Rc Collector Exhaust For Suzuki Gs550

EVALUATION

RC COLLECTOR EXHAUST FOR SUZUKI GS550

Thanks to the able men who design exhaust systems at the motorcycle factories, the old certainty of always getting more performance from after market parts has in recent years been not at all certain. Or even easy. Regular readers will recall that getting results with a Ka wasaki KZ650 required several weeks, a bit of parts juggling and the help of two exhaust system makers.

This time it was easy.

R.C. Engineering is the firm owned and operated by Russ Collins. a man who needs no introduction to drag racing fans. Russ is famous for his quarter-mile terrors. the latest being a wide-based Honda V-8 constructed by joining two Honda Fours and filling the Vee with a supercharger.

Collins' business is high-performance parts for street and competition. so natu rally his shop is experienced in working with the current crop of Fours from the major manufacturers.

Our long-term SuzukiGS550 ridden and equipped for use as roadster. R.C. Engineering was choice for an exhaust system. In went. Couple days later, back fitted with a collector. is being a sports an easy the bike it came.

The design is conventional, being four new head pipes. 1 3/s-in, O.D.. each with a primary length of 28 in. That's on the short side for the street. While the factory may choose a primary length that looks neat and doesn't require bending and sweeping. proper exhaust tuning must have a precise length. with each pipe being the same length and that length picked on a sliding scale. The shorter pipe. within the for mula. the higher the rpm at which that pipe works best. A 28-in, primary pipe gives power on top.

The primaries join on the right side.just aft of the transmission case, and feed a rotational collector. The four pipes merge into a tapering cone in firing order. 1. 3. 4. 2, counting clockwise. The collector and head pipes are welded together and the muffler/megaphone slips onto the collec tor. The combined word is used here be cause the outer portion of the unit is a megaphone. just like the racers use. R.C. builds muffling cores. tapered with a vari ety of holes and baffles wrapped in fiberglass. The muffling cores slip neatly into the cone and are fastened with a bolt that meets a fixed nut on the core.

The buyer thus has a choice of noise level.

First, though. the R.C. system bolted right on. no hassles. And the complete package weighs 19 lb. less than the stock head pipes and twin mufflers.~

Because we are allowed to experiment.

we got the system with two cores, loud and quiet, the better to experiment with.

First experiment was performance:

That's about as nice a sliding scale as one can ever hope to see. The R.C. system works. Better, it works best as a system. that is. the tuned head pipes and collector do more for the bike than does the lack of silence, as proven by the biggest gain com ing between stock and quiet. Gets harder and harder to pretend that noise equals power.

About that noise. Our test program in cludes a sound level meter. which we use in a simulated version of the test developed by the California Highway Patrol. Now. We do as accurate a duplication as is practical. We do not claim this test is an exact duplicate. We do not say it proves a system to either meet or not meet legal requirements. in California or elsewhere. This test is for comparative purposes only. And because sound levels aren't part of our standard road test, we have no figures for the bike when stock.

So. Our meter. 50 ft. away from the bike. which made passes at full power in second gear. told us:

At the beginning of this scale, we have an exhaust system which is definitely sporting. Nice smooth hum becoming a moan as revs rise, like the four-stroke GP hikes of the past. more's the pity.

The loud core surely is loud. It was too loud for us. even, on the road. And the open megaphone is useless in public. Sound levels of more than lOOdBA will cause hearing damage over an extended period of time.

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All the sound level testing is open to interpretation. We suspeet that the quiet core will emit more noise than the stock system, and thus may be illegal on the public highway in some states. Check local authorities, as they say. The loud core will have this problem magnified and we can’t recommend it even where legal. Too much to lose in public image for the slight gain in performance.

No other changes were made to the bike and none were needed. The GS550 ran perfectly with the R.C. system and stock jets and plugs. Throttle response was excellent and there was more torque all along the rev range. The short pipes do their best work at the high end and we got our best times shifting at 9200 rpm. There was slight detonation in the mid-range at part throttle. Riders whose style makes this appear consistently could probably cure it by raising the needles one notch.

Fuel use with the RC system is so good we suspect the bike may be improving with miles as well as with modification. The original test figure was 42.4 mpg. Since the RC system went on, the 550 has been returning 47 mpg, with one tankful at 50.4. Whatever the cause, the results are most welcome.

Meanwhile, price for the RC collector exhaust system, complete with all hardware and choice of cores, is $159, chrome only. Check your local dealer or R.C. Engineering. 16216 S. Main St.. Dept. B. Gardena, Calif. 90248. ¡3