BoonDocker ARCTIC CAT: 700/800 Turbo - Manual (Page 12)

BoonDocker – 1585 Hollipark Dr. Idaho Falls, ID 83401 – (208) 542-4411
website: www.boondockers.com - email: [email protected]
Revised 12-01-00 Page 12 of 15
Air/Fuel gauge:
A good wideband O2 gauge is highly recommended as an effective tuning tool. The sensor will have a limited
lifespan due to exposure to pre-mix oil and leaded racegas, but in many cases it can last for a season and it is a very
valuable tuning tool. If desired, after initial tuning is completed the probe may be removed to prolong its life.
Be aware that too rich a mixture can cause the gauge to read lean due to unburned fuel not being read by the gauge
(the oxygen will produce a lean reading). Whenever the engine is decelerating, your A/F numbers will be lean - these
readings can be ignored. However, whenever the throttle is being applied, pay attention to the readings!
Higher numbers are leaner (less fuel), lower numbers are richer (more fuel). A 14.7:1 ratio means all the available
oxygen has combined with all the available fuel. Numbers from 11:1 to 13:1 generally produce the best power (extra
fuel helps cooling and can help prevent detonation). A lower A/F ratio (10.8 to 11.2:1) is considered safer on a turbo
since the extra fuel prevents heat build-up and helps prevent detonation. We recommend you find the lowest ratio
where the sled still runs without being too rich.
EGTs:
Exhaust Gas Temperature gauges can also be an effective tuning tool, but they are not a substitute for reading spark
plugs and piston wash and for a general feeling of how the engine runs. Use EGTs only as a backup to verify what
you see. They can be misleading under certain conditions and safe readings can vary greatly from engine to engine
depending on such things as probe placement, fuel, timing, pipe design, porting, etc. For this turbo, typical EGT
temps seem to be around 1300 – 1325degF after a long pull.
Plug and Pipe Color:
Color will develop inside the pipe and on the plug after running a while which can be used to determine fuel mixture.
A tan/cardboard brown color is desired. Light-gray is too lean, and dark brown is rich.
Tuning Tips:
Important: Find the settings where your motor runs RICH before you decide to go lean!
1. Tune with the engine and pipe at operating temperature. The sled’s ECU will make adjustments as the engine
warms up – you might think the engine needs leaner settings then later realize you are too lean once the engine
warms up.
2. Use the Load/Save Map feature to quickly change and compare fuel settings when testing. This can also be useful
for riding under different conditions. For example, changing elevations or temperatures may require different
adjustments if the stock ECU does not compensate properly for your modifications. For drag racing, you might
want to run richer settings to be safer for longer distances than you would for short distances.
3. To find out where a fuel adjustment setting is effective, greatly increase only that setting. Run the engine to find
out when it suddenly becomes too rich – this is where that setting is effective. Be careful – you can easily flood
the motor, especially with LO load or low RPM settings. To restart a flooded engine you may have to pull several
times with the throttle held wide open and/or the injectors uplugged.
4. The nitrous button can be used to add or subtract fuel interactively. When the nitrous button is pressed, the
amount of fuel set in the nitrous menu will be added in addition to the fuel adjustments that are already made.
Also consider the following:
A/F Mixture Generally EGT’s get hotter as the motor gets lean, but too lean and the temps can actually drop! As
oxygen is added, the flame gets hotter to a certain point, then too much air can can gradually cool things
off.
Detonation Detonation often requires an experienced tuner to detect – in most instances it cannot be heard or
noticed. Careful examination of the piston and sparkplug are required. Watch for melted