Angry Engine

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When engine knock is detected by the knock sensor in the Clarity internal combustion engine, the engine control module retards the spark timing to reduce the knock. Since the Clarity engine has a 13.5 to 1 compression ratio, such knock is not uncommon when using 87 octane fuel. One can observe the retarding by observing the ignition timing output with an OBDII dongle. And yes, the European Union now requires a minimum RON (about 90-91 US AKI) for automotive fuel. If the US had such a requirement, many modern vehicles, with a knock sensor, would see a noticeable increase in fuel economy. Unfortunately, the current $.40 to $.60 per gallon increase in retail US fuel cost wipes out any savings from the decreased fuel use.

LeoP
 
Boston_Pilot said:
Lol, I hope you’re trolling…..The whole continent of Europe, eh? Changes spark plug timing, Seriously…..
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@Agzand was pretty close to correct if not absolutely as far as I can tell. The ECU may advance the timing slightly (or not retard it as much) if the ceiling for changes has not been reached by the input from the knock sensor. As such, the timing is probably changed based on the octane of the fuel. Also, the octane requirement for Europe does seem to be overall different than the USA, and is probably more like 91.

Here's a link to one source of this information:

https://www.roadandtrack.com/new-cars/car-technology/news/a18008/premium-fuel-futures/

All that said, I've never experienced the "angry bees" or even really winced over the sound of the ICE, so I can't really test whether 91 or 93 octane would help the noise level. I can say that some that post here seem pretty convinced that it has helped them. I rarely drive in HV mode (on gasoline) with the battery depleted, though. That may help with my lack of experience with a noisy engine. I generally burn gasoline first and hold the battery for the end of the trip (at a charging location).
 
I am one of the believers in premium gas.

My experience has a twist. My engine was very loud for 70K miles of 87 octane gas use. It did not sound like engine knock, it sounded like exhaust noise. I switched to 90+ octane for 20K miles, and noise was dramatically reduced and different.

I run with an OBDII recorder operating, so I decided to record engine timing (spark plug timing). Then I switched back to regular gas. The engine timing changed about 4 degrees, but the sound stayed quiet.

I have run 5K miles on 87 octane, and the engine noise is dramatically reduced from the first 70K miles that I drove on 87 octane. Seems like the algorithm for engine operation had a bias set incorrectly, and could not get something right.

Someone posted here that their engine sounded like a postal van: I understand that description, and I would agree with the description of my noisy engine.

I can also understand that if someone never had that noisy operation, they may not understand what is being discussed.

Premium gas does not reduce the engine RPM.

Again, if you believe your engine noise is excessive, try using premium gas for a tank or two, and report your impressions of the engine noise.
 
ClarityBill said:
I switched to 90+ octane for 20K miles, and noise was dramatically reduced and different.

I run with an OBDII recorder operating, so I decided to record engine timing (spark plug timing). Then I switched back to regular gas. The engine timing changed about 4 degrees, but the sound stayed quiet.

I have run 5K miles on 87 octane, and the engine noise is dramatically reduced from the first 70K miles that I drove on 87 octane. Seems like the algorithm for engine operation had a bias set incorrectly, and could not get something right.
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When you switched back to 87 octane, did the car revert to the original timing you had seen for the first 70K miles?

I’m interpreting your statement that “timing changed about 4 degrees” as, when you switched back to 87 octane it changed about 4 degrees from the readings you observed while using 90+ octane.

What timing change did you observe when the switch was made from 87 to 90+ octane?
 
I do not think that the angry bees noise is engine knock noise. The Clarity PHEV engine is an Atkinson cycle (a modified Otto cycle) engine. The goal of an Atkinson cycle engine is to have the cylinder pressure equal the atmospheric pressure at the end of the power stroke (about when the exhaust valve opens). This way the maximum energy is extracted during the power stroke. If the ignition timing is retarded to prevent knock, the whole combustion progress is delayed. Thus, the pressure at the end of power stroke will be greater then the atmospheric pressure. This makes for more exhaust noise (kind of like more pop when the exhaust valve opens).

LeoP
 
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Landshark said:
When you switched back to 87 octane, did the car revert to the original timing you had seen for the first 70K miles?

I’m interpreting your statement that “timing changed about 4 degrees” as, when you switched back to 87 octane it changed about 4 degrees from the readings you observed while using 90+ octane.

What timing change did you observe when the switch was made from 87 to 90+ octane?
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I was not recording engine timing for the first 88K miles. I have always recorded RPM, SOC, etc. but not engine timing. I added ignition timing to the record for a couple thousand miles on 90+ octane, then switched to 87. You are correct that the 4 degree change was going from 90+ back to 87.
 
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leop said:
I do not think that the angry bees noise is engine knock noise. The Clarity PHEV engine is an Atkinson cycle (a modified Otto cycle) engine. The goal of an Atkinson cycle engine is to have the cylinder pressure equal the atmospheric pressure at the end of the power stroke (about when the exhaust valve opens). This way the maximum energy is extracted during the power stroke. If the ignition timing is retarded to prevent knock, the whole combustion progress is delayed. Thus, the pressure at the end of power stroke will be greater then the atmospheric pressure. This makes for more exhaust noise (kind of like more pop when the exhaust valve opens).

LeoP
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I agree with this evaluation. The key point is that ignition timing can be retarded enough to create exhaust noise. Additionally, there may be an ignition timing can avoid knock, and avoid exhaust noise. It seems my Clarity had trouble finding that spot until I gave it a jump to new octane, and new timing. It was able to come back to the correct spot, on the 'second' try.
 
ClarityBill said:
I am one of the believers in premium gas.
.
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me, too. I am coming from carbon buildup considerations, however. My experience from working on multiple family owned cars is that premium gas does provide better protection against carbon buildup in engines. But you have to use premium gas all the time, not occasionally. Other than that, modern cars have tuning mechanisms to prevent knocking. Having premium gas has no clear advantage for Clarity from knocking prevention perspective, IMHO.
 
My wife and I often joke when it seems like our Clarity’s bees are starting to get perturbed.

We’ve only run regular gas to date. Most of you know we live in the foothills of the Appalachians, so elevation gains of 1,000’ to as much as 4,000’ are not unusual. As long as we have an EV reserve - we normally switch to HV at about 10EV miles remaining - the engine has never gotten annoyingly loud. At some points in a long climb the engine will “race” a little, but even then it’s far quieter than, let’s say, our Honda Element 5-speed when we downshift on that same grade. It certainly is not loud enough that we’d pay the extra for premium gas to avoid it.

Karen’s dad had a used car dealership. If someone complained about a noise during a test drive, he’d just advise them to turn up the radio! And you know what? That works!
 
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No one here has mentioned switching to HV Charge, under less extreme conditions it keeps the revs from varying so much but I don't know if it works when the engine is screaming.
 
lessismore said:
me, too. I am coming from carbon buildup considerations, however. My experience from working on multiple family owned cars is that premium gas does provide better protection against carbon buildup in engines. But you have to use premium gas all the time, not occasionally. Other than that, modern cars have tuning mechanisms to prevent knocking. Having premium gas has no clear advantage for Clarity from knocking prevention perspective, IMHO.
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Carbon buildup comes from using gas without cleaners, not low octane. Use a Top Tier gas to reduce carbon.
https://www.consumerreports.org/car-maintenance/study-shows-top-tier-gasoline-worth-extra-price/
 
ClarityBill said:
I was not recording engine timing for the first 88K miles.
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That’s unfortunate. It would be interesting to know if the timing was “off” originally and did somehow correct from the use higher octane fuel or some other method. From your description it sounds like something has changed since it is now quieter on 87.

I wonder if the hard reset, disconnecting 12V battery, would solve the problem for others?
 
My car went from noisy to quiet. I am wondering if the OP had the opposite transition: quiet to noisy. Dan Albrich indicated the hard reset fixed his noise problem. If my car goes back to noisy, I will probably try two tanks of premium first (easy to push a different button on the gas pump and less than $10 extra cost). If that does not work, I would try the hard reset.

The fact that the engine can be quiet or noisy is important information for any owner: My definition of normal / acceptable operation has changed. Boston_Pilot indicated 'angry bees' is normal: I don't believe that anymore.

It would be interesting to see the timing of noisy engines, but the operational timing jumps and it is tough to quantify differences without graphing and analytics. I don't know if timing was the change in noisy to quiet, but it is a possibility.
 
lessismore said:
are you saying anything different? I am not sure if you are supporting my statement or challenging it.
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I interpreted his statement to be different from yours.

David Towle was emphasizing that carbon buildup is reduced by cleaners added to the gas, and these are best in gasoline rated as "Top Tier"

Your statements have referenced 'premium' gas, which normally refers to high octane, but has no correlation to cleaning additives.

There may be confusion between the terms "Top Tier" and "Premium"
 
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