Unfortunately, the camshaft can call only one play.  The engine designer must choose a stronger running engine at low speeds or one that runs stronger at higher engine speeds.  Choosing one gives up the other.  Ideally, there would be at least three (3) camshafts in an engine - one for low speed acceleration, one for middle range cruising and one for maximum high speed output.  Since this is not feasible, the designer chooses which is most important and compromises the others.  Fuel economy is similarly affected by the camshaft choice.

     For decades, engineers have dreamed of having variable valve actuation for their engine designs.  This would avoid surrendering power at one range in order to have it at the others, and give the most efficient use of fuel at all engine speeds.  Two types of devices are now being used as original equipment by some manufacturers.  Mercedes-Benz, Lexus, Infinity and Alfa-Romeo have installed devices on some engines that retard or advance the intake camshaft to alter intake valve timing and valve overlap.  These designs allow more radical camshafts to be used for higher horsepower at high engine speeds without as much loss at lower engine speeds where most of the driving is done.  Such devices are referred to as VVT, for variable valve timing.  These devices are installed only on double overhead camshaft (DOHC) engines.

     Honda installs its V-TEC device on many of its Honda and Acura models.  The device differs from VVT by altering valve lift as well as valve timing.  It can be installed only on overhead camshaft engines.  All of these devices are so complex they must be designed into the engine from the beginning.  None of these are aftermarket equipment, and are available only to an owner of one of these select models.

     The typical car owner wanting to increase the power of his engine will remove some stock engine parts and replace them with parts purchased from aftermarket speed equipment manufacturers.  Replacing the stock camshaft with one designed to open the valves sooner, hold them open longer and open them farther is one of the most frequent modifications.  Unfortunately, the car then usually gets poorer gas mileage, loses power in the lower speed ranges where most of the driving is done, becomes more tempermental and has reduced driveability.

     The Hotrocker gives the equivalent of multiple camshafts in an engine, each taking its turn when that design is the best for a given engine speed, with the valve actuation changing as engine speed (RPM) changes.  Our device is notable for being more simple than any of the other VVT or VVA designs.  It uses the valve train parts already found in standard engines; it merely machines them differently.  It is disarmingly simple in concept, and as trouble-free as the standard components already on production engines.  Hotrocker replaces the stock rocker arms in an engine with rocker arms that have different ratios at different engine speeds.  Typical ratios on most engines are 1.5-to-1 or 1.6-to-1, and are fixed.  The variable ratio rocker arms can operate with ratios from as little as 1-to-1 and as big as 1.9-to-1.  Each position produces a different power curve as though the camshaft had been replaced by a different one.  This means an engine so equipped will get the benefits of a mild camshaft so desirable for most traffic driving, a more radical camshaft for faster cruising and an even more radical camshaft producing the most power at higher RPM.

     In dynamometer tests, this device has shown significant increases in the power and torque created by the engines.  These tests show that utilizing the Hotrocker in place of the usual rocker arms will enable virtually any camshaft to produce more power both at low speeds and at high speeds.

     In short, this device does give the equivalent of multiple camshafts that engineers have long wished for.  It does it with great simplicity, is easily incorporated in most engine designs currently in production and should have the durability of the valve trains currently being used.  An automobile in which this device is incorporated will perform as though a measurably larger engine has been installed in place of the existing one.  Yet, due to the increase in efficiency achieved by the Hotrocker, the fuel consumption will be less.

     You can read Jim McFarland's article on the Hotrocker in the May, 2000 issue of Hot Rod magazine, for additional discussion on the Hotrocker™ concept.
 

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