Flex
FLEX F55 Turbo 4JJ3 Bolt-On
FLEX F55 Turbo 4JJ3 Bolt-On
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Flex Ultimate Performance
FLEX F55 Turbo, Bolt-On for the 4JJ3-TCX
Isuzu D-MAX, Isuzu MU-X and Mazda BT-50 (2020 on)
The FLEX F55 turbo is the big-power bolt-on for the 4JJ3 platform. With 48.5mm compressor and turbine wheels and a 3.25 inch inlet, the F55 moves substantially more air than the factory unit and supports up to around 300 rwhp on well-supported, professionally tuned builds. It mounts to the stock 4JJ3 manifold pattern, so there is no manifold swap required to get it on the truck.
Specifications
| FLEX F55 4JJ3 Bolt-On Turbo | |
|---|---|
| Engine | Isuzu 4JJ3-TCX 3.0L turbo diesel |
| Vehicles | Isuzu D-MAX (2020 on), Isuzu MU-X (2020 on), Mazda BT-50 (2020 on) |
| Compressor wheel | 48.5mm, 6/6 blade |
| Turbine wheel | 48.5mm, 11 blade |
| Inlet | 3.25 inch (larger than OEM, 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 tuning and supporting mods |
| In the box | FLEX F55 turbocharger, wastegate actuator, turbo inlet gasket, oil drain tube and gasket, oil feed line with turbo feed bolt |
Details
Fitment Notes
Suits the 4JJ3-TCX platform: D-MAX, MU-X and BT-50 from 2020 on. The turbo mounts to the factory exhaust manifold. The 3.25 inch inlet is larger than the OEM pipe, so an adapter or coupler is required to connect your intake.
Installation Notes
- Trim the factory oil drain and join it to the supplied drain tube with oil-rated hose.
- Professional tuning is required to achieve 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
To make the most of the F55: 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 to reduce backpressure, 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 for the 4JJ3: larger wheels, more airflow, and 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 upgrade may be the better match. Unsure? Send us your power goal and mod list and we will steer you right.
Warranty & Returns
Covered under our standard warranty and Australian Consumer Law. Full terms are in our Refund, Returns & Warranty Policy.
Shipping
Free express shipping Australia wide with tracked dispatch. See our Shipping Policy for details. Afterpay, Humm, Klarna and Zip are available at checkout.
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 it can handle significantly more boost than the factory unit, around 35 to 40 psi on tuned builds versus the stock turbo's operating range.
Do I need an ECU tune after fitting the F55?
Yes. A professional remap is required to set safe boost, rail pressure and fuelling, and to unlock the performance safely. 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 means you will need 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, and injectors or fuel system upgrades as required for your power goal, plus 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.
Disclaimer: Common Rail Cowboys is not affiliated with Isuzu Motors or Mazda Motor Corporation. Installation should be performed by a qualified technician. Proper tuning and supporting modifications are the buyer's responsibility.
