26/03/2015
The Pinnacle of Engine Breathing: Understanding Individual Shaftless Throttle Bodies (ITBs)
For enthusiasts and racers seeking the absolute zenith of engine performance, the realm of Individual Throttle Bodies (ITBs) represents a significant leap forward from traditional carburettor or single-throttle injection systems. Specifically, the innovative Individual Shaftless Butterfly Throttle Bodies (ITBs) offered by AT Power are engineered as a no-compromise Electronic Fuel Injection (EFI) solution, meticulously designed for competition engines. These systems arrive fully assembled, factory vacuum balanced, precisely spaced to match your engine's cylinder centre distances, and are ready for direct installation onto your inlet manifold flanges, promising a substantial uplift in both power and throttle response.
What Exactly Are Individual Shaftless Butterfly Throttle Bodies?
At their core, ITBs are a series of individual throttle bodies, each dedicated to a single cylinder. This contrasts sharply with a single throttle body controlling all cylinders, or with carburettors that manage fuel and air mixture. The 'shaftless' design, a patented innovation by AT Power, is a game-changer. Traditional throttle bodies have a butterfly valve mounted on a shaft, which can obstruct airflow. AT Power's design eliminates this shaft, utilising a knife-edged butterfly valve instead. This ingenious engineering minimises airflow restriction, leading to significantly increased induction airflow speed and, consequently, enhanced engine performance.
Key Features and Benefits of AT Power's ITBs
AT Power's ITB systems boast a lightweight, precision-machined billet aluminium construction. The individual round housing design, coupled with their unique patented 'Shaftless' technology and knife-edged butterfly valves, is the driving force behind their proven ability to improve induction airflow speed and boost engine performance. They are available in a comprehensive range of bore diameters, from 36mm to 55mm, and in configurations to suit 4-cylinder, 6-cylinder, V8, and V12 engines. Furthermore, you have the choice between injected and non-injected individual housings, offering flexibility to meet diverse engine tuning requirements.
The customisation options are extensive, reflecting AT Power's commitment to providing tailored solutions. These include:
- Billet Machined Throttle Linkage Configurations: Including options for Drive-By-Wire (DBW) systems.
- Throttle Positional Sensor (TPS) Mounting Kits: Ensuring accurate feedback to your engine management system.
- Billet Aluminium Extension Tubes (Runners/Velocity Stacks): Available in various lengths to fine-tune airflow characteristics.
- Billet Aluminium Ram Pipes (Trumpets): Also offered in different lengths to optimise performance across the rev range.
- One-Piece Billet Aluminium Fuel Rails: Complete with brackets designed to accommodate a range of fuel injectors, eliminating potential leak points often found with hose connections.
Optional extras further enhance the system's adaptability. These include rotary contact or Hall Effect contactless TPS, central V-engine linkage kits, and a choice of 18 different anodising colours to match your aesthetic preferences. To facilitate a complete installation, AT Power also supplies essential ancillary parts such as fuel injectors, air filtration, motorsport cables, tuning aids, fuel pressure regulators, and engine management systems (ECUs).
How Do ITBs Improve Engine Performance?
The fundamental principle behind ITB performance enhancement lies in their ability to allow the engine to 'breathe' more freely. By providing each cylinder with its own dedicated, precisely controlled air intake, ITBs minimise restriction and optimise airflow. This results in:
- Faster Engine Response: With the throttle plate positioned much closer to the cylinder, the engine requires less air to fill the intake path between the valve and the cylinder. This proximity means the engine reacts far more rapidly to accelerator pedal inputs, providing a more connected and controlled driving experience.
- More Power Through Better Fuel Mixing: Mounting the fuel injector closer to the throttle plate, and further from the inlet valve, allows for a more homogeneous and efficient mixture of fuel and air before it enters the combustion chamber. While this can sometimes lead to a trade-off in low-end torque and potentially affect emissions, it is highly beneficial for high-performance, track-oriented engines where peak power is paramount.
- Direct Airflow Path: Compared to traditional DCOE-style replacement throttle bodies, direct-to-head ITBs offer the most unimpeded path for air to reach the cylinder. This eliminates unnecessary bends and changes in direction within the intake tract, reducing inlet length and further contributing to increased power and quicker throttle response.
Direct to Head ITBs vs. Carb Replacement Bodies
The advantages of direct-to-head ITBs over carb replacement units are substantial:
| Feature | Direct to Head ITBs | Carb Replacement Bodies |
|---|---|---|
| Design Philosophy | Engineered and tailored specifically for the engine, optimising throttle plate, injector, and runner profiles for maximum inlet system efficiency. | Designed to directly replace existing carburettors, often retaining some of the original intake path limitations. |
| Airflow Path | Provides the most direct path for air to travel to the cylinder, minimising restrictions and direction changes. | Can involve less direct airflow paths due to adapter plates and the original manifold design. |
| Compactness | Often results in a more compact installation, allowing greater flexibility with trumpet lengths and fitting into tighter engine bays. | Can be bulkier, sometimes leading to packaging challenges. |
| Throttle Response | Superior throttle response due to the proximity of the throttle plate to the cylinder head. | Generally good, but can be less immediate than direct-to-head systems. |
| Port Matching | The head flange can be detached for perfect port matching to a modified cylinder head, ensuring a seamless airflow transition. | Port matching is often more challenging or less precise. |
Choosing the Right ITBs for Your Engine
Selecting the correct ITBs involves considering several crucial factors to ensure optimal performance for your specific application:
- Driving Style and Engine Use: The primary use of your vehicle – whether for road, track, or competition – will dictate the desired engine characteristics. Some ITB setups excel in delivering sharp throttle response and high-end power, ideal for track days, while others might prioritise low-end torque and drivability for spirited road use.
- Bore Size: The diameter of the throttle body bore is a critical determinant of performance. Generally, larger bores and shorter intake lengths favour high-RPM power, whereas smaller bores and longer runners contribute to better low-down torque and drivability. The following table provides a useful starting point for selecting an appropriate throttle size based on engine capacity:
| Engine Size (Litre) | Recommended Individual Throttle Size (mm) |
|---|---|
| 1.6 | 42 |
| 1.8 | 45 |
| 2.0 | 48 |
It's important to note that these are starting recommendations. Custom sizes can also be manufactured if your engine build warrants a non-standard bore diameter. AT Power can also provide bespoke solutions for rare or special project engines to unlock their maximum potential.
Installation and Requirements
Crucially, all AT Power Individual Throttle Body systems (Injected Housing Type ONLY!) require an aftermarket engine management system (ECU) for correct operation. AT Power offers a selection of compatible ECUs and wiring looms. It is vital to understand that base maps provided with aftermarket ECUs are typically offered on an "as-is" basis, and professional dyno tuning is strongly recommended to avoid potential engine damage and to achieve optimal performance.
Before placing an order, it is essential to confirm your specific requirements. AT Power's sales team will contact you via email after an order is placed to verify the exact dimensional spacing required between each throttle housing before manufacturing commences. For boosted applications, standard aluminium extension tubes will be replaced with SLS 3D printed versions to better handle increased intake pressures.
Frequently Asked Questions
Q1: How do ITBs improve engine performance?
ITBs improve performance by allowing the engine to breathe more efficiently, providing a more direct and unrestricted airflow path to each cylinder. This results in increased power, sharper throttle response, and a more engaging driving experience.
Q2: What is the advantage of 'shaftless' technology?
Shaftless technology eliminates the obstruction caused by the traditional throttle shaft, allowing for smoother, faster airflow and reducing turbulence. This directly translates to improved volumetric efficiency and power output.
Q3: Can I use ITBs with my factory ECU?
No, ITBs, particularly those requiring precise fuel delivery like the AT Power injected systems, necessitate an aftermarket engine management system (ECU) for proper fuelling and engine control.
Q4: What is the difference between injected and non-injected housings?
Injected housings are designed to directly mount fuel injectors, placing them closer to the combustion chamber for improved fuel atomisation and mixing. Non-injected housings are typically used in conjunction with carburettors or remote fuel injection setups.
Q5: How do I determine the correct bore size and runner length?
Bore size and runner length significantly influence the engine's torque curve. Larger bores and shorter runners favour high RPM power, while smaller bores and longer runners enhance low-end torque and drivability. Consulting the provided tables and seeking expert advice is recommended for optimal selection.
In summary, Individual Shaftless Butterfly Throttle Bodies represent a sophisticated upgrade for any performance-oriented engine. By embracing cutting-edge design and offering extensive customisation, systems like those from AT Power provide enthusiasts with the tools to unlock their engine's true potential, delivering exhilarating performance and a truly connected driving sensation.
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