Ask the Editors: You Down With VC?
Infinity’s VC production engine layout.
VC means variable compression and, like the name suggests – it is literally a system that allows for cylinder compression to be adjusted on the fly.
How it works is a bit complicated so we’ll do our best to simplify it – cylinder pressure is the result of how big around the piston (bore) and how far up and down said piston travels per cycle (stroke).
Since there is no conceivable way to change the piston diameter on the fly, VC instead alters the stroke to achieve its changes in compression. Whereas with a normal 4-stroke, internal combustion engine connecting rods serve to transfer the motion of the piston to the crankshaft. A VC system uses linkages on pivot points to be able to actually move the piston higher or lower inside the cylinder so that the distance it travels per cycle is shortened or lengthened depending on the situation.
Honestly, we hope never to see this technology come to ATVs but fear it just might in the future. Why? Well two reasons. First it adds a great deal of complexity to a system that is already getting more complex by the minute. That means more parts to potentially wear out, higher repair costs and likely a hike in MSRP.
Secondly, VC really isn’t a performance booster. Sure it looks like one when you think the compression ratio can be changed on the fly for max performance but think about what’s really happening here – right now your ATV already comes tuned with the compression ratio for the performance numbers the manufacturer is after. What the variable compression is really doing is decreasing that performance when it’s not called upon to slightly increase fuel economy/ put out less emissions. This is a technology being pushed more by politicians than one designed to give you a competitive edge.
