Description Total Performance Intake Valve The Total Performance Intake Valve (TPI valve) is designed to increase air flow into your air box and carburetors in a controlled manner. Racers and tuners as well as many trail riders have known for many years that opening up the air box in order to flow more air makes more horsepower. This is usually called “ventilating” or “gutting” the air box. They also know that more air means that the engine will be running leaner exactly the same as installing a smaller main jet. Only one thing was missing, and that was the ability to go back to the richer jetting required for colder weather or lower altitudes. What did they do about this? They tried to tape or stuff foam rubber in the openings they had created. All of this was very messy and imprecise. Much of the time they were either too rich or too lean or they had to start changing main jets in order to be jetted correctly. There must be a better way. There is!! It’s called a Total Performance Intake Valve. The TPI Valve can be opened completely to the leanest position or closed completely to the richest position or any position in between. The Total Performance Intake (TPI) Valve gives you a range of two to four jet sizes of adjustment providing you use the recommended number of valves in your air box. For more information on airbox modifications, read: Airbox, Friend or Foe? The TPI “Knobby” Valve is 1 1/2″ diameter and 1 1/2″ high. The TPI “Low-Boy” valve is a flush mounting version which is 2 5/8″ square overall. TPI comes with black filters. Extra filters are available in Black for Knobby and Black and Red for Low-Boy. A cutting template is available for the Low-Boy Valves. TPI Low Boy – Adjustable Intake Valves Speed shops all across the snow belt are delighted with the results they’re seeing installing the new TPI (Total Performance Intake Valve) Low Boy adjustable intake valves from Thunder Products. This tight-clearance version of the adjustable TPI valves first previewed in the September 2002 issue of SnowTech Magazine has proven to be even more popular than the original version. The TPI Low Boy mounts into the airbox and allows you to open or close the added intake area to provide “air jetting”; more or less air intake surface area with the sliding “gate” on the valve. The installation of TPI Low Boys into the new MX Z 800 REV airbox provides an increase of up to five horsepower. They run with the valves open down to about –10 F, close one off at that temp, and close off both valves at –20 F. We’ve also heard from some mountain riders who have been adding the Low Boy valves to the RX-1 Mountain intake to provide added airflow when the stock intake starts to become restricted with snow. You can install TPI Low Boys on the cover. This provides an increase in airflow, requiring larger main jets and some other tweaks to compensate, with the result being an engine that is “way more responsive”. We have also seen excellent results using the Low Boys on the new Arctic Cat twins, integrating the TPI Low Boys into power-up performance packages for many models. We’ve even found the Low Boy valves to work extremely well on four-stroke dirt bikes; we installed one into the airbox on a four stroke Honda enduro bike and immediately realized more power, easier starting, more tractability, and less stalling. The possibilities are endless! Ask for the Low Boy valves at your favorite speed shop or contact Thunder Products directly at 320-597-2700. They present an attractive option to permanent airbox modifications and provide the tuner with yet another option in increasing the airflow characteristics of the engine. Technical Articles published on TPI – Total Performance Intake Valve Knobby Valve Low-Boy Valve Product Evaluation – 4 Wheel ATV Magazine Thunder Products, Total Performance Intake Valves Open it up! TPI valves allow air in, can be closed to keep water out, are simple to install, and don’t disable airbox lid’s air filter locating function. With these things, there’s no reason not to open it up – your airbox, that is. It’s a proven fact that many ATVs gain some power when their airbox lid s are removed. Unfortunately, not all airboxes are designed to go topless. Some use the lid to position the filter. If the filter isn’t seated properly, you could lose power – and your engine. Often, you can create a noticeable performance gain by merely cutting a few big holes in the airbox lid. That’s a great idea until you encounter water. Then, as you struggle to restart your drowned machine, you’ll realize why the airbox lid doesn’t have big holes in it to begin with. Thunder Products has a way for ATV riders to get extra air to their machines’ engines and still be prepared for deep water crossings. They’re called Total Performance Intake Valves, or TPI valves. They’re closeable guillotine-type valves that let you have big openings in your machine’s airbox lid when you want them and close them when you don’t. To install them, you cut a two inch by two-inch square hole for each TPI valve and fasten the valve assemblies in place with the provided sheet metal screws. Simple, really. The valves even have course foam filters of their own to keep splashes and heavy dust out of the airbox. We managed to fit two TPI valves on a Yamaha Raptor 660R airbox lid, opened them fully and did back-to-back trail and top speed runs with the valves open and closed. On the trail, the Raptor felt a bit more energetic with the valves open, but only after we opened the main carb’s fuel screw an additional two turns. In top speed runs on our “dyno straight”, a long, straight, slightly uphill road where the Raptor was still pulling when it reached the speed trap in fifth, the machine managed a best of 65.6 mph stock and 67.7 mph with the two TPI valves full open. It’s likely that a richer pilot and main jet would be needed to take advantage of the extra air flow, had we not been testing at 3000 feet above sea level in 75-degree weather. In our case, the elevation and temperature effectively richened the jetting to make the extra air beneficial. The neat thing about TPI valves is, you can close them partially or fully to take advantage of jetting and riding conditions. All things considered, we think they’re the most intelligent way to vent any machine’s airbox for more performance. They allow air in, can be closed to keep water out, are simple to install, and don’t disable the airbox lid’s air filter locating function. Total Performance Intake Valve Total Performance Intake Valve
