Hybrid engine racing going downhill

[Nosrepmodnar]

So I live in Nevada and every day I have some pretty good hills and never have any issues, just goesinto recharge braking and slows the truck down to the cruise control speed..
Traveled to California this weekend and going down a hill and the engine just started racing when it should have been doing the regen braking.
Did this a couple times.
I tapped he brakes to kill cruise and it still continued.
Hit the gas a while then let coast and still whining.
Has anyone had this, should I be concerned?

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[Waterick]

This is normal operation for the hybrid once the HVB is fully recharged through regeneration recharge. The battery can take no more, so the ICE helps in the braking going down hill. The system is programmed this way.

 

[MaverickDragon]

+1 on post 2..

 

[Esquire1990]

I am assuming you have the L button selected on the shifter or are Tow/Haul maybe? Once the battery is max charged the regen braking can't be used to produce any more energy to the battery. The truck kicks on the engine and uses it as an engine brake like long haul trucks to slow you down. Unselecting the L button will return it to normal, though you will probably need to use the brakes yourself.

 

[Red Eyes - Wide Shut]

That's interesting. I have never once had that happen to me. It seems that this would create a higher mpg. When coasting downhill my engine will shut off or just run like a nonhybrid at a normal rpm range. No load no revving.or racing unless quick deceleration.

 

[Glen Baker LLC]

Brad,
I also live in Nevada.
The L button has nothing to do with it.
Going downhill the hybrid will automatically change to engine braking once the battery is full.
You'll get used to it.
It does its best but there isn't a whole lot of engine braking to that little four-cylinder as "Esquire1990" suggested above you'll have to use you brakes a little.

 

[cyberdog]

As they stated, the engine spins without actually running to use the engine compression to slow the vehicle. It also occurs when letting off the accelerator once the HVB is at 80% capacity (System only charges to ~80%), even on flat terrain. Its also seems more likely to do so in cold weather, which lowers the battery capacity a bit.

The first time or so it occurred it certainly grabs your attention, making you think there's something severely wrong with the truck with the sort of racket or odd sound it makes. I know my gut wrenched, and had my mind freaking out a little, until I calmed, and though through what had occurred.

 

[MaverickDragon]

On a semi-related topic, what happens if you are light on the brakes to engages the regen function coming up to a stop, and during that process, the battery hits its max charge...

Would the Mav go into engine braking, and/or require a sudden increase in brake pedal to complete the stop....
That hasn't happened to me yet, but I can see where that scenario could happen.

 

[MakinDoForNow]

I am assuming you have the L button selected on the shifter or are Tow/Haul maybe? Once the battery is max charged the regen braking can't be used to produce any more energy to the battery. The truck kicks on the engine and uses it as an engine brake like long haul trucks to slow you down. Unselecting the L button will return it to normal, though you will probably need to use the brakes yourself.

Happens whether "L" button pushed or not but will happen sooner and faster rpm if button is pushed.

 

[HeyBales]

I am assuming you have the L button selected on the shifter or are Tow/Haul maybe? Once the battery is max charged the regen braking can't be used to produce any more energy to the battery. The truck kicks on the engine and uses it as an engine brake like long haul trucks to slow you down. Unselecting the L button will return it to normal, though you will probably need to use the brakes yourself.

L doesn't matter actually.
A Drive mode with stronger regen doesn't matter.
You braking more or less hard doesn't matter.

If HVB is full - ICE is spinning. And 4500 RPM sounds loud usually.

Neutral would make a difference - and totally into pads with brake pedal.
Which for a long downhill - well, there's a reason why they say shift into a lower gear - and the Mav is attempting to do that keeping the regen up.

 

[Mavster Mechanic]

On a semi-related topic, what happens if you are light on the brakes to engages the regen function coming up to a stop, and during that process, the battery hits its max charge...

Would the Mav go into engine braking, and/or require a sudden increase in brake pedal to complete the stop....
That hasn't happened to me yet, but I can see where that scenario could happen.

Happens to me almost every day.

I come off a freeway going steeply downhill. I need to lose 65 MPH and 300 feet of elevation at the same time.

The battery is tiny and gets full in about 30 seconds. Really.

2022 Mav regens for as much as possible. The hybrid battery limit is 70% charge. When it hits 70% engine brake will come on every single time.

Unless under 15 MPH.
I have a scanner.
I try to empty my battery before this decent. With practice this is possible.
Then I have "just" enough battery space to regen 65 MPH to 15 MPH with engine off, not spinning. Under 15 MPH (about) it will use brake pads only to come to a full stop.

Else if I hit 70% charged at 18 or 20 MPH engine will spin up for just a few seconds. Annoying. But programmers had to draw the line somewhere I guess.

The programming is not as refined as a luxury hybrid. But you won't have to adjust pedal pressure in those last few seconds.

 

[HeyBales]

On a semi-related topic, what happens if you are light on the brakes to engages the regen function coming up to a stop, and during that process, the battery hits its max charge...

Would the Mav go into engine braking, and/or require a sudden increase in brake pedal to complete the stop....
That hasn't happened to me yet, but I can see where that scenario could happen.

I get that often on way to work with short downhill.
Even funner when ICE is running due to not reaching 120 F yet, or whatever the minimum is for my temp selected.

Now that is some unsmooth action.

But to your scenario - yes I've seen the ICE spun up at about 10 mph while braking to a stop - just for the pads to be brought in fully around 8 mph anyway.
It can feel grabby - but no change to brake feel I've noticed. Pressure to me is the same - whether that means pressure to brake lines or calling on Traction Motor resistance.

 

[HeyBales]

That's interesting. I have never once had that happen to me. It seems that this would create a higher mpg. When coasting downhill my engine will shut off or just run like a nonhybrid at a normal rpm range. No load no revving.or racing unless quick deceleration.

Your hill steepness must be such that the ICE RPM is low and not noticeable.
If your HVB is actually full to 70%.
If not - then you don't see it.

 

[Wahjahbvious]

"Local driver discovers engine braking. This story and more, at 11!"

 

[Escapologist]

It's got "Jakes" and ppl still say it ain't a real truck

Seriously though engine braking has been a Semi Truck thing since 1965.

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