Does engine break consume gas in PowerBoost?
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Joined: Jul 2021
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Does engine break consume gas in PowerBoost?
There's a long down hill road near my house. Every time when I drive on that road, it starts with engine off charging the battery, but at the end of it (still has a deep downhill slope) engine always kicks on. I was curious at the beginning because I thought it should be in charging mode, at least it doesn't have to start the engine because it's downhill and my foot was on the break paddle. Latter on when I turned on the power flow and saw that engine was on due to "low gear and engine break".
My understanding is that before reaching the end of the slope, the battery has been fully charge, so it couldn't charge any more and couldn't use regenerative break. So my question is does engine break consume gas? And is there any way to avoid that? Thanks!
My understanding is that before reaching the end of the slope, the battery has been fully charge, so it couldn't charge any more and couldn't use regenerative break. So my question is does engine break consume gas? And is there any way to avoid that? Thanks!
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Joined: Sep 2010
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From: Livonia, MI
Engine braking should almost never consume gas, it wouldn't make a very good brake if it did. All engine braking is done by allowing the engine to intake air, compress it, then exhaust it. Gasoline doesn't have to be added to the mixture since you aren't making power. Most modern engines, maybe all, are smart enough to turn off the injectors so you compress air and that's it. No spark or anything either AFAIK. This isn't a PowerBoost specific thing, as mentioned basically all engines should do that.
You may hear the engine "run" in this situation and your RPMs may increase, but that is just due to back feed of power from the rear axle into the driveline and then to the engine. If you were driving a V8 it would be much more obvious the difference between powered and engine braking situations. But in the PB you won't notice much unless going down a serious hill and the engine is spinning at a high RPM. I remember engine braking when driving through the smokey mountains with our Flex (3.5L EB) and had that engine revving pretty good on some of the downhills.
The PB has a little extra help in some situations with the electric motor, since it can add resistance as "regenerative braking", but the effect on a hybrid like the F-150 is pretty small. A Mach E or the future Lightning could probably bring the vehicle to a stop on full regen even on a down hill.
You may hear the engine "run" in this situation and your RPMs may increase, but that is just due to back feed of power from the rear axle into the driveline and then to the engine. If you were driving a V8 it would be much more obvious the difference between powered and engine braking situations. But in the PB you won't notice much unless going down a serious hill and the engine is spinning at a high RPM. I remember engine braking when driving through the smokey mountains with our Flex (3.5L EB) and had that engine revving pretty good on some of the downhills.
The PB has a little extra help in some situations with the electric motor, since it can add resistance as "regenerative braking", but the effect on a hybrid like the F-150 is pretty small. A Mach E or the future Lightning could probably bring the vehicle to a stop on full regen even on a down hill.