When we did our dyno testing it was in the mid fifties F, and the enthanol wires had no measurable effect on fuel flow, plugged or unplugged. According to our Polaris tech support, with the temp we were testing at we were in the lean mode. In cold winter weather it's 5% added or thereabouts in ethanol mode. I think I had that backwards.
We don't ride in 55 degree weather either, air density changes with elevation and also temperature and humidity. Is the Polaris fuel map "right" in the off snow conditions tested. You can adjust dyno results for these factors, not necessarily how the engine performs or how the ECU is mapped.
We ran the pipe center section temp as hot as 1100-1150 degrees F. The question is how hot is everyone's pipe center section temp when you ride? Everyone who is into performance sledding would benefit from knowing that, and knowing where his HP peaks at from cool, on takeoff to as hot as it ever gets on your longest period at WOT.
OK, but what about pipe temperature at the sensor location on the outside of the pipe? Won't that outer temp build higher than center section temps? If not, then what has Polaris set at the probe as the hot pipe limit that changes fuel and the advance curve?
During dyno testing we have the advantage of holding the engine WOT steady state at lower revs where leaner 13/1 A/F ratio occurrs, allowing CS temp to climb quickly to 850ish to begin each test, with the idea of being well over 1000 at peak revs which was our target.
From our charts you can see how stock fuel flow peaks at 113 lb/hr and close to 10/1 around the torque peak creating that camel-hump in the HP curve, and the higher you rev it the lower the fuel flow drops. The PCIII map we created flattens out the fuel curve, and drops it at peak HP to below 100 lb/hr, then remains fairly flat beyond that. By eliminating that huge pile of fuel, we get the pipe hotter, quicker which combined with two points leaner A/F ratio adds 5-10 HP depending on pipe temp that we're operating at.
Next time we test Casey's stocker I'll try to put together a chart of just where peak HP occurs, from 500 to 1200 deg F (I don't think it's possible to exceed 1200 in the field, even mountain climbing). Then all you guys can know exactly where to clutch to for max HP in any condition. The change in the speed of sound has nothing to do with altitude, just temperature so the CS temp/ HP peak RPM chart we create here at 1000 ft should apply at 10,000.
See above-air density, probe location?
As Donovan suggests, and as you see in our test data, we surely make more HP at lower coolant/ engine temps (100 vs 125) but the main benefit of 100deg F coolant for low altitude riders is avoiding detonation, keeping peak combustion chamber temps low enough to prevent the formation of those nasty active radicals even with leaner more powerful A/F ratio that we created with the PCIII. And this also prevents the very protective 09 ECU from sensing the slightest knock, pulling timing, adding fuel and further reducing HP.
For now, the only ones I know of who have ridden hard in the field while measuring the pipe CS is Bill and Donovan from Xtreme, on last years RMK800s. No sense guessing and arguing about what it is, just measure it and hopefully the temp/ HP peak RPM data we create will be extremely useful.
