Loud whooshing noises may startle picnickers in Rock Creek Park this Sunday. It'll be the passing pack of cyclists competing in the National Capitol Open Race, one of a series that's a proving ground for national and Olympic bike-racing teams. About 150 champions and aspiring champs have entered. Sunday's also the first day of D.C. Bike week: a series of repair clinics, commuter caravans and rallies.

If you like pizazz - and who doesn't? - racing is the spectacular cycle sport. Unless you're totally fit - and who is? - watching a race is the closest you'll get.

If you ride your bike to the race, you won't have to park your car: Parking's a problem. Except for Military Road, streets along the race route will be closed to traffic from 9 until 2. Park at the Carter Barron Amphitheater and walk to the race area.

Starting at 10, the men race for 10 laps, going 76 miles in about three hours. Women go three laps, or about 23 miles.

The fearless cyclists should circle the 7.6-mile course in about 17 minutes. Since you have to wait for each pass, it's important to bring a little lunch, a little beer, a Frisbee. Or you can, by means of bike trails, visit other vantage points. If you get lost, ask the race marshals - wearing orange sashes - for directions. They don't want you walking on the course.

The terrain is everything. Caroline DuBois in the D.C. Department of Transportation bike office says the exciting race-watching is at steep slopes. "Especially coming down a steep turn. There are - there's only one way to say it - wrecks."

There are really scary curves on this course: a 90-degree curve near the Equitation Field (see map) leads into a 180-degree hairpin.

From picnic area 8 to the start-finish area is straight going, and here's where you'll see the speed - from 30 mph to almost 50 mph. There's lots of room for spectators. The sprint to the end of the final lap determines the winner. Here, a good sprinter can cream the front-runner.

An abbreviated glossary of race terms may help you figure out what's going on, so you can get really excited at all the right times.

HE PACK The main group of cyclists.

THE SLIPSTREAM The draft the front cyclists create. At race speeds, above 15 mph, you've already overcome the friction of the road on the tires, and what's left is to push yourself through the air. If you're in a slipstream, you may be exerting 30 per cent less effort than the person who's playing windbreaker. In the middle of the pack's slipstream, you can go 30 mph without much exertion. When you're in an endurance race, saving yourself this way is vital.

THE BREAKAWAY Usually after two laps or more, some individuals get ahead of the pack and make a group effort to cut down on wind resistance. It's usual to see three-man breaks, where riders can take advantage of each other's slipstream by . . .

WORKING TOGETHER One rider in a breakaway leads for 30 seconds, then pulls off, the next comes up to lead for 30 seconds, and so on. The larger the group, the shorter time you stay in front. In a four-man break, there's a constant whirlpool, with a person in front only 10 or 15 seconds. There's no law that says racers have to work together, but if you let others do the work you're . . .

SITTING IN Also called a lot of other things. It's wise to cooperate. The front people who are bucking the wind tire, and consequently slow the breakaway group, including the person sitting in behind them. The pack passes them by.

HONKING Leaning far forward on the bike; getting "out of the saddle" to go up a hill.

DRAFTING, or pacing. You're accepting the pace of the person in front of you, you're close on his wheels. As in the bumper sticker, "If you can read this, you're pacing."

OFF THE FRONT The direction a breakaway wants to go, as opposed to . . .

OFF THE BACK They can't keep up. If they're too slow, they'll be ordered out of the race.

Peter Stevens is organizing the Junior World Cycling Championships to be held in Rock Creek Park June 25. He calls Sunday's race "a dress rehearsal," and cites the favorites: U.S. national road champ Wayne Stetina and former D.C. resident Mary Jane Reoch. "These guys really suffer," Stevens says. "They suffer less when there's a crowd."