Additional fuel consumption when switching from EV to ICE?

[Ryan]

Hi everybody. This is my first post on the forum. Been driving my 2014 FFH since October; first hybrid I've ever driven. I feel like that initial adjustment period is over where I pretty much had to learn to drive all over again, but there's still a lot of room to improve my fuel consumption and capitalize on what this vehicle has to offer. I spent the weekend reviewing a lot of the forum and didn't see this particular question asked; apologies if it is there and I've missed it.

 

I'm curious if any of you might know (or speculate) whether or not it's costly each time the engine switches from EV to ICE. Is there any additional surge of fuel being consumed in that moment, just to start the engine (I refer to it as a tax for lack of a better term)? I don't know if it's because I still have some FFH driving to learn or if it has to do with the cooler climate, or both, but my engine goes in & out of EV quite regularly. Sometimes it's a case of me trying to force it back into EV by edging off the pedal, only to have it jump right back into ICE moments later to keep the engine warm.

 

I'm not so concerned if this fuel "tax" is tiny; I'm more worried that it's significant and I'd be better off trying to keep the engine in ICE. Thank you so much for taking the time to read my post, and thank you in advance if you take a stab at answering it.

[hybridbear]

Great question. This is something I have often thought about too...

 

There is certain to be some inefficiency in the momentum of the ICE which is lost when it turns off. With the ScanGauge I can also see the spike in amps flowing out of the battery when MG1 draws power to spin the ICE up to speed. I don't think there is much gasoline burned extra since the injectors don't inject gas into the cylinders until MG1 has spun the ICE up to speed. However, all the electricity in the battery comes from gas and starting the ICE requires electricity.

 

I have subconsciously begun planning while driving to try not to start the ICE unless I know I'll be able to keep it on for awhile. For example, if I'm driving in a residential neighborhood from stop sign to stop sign, I will try not to start the ICE since it would only come on for a few seconds. In these situations, the SOC of the battery doesn't increase at all. I like to try to plan my sessions of running the ICE to not only use it to propel the vehicle, but also to add charge to the HVB since the ICE is most efficient under a high load. It takes a few seconds after the ICE starts for it to generate enough electricity to replace what was used to start it.

[snowmonster]

I thought about this today while driving my 140 miles round trip on state highways averaging around 60 mph most of the time. Spent some time at 60 mph playing around with EV and watching the instantaneous MPG (Empower mode). Yeah, you gain a lot by driving in EV mode initially but then your instantaneous MPG tanks into the 20 range as it starts recharging the battery once the ICE kicks back in. I'm not sure you gain anything? The battery indicator did seem to indicate there was a battery "boost" or down-arrow for the ICE at times while the ICE was running and my net average never seemed to fluctuate one way or the other once the EV/battery recharge cycle was done. It seemed that the instantaneous MPG always stayed around 40 mpg if I never entered EV mode.

[acdii]

I found keeping the battery at 3/8ths or more while driving keeps the instant above 20 MPG. If I let it go below that point then the instant drops to 20.