chromedome

So I'm driving home late at night, few cars on the highway, I turn off the radio and I hear a faint, very high pitched whine coming from the engine bay when going 40-50 mph. It sounds like an electric motor spinning at high speed and frankly it's a bit irritating. The sound is there whether the engine is running and charging the battery, the car is using the traction battery or it's coasting and regenerating power. The sound stops for a moment if I gently accelerate and then lift off, but it comes back on coasting.

It's different from the louder, low pitched subway-train sound that comes from regen braking at low speed. Could this be the dreaded CVT whine reviewers complain about? Or is it the normal sound of the MG1 unit? This car is really quiet so weird noises pop up more.

SLH

If it sound like an electric motor spinning at high speed, it very likely is an electric motor spinning at high speed. These cars have two electric motor-generators, and either or both of them can spin at high speed. The computer decides how to operate them, based on driving requirements and battery charge condition.

I hear them occasionally, when I turn the radio off. If it bothers you, I suggest you turn your radio on.

Arty101

I agree with SLH. I think it's one of the two motors spinning at a high rpm. I also agree you should just leave your radio on so it won't bother you.

PirelliRC

i hear it but it doesn't bother me anymore than a ICE decelerating or engine braking. I think you drove a hybrid for so long that you forgot how loud engines are

chromedome

I can't believe it's been almost a year of hybrid ownership. I'm not sure I'd ever go back to a normal car after being spoiled by the lack of vibration and noise.

I read up more on the Toyota Camry Hybrid, it uses the same drivetrain as the ES300h and it's a bit different compared to a Prius. There's a second planetary gearset to multiply torque going to MG2; the MG2 unit is also redesigned to have stronger low-speed regen, hence the loud subway-train sound when slowing down. The high pitched sound is from MG2 spinning at high rpm and the whine gets masked by road and wind noise at higher speed - that's why I could hear it with energy flowing both to and from the motor.

TLDR; I'll keep the radio on

Arty101

I personally think that is the sound of saving money.

PirelliRC

especially when you are getting 44 mpg

chromedome

If you guys really want to get technical, here's a detailed report by ORNL on the 2007 Camry Hybrid. The 2012 Camry/Avalon/ES300h systems are pretty similar.

http://info.ornl.gov/sites/publicati...es/Pub7568.pdf

xclream

It doesn't bother me.

sound of the future is here now.

chromedome

The reason I brought it up is that one reviewer comparing a Volt, Leaf and Prius commented that the Leaf made a continuous, very high pitched sound at highway speeds that gave some people headaches. Teslas don't have this issue so it's down to motor design and a person's hearing ability. Personally I find it very irritating, almost like a mosquito whining, but the radio fixes it

Riles

Mine makes this noise too. I agree that 50mph is probably about where it is the worst, since the engine is very quiet and the road noise is also very low. I do still hear it at 75mph, but it's very faint as it gets drowned out by the (small) road noise.

I'm coming from a Prius, which didn't make this noise. However, that car was so loud at highway speeds, you wouldn't notice it if it did.

I was annoyed for a day or two but then learned to live with it. I bought this car because it was rated to be one of the quietest reviewed by Car & Driver aside from the crazy expensive top of the line cars (i.e. LS/S-class/7 Series), and it holds up to that expectation for the most part.

zes

It is MG1. That little guy really spins at high rpm. I read somewhere that is why the top speed of the 300h is limited to about 110mph or so, as MG1 is spinning like crazy. I am surprised at how they can make it last so long with such high rpm. Especially when the transmission does not even need an oil change.

chromedome

I think I also read about it somewhere on a Prius forum. The top speed in these hybrids is low because they're limited by MG1 spinning backwards to take up the engine's rotation - 14000 rpm on MG1 equates to 114 mph. Or something like that. Why they can't decouple MG1 at high speed, who knows.

I also read that the new Camry/ES hybrid system adds a second gearset to reduce MG2 speed. Now the max rpm is 4200 rpm instead of 14000 rpm in the old Prius. That's why I thought it was MG2 making that mosquito whine but it could definitely be MG1.

Does anyone have a proper technical breakdown of the Camry/ES hybrid system? I can only find stuff on older models.