Flex
FLEX F55 Turbo 4JJ3 Bolt-On
FLEX F55 Turbo 4JJ3 Bolt-On
Taxes included. Shipping calculated at checkout.
Complete the install
Couldn't load pickup availability
48.5mm Wheels | 3.25 Inch Inlet | Up to 300 RWHP | Isuzu D-MAX, MU-X and Mazda BT-50 (2020 on)
The Flex F55 is the big-power bolt-on for the 4JJ3 platform. 48.5mm compressor and turbine wheels and a 3.25 inch inlet move substantially more air than the factory unit, supporting up to around 300 rwhp on well-supported, professionally tuned builds.
It mounts to the stock 4JJ3 manifold pattern. No manifold swap to get it on the truck.
What Is Included
- Flex F55 turbocharger
- Wastegate actuator
- Turbo inlet gasket
- Oil drain tube and gasket
- Oil feed line with turbo feed bolt
Specifications and Power
| Spec | Value |
|---|---|
| Engine | Isuzu 4JJ3-TCX 3.0L turbo diesel |
| Compressor wheel | 48.5mm, 6/6 blade |
| Turbine wheel | 48.5mm, 11 blade |
| Inlet | 3.25 inch (larger than factory, adapter or coupler required for your intake pipe) |
| Flange | Stock 4JJ3 manifold pattern, direct bolt-on |
| Boost capability | Approx 35 to 40 psi, build and tune dependent |
| Power potential | Up to approx 300 rwhp with supporting mods and appropriate tuning |
Vehicle Fitment
| Vehicle | Engine | Years |
|---|---|---|
| Isuzu D-MAX | 4JJ3-TCX | 2020 on |
| Isuzu MU-X | 4JJ3-TCX | 2020 on |
| Mazda BT-50 | 4JJ3-TCX | 2020 on |
Mounts to the factory exhaust manifold. The 3.25 inch inlet is larger than the factory pipe, so an adapter or coupler is required to connect your intake.
Fitting Notes
- Trim the factory oil drain and join it to the supplied drain tube with oil-rated hose.
- Professional tuning is required for safe fuelling and EGT control. This is not optional.
- DPF-equipped vehicles may need custom dump or exhaust adaptations.
- Professional installation recommended.
For off-road and competition use only. Turbo modifications may affect compliance. Check local regulations before purchase.
Recommended Supporting Mods
A front-mount intercooler to handle 35 to 40 psi, a high-flow intake to feed the 3.25 inch inlet, a 3 inch exhaust, boost and EGT monitoring, upgraded 4JJ3 injectors as required for your power goal, and an ECU remap.
Which turbo suits my build? The F55 is the top-end option: larger wheels, more airflow, headroom to around 300 rwhp. If your build is focused on quick spool, towing and mid-range response in the 240 to 280 rwhp range, the SAK 44mm 4JJ3 turbo may be the better match. Unsure? Send us your power goal and mod list.
Shipping and Payment
- Afterpay, Humm, Klarna and Zip available
- Free express shipping Australia-wide with tracked dispatch
- Warranty and returns: see our refund policy
Frequently Asked Questions
What is the difference between the Flex F55 and the stock 4JJ3 turbo?
The F55 runs larger 48.5mm compressor and turbine wheels and a 3.25 inch inlet, and handles significantly more boost than the factory unit: around 35 to 40 psi on tuned builds.
Do I need an ECU tune after fitting the F55?
Yes. A professional remap is required to set safe boost, rail pressure and fuelling. Running the F55 untuned is not recommended.
Will the F55 bolt to the factory 4JJ3 manifold?
Yes. It is designed for the stock 4JJ3 manifold pattern. The larger 3.25 inch inlet needs an adapter or coupler for your intake pipe.
What supporting mods does the F55 need?
A front-mount intercooler, high-flow intake and exhaust, boost and EGT monitoring, injectors or fuel system upgrades as required for your power goal, and a professional tune.
Do I need to modify my exhaust?
DPF-equipped vehicles may need custom dump or exhaust adaptations. Non-DPF setups typically bolt on with minimal modification. Consult your installer.
Up to 300 RWHP on the Stock 4JJ3 Manifold
Flex F55 for D-MAX, MU-X and BT-50. Tune required. Free express shipping Australia-wide.
Common Rail Cowboys is not affiliated with Isuzu Motors, Mazda Motor Corporation or Flex. Installation should be carried out by a competent person and professional tuning is required. Fitment to your vehicle is the buyer's responsibility. Performance modifications may affect your vehicle's warranty, insurance and road compliance. Power and boost figures depend on supporting mods, fuel quality, tune and dyno.
