Is this engine noise normal in the cooler months

The engine in the hybrids will generate different sounds than you are used to.

Reasons are several, the most significant one being the engine is tuned electronically to an "atkinson cycle" (expansion stroke that is longer than the compression stroke, via electronic valve timing controls) which boosts fuel economy some but does so by messing with combustion timing. Plus, in cooler weather, the engine control unit will set the idle speed higher until the engine warms sufficiently as well. Couple that with the fact that the engine is doing a range of things other than powering the wheels in a hybrid and you can expect a number of different acoustics from this engine compared to the older K series and the newer 1.5Ts.

Best thing here, if it concerns you is to head to your dealer, and see if you can listen to other hybrids on the lot and compare. You also could leave it with them to check and evaluate when it is cold too... but generally the best practice is to not do this... because you generally will get back "sounds normal, no problems found" when you just drop it off with a vague description of your concern.

JeffJo said:

How exactly did they describe it, and what did they say it was?

I ask, because there is no part on a Toyota or Lexus Hybrid that is remotely similar. It might make noises on a cold start, but it is not this one. I even looked through an ES300H manual to see how it was "verbosely disclosed," and didn't find such a list. Or any descriptions of noises other than the likes of "loud," "abnormal" or "electrical."

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I know you are a technical detail person, and love to deep dive on these systems. Lexus does not dive into the "why", only the "what", "what about it", and "it's normal". Honda and Lexus/Toyota systems are clearly different, so the actual sources and reasons of noises are likely different, though the audio and vibrations characteristics are similar in nature.

Lexus devotes a sub-section in section 7 of the interactive manual titled: Sounds and vibrations specific to a hybrid vehicle It delineates a set of 10 different types of noise sources you may hear in your hybrid which are specific to the hybrid... including from the engine, the transmission, the trunk, the HV battery pack, and the rear seating area. So far I have only actually heard 4 or maybe 5 of them. Some are described as "cold start rattles or vibrations" only, others are described as conditional noises as part of normal system operation.

I won't list them all here since it's off topic and will take up needless space in the thread. Rattling and vibration from the engine on cold start being one, but is minor in my view (maybe because cabin sound insulation is so good). The most annoying of sounds from a Lexus hybrid, in my view is actually from the transmission and Lexus specifically states: Sounds may be heard from the transmission when the gasoline engine starts or stops, when driving at low speeds, or during idling. Sure enough, particularly when the vehicle is powered up or down, odd mechanical type sounds come from under the vehicle if you are standing outside it, and in poking my head under the vehicile, yeah it definitely sounds like it is coming from the transmission.

williamsji said:

Lexus, unlike Honda... actually takes time to verbosely disclose in their owners documents this and other odd sounds and effects owners can expect.

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williamsji said:

Lexus does not dive into the "why", only the "what", "what about it", and "it's normal".

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Okay, I only searched for "noise," not "sounds." You refer to this, from page 60 of the ES300H Owner's Manual I downloaded, in section 4-1 covering the hybrid system:

• Sounds and vibrations specific to a hybrid vehicle
• There may be no engine sound or vibration even though the vehicle is able to move with the “READY” indicator is illuminated. For safety, apply the parking brake and make sure to shift the shift lever to P when parked
• The following sounds or vibrations may occur when the hybrid system is operating and are not a malfunction:
  • Motor sounds may be heard from the engine compartment.
  • Sounds may be heard from the hybrid battery (traction battery) under the rear seats when the hybrid system starts or stops.
  • Relay operating sounds such as a snap or soft clank will be emitted from the hybrid battery (traction battery), under the rear seats, when the hybrid system is started or stopped.
  • Sounds from the hybrid system may be heard when the trunk lid is open.
  • Sounds may be heard from the transmission when the gasoline engine starts or stops, when driving at low speeds, or during idling.
  • Engine sounds may be heard when accelerating sharply.
  • Sounds may be heard due to regenerative braking when the brake pedal is depressed or as the accelerator pedal is released.
  • Vibration may be felt when the gasoline engine starts or stops.
  • Cooling fan sounds may be heard from the air intake vent under the rear seat.

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I quoted the entire thing for comparison to the Honda manual. But also to show that there is no mention of sounds or vibrations specific to cold start (which is different than starting and stopping during normal operation), and no mention of rattling.

What you apparently missed is this, from page 15 of the CR-V Hybrid Owner's Manual, in the Quick Reference section prefacing the more technical portions of the manual:

• Sounds Unique to the SPORT HYBRID i-MMD System
  • When you first start driving this vehicle, you will likely hear some unfamiliar sounds, particularly when you turn on the power system, or while you are driving or accelerating from a stop. Some of these sounds are unique to this vehicle‘s powertrain, fuel, and climate control systems; others are similar to sounds generated by conventional automobiles that typically are masked by louder noises absent from a vehicle of this design. These sounds are not a cause for concern, and you will soon recognize them as normal and thus be able to detect any new or unusual noise should one develop.
• After shutting off the engine, you may hear certain noises coming from the vehicle. Here’s the lowdown:
  • Noise from Under Vehicle: This noise is caused by the vacuum pump inside the fuel evaporation leakage check module (ELCM). Depending on conditions, the pump will come on for about 15 minutes about 5 to 10 hours after engine shutoff. This noise is just normal vehicle operation and doesn’t indicate a vehicle problem.

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These two manufacturers document things in very different ways. Personally, I find Honda's method more understandable, more informative, and more accessible to someone who does not "deep dive on these systems." You may not. But outside of delineating each sound, I see no useful difference in the information conveyed. In fact, delineating them makes it harder, and so less likely, to be read. And the only sound that is "verbosely disclosed" is Honda's "Noise from Under Vehicle," which is the one that I have seen the most confusion over.in these forums.

What I object to is not Toyota's methods, as much as assuming - and stating - that Toyota's are superior without actually comparing them to Honda's.

williamsji said:

Honda could definitely learn a few things from Toyota/Lexus in terms of owner documentation disclosure on the subtle things owners, particularly new owners, will fixate on after spending big bucks on a new high tech vehicle.

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And I think that Toyota/Lexus could learn a few things from Honda. Like, if it is meant for new and inexperienced owners, it needs to be stated more conversationally. And in a section of the manual intended for, well, new and inexperienced owners.

JeffJo said:

And I think that Toyota/Lexus could learn a few things from Honda. Like, if it is meant for new and inexperienced owners, it needs to be stated more conversationally. And in a section of the manual intended for, well, new and inexperienced owners.

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We can agree to disagree.

The Honda paragraph you quoted about iMMD noises:

• When you first start driving this vehicle, you will likely hear some unfamiliar sounds, particularly when you turn on the power system, or while you are driving or accelerating from a stop. Some of these sounds are unique to this vehicle‘s powertrain, fuel, and climate control systems; others are similar to sounds generated by conventional automobiles that typically are masked by louder noises absent from a vehicle of this design. These sounds are not a cause for concern, and you will soon recognize them as normal and thus be able to detect any new or unusual noise should one develop.

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Incredibly NON-SPECIFIC and hence largely useless, in my view.

Paraphase: you will hear unusual noises from your new Honda hybrid, but we are not going to be very specific as what they are and where they originate, but we will scatter the information around in the manual like a scavenger hunt. THAT is bad technical writing.

Honestly, I find the Lexus owners documentation to be much more complete, coherent, and informative compared to the Honda owners documents. It actually follows a much better flow for the new owner looking to learn their vehicle without being lead in circles. Lexus documents are much more conversational in their style, are better laid out, flow more logically, and better illustrated compared to my gen5 CRV documents or my 2018 Accord documents. Too much jumping around and errors in my CRV manual really for Honda being one of the top vehicle producers in the world.

Credit to Honda though for producing a web based interactive manual for the gen6... because that really is the way to go if you want owners to be able to quickly and easily follow the topics and find the topic they seek. Much better than a PDF or print copy. Easily accessible to anyone with their smart phone if needed too.