FAST 54088 Big Mouth LT 87mm Throttle Body

Drop-In 87mm Drive-By-Cable Throttle Body That Unlocks the Full Airflow Potential of Your Gen III Chrysler Hemi

The FAST 54088 Big Mouth LT is a billet aluminum 87mm drive-by-cable throttle body engineered specifically for Gen III Chrysler Hemi V8 engines spanning the 5.7L, 6.1L, and 6.4L displacements found across the Challenger, Charger, 300, Grand Cherokee, Durango, Ram 1500/2500/3500, Commander, and Magnum platforms from 2003 through 2018. The enlarged 87mm bore is a substantial airflow upgrade over the factory throttle body, supporting higher horsepower builds without requiring intake manifold modification. FAST redesigned the Big Mouth LT with an increased throttle blade thickness to eliminate deflection under boost, a smoother offset blade pivot for faster throttle response, a progressive throttle pulley that improves drivability at partial throttle, and a dual return spring mechanism for a positive feel and added safety. Because the FAST 54088 converts throttle operation from drive-by-wire to drive-by-cable, it is an ideal pairing for Hemi engines running the FAST XFI or EZ-EFI aftermarket fuel injection systems that require cable-actuated throttle input. Does not include throttle position sensor or idle air control valve. GM-style IAC and TPS are required and sold separately. See part 54089 if you need sensors included.

Key Features

• 87mm bore provides a substantial airflow increase over the factory Hemi throttle body to support higher horsepower applications
• Drive-by-cable conversion makes the FAST 54088 compatible with aftermarket EFI systems including FAST XFI and EZ-EFI that require cable-actuated throttle
• Increased throttle blade thickness eliminates blade deflection under boost, a common failure point in stock and competing aftermarket units
• Offset blade pivot delivers smoother, faster throttle response compared to center-pivot designs
• Progressive throttle pulley improves low-throttle drivability and linearity across the pedal travel range
• Dual return spring mechanism provides positive feel and an additional layer of safety
• Billet aluminum construction is lighter and more dimensionally stable than cast alternatives
• Black wrinkle powder coat finish for under-hood durability and clean appearance
• Direct bolt-on replacement for the factory Hemi throttle body with no intake manifold modification required
• Does not include TPS or IAC; compatible with GM-style IAC and TPS sensors sold separately

Vehicle Fitment

Specifications

What's Included

• One FAST 54088 Big Mouth LT 87mm throttle body
• Throttle body gasket
• Note: TPS sensor and IAC motor are NOT included and must be sourced separately (GM-style)

About FAST

FAST (Fuel Air Spark Technology) is an American performance fuel management and induction company based in Memphis, Tennessee. FAST engineers fuel injection systems, throttle bodies, ignition controllers, and intake manifolds for high-performance domestic V8 applications. The Big Mouth throttle body line is FAST's flagship mechanical induction upgrade and is widely used in Hemi-powered builds running aftermarket EFI systems. FAST products are manufactured in the United States and backed by the company's performance warranty.

Frequently Asked Questions

The FAST 54088 is designed for Gen III Chrysler Hemi V8 engines: the 5.7L (345 cubic inch), 6.1L (370 cubic inch), and 6.4L (392 cubic inch) versions found in the Challenger, Charger, Chrysler 300, Grand Cherokee, Durango, Magnum, Commander, and Ram 1500/2500/3500 from model years 2003 through 2018. It does not fit the 6.2L Hellcat/Trackhawk supercharged Hemi or the 2019-and-later Gen IV Hemi applications.

No. The FAST 54088 does not include a TPS or IAC motor. You will need to source a compatible GM-style throttle position sensor and idle air control valve separately. If you want sensors included from the factory, FAST part number 54089 is the same throttle body with both sensors pre-installed.

Later model Hemi applications (roughly 2011 and up) use electronic drive-by-wire throttle control with no cable. Aftermarket EFI systems like the FAST XFI and EZ-EFI require a cable-actuated throttle body to function correctly. The FAST 54088 provides that cable interface while simultaneously upgrading the bore size and throttle blade design. If you are running a standalone aftermarket EFI system on a factory drive-by-wire Hemi, the 54088 is the correct solution.

Yes, tuning is required. Increasing the throttle body bore from stock to 87mm changes the airflow characteristics at every throttle position. An aftermarket ECU tune ensures the fuel and ignition tables are calibrated to the new throttle body flow data, preventing lean conditions at wide-open throttle and poor drivability at partial throttle. If you are running the FAST XFI or EZ-EFI system, the tuning is performed within those platforms. For OEM ECU vehicles that have been modified to accept this throttle body, a custom tune from a Hemi specialist is required.

No. The FAST 54088 is engineered for the naturally aspirated Gen III Hemi family (5.7L, 6.1L, 6.4L) and is not designed or rated for the supercharged 6.2L Hellcat engine found in the Challenger SRT Hellcat, Charger SRT Hellcat, Durango SRT Hellcat, Grand Cherokee Trackhawk, or RAM 1500 TRX. The 6.2L Hellcat uses a different throttle body interface and boost pressure considerations that the 54088 is not built to handle.

Yes. The FAST 54088 uses the same bolt pattern and flange dimensions as the factory Gen III Hemi throttle body and is designed to bolt directly onto the OEM intake manifold without any modifications. No spacer, adapter, or re-drilling is required.

The FAST 54088 does not include a throttle position sensor or idle air control valve. The FAST 54089 is the same throttle body with a GM-style TPS and IAC pre-installed. If you are building a custom setup and already have sensors, the 54088 is the more cost-effective choice. If you need a complete out-of-the-box unit, the 54089 includes everything you need.

The FAST 54088 requires a cable-throttle input, so it is not a drop-in replacement for factory drive-by-wire setups without additional modification. On older 2003-2010 cable-throttle Hemi applications, fitment is more straightforward. On 2011 and later drive-by-wire applications, this throttle body is intended for use with an aftermarket standalone EFI system. Power gains on otherwise stock engines will be modest; the real benefit comes in combination with other supporting modifications like a cold-air intake, camshaft, and supporting tune.

Yes. A throttle body gasket is included. The throttle position sensor and idle air control valve are not included and must be purchased separately.

Installation Instructions

1. Disconnect the negative battery terminal before beginning.
2. Remove the factory air intake tube and any connected sensors or breather hoses attached to the factory throttle body.
3. Disconnect the throttle position sensor and idle air control valve connectors from the factory throttle body if applicable.
4. Remove the four factory throttle body mounting bolts and pull the OEM unit off the intake manifold.
5. Clean the intake manifold throttle body mounting surface to remove any gasket residue.
6. Install the supplied gasket onto the FAST 54088 throttle body mounting flange.
7. Position the FAST 54088 onto the intake manifold and install the mounting bolts. Torque to factory intake manifold specification (typically 105 in-lb / 8.8 ft-lb for Gen III Hemi applications).
8. Install the GM-style TPS sensor and IAC motor (purchased separately) per their respective installation instructions.
9. Route and connect the throttle cable to the progressive throttle pulley on the FAST 54088.
10. Reconnect all vacuum hoses and breather connections to the new throttle body as applicable.
11. Reconnect the negative battery terminal.
12. Start the engine and verify idle quality; allow the IAC to perform initial idle relearn before performing a road test.
13. Have the vehicle tuned by a qualified Hemi performance specialist before full-throttle operation.

WARNING: This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov.