The IO-360-L2A is the engine that most modern private pilots will fly behind at some point: the Cessna 172S is the world’s most-produced training aircraft, and the L2A is its factory engine. Fuel injection replaced the carburetor, eliminating icing risk and improving fuel distribution, at the cost of slightly more complex starting.
IO-360-L2A Design and Specs
The primary subject of this technical guide focuses on the Lycoming IO-360-L2A engine, engineered specifically for Horizontally Opposed 4-Cylinder, Air-Cooled, Fuel-Injected applications. Below is an essential digest of this powertrain configuration.
• 180 hp fuel-injected four
• Standard Cessna 172S engine
• 8.7:1 compression
• No carburetor icing
IO-360-L2A Technical Reference
361 cu in (5.9 L) displacement; 180 hp at 2,700 rpm; fuel-injected; compression ratio 8.7:1; dry weight approximately 280 lb.
The L2A’s fuel injection system meters fuel directly to each cylinder, which removes the carburetor icing hazard that affects O-360-powered aircraft and delivers more even mixture distribution. The trade-off is a hot-start procedure that demands technique—vapor lock in the fuel lines can make a warm engine reluctant to fire. The engine is rated for 91/96 avgas minimum but commonly runs on 100LL.
| Configuration | 4-cylinder, horizontally opposed |
|---|---|
| Bore | 5.125 in (130 mm) |
| Stroke | 4.375 in (111 mm) |
| Displacement | 361 cu in (5,916 cc) |
| Power | 180 hp @ 2,700 rpm |
| Compression | 8.7:1 |
| Induction | Fuel injected |
| Fuel | 91/96 avgas minimum |
Aircraft Using the IO-360-L2A
This engine model is deployed across various operational frameworks. Here is a breakdown of the typical machine or vehicle applications using this unit:
Cessna 172S Skyhawk, Cessna 172R (derivative), various STC installations
Pros & Advantages
No carburetor icing; even fuel distribution; proven Cessna 172 reliability.
Cons & Disadvantages
Hot-start technique required; vapor lock risk; higher compression demands quality fuel.
Frequently Asked Questions (FAQs)
Q1: What is the difference between O-360 and IO-360?
A1: The “I” indicates fuel injection. The IO-360-L2A meters fuel directly to each cylinder rather than through a carburetor, eliminating carb ice.
Q2: Why is the IO-360 hard to hot-start?
A2: Heat soak after shutdown can vaporize fuel in the lines, causing vapor lock. The standard technique involves a specific throttle and mixture sequence to purge vapor.
Q3: What is the IO-360-L2A’s compression ratio?
A3: 8.7:1, higher than the 8.5:1 of the carbureted O-360-A1A.
The Cessna 172S Skyhawk is the primary factory installation.