Natural gas as a fuel produces less power than diesel. When air and gas are compressed above an 11.5:1 ratio, spark ignition cannot consistently ignite the fuel. This means that spark ignited natural gas engines cannot use the high compression ratios that make today's diesels so powerful and efficient. Furthermore, spark ignition requires an air throttle in the intake system.

Dual-Fuel™ is easier to implement than Spark Ignited Natural Gas Commercial Engines

	Dual-Fuel™ Requirements			SI Natural Gas Requirements
	No changes are required to the base engine – a modification is carried out on the induction system only;			New cylinder head, piston, lower compression ratio (CR), turbocharger, modified cooling system & ignition system;
	Retains diesel FIE (Fuel Injection Equipment) as the ignition source;			Potentially lower cost ignition system with higher maintenance requirement;
	Easy to retro-fit, dealer fit and factory fit with minimum parts and process complexity – suitable for higher volume, lower cost production;			Requires new dedicated gas engine manufacture – requires modified factory line or significant and expensive off-line processes;
	Does not require production line commitment for product launch;			Dedicated to gas - no fall back or limp home system
	Product manufacture and launch can be managed via dealer network;			Requires a high level of commitment from production engineering;
	Can fall back to 100% diesel, or via a diesel limp home strategy.			Very difficult to retro fit or dealer fit;

Dual-Fuel™ technology offers a better solution. Compression ratios of today's diesel engines are about 16:1. By using a small amount of diesel fuel as a "liquid spark plug," Dual-Fuel™ natural gas engines operate at the same compression ratios of a diesel-fuelled engine.

Neither an air throttle nor spark plugs are required.