The sound shakes the eardrums.
Inside his small Thunder Mountain Performance shed on the west edge of Steamboat Springs, Shawn MacIntyre starts up his 1976 vintage snowmobile. His attention shifts to his 1998 Ski-Doo snowmobile. He gives the starter rope a sharp tug, and the 800cc engine roars to life. The sound bounces off the walls.
"I've been on sleds since I knew what they were," the Hayden resident said.
To most people, sleds, or snowmobiles, are just that -- a mode of transportation used to get around on snow.
But MacIntyre and his wife, Deb, have discovered a way to keep their snowmobiles running year-round. It's called grassdrag racing, and as the name suggests, the sport is comparable to auto drag racing except that it's on grass and done with snowmobiles.
"I've never felt my heart pound in my neck before," Deb MacIntyre said about her first grassdrag race experience. "But as soon as you get to the start, you forget everything. You just focus on the lights."
Red. Yellow. Green. And when a grassdrag sled speeds from the start line, it feels like a plane is taking off. The sled's front end lurches off the ground and remains airborne until the racer crosses the finish line about 500 feet down a straight, flat track.
"You just hammer the throttle down," said Deb MacIntyre, who placed second in a coed field in her first race in the 700cc stock division.
Shawn MacIntyre can make his vintage sled, which he rarely races, travel 70 mph or faster. He tops 100 mph in his improved Ski-Doo sled, averaging six seconds from the all-important start to finish.
"I work hours on clutching," he said.
The start is where a race is won or lost. This year, MacIntyre, who began racing sleds in upstate New York 15 years ago, has done his fair share of winning.
"This is my best year so far," he said.
On Oct. 30, MacIntyre took first in the 800cc, 900cc and 1,000cc improved stock divisions, as well as first in the 800cc open modified division at the Rocky Mountain Snowmobile Grassdrags at the Xtreme Performance Center in Denver.
MacIntyre did not change his engine for the improved stock races and still won by four sled lengths. After warm-ups, he played ball with his dog Rev while other racers and mechanics tinkered with their machines, to no avail.
"The enjoyment is to build it and make it go down the track whether I win or lose," MacIntyre said.
But he acknowledges winning is fun. Grassdrag racing is popular in Wyoming, Utah and Idaho -- MacIntyre is the only grassdrag racer he knows of in this area -- so he travels to Wyoming frequently during the summer.
This year, he took first in the 800cc and 900cc improved stock divisions in Pinedale, Wyo. He was second in the 800cc and 900cc improved stock divisions in Riverton, Wyo., and was third in the 800cc improved stock division at the state finals in Casper, Wyo.
Denver's elevation -- higher than 5,000 feet -- is the lowest MacIntyre has raced at since leaving the East Coast.
Building, tearing apart and modifying snowmobiles has only increased MacIntyre's knowledge of the machines -- something he thinks has benefited his career as a mechanic.
"This will help my customers," he said. "Racing on grass gives a snowmobile enthusiast a reason not to put it away."