On the SuperFlow dyno- the F-5 made 93.1 Chp @ 8000 rpm with a .72 BSFC-- plenty safe for pump gas at 15 degrees. If we were dyno tuning for max power, we would normally jet down @10% to achieve a 93 octane safe .65 BSFC (on this engine we estimate 96 HP x .65 BSFC = 62 lb/hr fuel needed which is 10% less than stock fuel flow), but this is box-stock certification to ensure "stockness". Leaner jetting should also raise pipe temperature and raise the power peak slightly. On the dyno sheet for this sled, notice the 14 Chp jump at 7800 rpm. This seems to be evident on the Artic-Cat exhaust valve equipped models when dyno testing in the transient mode (acceleration testing). We believe the Cats' exhaust valve opening time is set to match a smoking hot pipe (like you'd experience on a long lake blast, hillclimb or multi-minute steady state dyno test) and its accompanying higher RPM where the power peak occurs. Hence, if the engine is operated with a cooler pipe, the opening time will be too late for optimum performance. With most mechanical pressure-activated exhaust valves we are able to dyno-tune to produce optimal smooth torque/ power curves. When dyno tuning exhaust valves, we normally lock the valves closed and make a dyno "run" and then lock the valves open and make another run. This gives us two distinct power curves, and we then pick a spring rate to give us the best of both power curves, ideally connecting the peaks of both curves (you can see an example of such a situation in Volume 1 #2 when we fine tuned the first SkiDoo RAVE valve calibration). This would seem even easier to accomplish with electronic controls, but it appears as though the Cat computer doesn't alter the opening point with pipe temp. So what you see here is what you get with more typical warm-pipe dragracing or trail riding conditions, which some subscribers report feeling when accelerating out of corners, etc.

At the field shootout- on the box stock runs the sled loaded up really bad off the line. Seemed as though the pilot and /or needle was rich. The tach climbed slowly to 8150 and stayed there. It would appear that the clutching was a little on the light side and the bottom end jetting should be addressed. On the dealer prep. runs the rear coupling blocks were removed and the air box was drilled to accepted some breathers from D&D Powersports. The guys from Big Moose Artic-Cat figured that the increased airflow would lean down the blubbery bottom end and help a little on top. The sled hooked better but bogged almost as bad. The tach climbed to 8200 and stayed there. 2003 Polaris

On the SuperFlow dyno the Pro-X 600 made 110 Chp @ 7700 with a .70 BSFC. 440 main jets were stock. To jet to a .65 BSFC like last years model we would jet down to a x main jet and the power should increase to approximately 116. While dynoing this sled I goofed slightly. The first run was actually 112 Chp but I had forgotten to change the dyno ratio back to 2:1 from 2.38:1 from the RX-1 from one day ago. So we didn’t use that sheet. Sorry, Polaris guys.

At the field shootout- on the box stock runs the sled spun and then quickly overrevved to 8000 where the warm pipe HP drops off drastically. On dealer prep the rear blocks were removed, clutching was changed to shift harder and pull revs down, and main jets were changed to 390’s. The sled transferred a little too well creating more upward lift than forward momentum, which probably cost several tenths. The tach climbed right to 7900 rpm and stayed there. With a net .4 sec reduction in ¼ mile time the clutching seemed good on the dealer prep run. We believe that the new Polaris CDI's have engine protection that retards timing something like 4 degrees when engine coolant temp exceeds 140 degreesF. It is possible the Polaris guys got the coolant temp hotter than that while trying to get pipe temp up prior to the dealer prep runs by wailing the engine on the jackstand. If so, the retarded timing may have offset the benefit of the hot pipe in that situation.

On the dyno the Rev 600 made 117.3 Chp. @ 7900 rpm. Stock main jets were 380 which gave us a .72 BSFC at peak CHp.. The timing was advanced 3 degrees prior to dynoing (Ski-doo’s break-in procedure suggests operating for a period with timing retarded). Note that the horsepower dropped off 32.3 hp at 8000 rpm, only a 100 RPM overrev! Our second dyno pull resulted in the power peak sliding up to 8000, and then dropped 20 HP at 8100. You definitely want to make sure you have this engine under- rev slightly when clutching it to start with. We initially thought that the timing dropped off severely at 8100 but we now believe it may be in the pipe design. Bender Racing’s Terry Paine used our dyno to do some silencer testing on a Rev 600 and ended up improving the over-rev power with one of his silencers, probably because it's "tighter" (more restrictive) which raises pipe center section temp.

At the field shoot-out – on the first box stock run the sled spun violently and I noticed a "wah-wah-wah" sound out of the exhaust. This usually tells me that the sled is not shifting hard enough and the cool pipe acts as the rev limiter. The tach was at 7850 rpm, holding right at that 85 hp "rev limit" shown on our dyno sheets. The second box stock run was the same but the tach slid to 8000.

On dealer prep Doug from Smith Marine dropped the clickers down and leaned the main jets down 2 sizes and also changed the primary spring for a little more engagement. The Rev 600 still spun but the clutches shifted hard at 7800, seemingly correct. On the second pass, the revs climbed to 7900. While the jet size reduction would help HP a bit, most of the "dealer prep" improvement on this sled resulted from pulling the revs down, away from the "wall"--the RPM where power plummets on overrev.

On the dyno- Typical of other three cylinder single-pipe engines, the SXR600 has an extremely "forgiving" horsepower curve with power being very flat from 8000-8700 RPM. Like the other small-bores tested here, jetting is conservative.

At the field shootout- During the box-stock runs, the biggest problem was a bog on takeoff which hurt the 60' times. Down the track, the engine pulled at about 84-8500, safely in the engine's powerband.

For the dealer prep session, the Big Moose techs installed a Bender clutch kit. Also, the front limiter strap was shortened in an attempt to improve the "approach angle" from the track to the slide rails. During the dealer prep runs, the 60' times improved dramatically since the slightly higher engagement eliminated the bog. On top end, some of the benefit of the improved approach angle was negated by the ski pressure being increased.