I did a little investigation on my car with my SGII and laptop.... Essentially if you monitor the Open/Closed Loop operation mode on the SGII, this is an accurate indicator of whether the ECU is injecting fuel or not. There is a multi-frame PID that is set to true when the ECU has cut fuel to the ICE -- and I verified at speeds up to 60mph that it mirrors the Closed/Open loop operation pretty much exactly. Open Loop = No fuel being injected into the ICE, even if ICE is spinning Closed Loop = Fuel being injected This was always assumed, but I'm not sure anyone verified this. I found that even at 60mph, if you SoC is decent, you can get about 1/6 of the way up the HSI before the ECU starts injecting fuel again.
I thought that there was no fuel use when the instant MPG gauge (on the Prius dashboard, next to speed) was close to 100 and it goes down as soon as fuel is used. Can you confirm that?
friendly, you can have fuel flowing and be at or above 100 mpg, so that doesn't always work. adrian, open loop with fuel flow will occur during stages 1 and 2 of warmup, correct?
That's right .... the MPG gauge is not an indicator of fuel cut as you can be giving fuel but be at 100mpg. I also noticed you can't really feel the difference when fuel is added. I kept adding throttle until fuel cut was disabled but couldn't really feel a change. (Other than more acceleration.) You can feel it when you go from decelerating to accelerating. I didn't pay attention to Stage 1 and 2 and the operating mode, but I don't think the Prius ever runs in open loop mode. I know my old Mazda Protege only went into open loop briefly when you turn on the car but it was very brief..... Because the car is warming up the catalyst in stage 1 and 2, I doubt that you will even go into fuel cut in those modes.......
Weird, I thought this was the sole purpose of this gauge, to let the owner know that car goes electric and no fuel is used. Well, I'm still learning. However, I must be a fast learner as my typical trip MPG is at the 60 MPG mark (city and suburban) and I had the Prius for less that a week. It was 50 MPG when I started driving it. BTW, I don't drive it slowly, usually 5-10 miles above the limits. This is probably best time of year for fuel efficiency as no need for AC and cold starts are not too cold yet.
No the guage is to show instant MPG. If you want to see the battery or ice status there is another screen for that on the HSI
Best way to watch the engine status is with a scanguage (or similar). rpm at 992 or so is generally fuel cut in my mind. zero is well, zero, and obviously fuel cut.
Friendly, with a ScanGuage you can acutally see instance MPG @ something like 1857mpg going down a hill and if the fuel is cut, 9999mpg.
I missed that. What is the screen to see the ICE on/off status? I'm familiar with the energy display, but it doesn't show ICE on/off, does it?
I think he is referring to the picture of the car with the arrows. I don't think it really truly tells whether the ICE is on/off, at least not timely.
No screen shows ICE status on the HSI.... A ScanGauge is the only easy way to do it easily. Fuel cut isn't always ~990 rpm. B mode revs up the engine and if your battery level is too high the ECU spins the ICE quickly to burn off extra battery power. But just display Open/Closed loop and you will know when you are not using fuel, even with the ICE spinning quickly.
^ It will at least tell if any "power" is coming from the ICE (red arrow). It could still be spinning though (no arrows). Yeah it is not a terribly accurate indicator of fuel burn.
