Bosch develops direct CNG injection

Compressed natural gas used as motor fuel offers significant advantages, primarily emissions reduction and lower costs at the pump. However, since practically all CNG-powered cars are bivalent, based on petrol-powered equivalents and capable of sipping petrol due to range anxiety (if you run out of methane in the middle of nowhere, you can't just refill from a small portable tank), problems are beginning to amount. How so?

© BoschWithout direct fuel injection, CNG won't be able to progress as true petrol replacement

First of all, today's petrol engines feature direct fuel injection. CNG cannot be applied directly into combustion chambers the way petrol is, so bivalent engines require additional manifold injection systems for methane. This in turn makes it difficult to optimise the combustion process, efficiency and emission control. Certain compromises and sacrifices need to be made today, causing CNG-powered engines to be slightly less powerful than their petrol-powered counterparts. Injecting methane directly would solve today's issues instantly.

However, for this to happen, lots of hard work must be invested, because natural gas combusts differently from petrol, so again certain optimisation is required, but it's easier to achieve if both fuels are injected directly into the cylinder. The "quest” for direct CNG injection is called Direct4Gas and aims at developing a precise, robust and reliable methane injector that can withstand the rigours of working inside the combustion chamber. Introducing as few changes to the entire engine as possible is also a factor – CNG units shouldn't be more expensive to manufacture than petrol ones, or at least as little more expensive as possible.

As we said in the beginning, the development of the new technology is conducted by a consortium rather than a single company. It consists of automotive suppliers and automakers, including Robert Bosch GmbH, Daimler AG and the Research Institute of Automotive Engineering and Vehicle Engines Stuttgart (FKFS). Experimental engines and vehicles featuring them are "under construction”, but it will probably take 2-3 years before the ultimate solution is made commercially available. Let's be patient – this should be worth the wait!