It might sound unconventional, but the answer is yes, glow plugs can indeed function in gasoline engines, and surprisingly well under certain conditions. The narrative around this possibility gained traction when NV-Engines showcased the effectiveness of the OS P5 turbo glow plug with gasoline. Interestingly, the OS P5 turbo plug shares its design with the larger turbo plug size, hinting at a design lineage. Following NV-Engines’ demonstration of the P5 plug’s gasoline compatibility, OS likely leveraged the coil element design to develop the G5 glow plug specifically. Intriguingly, some enthusiasts have successfully utilized the G5 glow plug in small gasoline engines, effectively replacing the traditional spark plug system, and reported satisfactory engine performance.
The Importance of Engine Preheating with Glow Plugs
A crucial aspect to consider when using a glow plug in a gasoline engine is preheating. Once the engine starts, it’s essential to allow it to heat up adequately before demanding full performance, such as during flight in model aircraft. This preheating phase is vital for ensuring the glow plug operates optimally. Attempting to operate the engine from a cold start might lead to inconsistent or unsatisfactory engine behavior.
Compression Ratio and Fuel Considerations
However, it’s not as simple as just swapping a spark plug for a G5 glow plug in any standard glow engine and expecting it to run flawlessly on gasoline. Many conventional glow engines are designed with higher compression ratios, which can become problematic when using gasoline. This can lead to undesirable phenomena like pre-ignition or detonation, which can damage the engine.
One potential workaround to mitigate these issues is to use high-octane aviation gasoline. The higher octane rating can help to resist pre-ignition in high-compression engines. Alternatively, reducing the compression ratio by incorporating head shims might be a more effective solution in the long run.
Another critical factor is fuel delivery. Standard RC glow engine carburetors are calibrated for methanol fuel and are engineered to operate with a richer air-fuel mixture. Gasoline, in contrast, requires a much narrower and more precise air-fuel mixture range for efficient combustion. This is why gasoline engines often incorporate fuel pressure regulators and more sophisticated carburetor designs. For applications like free flight or control line models, adjusting the carburetor needle might suffice to compensate for the fuel difference. Methanol is more forgiving and will combust across a broader spectrum of air-fuel ratios compared to gasoline.
Engine Design Adaptations for Gasoline
It’s worth noting that dedicated gasoline engines, such as the NV-Engines GX-40 .40 gas engine, incorporate significant internal design changes to optimize performance and reliability with gasoline fuel. These modifications can include alterations to the combustion chamber shape, porting, piston design, and other critical engine components. These changes are essential to maximize efficiency and durability when running on gasoline rather than methanol.
In conclusion, while glow plugs can indeed function in gasoline engines, particularly in smaller model engine applications, it’s not a straightforward plug-and-play conversion. Factors like engine preheating, compression ratio, and fuel system calibration are crucial considerations for successful and reliable operation. For optimal gasoline engine performance, engines specifically designed and engineered for gasoline, like the NV-Engines GX series, represent a more refined and robust approach.
