Hybrid Revs Coasting Down Hill

[Grabber Rick]

To all members with a hybrid. I have a 2023 with just over 13,000 miles on it. While going down a hill in normal or eco mode my truck revs like I am in a low gear. If I had a tachometer it would be showing very high rpms. I let my truck warm up then drove about 9 miles down the road. When I went down the hill my engine was definetly coasting with the rpms pretty high. It happens on a hill I go down by my house. It sounds like the truck refuses to shift into a higher gear. I know it does not have gears but near the bottom it will just stop that high rpm sound. Feels like it just shifts to a higher gear.
Has anyone else with a hybrid experienced this? Thank you and I will wait for some answers. Should I be concerned? Is this normal? My experience with my 5 speed Focus when shifting to a lower gear creates a high rpm. So does a automatic when pulling it into 2 or L creates this reving high rpm also. These scenerios are expected because I put it in a lower gear. My hybrid does it just by coasting down hill. I even pushed the throttle a bit and it still was reving like a low gear.

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[Ray-n-AVL]

Sounds like Hill Descent Control (If Equipped). Check your manual.

 

[Propane Burning Man]

I am not convinced what you are hearing is the ICE revving. Your ICE should not even be running going down hill, should be in electric mode. I have plenty of hills in my area and quite often I put it in L so I am not on the brakes going down hill and I can hear the regen braking revving the regen motors and it sounds similar to an ICE revving.

 

[Glen Baker LLC]

To all members with a hybrid. I have a 2023 with just over 13,000 miles on it. While going down a hill in normal or eco mode my truck revs like I am in a low gear. If I had a tachometer it would be showing very high rpms. I let my truck warm up then drove about 9 miles down the road. When I went down the hill my engine was definetly coasting with the rpms pretty high. It happens on a hill I go down by my house. It sounds like the truck refuses to shift into a higher gear. I know it does not have gears but near the bottom it will just stop that high rpm sound. Feels like it just shifts to a higher gear.
Has anyone else with a hybrid experienced this? Thank you and I will wait for some answers. Should I be concerned? Is this normal? My experience with my 5 speed Focus when shifting to a lower gear creates a high rpm. So does a automatic when pulling it into 2 or L creates this reving high rpm also. These scenerios are expected because I put it in a lower gear. My hybrid does it just by coasting down hill. I even pushed the throttle a bit and it still was reving like a low gear.

IT IS NORMAL OPERATION for a hybrid (even without Hill descent) going downhill when the battery is at capacity. When you're coasting regen is on if the battery is full the ice engine will rev (Engine Brake) to try and slow things down. I hope I explained it correctly.
You're Not hearing the electric motor revving during regen going downhill. It's the ICE

 

[Clarkdonbran]

Scary, but normal. I’m dumb, but I think your engine needs to expel the excess energy created by the regen.

 

[icegradner]

NORMAL OPERATION for a hybrid going downhill when the battery is at capacity. When you're coasting regen is on if the battery is full the ice engine will rev to try and slow things down. I hope I explained it correctly.

Yup, just a case of engine braking.

 

[HeyBales]

Normal - even though it sounds terrible when around 4500 RPM on some steep downhills.

Wasting the generated electric that can't be sent to the battery because it's full.

You braking - or the Hill Descent Control, will both cause regen and that effect.
At some point the HDC won't be enough to keep the speed, you'll have to dig into the brakes.
Which changes nothing on that RPM.

@Propane Burning Man - you've been hearing the sounds of ICE revving this whole time.

Ever been going 50 mph, and slowed up enough to slip into EV mode and keep the power up enough to stay there?
That's the sounds of the motors at high speed - almost silent.

 

[Propane Burning Man]

Normal - even though it sounds terrible when around 4500 RPM on some steep downhills.

Wasting the generated electric that can't be sent to the battery because it's full.

You braking - or the Hill Descent Control, will both cause regen and that effect.
At some point the HDC won't be enough to keep the speed, you'll have to dig into the brakes.
Which changes nothing on that RPM.

@Propane Burning Man - you've been hearing the sounds of ICE revving this whole time.

Ever been going 50 mph, and slowed up enough to slip into EV mode and keep the power up enough to stay there?
That's the sounds of the motors at high speed - almost silent.

I did not know that. Does the ICE actually fire up? In other words, are the spark plugs sparking and fuel being injected and burned just to slow the truck down? I hope the answer is no.

 

[HeyBales]

No fuel.

Purely just air braking.

Though - I have wondered what happens when the ICE hasn't met say the min 120F to be turned off yet in the cold, but you hit the point of needing to waste regen.

I've seen that a couple times this winter - but wasn't logging to review, or forgot by the end of the drive to review.
I'm guessing the fuel stops while it engine brakes, then ICE fires right back on for the needed heat.

 

[Cherokee]

“Normal - even though it sounds terrible when around 4500 RPM on some steep downhills.”

“Though - I have wondered what happens when the ICE hasn't met say the min 120F to be turned off yet in the cold, but you hit the point of needing to waste regen.”

I still can’t get my brain past the fact that this ICE can withstand this RPM when that cold.

And not wear at a very accelerated rate.

How are the rings not bypassing oil ? At those temperatures ? What was the secret to building an engine that can do this?

I mean, obviously Ford did it.
Is it the advanced oil’s we have now ?

 

[Jay H.]

To all members with a hybrid. I have a 2023 with just over 13,000 miles on it. While going down a hill in normal or eco mode my truck revs like I am in a low gear. If I had a tachometer it would be showing very high rpms. I let my truck warm up then drove about 9 miles down the road. When I went down the hill my engine was definetly coasting with the rpms pretty high. It happens on a hill I go down by my house. It sounds like the truck refuses to shift into a higher gear. I know it does not have gears but near the bottom it will just stop that high rpm sound. Feels like it just shifts to a higher gear.
Has anyone else with a hybrid experienced this? Thank you and I will wait for some answers. Should I be concerned? Is this normal? My experience with my 5 speed Focus when shifting to a lower gear creates a high rpm. So does a automatic when pulling it into 2 or L creates this reving high rpm also. These scenerios are expected because I put it in a lower gear. My hybrid does it just by coasting down hill. I even pushed the throttle a bit and it still was reving like a low gear.

Yes, mine does the same thing. When on a long downhill, once the battery is full the ICE engine will rev up for engine braking. I guess the algorithm really doesn't want us to use the brakes. Anyway, that's just what it does, no harm done.

 

[SteveM]

Your truck will charge your HV battery, while going downhill. It varies the charge rate as required to help hold your speed even. Once the HV battery is fully charged, the ICE kicks in to utilize "engine braking" to help reduce your speed. It sounds like it is reving, because it is. This is normal operation. I drive over 2 mountains on my daily commute, (2 each way, so 4 mountains total round trip). Yhis happens 4 times per day for me.

 

[Glen Baker LLC]

I did not know that. Does the ICE actually fire up? In other words, are the spark plugs sparking and fuel being injected and burned just to slow the truck down? I hope the answer is no.

Will,
Deceleration fuel cut off was basically implemented around 2010 on fuel injected vehicles.
Here's a little more information.

 

[MakinDoForNow]

The ice will rev up WITHOUT GAS OR SPARK COMPRESSING AIR TO BRAKE!!! It will only do so for a time and will add gas and spark as needed. The oil pump is working while ice is compressing air.

 

[OB1e]

Going down a long hill, turn the L off, otherwise it will sound like na airplane taking off

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