A V6 engine is a six-cylinder internal combustion engine with the cylinders arranged in two banks of three cylinders, usually set at a 60° or 90° angle to each other. One advantage of a V6 engine over a straight-six engine is that it is shorter and thus easier to fit into an engine bay.
The V6 configuration generally results in anEngine balance shaft being required to counterbalance the first order rocking couples produced by the offset power strokes of the pistons. The firing order for most V6 engines with natural aspiration follows a 1-6-5-4-3-2 sequence, which results in perfect primary and secondary engine balance. This firing order allows for even torque delivery from cylinder to cylinder and prevents excessive vibration. However, this ideal firing order also causes each spark plugto fire once every 240 degrees of crankshaft rotation (360/150), which can lead to increased levels of unburned hydrocarbons in the exhaust gas if not enough fuel is injected during the intake stroke.
Many automakers have introduced gasoline direct injection (GDI) on their modern V6 engines to help reduce emissions while maintaining power output and fuel economy numbers similar to those achieved by earlier generations of port fuel injected (PFI) designs. GDI technology injects fuel directly into the combustion chamber rather than into the intake port upstream of the valves as in PFI designs, allowing for more precise control over both air/fuel mixture preparation and timing of ignition events.