Now lets say you have an un-calibrated system. For this demo we'll use TPS 25% TPS 100% (This is what I did in the video, by setting the throttle lock to ~25% and running the calibration.) Now the ECU and TPS are mismatched. The ECU see that when the throttle is fully closed, the TPS Voltage is 1.46V, therefore it needs to spray 200CC's of fuel in.
[CHART 3]
ECU 0% - 1.46V - 200CC
ECU 25% - 2.04V - 275CC
ECU 50% - 2.62V - 350CC
ECU 75% - 3.20V - 425CC
ECU 100% - 3.78V - 500CC
The ECU is now programmed to see that when the throttle is fully closed, the TPS Voltage is 1.46V, therefore it needs to spray 200CC's of fuel in. Because it's a simple computer, it cannot detect a negative percentage, so when you close the ACTUAL THROTTLE, the ECU is still putting out it's current minimum amount of fuel set for TPS 25%, because according to the ECU's calibrated programming, TPS 25% = ECU 0% Thus when you close the throttle completely, and the ECU is still putting out TPS 25% of fuel, but the Throttle is a 0%, you run into an extremely rich condition, thus making the engine run rough and inefficient.
[CHART 4]
Correct
Fuel CC
TPS 0% = 0.68V 100CC ECU OUT OF RANGE - 200CC - RICH CONDITION (HESITATION OCCURS HERE due to incomplete combustion)
TPS 25% = 1.46V 200CC ECU 0% - 1.46V - 200CC - Correct A/F Mixture (SPIKE IN RPMs OCCURS HERE)
TPS 50% = 2.23V 300CC ECU 33% - 2.23V - 232CC - Lean condition, less power, requiring slightly more throttle, using more fuel to maintain speed
TPS 75% = 3.01V 400CC ECU 67% - 3.01V - 364CC - Less lean condition, but still down on power, requiring slightly more throttle so on...
TPS 100%= 3.78V 500CC ECU 100% - 3.78V - 500CC - Proper A/F mixture
Again, someone correct me if I'm wrong in my thinking... I'm not an engineer.
Stephen, it took me a while but I think that I found the mistake in your logic. I marked the sentence that leads to the mistake. As one can see from Chart 3, the ECU is not programmed to
"see that when the throttle is fully closed, the TPS voltage is 1.46V"
but instead, the ECU is programmed to
"see that when the TPS voltage is 1.46V, the throttle is fully closed" --> although in our example it
isn't because we stopped it from closing by using a Go-Cruise.
Hence, any voltage below the 1.46 threshold will be seen by the ECU still as 0% throttle opening (because it cannot deal with negative %) and will be injecting the fuel for that throttle opening, which as Rembrandt pointed out, is idle. Therefore, although the throttle is slightly open (between 0% and 20%), the ECU thinks that it's fully closed and it injects too little (just enough for idle) --> lean condition. In fact, if the 100% throttle opening is correctly calibrated, the bike will run lean up until that point, all over the throttle opening range.
I added a table below, and also an example in which the WOT has been incorrectly calibrated. In particular, a case in which at the time of calibrating the full open throttle, the throttle was opened only to 80%, so the ECU learns that 4V mean 100% throttle opening. The bike will then run rich.
For my table, I assumed that the voltages go from 0V at closed throttle, to 5V at wide open throttle. I also assumed that at closed throttle the engine needs 1 cm³ of fuel (to keep it at idle), and at WOT it needs 20 cm³.
BTW, I am an engineer, but that's no guarantee, is it?
Regarding Rembrandt's measurements, of course the voltages stay the same. It's not important the voltages that the ECU sees, what's important is how it converts them to throttle opening.
Poll