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Colt Cams "Tri-Flow" hydraulic roller profile (TFII DOHC) TFII specifications: Primary Intake: 280 @ .383" Secondary Intake: 270 @ .386" Exhaust: 270 @ .386" Tri-Flow explanation: The most common problem among multi-valve engines is the "bogging" sensation felt when the throttle is opened all the way. When there is more than one valve opening at a time, a significant amount of air is allowed to pass through a given point. This is great...if the engine can use the extra air. If it can't, then the air is slowly pulled into the chamber, making its way (with the fuel) to the sparkplug. This slow-moving air is what causes problems with cars that have large cams or intake manifolds. High-performance engines require more air to make more power, but the power is made at high-RPM. At low RPM, there is much less air required. Since the air takes the same path whether it's moving fast or slow, the path will be efficient for one but not the other. An efficient “all-around” profile is what robs most factory engines of high-RPM horsepower that can be re-found by installing a performance camshaft(s). This phenomenon has been more and more prevalent with high-revving, multi-valve engines. When two valves open at the same time, there is twice as much room for the air to move through. Picture a vacuum hose that has a diameter of say 1”. It could quite easily suck up marbles or small rocks. If that same vacuum was hooked up to a vacuum hoe of say 5” diameters, what could it pick up? Maybe a feather, but the marbles and small rocks are totally out of the question. An engine works the same way! At high-RPM, there is a need for lots of air. At low-RPM there is a need for much less air. An engine can either be optimized for high-ROM, or low-RPM. At high-RPM, it is best to have the larger diameter “hose”. At low-RPM, it is best to have the smaller diameter “hose”. This “hose” can be easily equated to how far a value opens. The larger “hose” signifies a high-lift cam. The smaller “hose” signifies a low-lift cam. When an engine is optimized for high-RPM power, the low-RPM power will unfortunately have to be sacrificed…or will it? Over the years, racers have come to except the fact that their engines can have high-RPM power, or low-RPM power, but not both. Tuning an engine to get the most power in the RPM range that the vehicle will be used at the target most tuners go for. What if someone could make a performance camshaft that could make better power at high-RPM AND low-RPM, without the use of a variable lift cam system? Geoff Bardal at Colt Cams has managed to do just this for virtually ANY multi-valve engine. By staggering the opening and closing times of the two intake lobes, he has caused a change in the system. With the tri-flow, the engine starts the air moving with high vacuum when the first valve starts to open. Just when the engine begins to want more air, the second valve opens. This gives the equivalent to the secondaries opening up in the carburetor. In turn, the engine has better vacuum at idle with a larger cam since there is less overlap, but all the high-RPM power is still present because of the “secondary action” in the tri-flow setup. The result is a smooth, strong low-RPM powerband, with all the power and performance of a high-RPM performance camshaft. The engine becomes more manageable and responsive at low-RPM. These two traits can now be found in a camshaft that creates high-RPM power as well! Geoff’s theories on the “Tri-flow” have been proven time and time again, on several different engines, in several different classes, in several different events. The testing has proven the theory, and how it is time to let the world see the results.
David Atchison |