In brief, no production Civic Si left the factory with a K24 engine. The K24 is a larger 2.4-liter member of Honda's K-series used in other models, but not in the factory Si lineup. Enthusiasts, however, regularly swap K24 engines into Civic chassis for increased displacement and torque.
Context: how the Civic Si engine lineup has evolved
The Honda Civic Si lineage has historically leaned on smaller, high-revving engines rather than the larger K-series 2.4L. In North America, Si models have predominantly used 2.0-liter K-series powerplants (the K20 family) rather than the 2.4-liter K24. The K24 family powers models such as the Acura TSX, Honda Accord, and several other non-Si Hondas, but there has never been a factory, production Civic Si that shipped with a K24 engine. In recent years, Honda shifted the broader Civic lineup toward turbocharged engines, with the Si variant following that trend in some markets, rather than adopting a naturally aspirated K24. The result is a clear distinction between factory engine choices and aftermarket swap possibilities.
Below is a quick look at how this question plays out in practice:
- The factory Civic Si has never been offered with a K24 engine in any major market. Si models have used K-series 2.0-liter powerplants (and more recently turbocharged options in the broader Civic lineup) rather than the 2.4-liter K24.
- The 2.4-liter K-series family (K24) is widely used in other Honda/Acura models such as the TSX and Accord, not in the Civic Si as built by Honda.
- Swapping a K24 into a Civic Si is a common enthusiast project, but it is an aftermarket modification rather than a factory option.
Conclusion: There is no factory K24 Civic Si; K24-powered Civics exist only as aftermarket builds or donor swaps.
Popular K24 swap options for the Civic chassis
Before diving into specifics, note that swapping a K24 into a Civic requires substantial mechanical and electrical work, including engine mounts, transmission compatibility, wiring harnesses, ECU tuning, cooling, exhaust routing, and emissions considerations. The overview below outlines typical donor sources and considerations used by builders.
- Donor engines: The most common K24 donors come from Honda/Acura models such as the TSX and certain Accords. Builders often source a complete K24 from these cars to maximize compatibility and reliability.
- Compatibility considerations: Transmission fitment, engine mounts, engine harnesses, ECU/tuning, and compatibility with the Civic’s chassis electronics all need careful planning. Some swaps require adapters or aftermarket solutions to align with the Civic’s drivetrain.
- Expected outcome: A K24 swap can yield more torque and potential horsepower than the stock K20-based Civics, but it comes with increased complexity, potential reliability considerations, and regulatory implications depending on location and emissions rules.
Summary: For factory options, the Civic Si never used a K24. For performance-minded enthusiasts, a K24 swap is a well-trodden aftermarket path, but it requires careful planning and professional guidance.
Summary
Bottom line: no production Civic Si left the showroom with a K24 engine. The K24 family powers other Honda/Acura models, while Civic Si builds have relied on smaller K-series engines or turbocharged configurations in more recent years. If you’re curious about performance goals, a K24 swap is feasible but involves extensive modification and validation.