ULTIMATE MOD
Words and PHotos By Jim Zuccone When Yamaha and Arctic Cat announced their new Viper/7000, 100LL Avgas, or modest boost on straight pump gas. This goal was which was to be based upon the Arctic Cat Pro Chassis with a Yamaha engine, the crew at Evolution Powersports immediately saw the potential for this marriage. Arctic Cat’s excellent handling chassis combined with Yamaha’s lightweight, torquey and sweet-sounding triple would be a home run…with BOOST.
accomplished with the EVO Advanced Piggyback Controller (EAPC). The EAPC allows EVO to retard the ignition timing to create a more boost-friendly timing curve, which makes the cylinder pressures safe for stock compression at the higher boost pressures than the kit is capable of.
The Evolution Powersports “Special Ops” division was tasked with creating a “no compromise” turbo kit for this family of vehicles from Arctic Cat and Yamaha. It was important to the owners of EVO to strike out in a new direction with respect to electronics and turbocharger and intercooling design. A brand new Yamaha Viper was purchased from Century Powersports in Stillwater, MN and shipped to the EVO facility. R&D began immediately to source the correct hardware and electronics to achieve the no compromise goal.
The EAPC also controls injector sizing. This means that rather than use auxiliary injectors, the stock injectors are replaced with larger ones that can supply enough fuel at the rated 275 hp. The magic in this is to not only supply enough fuel for top end power, but also have the part throttle drivability be crisp and responsive. The EAPC accomplishes this.
The sled had to have liquid-to-air intercooler technology. The reasons are simple; on a snowmobile, the airflow that a typical air-to-air intercooler receives is virtually nil, so the intake temperatures vary over a huge 150+ degree range. This makes it difficult to properly tune an engine management system that does not have the sophistication to handle these huge temperature swings.
The sled was immediately loaded onto a trailer and brought to the mountains in Steamboat Springs, CO for on-snow testing. The sled proved to be an animal. Throttle response was absolutely stunning. This was no doubt due to the decision EVO made to not lower the compression ratio and instead deal with cylinder pressures through timing changes with the EVO APC.
EVO’s liquid-to-air system is unique; it takes coolant from the tunnel heat exchanger, routes it through an EVO-designed secondary heat exchanger (mounted on the belly pan), then through the liquid-to-air intercooler and back to the engine. The system provides the engine with intake air that is always within a 20 degree range. The result is a turbo system that is virtually flawless in its running quality.
The EVO crew brought the sled to many locations throughout the US and Canada in order to test and refine the calibrations for all elevations and conditions. After polishing this kit for an entire season and putting the kit through its paces, the EVO crew believes the Big Chute Viper/7000 is the next “Evolution” of four stroke technology for mountains. It handles almost as easily as an 800 class sled, but with the torque and horsepower to put you over the top of just about any climb you can find.
The last hurdle was making this system easy to install. Since the EVO APC needed feedback from many of the factory sensors, it would EVO’s technology partner TiAL Sport was consulted for the have been a wiring nightmare to try to have customers cut and turbocharger, which needed to provide immediate turbo response splice the various required inputs. All of the correct male and female at high elevation and still make big horsepower. The turbocharger connectors were added to make the system 100% plug and play. selected is a custom Garrett GT28 series with a proprietary, divorced- The kit was fabricated at the Special Ops division of Evolution flow exhaust housing and 90 degree discharge compressor cover. Powersports/Motorsports facility in Tempe, Arizona and codenamed The turbocharger is capable of supplying enough flow for 350+ the “BIG CHUTE VIPER”. Initial dyno testing was completed and the horsepower at altitude, yet spool instantly. results were very promising: 275 horsepower at 14 lbs of boost!
The other big technological hurdle was to create an engine management system sophisticated enough to provide timing control, altitude-compensated boost control, injector scaling capability along with the correct fueling as altitudes and temperatures change, yet still be cost-effective and easy to install. The other crucial requirement was to have multi-map capability so customers could have the choice of running high boost with
38 Mountain Sledder