperature.  Also using a good synthetic oil significantly reduces the coking potential.

 

2.                  THE BIGGER THE COMPRESSOR WHEEL

·        Produces more air to the engine per engine rpm

·        Provides more horsepower potential but less low end torque

·        Results in slower spool-up and increased turbo lag

·        Requires a higher stall converter

 

3.                  THE SMALLER THE COMPRESSOR WHEEL

·        Produces less air to the engine per engine rpm

·        Provides less horsepower potential but provides more low end torque

·        Results in faster spool-up and decreased turbo lag

·        Requires a lower stall converter

4.                  THE BIGGER THE TURBINE WHEEL

·        Produces less air to the engine per engine rpm

·        Provides more horsepower potential due to reduced back pressure but provides less low end torque

·        Results in slower spool-up and increased turbo lag

·        Requires a higher stall converter

5.                  THE SMALLER THE TURBINE WHEEL

·        Produces less air to the engine per engine rpm

·        Provides less horsepower potential but provides more low end torque

·        Results in faster spool-up and decreased turbo lag

·        Requires a lower stall converter

6.                  THE BIGGER THE TURBINE WHEEL

·        Produces less air to the engine per engine rpm

·        Provides more horsepower potential due to reduced back pressure but provides less low end torque

·        Results in slower spool-up and increased turbo lag

·        Requires a higher stall converter

 

7.                  THE BIGGER THE COMPRESSOR HOUSING A/R

·        Produces more air to the engine per engine rpm

·        Provides more horsepower potential but less low end torque

·        Results in slower spool-up and increased turbo lag

·        Requires a higher stall converter

 

8.                  THE SMALLER THE COMPRESSOR HOUSING A/R

·        Produces less air to the engine per engine rpm

·        Provides less horsepower potential but more low end torque

·        Results in faster spool-up and decreased turbo lag

·        Requires a lower stall converter

9.                  THE BIGGER THE TURBINE HOUSING A/R

·         Produces more air to the engine per engine rpm

·        Provides more horsepower potential but less low end torque

·        Results in slower spool-up and increased turbo lag

·        Requires a higher stall converter

10.             THE SMALLER THE TURBINE HOUSING A/R

·        Produces less air to the engine per engine rpm

·        Provides less horsepower potential but more low end torque

·        Results in faster spool-up and decreased turbo lag

·        Requires a lower stall converter

 

This is THE most common mistake made by the avid performance enthusiasts.  As you can see from the above generalities the correct blend of components is not only desirable but mandatory for optimum turbo performance. 

 

Example #1:  If the turbine wheel or turbine housing is too big excessive turbo lag and soggy low end performance will result.  This may be offset with a high stall torque converter. [If that meets your driving or budget criteria.]   However, if the turbine wheel or the turbine housing is too small the vehicle will exhibit good turbo response and bottom end torque but will be choked off on the big end due to the excessive exhaust back pressure.

 

 

Example #2:  If the compressor wheel or compressor housing is too small the turbo may be unable to supply enough air volume to the engine at upper rpm levels thus significantly limiting the ability to make boost at maximum horsepower levels.

           

As you can see from the above "4-T's" that there are many trade-offs to be considered before selecting your turbo.  The following section provides a systematic approach to categorize and list your specific turbo requirements.  I hope you find it is useful.

 

4.3       How to select your turbocharger.

There are several key points to be considered when selecting the proper turbocharger for your performance and driving needs.  Answering the following questions should simplify the selection process.

1.         What are my driving requirements?

2.         How much horsepower do I want to support?

3.         Do I want it to be stock appearing?

4.         Do I want to add peripherals?

5.         How much money do I want to spend?

 

4.3.1   What are my driving requirements?     

This is probably the most important question of the group.  It needs to be clarified to get the proper results.

·        What kind of performance?  Highway or drag strip?

·        Is immediate turbo response and bottom end torque a concern?

·        Is economy and reliability the main concern?

·        Are the performance upgrades for the track only?  Must remain emissions legal?

 

As noted in the "4-T's" the wheel/housing configuration directly impacts the driving characteristics.  Too big of anything greatly reduces throttle response and can significantly increase turbo lag and hurts performance.

 

 

4.3.2   How much horsepower do I want to support?

 

Horsepower requires both fuel and air.  The greater the horsepower level > the more air required > and the bigger the turbo capacity required to flow it.  Again, remember that TOO BIG is worse than too small.  Be realistic in your horsepower goals.  

Table 4.2 is a Turbo Selection Tree.  It lists many of the more popular turbo alternatives available today and are rated by horsepower levels. 

You may have noticed that several of the units fit into more than one category.  This is due to the wide variety of wheels, housings and trims available.  Your turbo can be specifically tailored for your exact high performance needs.  Be sure to consult your turbo supplier or performance parts vendor for your unique application.

 

 

 

 

 

 

 

 

Table 4.2

                                                Turbo Selection Tree

                                    How much Horsepower is required?  

                        │             │               │              │            │     │      │       ║

               <400HP      <500HP        525HP+  625HP+  800HP  900HP+ 1100HP+ 

            Tweak Stock            │                         │                   │            │           │      │       

              Turbo                       │                         │                    │            │           │      │       

                                                │                         │                    │            │           │      │      

│ Stock           │ │ Not Stk.│              │                   │  │"#67-1"│ ││ Magnum 40V"│║  │Appearing│ │Appearing│       │        │  │"TD-08"│ │└────────────┘║

 

│ "TE-48" │      │         │                   │            │              ║

│"TB-0348"│┌─────┴───────┐ │   ┌────┴────┐   ┌───┴───┐          ║

└─────────┘│  "TE-34"          │ │     │ "#62-1" │   │"TF-08"│          ║

                          │T-04 Upgrade │ │  │ "#67-1" │   └───────┘          ║

                          │ "Cheetah"           │ │  │"#TD-07S"│                      ║

                          └─────────────┘ │ │"#TD-08" │                      ║

                                                               │       └─────────┘                      ║

                                                    ┌───┴───┐                               ║

                                                    │"#60-1"│                             

                                                    │"#62-1"│                              

                                                    │"TE-44"│                              

                                    └───────┘                              

 Note:  The horsepower ratings above imply that the turbo can move enough air to support that horsepower rating.

 

As noted in Table 4.2 above we have three turbochargers that readily meet our needs for a 10.90 car with 527HP.   If we move up to the next level we should have additional high performance components to utilize them satisfactory. [But that is in another section.]

 

 

4.3.3   Do I want it to be stock appearing?

 

If the answer to the above question is yes, then the following turbos may fit your needs.

 

The first option of stock appearing is an enhancement of the stock unit that we affectionally call "Tweaking" the turbo.  Basically, the compressor housing, turbine housing and stock wastegate elbow assemblies are ported, re-contoured and polished to greatly enhance its air flow.  Performance gains in excess of .15 seconds and 2+ mph in the quarter mile are not uncommon.  Also, faster spool-up and less turbo lag are other characteristics of this upgrade.

Over the last couple of years a very popular class at the NMCA “National Muscle Car Association” and the GSCA “Gran Sport Club of America” has been the Turbo Regal "Stock Appearing" class.  Basically anything is legal as long as it looks stock externally.

This has prompted the development and marketing of the Stock Appearing Turbo.  The Garrett Stage II [TB-0348] turbo preceded these but was the first, true bolt-on, stock appearing unit readily available to the public.  It is readily identifiable by the .82 A/R exhaust housing rather than the stock .63 A/R housing.  The compressor wheel is bigger than stock.

 

If you do not care if the turbo looks stock or not then a wide variety of manufacturers and types of turbos are available for your driving needs.

 

4.3.4   Do I want to add peripherals?

 

As your horsepower requirements increase so does your need for auxilliary hardware.

Previous chapters have demonstrated that as horsepower levels increase the fuel pump capacity must increase, the injector size must increase, the turbo capacity must increase, a higher stall torque converter probably will be required, etc.  As you can see in the following table a homogeneous, well integrated performance package is mandatory to attain maximum, efficient performance.

 

Table 4.3 represents some of the additional hardware required to support different horsepower level.

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 4.3

=================================================================

  Manufacturer            HP               Hardware Requirements            

   Model #        Level           

=================================================================

  Garrett        475HP

   [Stage II]                                                      

   #TB-0348                                       [1],[2]

  Garrett                       

   [Stk Appear]

   #TE-48 "Shootout"                     [1],[2]

=================================================================

  Turbonetics    500HP                  

   #T-04 Upgrade                             [1],[2],[3],[5],[9],[10],[12]

   "Cheetah"                                     [1],[2],[3],[6],[9],[10],[12]

  Garrett                       500HP                       

   #TE-34 = #TK-1                            [1],[2],[3],[5],[9],[10],[12]

=================================================================    Turbonetics         525HP+

   #60-1                                                           [1],[2],[3],[5],[9],[10],[12]

   #62-1                                                           [1],[2],[4],[6],[9],[10],[12]

  Garrett                      

   #TE-44                                                        [1],[2],[4],[5],[9],[10],[12]

=================================================================

  Turbonetics             625HP-700HP+

   #62-1                                                           [1],[2],[4],[6],[8],[9],[10],[12]

   #67-1                                                           [1],[2],[4],[7],[8],[9],[10],[12]

  Mitsubishi

   #TD-07S                                         [1],[2],[4],[6],[8],[9],[11],[12]

   #TD-08                                                        [1],[2],[4],[7],[8],[9],[11],[12]

=================================================================    Turbonetics         800HP+      

   #67-1                                                           [1],[2],[4],[7],[8],[9],[11],[12]

  Mitsubishi

   #TD-08                                                        [1],[2],[4],[7],[8],[9],[11],[12]

   #TF-08                                                        [1],[2],[4],[7],[8],[9],[11],[12]

=================================================================

  Mitsubishi     900HP+

   #TF-08-30V                                                [1],[2],[4],[7],[8],[9],[11],[12]

=================================================================

  Precision      1100HP+                

   "Magnum 40V"                            [1],[2],[4],[7],[8],[9],[11],[12]

=================================================================

 

 [1]                  Fuel pump upgrades. [See Chapter #____]

 [2]                  Bigger injectors.   [See Chapter #____]

 [3]                  Single External Wastegate.

 [4]                  Dual External Wastegates.

 [5]                  Higher stall converter (2800+).

 [6]                  Higher stall converter (3500+).

 [7]                  Higher stall converter (4500+).

 [8]                  Fuel management - low impedence injectors.

 [9]                 HD Axles and differential hardware.

 [10]    HD #TH200-4R Transmission components.

 [11]    HD #TH400 Transmission of Powerglide.

 [12]    Bigger HP Intercooler.

 

 

4.3.5   How much money do I want to spend?

 

As you can see in Table 4.3 the hardware requirements significantly increase as the power level increases. As the hardware increases so does the incremental costs.

 

 

The following is chart represents a generalized estimate of costs per performance level.  There may be some exceptions to this but we are talking about average expenses for average performance results.

 

           

Quarter Mile Performance Level	Total COSTS	COST / 0.1 sec
13's	<$300	+$150 / tenth
12's	<$1000	+$200 / tenth
11's	$5000	+$500 / tenth
10's	>$10K+	+$750 / tenth
9's	>$30K+	+1000 / tenth
8's	>$50K+	+1500 / tenth

 

Now that we have defined our performance goals, our driving requirements, our hardware and budget criteria we should have enough data to make an educated selection of our turbo with some assurance that it will work.