Results of Tomei ARMS M7760 Turbo & Tomei Equal length Exhaust Manifold On 2008 Subaru STi

Prepared by: EDO Performance, LP
16182 Gothard St, Unit P
Huntington Beach, CA92647
www.edoperformance.com

TABLE OF CONTENTS

1. INTRODUCTION
2. THEORY & BACKGROUND
3. METHODOLOGY & PARAMETERS
   1. METHODOLOGY 1
   2. PARAMETER
4. RESULTS & ANALYSIS
   1. RESULTS
   2. ANALYSIS
5. CONCLUSION

REFERENCES 

1. INTRODUCTION

The goal of the experiment was to quantify the gain of wheel horsepower (whp) on a 2008 Subaru STi from the installations of Tomei® ARMS M7760 Turbo, Tomei® Equal Length Exhaust Manifold, Blitz® Exhaust System, Blitz® Air Intake, Blitz® Radiator, Power Enterprise® 800cc Injector and Cobb® Down pipe. The secondary goal of the experiment was to demonstrate the fitments of Tomei® ARMS M7760 and Equal Length Exhaust manifold on the new Subaru GRB chassis.

2. THEORY & BACKGROUND

A turbo is a gas compressor used for force-induction of internal combustion engine. The purpose of a turbo is to increase the mass of air flow into the engine to create more power thus improving the size-to-output efficiency of an engine.

An exhaust manifold is to decrease flow resistance, also known as back pressure, and to increase volumetric efficiency of an engine which result in gains in power.

Fuel injector is one of the central components in Electronic Fuel Injection system which completely replaced carburetors as the primary fuel delivery system in cars. Fuel injectors atomize fuel by forcibly pumping through small nozzle under high pressure into the engine air stream. Modern fuel injectors are electronically- controlled and dispense fuel according to the electronic pulse widths for accuracy.

Engine radiator is used to cool internal combustion engine. The liquid coolant is connected to channels running through the engine and cylinder head. The radiator simply transfers the heat from the fluid inside to the air outside, thereby cooling the engine. Radiators are typically mounted in a position where air flow is at the maximum. 

The function of air intake is to introduce cold air into the internal combustion engine. It may also increase the life of the engine and fuel economy of the car. In principle, the air intake maximizes the amount of oxygen available to the engine for combustion with fuel by introducing “cold” air into the engine because cold air has higher density for a given volume. However, the term “cold” air does not always literally mean cold air. It can also mean introducing higher amount of oxygen to the engine. Cold air intakes have the following design:

1. Larger diameter of intake
2. Smooth interior of intake for less resistance
3. Better direct route to the intake
4. Optimizing the length of the intake to maximize airflow at certain RPMs
5. Using less restricting air filter

Exhaust System (Cat-Back) refers to the portion of the exhaust system from the outlet of the catalytic converter to the final vent to open air. The design of the cat-back is usually large pipe diameter that allows the gas to exit with as little back-pressure as possible such that not restricting the power of the engine.
The design of downpipe is to provide better flowing unit of exhaust gas. This usually achieved by its larger diameter of the exhaust.
ECU Controls various aspects of a car’s internal combustion operations. At its simplest form, the ECU controls the quantity of injected fuel to the engine cylinder at each engine cycle. With advances in technology, most ECU controls the ignition timing, variable valve timing, level of boost maintained by the turbo charger and other peripherals. These controls are monitored by sensors located on different parts of the engines.

3. METHODOLOGY & PARAMETERS

All experiments were completed at sea-level altitude and average humidity of 30%. The average outside temperature was 860F.

1. Methodology

Dynapack 5000® Dynamometer was used to measure the wheel-horsepower (WHP) and the ECU of the car was reset before each configuration to eliminate skews in the dynamometer reading. The horsepower reading was calculated from the average of three dynamometer pulls of each configuration. ECU tuning was performed to measure the power at every configuration.

2. Parameters

Configuration 1 (Baseline): Original 2008 Subaru STi
The car was purchased on January 2008 with its original settings (Factory ECU Calibration) and hardware intact.
Configuration 2: Installations of Blitz® Quad Tip Nur Spec Exhaust System, Blitz® Air Intake & Blitz® Radiator
From configuration 1, the original exhaust system and radiator were replaced with Blitz® exhaust system and radiator. A Blitz® air intake was also installed as an addition.                                                                    
Configuration 3: Installations of Tomei® ARMS M7760 Turbo and Tomei ® Equal Length Exhaust Manifold
From configuration 2, the original turbo and exhaust manifold were replaced with the Tomei® brand respectively. The Tomei® ARMS M7760 turbo and Exhaust Manifold demonstrated perfect fitments on the GRB chassis.
Configuration 4: Installations of Power Enterprise® 800cc Fuel Injector and Cobb® down-pipe
From Configuration 3, the original fuel injectors and down-pipe were replaced with Power Enterprise® injectors and Cobb® down-pipe respectively.

4. RESULTS & ANALYSIS
   1. Results

Configuration 1 (Baseline): Original 2008 Subaru STi

Figure 4. Configuration 1 graph

With original settings and hardware, the 2008 Subaru STi registered 223.5 whp at 5000 RPM.  
Configuration 2: Installations of Blitz® Quad Tip Nur Spec Exhaust System, Blitz® Air Intake & Blitz® Radiator

Figure 5.Configuration 2 graph

With Blitz® Air Intake, exhaust and radiator, and a custom tune the car registered 293.6 whp at slightly over 5000 RPM, a gain of 70.1 whp. The torque registered at 320 lb.ft.

Configuration 3: Installations of Tomei® ARMS M7760 Turbo and Tomei ® Equal Length Exhaust Manifold

Figure 6. Configuration 3 graph

With the original turbo and exhaust manifold replaced with Tomei® ARMS and Equal length exhaust manifold respectively, the car experienced a gain of 30 whp with torque of 344lb.ft.

Configuration 4: Installations of Power Enterprise® 800cc Fuel Injector and Cobb® down-pipe

Figure 7.Configuration 4 graph

The replacement of original fuel injectors with Power Enterprise® 800cc injectors and original downpipe with Cobb® downpipe produced wheel horse power of 340 and torque of 372.9 lb.ft, gains of 17 whp and 28 lb.ft respectively.

1. Analysis

The following table summarizes the results of the experiment.

Table 1. Summary of results from different configurations

Although original configuration provided stable power output at high RPMs, replacements to after-market performance parts boosted the car’s power output to 340 whp from 223.5whp, an increase of 50% over original configuration. 

The Tomei® ARMS M7760 and Equal Length exhaust manifold fit seamlessly on the 2.5L GRB chassis. Installations procedures were the same to the installations on the GDA/GDB chassis.

Installations of Tomei® turbo and headers, boosted the car’s response time. At 4000RPM, the car experienced a gain of at least 60whp over original configuration during dynamometer pulls. It also eliminated the bump (hesitation) on 4100 RPM as shown on graph 1. The additions of the turbo and headers also resulted in the torque increase to 345lb.ft. A noticeable trend is that with bigger turbo, headers and fuel injectors, there is a delay in achieving peak power. The peak power is achieved at 5300RPM with Tomei® turbo and 5700RPM with 800cc fuel injectors respectively.

5. CONCLUSION

Tomei® ARMS turbo M7760 and Exhaust Manifold fits perfectly on the new Subaru GRB chassis. Installations were breeze and similar to GDB chassis. While installations of Tomei® ARMS M7760 and exhaust manifold alone do not guarantee power as in configuration 3, the Tomei® turbo will improve response time and power. Building a balanced performance car requires combinations of suitable supporting hardware and engine tuning.