About that weird engine sound when coasting at low speeds

[Bob zimmerman]

On my truck, when I am decelerating in town and as soon as I hit 20 mph, I get that weird sound from the engine compartment that sounds like a steel rubbing sound. For a while I thought it was the electric motor or some other component but now I am rather convinced it’s a mechanical sound created to give the vehicle noise to alert pedestrians of my presence. It starts right at 20 mpg while coasting. Can you folks verify that what I hear is what you hear.
I am 100% not worried about anything under the hood, it’s just a curiosity.
Bob

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[710-oil-614]

https://www.pbs.org/newshour/nation/quiet-hybrid-electric-cars-must-make-noise-new-u-s-safety-rule

 

[ejouie]

It might be regenerative braking that you are hearing. In a loose nutshell, the electric motor is spinning as a generator to slow the vehicle and use that energy to charge the battery. 20mph is also slow enough that you can probably begin to hear it over wind noise,

Try playing with the drive modes to see if the noise is changed. slippery should make it the quietest while eco would make it more apparent.

 

[sprubs]

https://www.pbs.org/newshour/nation/quiet-hybrid-electric-cars-must-make-noise-new-u-s-safety-rule

it's this. it's a simulated engine sound. I wish reverse was the same sound instead of the beeping!

 

[zach57x]

Hybrids make a lot of weird noises

 

[Scupking]

My 25 acts a little different than my 22. For instance when I first drive it from cold it will keep the engine at a high rpm for the first few minutes. Does yours do that? I assume this is to top off the battery (my 22 did not do that). There is also a more noticeable vibration when the engine is running compared to my 22. As far as what you are hearing below 20 mph it's probably the simulated engine sound. I will have to keep the music down and listen next time.

 

[Tony Pandy]

Rattles me in that the sound reminds me of a water pump or Idler pulley bearing about ready to fail. Noisier than one of my first cars I owned (1963 VW Bug).

 

[ThisWas]

My wife and I own two hybrids. Her RAV4 makes a low-speed sound that people describe as a choir of heavenly angels; my Maverick makes a sound like it has a mechanical problem.

There's money to be made if someone lets us customize the electric-mode warning sound.

 

[710-oil-614]

My 25 acts a little different than my 22. For instance when I first drive it from cold it will keep the engine at a high rpm for the first few minutes. Does yours do that? I assume this is to top off the battery (my 22 did not do that). There is also a more noticeable vibration when the engine is running compared to my 22. As far as what you are hearing below 20 mph it's probably the simulated engine sound. I will have to keep the music down and listen next time.

Definitely does keep idle high, my assumption is to warm up the engine, more specifically engine oil and to cycle it through engine to provide protection, so it isn't kicking on and off when cold.

The engine isn't a true "Atkinson cycle" engine it achieves the atkinson cycle through variable valve timing.

If you listen when the engine kicks on and RPMs increase you can hear the change in the valve timing that brings the engine to a full crescendo. Would need someone more mechanically inclined than myself but I feel like in those 20-30 seconds the engine is operating more like an Otto cycle than the modified atkinson cycle.

 

[ejouie]

There's money to be made if someone lets us customize the electric-mode warning sound.

Tesla got sued over that.

 

[ThisWas]

Tesla got sued over that.

Interesting! I googled that and it's true. Tesla's implementation of a "Boombox" function for its Pedestrian Warning System had to be disabled in 2022.
However I think an alternative to the Maverick warning sound that isn't Tesla fart noises might be acceptable to the NHTSA.

 

[LimeMachines]

My '25 Hybrid makes a sound similar to that of a blow-off valve going off at low speeds.

 

[DJT]

I miss the absolute quietness of my 2019 Ford Fusion Titanium Hybrid, but I understand that not making any noise could be a safety hazzard. But still... it was soooo quiet; you could sneak up on someone and then hit the horn and watch them JUMP.

 

[Seand1109]

https://www.pbs.org/newshour/nation/quiet-hybrid-electric-cars-must-make-noise-new-u-s-safety-rule

Anyway to customize the sound, like to a Ferrari or McClaren?

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