Relooking at warm-up

Is there any way to force the car to skip the Open Loop process and begin using data from the O2 sensors earlier? i.e. is there a way to force the car to skip Stage 1a when warming up?

 

Maybe the first question should be: is there a substantial benefit? Then: how complicated involved would such a mod be? What are the draw backs?

And just my hunch, the direct answer's likely: no.

 

There is absolutely a benefit. In our Fusion Hybrid we can get the car to skip Stage 1a easily. This absolutely helps improve MPGs because during S1a the car is very slow to warm up. By skipping the Open Loop period the ICE warms up faster and thus shuts off sooner which greatly improves MPGs.

 

There is a substantial difference between warming in P and warming in N if you watch the battery amps. In P, the battery will charge (slowly) but in N it will discharge by as much as 10 amps. When you get to closed loop, the charging (in P) jumps to 20 amps or so as the engine moves into a more efficient phase. Since we are talking about hundredths of a gallon, this should be taken into account. My segment mileage is down by 10mpg or so when I warm up in P, but since it takes less time to finish the warm up (while moving), so I do not drive as far, it is hard to really draw a conclusion.

 

You can't skip open loop. Open loop means o2 sensor is cold and it doesn't work.

 

Yes you can. Our Fusion Hybrid can skip Open Loop and begin using readings from the O2 sensor immediately which is much more fuel efficient. Open Loop exists because of EPA emissions testing, it's bad for fuel economy. Nothing stops the O2 sensor from working when it is less than 40C.

 

Modern O2 sensors warm up very quickly because they have heating elements as referenced in the Wikipedia page you linked. The modern sensors too are very likely to be wideband sensors as well. Since the open loop phase exists as part of emissions reduction when the catalytic converter and O2 sensors are cold it's great in gas only cars. But in hybrids it doesn't seem to make a lot of sense since it limits how quickly the ICE warms up. In a gas only car in Open Loop the ICE RPM will still increase when you accelerate and the car will warm up. In a Prius in Open Loop the car will propel itself on battery and keep the ICE under a very low load at a low RPM for emissions purposes. This is how the smog score on the window sticker is so high.

My belief is that while this operating procedure is good for getting a high EPA smog score on the window sticker it is bad for real world fuel consumption and thus pollution. S1a generates less heat per unit of fuel burned compared to S1b or S2. Since S1a generates less heat per unit of fuel burned the car must burn fuel longer in S1a to achieve the same amount of warmth compared to if it ran in S1b to warm up. Burning more fuel means more pollution and lower MPGs. I've found in our Fusion Hybrid that forcing the car to skip S1a saves gas. Burning less gas makes less pollution.

 

Perhaps you could share the procedure used in the FFH to skip s1a?

 

The FFH has PRNDL with L being "Low". Low is similar to the B mode in Toyota hybrids. When the FFH is in S1a you shift to L for about 1-2 seconds and this causes the car to go into Closed Loop. Then you shift back to D.

It should be noted that the Ford hybrids don't automatically start the ICE and go into S1a when cold. The FFH won't engage the ICE even with a cold engine until it is demanded by acceleration. They then will stay on their own in S1a until the coolant reaches 40C unless the battery SOC gets too low. If the SOC gets low the car will automatically go into Closed Loop when cold.

You can also get the FFH to leave Open Loop early by pressing the pedal almost to the floor so that your power demand exceeds the maximum output of the electric motor.

Since we've only had the Prius a couple weeks I'm wondering if there's any way to get the Prius to go into Closed Loop early. As it stands now I get worse MPGs from the Prius starting with a cold engine that what I get from the FFH starting with a cold engine since I can skip the inefficient Open Loop operation in the FFH. Starting with a warm engine the Prius is clearly more efficient. I'm hoping to improve on the Prius' efficiency when starting cold since almost all our trips start with a cold engine.

 

I have never heard of a way to skip S1a, unless it is so warm it skips straight to s4 to begin with.

 

Interesting. Not even if you floor the pedal and exceed the power output of the electric motor? I haven't tried this yet in our Prius to see if it works. I didn't even know about that option in the FFH until another FFH Forum member commented on it when talking about the FFH warm up stages.

 

Bob - I tried shifting into B momentarily after the ICE comes on while accelerating but it didn't seem to do it...but I'll try it again. Mostly my wife drives the Prius, I typically only drive it when we're going somewhere together and take it rather than our Fusion Hybrid.

 

Good work bob and hybridbear!

 

So, swiching to B works? Will try that.

Flooring the pedal works only for the time you are flooring it, but then it reverts back to open loop, at least that is my impression.

Edit: how can I monitor Open/Closed loop with Torque app?

 

yes same here.....closed loop is quick on scanguage....almost immediate

so curious about what the fusion is doing or maybe one up for the prius

 

I guess the real goal/objective isn't Open vs Closed Loop. The goal is to skip Stage 1a. Where the ICE runs but doesn't power the car meaning that you burn a lot of fuel running rich for warm up but you power the car on battery and drain the HVB which then requires burning more gas later on to recharge the HVB.

When I drove the FFH last night I let it stay in Stage 1a for a few seconds and it says open loop. As soon as I shift to L and back to D the ICE begins powering the car and charging the HVB and the SGII switches to "Clsd Loop". My goal is to find something similar on the Prius to get past the inefficient S1a faster. Especially since the tests done by others indicate that come winter S1a will last a lot longer than the current 50-55 seconds. If we can get the ICE to run more efficiently (by burning gas under load not at idle like S1a does now) then that will save a lot of gas, or so I hope.

Last night I drove a very common 6.6 mile trip that we make numerous times per week. In the FFH I can consistently average 60 MPG on this trip starting with a cold engine. If I start with a warm engine I can average 65+ MPG. In the Prius in about 7 or 8 round trips the BEST I have gotten was 60 MPG when starting with a warm engine and no S1a. Commonly my results have been only 40-45 MPG. Another common 11.9 mile trip consistently averages 63 MPG in the FFH when starting with a cold ICE. I have tracked this trip for a few months and round trip average is 63 MPG in the FFH. In the Prius so far in 3 round trips my BEST has been 55 MPG starting with a cold engine.

This shows the penalty the Prius pays for Stage 1a. With a warm ICE starting out the Prius can easily beat the FFH in highway MPG and can barely beat it in city MPG from my experience. With a cold ICE the Fusion wins by a pretty wide margin in city MPG. This is quite disappointing as I expected the Prius to do better.

 

I was assuming that S1a was all Open Loop based on what I had observed but I guess I hadn't watched the SGII long enough. I'll watch it again this morning more carefully.