In a move that brings Harley Davidson engines nearer to modern engineering methodology and performance, the company will be releasing their CVO bikes (Custom Vehicle Operations) in early June with a 121 cubic inches…a first for the company in a production bike, albeit they do offer a 131 cubic inch engine as a separate upgrade purchase…and this 121 cubic inch engine will have variable valve timing?
So what is variable valve timing and how does it work? Well essentially it is a way of stabilising and improving performance of the engine throughout the RPM range and factoring in environmental conditions. It will potentially give more torque and horsepower by altering the opening and closing timing of the intake and exhaust valves in the cylinder heads according to how fast the engine is spinning and according to the pressure and temperature of the air of the period of the day…So how is this achieved.
Well there are various methods, however they are all similar and this is what we can expect from the Harley Davidson engine too.
The cam is adjusted or rather rotated either hydro-mechanically or electronically with a timing solenoid or a combination of both. At low rpm, the cam will be fractionally offset and will be proportionally rotated as rpms increase to change the valve opening and closing sequence. The ECM will be largely controlling this and will factor in air density of the day to make minute adjustments too.
Where most of the changes will take place will be the regulation of the intake valve and when it closes. There will likely be a delay in it’s closing meaning higher horsepower at higher rpms and higher torque at lower rpms too. Essentially the valve will stay open longer at varying amounts within the rpm range.
The question is whether the traditionalists will welcome this advancement or will it be seen as the final nail in the air cooled engine coffin.
Certainly VVT offers it’s own issues and compatibility is probably the first thing to consider especially if you would be looking to modify or change the cams at a later stage. Perhaps Harley Davidson and after market suppliers will not even offer a cam replacement or alternative, let alone an ECM reprogram for the CVOs. Perhaps an engine with VVT is all you will get…or most likely in time there will be simplified modifications, but this could be a while.
The last question is whether the VVT will make its way into other models or will buyers still favour the greater flexibility of manual tuning options? Will variable valve timing be the new buzz word in the v-twin world or will in be a flash in the pan that will soon be forgotten regardless of how good it really is for the stock performance of a bike.
And herein exposes the ultimate divide. Will VVT favour riders wishing to have their bikes relatively stock…certainly from an engine performance aspect? Will VVT repel those riders wishing to continue with the culture of stage upgrades, cam changes etc.
VVT could be the next best thing in performance terms that Harley-Davidson have done, but it could also be another reason for the old guard to not continue on the H-D adventure.
More details of the H-D VVT engines to follow soon…