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Discussion Starter #121
As Gbonebrake says it happens while just cruising at 52 MPH. It can be either a slight acceleration, de-acceleration or just steady speed so long as your at 52 MPH there's a loud roaring noise. It also happens at lower speeds. More noticeable (louder) in colder weather which is why I think there may be more (who live in warmer climates) with this issue.
 

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Discussion Starter #122
By my count, there's 37 of us on just this one site with 2018, 2019 and now 2020s with the same identical issue. All Honda says is that they are aware and working on a fix.
 

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Just took mine into the Honda service center this morning, since the noise has been so intermittent I've been hesitant to take it in without some proof (i.e. a recording) but got lucky and the mechanic that took it on the test drive was able to hear the deep roaring noise that seems to be coming from under the car.

1. As [email protected] mentioned he was fairly certain that the issue was with the noise cancellation system

2. He also verified that the noise goes away as soon as you roll down a window - I guess that is the temporary fix until Honda figures this one out.

I'm taking it in for next week where they will also fix the rattling noise coming from the HUD. I will post an update afterward... fingers crossed!
I was lucky enough to have both too. The primary reason I bought the car was quietness. I got a car that squeaks when its hot (HUD) and hums when it's cold (ANC). Great.
 

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No, this noise is not when the accelerator is floored. It is while cruising at around 50 mph. My understanding is that the lockup occurs in those exact situations, not during hard acceleration.
So I read an article on a test Car and Driver did and apparently it can charge the battery slightly when driving the wheels with the engine. What they said isn't clear is when exactly above 45mph this situation occurs but they said there are a number of factors, including when the system determines it's more efficient to do so based on the speed and load ect. Interesting. May have to look at the power meter more often to see if this issue occurs in my vehicle.

What other factors are involved I'm wondering? Are peoples phones connected through Bluetooth when this happens, what audio system, is the stereo on when this happens?
 
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So I read an article on a test Car and Driver did and apparently it can charge the battery slightly when driving the wheels with the engine. What they said isn't clear is when exactly above 45mph this situation occurs but they said there are a number of factors, including when the system determines it's more efficient to do so based on the speed and load ect. Interesting. May have to look at the power meter more often to see if this issue occurs in my vehicle.

What other factors are involved I'm wondering? Are peoples phones connected through Bluetooth when this happens, what audio system, is the stereo on when this happens?
The sure fire way to recreate the roaring noise is to set the cruise control to 52 mph. The sound occurs while on flat level surface or slight incline.

However, I do have a positive update on my car. On the 6th time bringing it to Tarrytown Honda in NY... They replaced all of the microphones and one of the speakers. Now the noise has gone from constant to only in the first few minutes and the sound cuts out once it is about to go into it's full roar. Not a complete resolution but an improvement. I will give it a week or two before I pass judgment. You know what "they" always say the 6th time is the charm... maybe.
 

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There is no point at which the engine is driving the wheels AND also charging the engine at the same time. Basically only time the engine is actually driving the wheels is when you have the accelerator floored.
Think about it. Why would it need to use the ice to power the wheels if your already up to speed and coasting. It very rarely uses the ice to power the wheels, again usually in situations where you have the pedal to the floor.
So I read an article on a test Car and Driver did and apparently it can charge the battery slightly when driving the wheels with the engine. What they said isn't clear is when exactly above 45mph this situation occurs but they said there are a number of factors, including when the system determines it's more efficient to do so based on the speed and load ect. Interesting. May have to look at the power meter more often to see if this issue occurs in my vehicle.
The ICE "powers the wheels" (gear symbols lights up in the center of the power flow diagram) under light acceleration only. The point of the clutch isn't to get a power assist, it is to skip the losses in the a.c./d.c. inverters. When the ICE is running, it is probably charging the battery more often than not.

You seem to want to help people understand the HAH, so please take this as helpful advice. You get a lot of things backwards. Like the points I just mentioned. Some things you claim to have observed about the HAH's operation are backwards from what everybody else observes. Some things you accuse people of having said are the opposite of what they actually said; I know, because I was one of them. Since I don't know what else you have backwards, I'm going to explain this with probably too-much detail.

The "normal" operation of the HAH, when not in EV mode, is:
  1. The ICE runs at 2000 rpm, and about 88 lb-ft of torque (or 33.5 horsepower). It is connected to only the generator.
  2. The Power Control Unit draws a/c current from the generator. This is what creates the countering force (drag) on the ICE.
  3. The PCU performs several electrical transformations on this current: A/C to D/C, a voltage change, and mixing with D/C power to or from the battery to get the right power for the motor. Then D/C to A/C, which is sent to the traction motor.
  4. The traction motor drives the wheels.
The numbers in step #1 represent the "sweet spot" for the HAH's ICE operation. It is 40.8% efficient. If more power is needed than what can be supplied at that level, the ICE steps up in to blender mode (blend, puree, liquify, etc.) to get more. This reduces efficiency, of course.

The problem is that there are small, but not insignificant, losses in step #3. So when the car's speed corresponds to something close to 2000 rpm (which is 54 mph with recommended tire inflation) and power demands are low:
  1. The clutch engages and the PCU disconnects from the generator.
    1. The generator spins freely; i.e., no drag.
  2. The ICE's rpms are roughly 37*mph. The ICE's power moves along what Honda calls "the hybrid line." It isn't quite a straight line, but is close to one that runs from (1500 rpm or 41 mph, 26 hp) to (2900 rpm or 78 mph, 53 hp). Exactly where its lower and upper speed limits are, I don't know. But efficiency stays above about 40% along this line.
  3. The traction motor either adds power from the battery, or pulls some off to charge the battery.
    1. On flat ground, it pulls off about half of the power. This is more than "slightly."
    2. If the car needs more power than what it can get from the hybrid line and the battery, the clutch disconnects and the ICE goes into blender mode.
The way the traction motor pulls power of is, quite literally, the same as regenerative braking. As long as the accelerator pedal is pressed, it is treated as the driver's power request; the tarction motor adds (powered by the battery) or subtracts (acts as a regerative brake) what is needed to achieve it. When the accelerator is released, the traction motor reverts to the level of regenerative braking set by the paddles (no carets is the same as one caret). This way, the system acts just like a conventional ICE car, which is what "simulates engine braking" means.
 

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The ICE "powers the wheels" (gear symbols lights up in the center of the power flow diagram) under light acceleration only. The point of the clutch isn't to get a power assist, it is to skip the losses in the a.c./d.c. inverters. When the ICE is running, it is probably charging the battery more often than not.

You seem to want to help people understand the HAH, so please take this as helpful advice. You get a lot of things backwards. Like the points I just mentioned. Some things you claim to have observed about the HAH's operation are backwards from what everybody else observes. Some things you accuse people of having said are the opposite of what they actually said; I know, because I was one of them. Since I don't know what else you have backwards, I'm going to explain this with probably too-much detail.

The "normal" operation of the HAH, when not in EV mode, is:
  1. The ICE runs at 2000 rpm, and about 88 lb-ft of torque (or 33.5 horsepower). It is connected to only the generator.
  2. The Power Control Unit draws a/c current from the generator. This is what creates the countering force (drag) on the ICE.
  3. The PCU performs several electrical transformations on this current: A/C to D/C, a voltage change, and mixing with D/C power to or from the battery to get the right power for the motor. Then D/C to A/C, which is sent to the traction motor.
  4. The traction motor drives the wheels.
The numbers in step #1 represent the "sweet spot" for the HAH's ICE operation. It is 40.8% efficient. If more power is needed than what can be supplied at that level, the ICE steps up in to blender mode (blend, puree, liquify, etc.) to get more. This reduces efficiency, of course.

The problem is that there are small, but not insignificant, losses in step #3. So when the car's speed corresponds to something close to 2000 rpm (which is 54 mph with recommended tire inflation) and power demands are low:
  1. The clutch engages and the PCU disconnects from the generator.
    1. The generator spins freely; i.e., no drag.
  2. The ICE's rpms are roughly 37*mph. The ICE's power moves along what Honda calls "the hybrid line." It isn't quite a straight line, but is close to one that runs from (1500 rpm or 41 mph, 26 hp) to (2900 rpm or 78 mph, 53 hp). Exactly where its lower and upper speed limits are, I don't know. But efficiency stays above about 40% along this line.
  3. The traction motor either adds power from the battery, or pulls some off to charge the battery.
    1. On flat ground, it pulls off about half of the power. This is more than "slightly."
    2. If the car needs more power than what it can get from the hybrid line and the battery, the clutch disconnects and the ICE goes into blender mode.
The way the traction motor pulls power of is, quite literally, the same as regenerative braking. As long as the accelerator pedal is pressed, it is treated as the driver's power request; the tarction motor adds (powered by the battery) or subtracts (acts as a regerative brake) what is needed to achieve it. When the accelerator is released, the traction motor reverts to the level of regenerative braking set by the paddles (no carets is the same as one caret). This way, the system acts just like a conventional ICE car, which is what "simulates engine braking" means.
I didn't get anything backwards I simply made a mistake that apparently so did the professional auto journalists who wrote the article said "contrary to what was thought" the engine can let the battery sip energy while driving the wheels. And yet again you make a ton of assumptions, just like you do with many other people onnhere, about things I never said, just to argue, and ignoring what I said just to repost it. I never accused you of anything you didn't say, and that's pretty hard to do considering there is a written record of everything. The second paragraph you quoted of mine is literally the end of your first one rephrased. None of this was an observation, so not sure where you got that from. Furthermore i had already admitted I made a mistake which is far more than you have ever done even when directly being proven wrong. Your reply is/was completely unnecessary.
 

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I didn't get anything backwards
You did, and you continue to by ignoring the backwards point you don't want to own up to, and misinterpreting the ones you try to own up to.

An example of the first is where you said "Basically only time the engine is actually driving the wheels is when you have the accelerator floored." If you look for the mode table somewhere about page 12 of your Owner's Manual, you will see that Hybrid Drive applies when the HAH is "Driven in high-load conditions (e.g., when accelerating, going uphill)" and Engine Drive applies when it is "Driven in high-speed, low-load conditions."

An example of the second seems to be (since you didn't say what C&D article you read, I can't verify your claims) when you just repeated that you finally understood that battery-charging occurs in Engine Drive. But you qualified this admission by implying it is only a very small amount of charging, and that a journalist told you this. Cruising at 55 mph, it come close to half of the power, and simple observation should have told you this.

And I do admit my mistakes, when I make them. Since I try to verify what I say with facts, I don't need to often. On the other hand, when you simply repeat your incorrect assertions that contradict what I say, you haven't proven anything.
 

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Is this a forum to discuss our issues with our Hondas or our personal issues?
Why do you think I didn't I didn't post the article or go further. He likes to pick apart individual words and make it seem as if everything else said is irrelevant and makes a ton of assumptions about what people think. Yesterday he was literally trolling me in two different forums contradicting everything I said. He just keeps going even after proven wrong he makes up more excuses and changes his phrasing to try and make himself right. Apparently because of where I live I am unable to tell the difference between hot and cold air coming out of my vents, that was a good one. Sorry I'll stop feeding the troll,.
 

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roaring noise



Mine is doing the same , it look like the engine is reving up because of the charge on the battery , nothing wriong just anoiing , try to press the gaz pedal to make a big demand in power it will go away , but ignore it.
Hi Benjojo, would be grateful for your advice regarding this problem, I just got a 2017 HAH with 29K miles. The car is spotless in every way and it is doing the same roaring thing as you are describing here. Did you find any resolution beyond stepping on the gas gas when that happens? I keep seeing people mentioning that a new 12V battey might be the way out. Thanks a lot. Len.
 

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Discussion Starter #132
Just checking in and to give all an update on my cars status. Honda has been unable to resolve the roaring noise in my car. While they admit its there they refuse to call it a problem. The multiple attempts to resolve the noise have all failed. At this point they won't even take it back in for any sort of fix (e.g. replace the ANC) service telling me to just wait and they will let me know. Know what I'm not sure. Good luck to all when you want to trade yours back in even to honda. Since it has a noise, they won't give you full trade in value. At least, that's what they told me.
 

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Any updates with this? I'm in Canada, 2019 HAH Touring. I confirm with many of your observations, happens between 70-80 km/h at constant speed, loud rotating, more pronounced in cold weather, goes away by decreasing gas pedal and it switches to EV.


After this C-19 thing is over, I will be bringing it into my dealer. Thanks for all the information and it's somewhat reassuring that I'm not the only one having this problem.
 

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FWIW, my almost new 2020 Accord Hybrid had 'the noise' from the start (though I didn't realize it and research it till after I had bought it, unfortunately). Took it to a local dealer (bought it from one not close enough to be practical for this purpose) and got their senior technician right away, because they obviously had some experience with this issue. After an extended test drive with the tech, during which he tried several 'quick fixes' that had worked on some other cars but did nothing on mine), he asked me to schedule it for a 2nd visit. He checked with Honda, then tried a couple of things that others have mentioned here already, with still no luck on my car. At that point, he checked with them once again and 'they' decided that just disconnecting the ANC was the next step--at least until (?) Honda came up with a better solution. So he disconnected the ANC and that 'solved' my loud noise issue entirely. Of course, I don't really know what benefit I'm missing in terms of noise reduction via the ANC--but I'm willing to accept this compromise for now and really don't hold out a lot of hope for a 3-year old Honda problem to really get resolved....
 
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I now try to warn people. Whenever there is a review of the accord hybrid, I add comment...Watch out they don't tell you about the horrible roaring sound at 52 mph, and then they tell you it is not a problem and they really can't fix it. I opened a case with Honda, They don't care.
 

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I have a 2019 HAH Touring and don't have this 52 mph problem. The car is super quiet, except if I floor it. It has been so hot this summer that I only recently have driven
with the windows down. Now I notice what seems like a sound bouncing off buildings when I'm driving at city driving speeds (<50km/hr). The sound is difficult to describe similar in tone to brake heat shield rubbing (metallic scratching sounds) it does not seem to be proportional to the road speed. With the windows closed I can't hear it at all.
 

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I have the exact issue. It is a droning noise that starts at 52 MPH and cuts off at 54. It also appears as a fainter noise at 25 or so. Really annoying. Dealer thought is was related to the noise dampening system; but replacing that module did not work.

I'm having the same issue in my Accord Hybrid Touring 2020. It happens at the same speeds. Have you found any resolution. I have my car in for the 2nd time. I only bought it 3 months ago.
 

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I'm glad someone mentioned the speed thing. I now consistently hear it between 52-54, as well. I carpool with someone who routinely says, "You must have hit 52" when he hears it, and he's right. I agree that I sometimes hear it at lower speeds, but it's not so pronounced and doesn't cut off so abruptly. I recorded the noise on my cell phone, but the sound is so low/deep (not volume, just pitch) you can only hear it with decent speakers. I can't hear it at all when I play it through my phone or laptop. I'm going back to the dealer and going to make him sit in the car and listen to it with me.

My car is at the dealer right now, for the second time. This is incredibly annoying.

Have you found any resolution?
 

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We all need to go to www.NHTSA.gov and place a complain on this issue the dealer keeps making me take the car and they have no Idea of what is happening if we all place the same complain Honda will have to do something about it any lawyers that want to take a group will me a killer on this issue. Honda cant find what is wrong with this cars and is very sad we pay $34000 dollars and it sounds like a Light pole with High amperage at pick hour, i spec soon to have this battery blow out or cashing on fire.
Thanks for the suggestion. I didn't know about this website and I am filling out the "Report a Problem".
 
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