<P> In most rear - wheel drive cars, the engine is longitudinally mounted and the front of the engine also points to the front of the car . In front - wheel drive cars with a transverse engine, the front of the engine usually points towards the right - hand side of the car . One notable exception is Honda, where many models have the front of the engine at the left - hand side of the car . </P> <P> In front - wheel - drive cars with longitudinally mounted engines, most often the front of the engine will point towards the front of the car, but some manufacturers (Saab, Citroën, Renault) have at times placed the engine' backwards', with #1 towards the firewall . One notable car with this layout is the Citroën Traction Avant . This layout is uncommon today . </P> <P> In a straight engine the spark plugs (and cylinders) are numbered, starting with #1, usually from the front of the engine to the rear . </P> <P> In a radial engine the cylinders are numbered around the circle, with the #1 cylinder at the top . There are always an odd number of cylinders in each bank, as this allows for a constant alternate cylinder firing order: for example, with a single bank of 7 cylinders, the order would be 1 - 3 - 5 - 7 - 2 - 4 - 6 . Moreover, unless there is an odd number of cylinders, the ring cam around the nose of the engine would be unable to provide the inlet valve open - exhaust valve open sequence required by the four - stroke cycle . </P>

What is the firing order of a straight 6 cylinder engine