FFH engine noise

[mydodgers88]

OK, I have 20k miles on my 2010 and it has started making a new noise. When you are just cruising at around 40 mph and the motor switches over to gas, if you are just feathering the throttle you can hear a whistling sound. Took it into the dealer and surprise-the mechanic heard the same sound! They said they had never heard that before but it definitely was not normal so they would need to keep it a couple of days to diagnose the problem. Three days later they changed their mind and said that it is normal. They also said they test drove a new one on the lot and were able to duplicate the noise. Anyone else have this issue? Any information would be helpful. TIA, Mike

[mort]

Hi mydodgers88,

My FFH (12000 mi) has always made a noise maybe like you describe, a whistle or whine. Highway speed on smooth road. I think it is the tires. I think it is more noticeable on a slight right turn.

-mort

[paulbuck]

OK, I have 20k miles on my 2010 and it has started making a new noise. When you are just cruising at around 40 mph and the motor switches over to gas, if you are just feathering the throttle you can hear a whistling sound. Took it into the dealer and surprise-the mechanic heard the same sound! They said they had never heard that before but it definitely was not normal so they would need to keep it a couple of days to diagnose the problem. Three days later they changed their mind and said that it is normal. They also said they test drove a new one on the lot and were able to duplicate the noise. Anyone else have this issue? Any information would be helpful. TIA, Mike

If you look in the Hybrid folder that came with the owners manual, it says in there that a 'whistling' noise is normal. Mine's had it since day 1.

What, me worry?

[mydodgers88]

I'll have to check the manual tomorrow when I get home. Thanks

[JavaOops]

If you can't fix it, document it.

[Vlad Soare]

Talking about engine noises, I noticed something odd.

When the engine starts due to my accelerating a bit harder (say, just hard enough to exceed the EV threshold), sometimes it also charges the HVB as well (as indicated by the arrow above the battery gauge). At other times, both the engine and the electric motor are used together, and an arrow appears below the battery gauge, indicating that the HVB is discharging. That's normal behaviour. But here comes the strange thing. In the first case the ICE can be clearly heard. In the second I can barely hear anything. The ICE is much, much more silent when it works together with the electric motor than when it delivers all the power by itself.

I suspect it might be related to the active noise cancellation. It feels as if the ANC did a great job in the second case, but not in the first case, if that makes any sense.

Has anyone else noticed this?

 

[mwr]

The ICE is much, much more silent when it works together with the electric motor than when it delivers all the power by itself.

 

Why wouldn't that just be the normal case; the ICE is working harder when it's powering the car and also charging the HVB (#1) and working much less when it shares powering the car with the electric motor (#2).

[Vlad Soare]

I think the difference in sound level is too great to be explained just by the higher load.

I read in another thread that the ICE needs about 14-15 HP to drive the generator. That's barely 10% of its rated power. It's not like it had to work extremely hard to charge the HVB. On the other hand, if you drive a regular, non-hybrid car with a manual transmission, and you accelerate suddenly without downshifting, the engine must suddenly work much harder, but its sound doesn't change (at least not to a noticeable degree). So why would a hybrid's ICE sound dramatically different with a bit of extra load?

Edited September 1, 2017 by Vlad Soare

[mwr]

I think the difference in sound level is too great to be explained just by the higher load.

I read in another thread that the ICE needs about 14-15 HP to drive the generator. That's barely 10% of its rated power. It's not like it had to work extremely hard to charge the HVB. On the other hand, if you drive a regular, non-hybrid car with a manual transmission, and you accelerate suddenly without downshifting, the engine must suddenly work much harder, but its sound doesn't change (at least not to a noticeable degree). So why would a hybrid's ICE sound dramatically different with a bit of extra load?

In my opinion, it's not a "bit of extra load", but instead a big difference in load on the ICE. My FFH does the same thing and I love the lack of engine noise when in your #2 mode. I wish there were a way to "prefer" that mode :-)

[Vlad Soare]

The ICE is rated at 140 HP. An extra load of 14-15 HP is just ten percent of that. I wouldn't call that a big difference. Besides, there's still the question of why the engine of a regular car doesn't sound differently, nor louder, when you step on the gas (which actually puts a higher load on it than the generator puts on our ICE).

That's why I suspect it might have something to do with the ANC.

[aschulz261]

My guess would be that in scenario #1, the engine is running in it's atkinson cycle and you will get some noise back through the intake because of that. In scenario #2, it's in it's power mode and the atkinson intake noise is gone.

[mwr]

My guess would be that in scenario #1, the engine is running in it's atkinson cycle and you will get some noise back through the intake because of that. In scenario #2, it's in it's power mode and the atkinson intake noise is gone.

I thought the ICE always operated as an Atkinson-cycle engine. What's this non-Atkinson cycle "power mode".

[lolder]

They've acoustically tuned the intake tubing to have the least Atkinson cycle noise somewhere between 40-70 mph. That's what those strange plastic shapes are connected to the plastic intake tubes.

[aschulz261]

The Atkinson cycle isn't a TRUE Atkinson cycle. It is an approximation accomplished by using variable valve timing to close the intake valve very late. It is purely for efficiency, not power. When the ICE needs to produce maximum power, the intake cam is rotated back to a more normal position.

[lolder]

I'm not sure Ford does that otherwise the ICE would have higher rated horsepower.

[aschulz261]

180-ish normally aspirated 2.0 liter is pretty decent. That's NOT going to happen with an Atkinson cycle. The modern versions that are being referred to "Atkinson" cycle engines are really a modified Otto cycle that simulate an Atkinson cycle engine. That is accomplished with variable valve timing.

 

When a large amount of power is not required, BUT, the ICE needs to be running, it shifts to the Atkinson cycle for fuel efficiency. (This is most of the time the ICE is running in this car, btw) When a large amount of power is required, it shifts back to a normal Otto cycle for power.

[Vlad Soare]

Even if that were true, it would still not explain the noise difference I'm talking about. The Atkinson cycle is noisier. So the engine would have to be noisier with low loads (that is, when it's assisted by the electric motor, and the generator is not driven) than at higher loads (when it also drives the generator, and the electric motor doesn't cooperate), while in reality it's the other way around.

Besides, it seems to me the sound of the engine is always the same. It's just the loudness that varies. I believe reverting to an Otto cycle would also change the sound itself.

Edited September 7, 2017 by Vlad Soare

[lolder]

To my knowledge Ford does not shift their hybrids back to the Otto cycle otherwise the rated HP would be higher. Some other hybrids may.