I have som problem with the autotune..
pro rmk 800 -13 with pa head and slp single pipe..
if I go 12.5:1 in afr on wot the autotune throws in 17% more fuel on top
if i go 13:1 in afr it throws in 12% more fuel and a afr at 13:1 it should be pretty lean.. my basemap is slp stage 3.. I loose about 300 rpm on top if i accept the trims?? if i go back to the stage 3 map the rpms on top are back..
why is it reading so bad? I have a spot down low it will throw in 20% of fuel and if i accept that the sled gets a bad bog down low..
the sensor is located next to the original exaust temp sensor.
thewayout84,
Installing the AFR bung next to the Exhaust temp sensor is a great location. It's in the fat part of the pipe, is far enough away from the engine to usually produce a laminar flow under sufficient exhaust movement, and is elevated to 10-2 O'Clock to prevent oil/moisture from draining in thus fouling the sensor.
A Major caveat here on these 2 Stroke CFI's is the sonic reflection under part throttle cavitating portions of the expansion chamber. From the factory, these engines run nearly 15:1 AFR on light cruise and skyrocket to 1300* in a hurry. Those readings came from installing a bung in the pipe vertically in the near straight part of the pipe ~12" from the skirt, another bung near the factory EGT probe, and another in the narrowed part before the silencer. Any of these locations yielded the same lean "reading" -- It is possible that the the engine is actually running there, or the gas flow is too sporadic to be accurately measured. All O2 sensors struggle in this condition.
Your option is to set your Target AFR higher (checking wash and plug color to verify partial throttle operation) and observe the trims. Since it becomes rich when you accept the trims down low, try a leaner AFR. An alternate option is to Not Autotune this partial throttle area, and tune it manually.
Another tidbit when using O2 for tuning and relying on the Trim tables: Only perform tuning under steady throttle usage. Blippy throttle movements wreak havoc on readings, induce countless accel pulses (Polaris uses a HUGE accel event), and jerks the duty cycles all over... which Autotune tries to follow... If you find a nice open area to tune, simply hold the throttle at those constant positions allowing the engine to rev out for as long as you feel comfortable. Then increase your throttle to a higher percentage making another pass. Repeat this until you reach 100%. (We even create throttle a stop by either drilling a hole in the lever and threading a screw to impact the grip ensuring stable throttle position, or by clamping an adjuster around the lever)
Since your Base map is SLP stage 3 and runs good there with RPM being sufficient on the top end, tuning to a "number" in your target AFR is still just a number. To obtain a chocolate brown plug color and good wash, your "sensor" might need to see 13.6:1 based on it's location, engine/pipe dynamic, etc., but the burn is optimal there - the
reading is irrelevant, the
condition is important.
A 13.1 AFR value attempting to add 12% or 17% on the top end may be too rich for the engine.
Steps to take:
1) Verify sensor condition. [I've run the same sensor on a 2 stroke for 3600miles, kept the same sensor when installing on a new machine and still had accurate readings (verified after swapping to a new sensor just for research purposes) even when running 50/50 premium/leaded race fuel.]
2) Ride with only your base map (no Autotune) watching your AFR reading, and examine engine condition at all throttles (checking wash/plugs). Relate the good condition to a number you witnessed.
3) Set up Target AFR tables to reflect your optimal burn conditions at each Throttle/RPM.
4) Enable Autotune and ride with constant throttle input.
5) Examine trim values and Accept All Trims if you are happy with the run and they appear reasonable.
6) Press "SEND MAP" once accepted (this is a highly overlooked step).
7) Repeat until you dial in on your Target AFR producing trims with values of +- 2 or less.
Hopefully this clear up a few questions and you are on your way to a well tuned machine -- and Happy New Year!
Regards,
~T.J.
