FAST 54104 Big Mouth 102mm Electronic Throttle Body for GM Gen III/IV LS Engines

Vehicle Fitment

• GM Gen IV LS Engines - Plug-and-Play with OEM ECU: L76, L77, L99, LS3, LS7
• GM Gen III/IV LS Engines - All Applications with Compatible Aftermarket EFI System (any system controlling a GM LS-style electronic throttle body)
• Engine Displacement Range: 5.7L (LS1/LS6), 6.0L (L76/L77/LQ4/LQ9), 6.2L (LS3/L99/LSA/LS9), 7.0L (LS7)
• Compatible with Edelbrock Pro-Flo 4+ EFI System

Fitment Notes

• Plug-and-play for most stock Gen IV LS ECUs - no modification required for L76, L77, L99, LS3, or LS7 applications
• Gen III LS applications (LS1, LS6, etc.) require an aftermarket EFI system capable of controlling a GM LS-style electronic drive-by-wire throttle body - not plug-and-play with Gen III cable throttle ECUs
• Uses GM LS stock 4-bolt flange - direct bolt-on to all standard GM LS intake manifolds including FAST LSX, LSXR, and LSXRT series
• Especially recommended when paired with a FAST intake manifold for maximum airflow benefit
• Designed for drive-by-wire (electronic throttle control) applications only - not compatible with cable-actuated throttle linkage
• Compatible with boosted applications - throttle blade and motor are engineered to maintain stable, rock-steady positioning under boost pressure
• Sold individually (1x throttle body)

Features

• 102mm bore - a significant airflow increase over the factory GM LS throttle bodies (typically 78mm-92mm), eliminating the intake restriction that limits peak power on high-performance LS builds
• Clean-sheet billet aluminum design - no components borrowed from a stock throttle body; every element engineered from the ground up by FAST engineers for performance, safety, and reliability
• High-performance, high-torque DBW motor - delivers faster throttle response compared to the weaker motors found in OEM and competing aftermarket electronic throttle bodies
• Dual return spring design - provides a critical safety redundancy for drive-by-wire applications, ensuring the throttle plate closes fully even in the event of a single spring failure
• Precision non-contact TPS (Throttle Position Sensor) - eliminates the wear, friction, and signal degradation associated with contact-type TPS designs; provides accurate, consistent throttle position data to the ECU
• Robust throttle blade engineered for boosted applications - maintains stable positioning under elevated manifold pressures found in supercharged and turbocharged LS builds
• Maintains stock idle characteristics - 102mm bore does not cause idle instability or require ECU recalibration for idle management on Gen IV OEM ECU applications
• Satin black anodized finish - corrosion resistant and visually distinctive under the hood
• Single-blade design - maximizes bore area and airflow potential at wide-open throttle

Specifications

• Part Number: 54104
• UPC: 00036584001638
• Brand: FAST (Fuel Air Spark Technology)
• Bore Diameter: 102mm
• Throttle Blade Quantity: 1 (Single Blade)
• Throttle Body Material: Billet Aluminum
• Finish: Satin Black Anodized
• Flange Style: Stock GM LS 4-Bolt
• Throttle Control: Electronic Drive-By-Wire (DBW)
• TPS Type: Non-Contact (Precision)
• Return Springs: Dual
• Injection Style: Multi-Port Injection (MPI)
• Shipping Weight: 4.50 lbs.
• Quantity: Sold individually

Included Components

• 1x FAST Big Mouth 102mm Billet Aluminum Electronic Throttle Body
• 1x Integrated Non-Contact TPS Sensor
• 1x Dual Return Spring Assembly

Product Description

The FAST 54104 is the Big Mouth 102mm Electronic Throttle Body for GM Gen III and Gen IV LS engines - a clean-sheet billet aluminum drive-by-wire throttle body engineered by FAST (Fuel Air Spark Technology) to maximize airflow and throttle response on high-performance LS builds. With a full 102mm bore, the 54104 eliminates the intake restriction imposed by the factory GM LS throttle bodies - which range from approximately 78mm to 92mm depending on application - delivering a substantially larger cross-sectional opening that maximizes airflow potential especially at wide-open throttle. The design is particularly effective when paired with a FAST LSX, LSXR, or LSXRT series intake manifold, where the 102mm inlet of the manifold and throttle body are matched for unrestricted flow.

Unlike competing aftermarket drive-by-wire throttle bodies that adapt OEM components, the FAST 54104 is a clean-sheet design - no stock throttle body parts are reused. The high-torque DBW motor provides noticeably faster pedal response over the weaker motors found in OEM units, while the dual return spring ensures the throttle plate closes fully under any condition - a critical safety feature for drive-by-wire applications. The precision non-contact TPS eliminates the wear patterns and signal inconsistencies that develop in contact-type sensors over time. The throttle blade itself is engineered to maintain a rock-steady position under boost pressure, making the 54104 a reliable choice for supercharged and turbocharged LS applications.

For Gen IV LS applications with an OEM ECU - including the L76, L77, L99, LS3, and LS7 - the FAST 54104 is plug-and-play with no ECU modification required, and idle quality remains stock. Gen III LS applications require a compatible aftermarket EFI system capable of controlling a GM LS-style electronic throttle body; the 54104 is not compatible with cable-actuated throttle linkage. The throttle body is also confirmed compatible with the Edelbrock Pro-Flo 4+ system and any aftermarket EFI platform using a GM LS DBW control strategy. The satin black anodized finish provides a corrosion-resistant, aesthetically clean appearance on any LS build.