Power Commander 5 cruising MPG issue, And tuning questions plus my experiences so far
I had the low rpm downshift stall (rarely, but it happened 3 times in 1000 miles, which is FAR too often for my tastes) and the cough into the airbox (very VERY often, probably 75% of the time when starting off from a stop)
So I bought a PC5 to fix it. The bike hasn't stalled since and the cough into the airbox is gone. The bike feels stronger. I am running the off the shelf map for an otherwise stock bike right now, until I get a slip on.
I like the extra power, I love that the bike doesn't die or cough anymore, but I HATE having lost 10+ mpg at steady state highway cruising in the 65-80mph range.
I am fairly experienced with EFI tuning from my years as a Subaru guy, so I called Dynojet and confirmed what I suspected, that a 0 in a cell means ECU fueling, and any number is a direct % added or subtracted from there. Not really sure how it can nail down OEM fueling with the O2 sensors out of the picture, I am assuming it uses the base fuel tables in the ECU. Not ideal, but good enough for now. Ill add the autotuner later.
Looking at the map for an otherwise stock bike, there are HUGE percentages of fuel added in the 3500-4750 rpm ranges in the 15 and 20% throttle columns, which is where I am 99% sure I am when in the steady state 65-80mph highway cruising situation. The one cell has fully 20% more fuel than stock.
What I want to know is, WHY!!??? You don't need more power when you aren't accelerating, and as soon as you ask for more power by turning the throttle grip, you have moved out of those throttle % ranges.
I can't see any reason not to 0 out, or close to 0 out those cells. From what I can tell that should give me back the same MPG that the bike had stock in that situation or so I would think. The one cell in that are is adding TWENTY PERCENT fuel over stock. WTF for??? Dynojet couldn't give me a solid answer and even seemed slightly evasive when I asked why on earth would you do that lol. I gotta think there is a reason, but I can't think of wtf it would be. Unless the bike runs dangerously lean there.
I DO have one theory of why it MIGHT be that way.
If they have extra fuel there, that means there is more power to be made there over the stock fueling.
Which means if I load the bike up with some weight, or hit a slight hill, there will be more power there, reducing or eliminating the need to give it more throttle to maintain the same speed. That is the ONLY advantage I can think of.
Its not a case of "what if you want to smoothly accelerate to pass someone?" because when you twist the grip to do that, you will move out of those cells and their values become irrelevant.
I think I am going to go pull 5% across the board in the 10-15-20% throttle columns from 3000rpm to 5000rpm. That will still give me fueling over stock in many of the cells. If the cell has less than 5% added, I will only pull out what it has added so I don't go to less fueling than stock.
Ill report back after I do that.