Home of Rich Daly "The Mad Scientist"
Tuning The Rotax 800 Triple
Ski-Doo dropped their Type 809 three cylinder 800 engine into the new CK3 chassis last season, and while it proved to be a torque monster in the low end and midrange, the peak power output and bandwidth was lacking. Ski-Doo followed up with calibration improvements that seemed to make a significant improvement, but was this the answer or just a quick fix? Now for '99 we're told that the Mach Z (and Mach 1) will return to an end outlet pipe design; for what reason?
Rich Daly of Dyno Port (315-258-5618) successfully campaigned a Rotax 800 triple in the asphalt drag circuit this past Summer, and with the performance of the '98 Mach Z he wanted to show us what could be done with the Rotax 800.
Adding to the fun, Ski-Doo made available two more models using a single pipe version of the 800 engine, a Formula III 800 and the Grand Touring 800, both of which could be fitted with triple pipes. Other than the carb and clutch calibration to go with the different pipes, these engines appear to be identical to the triple piped Mach Z.
Rich started with a single pipe Formula III 800, which Ski-Doo told us would produce very similar horsepower to the triple piped 700 Mach I, placing it in the 130+ HP area. The engine was jetted for the air temperature and the engine pulled 132.2 HP at 7700 RPM. Rich noted that the stock jetting was very good right out of the box.
The type 809 engine is also used in the triple piped Mach Z, so a set of stock Ski-Doo triple pipes and muffler were installed, and the following dyno run recorded. This engine produced a stunning 147+ HP all the way from 7800 to 8800! This is the horsepower which can be expected from a stock 1999 Mach Z. Rich noted that an ignition rev limiter appeared to kick in at 8950 rpm.
Stage 2- Stock Triple Pipes, V-Force Reeds, Dyno Port Silencer
Many riders have been simply adding a silencer to the existing stock pipes, so the next run was to replace the very quiet stock muffler with a Dyno Port Canister silencer. The stock muffler measured 88dB in the dyno room, and the Dyno Port silencer registered 92 dB. Note that while the fuel consumption is slightly higher and the water temp is still warm that the silencer made an unusual 5 HP gain. Rich noted that this could have been jetted down one more size to make even more power.
Stage 3- Dyno Port Triple Pipes & Silencer
Rich knew that his Dyno Port pipes made more power than the '98 Mach Z pipes, but would they be any better than the '99 Mack Z pipes? The V-Force reeds were removed and the stock cages re-installed. Compared to the stock pipes & silencer, the Dyno Port pipes did pull over 10 HP more, but compared to the V-Force Reeds and Dyno Port silencer on the stock pipes, the power gain only amounted to about 2 Ĺ horse at 200 rpm higher. Rich is quick to point out that the V-Force Reeds really help. Triple pipes w/ silencer ($699.95), V-Force Reeds ($358.00), silencer for stock pipes ($250.00).
Stage 4- Longer Headers, thicker base gasket, machined head
Time to get serious. Rich knew from his successful asphalt racing this past season that the 800 responded well to changing the port timing, so he installed a thicker base gasket to raise the ports. To maintain the stock compression, the head was machined to compensate for the gasket change. This brought the power up to 166.8 HP @ 8700 rpm. Next, the header section of the pipes were lengthened, pulling the following run of 167.2 HP @ 8500 rpm.
Stage 5- Trail Porting
For stage 5, the cylinders were removed and the Dyno Port engine builders performed some mild trail porting. All other modifications remained the same, as did the compression. The power increased by 7.7 HP, still spinning at 8500 rpm. Perhaps more impressive was that the torque took a healthy jump also, now over 100 foot pounds all the way from 7800 to 8800 rpm, peaking at 108.8 foot pounds.
Stage 6- Bored Carbs & V-Force Reeds
The next step was to increase the airflow, so Rich bored the Mikuni TM-38mm flatslide carbs out. This only resulted in a 1.3 HP gain, up to 176.2 HP @ 8600 rpm. V-Force Reeds, which boosted the power on the stock pipes by 3.6 HP, were re-installed, and the power jumped up to 180.7 HP @ 8600 rpm, a 4.5 HP gain!
Stage 1- Stock Triple Pipes w/ V-Force Reeds
Next, a set of Delta V-Force reeds were installed. The broad powerband remained intact, and the reeds accounted for a 3.6 HP gain. Rich noted that the water temperature was a bit warmer on this run, yet the engine still made good power.
Stage 7- Lake Racer Porting
Here is the final stage, lake racer porting and head work, raising the compression and requiring 100 octane fuel. We're now up another 4.6 HP at 8600 rpm with a fairly broad torque band of over 113 foot pounds from 8200 to 8600 rpm. This is still using the stock airbox! When the airbox was removed and the carbs jetted up, it made less power, Ski-Doo did an excellent job with their airbox design.
Due to the rev limiter at 8950 rpm, Dyno Port worked very hard on the pipes & porting to let the engine make good power below 8900 rpm in all of these stages. The asphalt engine Rich raced with made 201 HP @ 9500 rpm, but this was a Pro-Stock race engine with bigger carbs, a '98 ignition, and higher rpm race pipes. For more information on any of these modifications contact Dyno Port at (315-258-5618).
1912 Scipio-Fleming Townline Road Union Springs New York 13160 USA Phone: 315-255-3665