What size throttle body is the WRX STI?
The Subaru WRX STI, a high-performance sports car known for its turbocharged power and rally-inspired handling, features a throttle body of a specific size that contributes to its impressive performance. Let's dive into the details of the WRX STI's throttle body and understand its significance.
What is a Throttle Body?
A throttle body is a critical component in the engine's fuel delivery system. It is responsible for controlling the amount of air that enters the engine, which in turn regulates the engine's power output. The size of the throttle body directly affects the engine's response and overall performance.
The WRX STI's Throttle Body Size
The Subaru WRX STI is equipped with a 78mm throttle body. This larger-than-average throttle body size is a key factor in the car's impressive power delivery and responsiveness. The larger throttle body allows for a greater volume of air to flow into the engine, enabling the turbocharged 2.4-liter boxer engine to produce its maximum power output of 310 horsepower.
Benefits of the Larger Throttle Body
The WRX STI's 78mm throttle body offers several advantages over smaller throttle bodies found in more standard vehicles:
- Improved Throttle Response: The larger throttle body allows for a more immediate and responsive throttle input, providing the driver with a direct and engaging driving experience.
- Enhanced Power Delivery: The increased air flow enabled by the larger throttle body allows the turbocharged engine to produce more power, resulting in a more exhilarating driving experience.
- Better Airflow Efficiency: The larger throttle body reduces airflow restrictions, improving the engine's overall efficiency and contributing to the WRX STI's impressive performance.
These benefits, combined with the WRX STI's other performance-oriented features, make it a highly capable and engaging sports car for enthusiasts.
What size throttle body is on a TBSS intake?
The TBSS intake manifold has a 90mm opening, making a 90mm throttle body the ideal and recommended size for maximum airflow without creating a restriction. While some may try to fit larger throttle bodies, a 90mm is generally the optimal size for the TBSS intake, as a larger one can cause flow issues at the opening if not properly ported and tapered.
This video demonstrates how to measure the opening on the TBSS intake manifold and install a 92mm throttle body: 59sDTPerformanceYouTube · Nov 11, 2024
- Optimal size: The TBSS intake's opening is 90mm, so a 90mm throttle body is the factory-intended size for that intake.
- Maximizing airflow: A 90mm throttle body is considered a good upgrade, capable of adding horsepower depending on the application.
- Larger sizes: Attaching a throttle body larger than 90mm (e.g., 102mm or 105mm) can be detrimental unless the manifold opening is ported to match. Without porting, the abrupt edge can cause turbulence and reduce airflow, potentially performing worse than a correctly sized 90mm unit.
- Considerations for stock throttle bodies: While it is possible to use a smaller throttle body (like a 78mm) with an adapter, a 90mm throttle body will offer better performance potential due to increased airflow capacity.
You can watch this video to see a comparison of using a 78mm and a 92mm throttle body on a TBSS intake: 55sRichard HoldenerYouTube · Jul 13, 2025
Are the 5.7 and 6.4 throttle bodies the same?
So if you guys are wondering I've done some videos on this in the past i'll link them above for you guys. But this is a stock throttle body the 5.7. And the 6.4. Both share the same throttle bodies.
How much horsepower does a 90mm throttle body add?
12-15 Horsepower Gains Over Stock. Larger 90mm Throttle Body Bore for Maximum Airflow.
What size throttle body is a Z32?
NISSAN Z32 300ZX Billet Throttle Bodies (62MM)
