Our dyno guys gave us a bonus test for this issue. When we asked for data on the new Polaris Indy 700 XC, we wondered if we could get a 600 to run as a comparison. Thanks to a little digging, and some smooth talking, we have dyno numbers for both domestic Polaris engines.
The Polaris domestic project began a few years back when the dollar to yen ratio impinged on Polaris' profitability. Looking to control costs, the Roseau boys opted to bring the engine work home, to the good old US of A.
Beginning as a watercraft engine, the 700 made the transition to mountain snowmobiling because of their similar characteristics. "Both watercraft and mountain sleds need power at the low end," explained Polaris VP Chuck Baxter. "It was a natural progression because of that similarity."
For consumers, the 700 RMK hit the salesfloor last fall, with the short tracked Indy 700 XC coming in midseason. But this project had been in the works for two years prior to release. "We've been working on this [the domestic project] for years. We knew everybody would be watching when we came out with our own motor, so we wanted to take our time and get it right the first time," said Baxter. "Jack Struthers did a lot of testing for us out west when our first prototypes came along in the '94-'95 season. We've addressed a lot of durability issues with this engine group. For instance, we harden the entire crankshaft instead of the industry standard of localized hardening."
But cost efficiency and durability are not the only two foci of the project, performance was always a concern. "We made performance one of our priorities," continued Baxter. "We decided that we wanted to design and make the best performing machines in the class, with the best durability. When those
two factors are combined, we felt that the value would come naturally."
With the first engine on the market and performing well, the second was not far from release. The 593cc motor is built around the bottom end of the 700, with smaller jugs and heads. Both twin cylinder engines feature an oversquare bore and stroke, 74.5x68mm and 81x68mm, a design which delivers a lot of torque and reaches peak power at a lower rpm.
Judging from the dyno sheets, both Polaris motors have a very forgiving power band of several hundred rpm. The 700 motor managed to hit a best of 124.5 hp, with outputs above 120 horses from 7600 through 8100 rpm. It shouldn't be too hard to clutch this sled for optimum performance.
By contrast, the 600 motor topped out at 109.3 hp at 7700 rpm. Its power band is equally wide, but occurs slightly lower on the tachometer, with horsepower over 105 from 7500 up to 8000 rpm.
According to our dyno guys, both engines are solid performers. Problem areas typically found on other units, like air boxes that reduce airflow and thus lower performance, aren't an issue on the XCs. "We tried a modified airbox on the 700 and lost power," notes Rich Daly, of Dynoport. "It's not too often that we find that in high performance sleds."
While both motors have satisfying power output, a few bolt-ons will definitely
wake them up. One of the best things consumers can do for the money is replace the stock reed cage with a set of Moto Tassinari V-Force reeds. "We
got a full five horses out of just that modification at the same engine speed, with the same jets," said Daly. "We tried our silencer on the 700 with the new reeds, and got up to 130.5 hp at around 7900 rpm. For that, we did have to go up on jet sizes a little.
"With the lower and wider power band, consumers should have no trouble
getting these sleds up to peak performance in stock form. With a little clutching adjustment for the rider's weight and the right jets for the conditions, the new Polarises should be easy for guys to dial in."
Special thanks to Rob Schooping at Hot To Go Racing for loaning us the two test units. If you are interested in aftermarket bolt-ons for either of the XCs, call HTG at 716/773-6131.
American Snowmobiler is pleased to work with DYNOPORT in passing along
the dyno tests of key snowmobile models. DYNOPORT is an independent performance and dyno facility located in Union Springs, New York. American Snowmobiler and DYNOPORT make every effort to assure the accuracy of articles and technical information; DYNOPORT assumes no responsibilities for damages due to errors, omissions or applications of any information. DYNOPORT, 1896 Townline Road, Union Springs, NY 13160 · 315/258-9371.
1998 Polaris Indy 700 XC
BONE STOCK, AIR DENSITY: 92.4%
| RPM | CBT | CBHP | BSFC | FUEL | A/F |
| 7000 | 74.9 | 99.8 | .631 | 59.9 | 12.50 |
| 7100 | 76.6 | 103.6 | .625 | 61.5 | 11.76 |
| 7200 | 79.3 | 108.6 | .628 | 64.9 | 11.31 |
| 7300 | 80.7 | 112.1 | .615 | 65.6 | 12.15 |
| 7400 | 82.1 | 115.6 | .600 | 66.4 | 12.37 |
| 7500 | 82.7 | 118.1 | .587 | 66.0 | 12.55 |
| 7600 | 83.9 | 121.4 | .569 | 65.6 | 12.69 |
| 7700 | 84.0 | 123.1 | .560 | 65.1 | 13.13 |
| 7800 | 83.8 | 124.4 | .529 | 62.6 | 13.44 |
| 7900 | 82.8 | 124.5 | .516 | 61.1 | 14.29 |
| 8000 | 81.1 | 123.5 | .521 | 61.2 | 13.83 |
| 8100 | 79.3 | 122.2 | .550 | 63.9 | 13.26 |
| 8200 | 76.3 | 119.0 | .588 | 66.6 | 12.77 |
1998 Polaris Indy 600 XC
BONE STOCK, AIR DENSITY: 91.6%
| RPM | CBT | CBHP | BSFC | FUEL | A/F |
| 7000 | 69.4 | 92.4 | .579 | 50.7 | 14.52 |
| 7100 | 69.9 | 94.5 | .590 | 52.7 | 13.71 |
| 7200 | 70.7 | 96.9 | .597 | 54.8 | 13.47 |
| 7300 | 72.1 | 100.2 | .599 | 56.8 | 13.67 |
| 7400 | 73.5 | 103.5 | .590 | 58.1 | 14.09 |
| 7500 | 73.8 | 105.4 | .595 | 59.5 | 13.85 |
| 7600 | 74.9 | 108.3 | .585 | 60.0 | 13.59 |
| 7700 | 74.5 | 109.3 | .582 | 60.2 | 13.29 |
| 7800 | 73.2 | 108.6 | .588 | 60.4 | 13.14 |
| 7900 | 71.4 | 107.4 | .604 | 61.4 | 12.89 |
| 8000 | 68.9 | 105.0 | .607 | 60.4 | 13.13 |
| 8100 | 65.8 | 101.4 | .623 | 59.8 | 13.19 |
| 8150 | 63.3 | 98.2 | .640 | 59.4 | 13.47 |
RPM: Engine crankshaft speed.
CBT: Corrected Brake Torque.
CBHP: Corrected Brake Horsepower.
BSFC: Brake Specific Fuel Consumption.
FUEL: Actual fuel flow pounds per hour.
A/F: Air/Fuel Ratio.