China, May 2026 — WND Engine has completed a major production capacity expansion for its G4KJ 2.4L Theta II series replacement engines, with monthly output now exceeding 3,000 units.
The four-month expansion project introduced a new semi-automated assembly line, doubling the number of assembly stations from 6 to 12. The upgraded production line is now equipped with automated torque control tools, computerized engine testing benches and a more detailed quality inspection process before shipment.
This expansion is designed to meet rising demand from international distributors, engine importers, repair shop networks and fleet service providers, especially in the Middle East, Russia, Africa and South America.
Production Capacity: Before and After
| Indicator | Before Expansion | After Expansion | Change |
| Monthly Output — G4KJ | 1,800 units | 3,000+ units | +67% |
| Assembly Stations | 6 | 12 | +100% |
| Quality Checkpoints Per Engine | 3 | 5 | +67% |
| Lead Time for Bulk Orders (500+ units) | 35 days | 22 days | -37% |
| Annual Capacity — All Engine Series | 28,000 units | 45,000 units | +61% |
| On-site Technicians | 42 | 68 | +62% |
What the New Production Line Means for Buyers
With the upgraded assembly and testing system, every G4KJ engine goes through five quality checkpoints before shipment:
1. Hot Start Run-In Test
Each engine is started and operated under controlled conditions to verify idle stability, oil pressure response, cooling circulation, vibration level, abnormal noise and basic running performance before shipment.
2. Oil Pressure Verification
The pressurized lubrication circuit is tested to check for oil leakage, unstable pressure and possible oil passage blockage.
3. Compression Test
All four cylinders are tested to confirm consistent compression performance and engine sealing quality.
4. Leakage Analysis
A pressurized cylinder leakage test is used to detect potential issues related to valve seats, piston rings or cylinder head gaskets.
5. Final Visual and Dimensional Inspection
The final inspection verifies external surfaces, bolt torque marks, sensor installation, accessory condition and export packaging integrity.
WND Engine has also upgraded its engine dynamometer testing system from a single-station setup to a 10-station configuration. This allows up to 10 engines to be tested in parallel, significantly improving testing efficiency for bulk orders.
Each dynamometer test can generate a numbered test video and report, including key data such as power output, torque, oil pressure and coolant temperature curves.
Supporting Large-Volume International Orders
“The 3,000-unit milestone is more than just a number,” said a company representative. “It means we can now accept larger bulk orders that were previously limited by production capacity. For distributors in the Middle East and Russia, where quarterly orders of 500 units are common, this expansion helps remove a major delivery bottleneck.”
The shorter lead time is especially important for wholesale buyers and regional distributors who need stable inventory supply for repair shops, fleet maintenance companies and engine replacement markets.
G4KJ Engine Market Background
The G4KJ, also known as the Theta II 2.4L MPI engine, is one of the most in-demand Hyundai and Kia replacement engines in the global aftermarket.
It is widely used in models including:
- Hyundai Sonata YF / LF
- Hyundai Santa Fe CM / DM
- Hyundai Tucson LM
- Kia Sorento XM
- Kia Optima TF / JF
- Kia Sportage SL / QL
In regions such as the Middle East, Africa and South America, many Hyundai and Kia vehicles are now reaching an average age of 10 to 15 years. As a result, demand for reliable replacement engines is entering a peak cycle.
Independent repair shops, fleet operators and regional distributors are increasingly sourcing engines directly from Chinese manufacturers to reduce procurement costs, shorten supply chains and improve inventory flexibility compared with traditional dealer channels.
Expansion Also Supports G4NA, G4FC and G4FG Engine Production
Although the new production line was built around the G4KJ 2.4L Theta II engine, the upgraded tooling, testing benches and assembly infrastructure also support other Hyundai and Kia engine series, including:
- G4NA 2.0L Nu engine
- G4FC 1.6L Gamma engine
- G4FG 1.6L Gamma engine
Shared tooling and testing systems help reduce switching time between different engine series, allowing WND Engine to respond more efficiently to mixed-model bulk orders.
By the end of 2026, WND Engine expects the combined annual output of its G4FC, G4NA, G4KJ and G4FG engine series to reach 45,000 units.
About WND Engine
WND Engine is a China-based engine supplier focused on complete engine assemblies for global B2B customers, including repair shops, wholesalers, importers, fleet service providers and regional distributors.
The company supplies Hyundai, Kia, Toyota, Ford, Chevrolet and other engine series, with factory-direct supply, pre-shipment testing, export packaging and international logistics support.
For bulk orders, model matching or engine availability, buyers can contact WND Engine for quotation and technical confirmation.
