Premium Gas

[ClarityBill]

Replicable: I have been driving the same hill weekly for a year and half in the Clarity. The last three weeks have been on Premium, and the difference in noise on that hill is spectacular (80+ to 70- dba). I also drive a number of other hills on a regular basis, and the noise levels are similarly reduced.

I think this thread has been discussing / arguing the reasons that premium fuel may or may not make a difference. My original hypothesis (before the experiment) was the slower burn would give a more even combustion for the long power stroke.

 

[ClarityBill]

Nobody’s Clarity is that loud. Ever.

I tend to disagree, but that is just me.

the difference would be simply staggering...
That has been my impression, in case I did not convey that well enough.

I could give my qualifications, but that does not seem to matter.

 

[Mowcowbell]

Heck, as little gasoline I use in my Clarity, I won't mind paying an extra .40 cents a gallon for premium (current local price for 91 octane 100% gasoline: $2.40) if it means a quieter HV drive.

 

[David Towle]

I tend to disagree, but that is just me.

the difference would be simply staggering...
That has been my impression, in case I did not convey that well enough.

I could give my qualifications, but that does not seem to matter.

80 db is about ten times the volume level of 70 db. You have to agree that big a difference is hard to fathom. Does this happen only on hills? I could not find the sound meter you have but have installed another one on my phone and will see if I get anything like these numbers. All I have so far from today is 58db on a 45 mph flat with 87 octane. I'll do all my testing in HV Charge since that is more consistent than HV.

 

[Robert_Alabama]

I guess I'm in the minority, but I haven't found the Clarity to be noisy at all when engine is running. But I also drive about 65% electric and the terrain here is generally gently rolling or flat. If I ever do drive my car through the mountains, I will probably opt for 91 octane based on what I have read here just to avoid any irritation. Until then, I'll save the difference in 87 vs 91 unless the noise level increases to at least noticeable (a lot of the time it is really hard to even hear the engine when it is running - and yes, as far as I know my hearing is still good).

 

[ClarityBill]

Does this happen only on hills?

The spectacular (staggering) differences in noise happen anytime the rpm goes over 4500. This is generally hills, over 75 mph. I have also had this issue in a snow storm with full defrost on level terrain. I did mention that I tend to wear earplugs for those situations.

I mentioned that sound level is low at 78 mph in gear mode (level terrain) on 87 octane. It is quieter on 93, but I have not quoted dba measurements for that.

I'll do all my testing in HV Charge since that is more consistent than HV.

Are you planning a comparison to 93 octane, or just gathering data on 87? There was a thread that KentuckyKen talked about developing a 'standard' method for measuring sound level with these phone apps...

It seems there are many comments about noise (angry bees, high rpm) on this forum: if you do not have this problem, this solution is not for you.

 

[Fast Eddie B]

For those with iphones, here’s a versatile little app that displays the output of various sensors in the phone, including a decibel meter:

 

[David Towle]

Are you planning a comparison to 93 octane, or just gathering data on 87? There was a thread that KentuckyKen talked about developing a 'standard' method for measuring sound level with these phone apps...

It seems there are many comments about noise (angry bees, high rpm) on this forum: if you do not have this problem, this solution is not for you.

Yes my next tank will be 93. I don't have a noise problem but would like to see the octane volume change myself. I have a good parkway hill near my house I will include in my comparisons. Its steep enough that I can maintain speed down it by going to 4 chevrons (max regen).

 

[David Towle]

The spectacular (staggering) differences in noise happen anytime the rpm goes over 4500. This is generally hills, over 75 mph. I have also had this issue in a snow storm with full defrost on level terrain. I did mention that I tend to wear earplugs for those situations.

I mentioned that sound level is low at 78 mph in gear mode (level terrain) on 87 octane. It is quieter on 93, but I have not quoted dba measurements for that.


Are you planning a comparison to 93 octane, or just gathering data on 87? There was a thread that KentuckyKen talked about developing a 'standard' method for measuring sound level with these phone apps...

It seems there are many comments about noise (angry bees, high rpm) on this forum: if you do not have this problem, this solution is not for you.

OK I tried to repeat some of Bill's tests on my car this morning. Had to do it in the morning when traffic is light because people do not normally drive those kinds of speeds here, curvy roads, entrances with stop signs because there's no room to merge, etc. I sat the phone on my right thigh with the microphone facing the dash.

I pretty well replicated his 87 octane db, getting 79-83 db at speed in the high seventies.I also checked flooring the throttle and got 90-94. Funny thing is, when I went to HV Charge the numbers were quite a bit lower, 72-76 db, although same 90-94 with the throttle floored.

I filled up with 5 gallons of 93 octane, so averaged probably have about 91 octane in the tank now. In the high seventies in HV I got 76-80 db, a reduction but not near as large as Bill has found. Got the same 90-94 with the throttle floored.

I did not get the feeling that the engine was any quieter, but it felt like the octane was influencing the program to run at lower revs. I don't have an rpm indication, I think Bill does so I'll go back and see if he saw an rpm reduction. If you didn't post that Bill please do, and also check numbers when flooring the throttle.

So it looks like another way to reduce volume on big hills is to switch to HV Charge.

 

[David Towle]

After using up this tank I will fill with 93 again to bring the octane up further and run the test again.

 

[Fast Eddie B]

After using up this tank I will fill with 93 again to bring the octane up further and run the test again.

Cool! Thanks for your efforts.

Hard to envision why HVCharge would be quieter - you'd think the engine would need more power/rpm to add charge to the battery rather than to simply maintain charge for any given situation. Weird.

 

[David Towle]

Cool! Thanks for your efforts.

Hard to envision why HVCharge would be quieter - you'd think the engine would need more power/rpm to add charge to the battery rather than to simply maintain charge for any given situation. Weird.

I think the HV Charge program takes more of a long term view of the charging situation, I have seen the EV range drop by a mile or two going up long hills with it on. HV responds more like a standard hybrid system with a battery a tenth the size of the Clarity's.

Its been my guess from the beginning that the HV program was pretty much borrowed from a standard Honda hybrid, whereas the HV Charge program would have to be written for the Clarity.

 

[Landshark]

So it looks like another way to reduce volume on big hills is to switch to HV Charge.

The only catch with this, is that the SOC would need to be below ~60% in order to engage HV Charge.

I think the HV Charge program takes more of a long term view of the charging situation, I have seen the EV range drop by a mile or two going up long hills with it on. HV responds more like a standard hybrid system with a battery a tenth the size of the Clarity's.

That is an excellent description. In HV Charge the engine is working to bring the battery to a ~60% SOC. If there is no demand for maximum, or significantly increased power, the engine will run at a more steady and lower rpm than it may in HV mode. It just keeps chugging along until reaching ~60%.

In HV mode the engine may, at times, work more frantically to maintain a set charge level.

 

[ClarityBill]

I did not get the feeling that the engine was any quieter, but it felt like the octane was influencing the program to run at lower revs. I don't have an rpm indication, I think Bill does so I'll go back and see if he saw an rpm reduction. If you didn't post that Bill please do, and also check numbers when flooring the throttle.

I did not see any reduction in RPM with higher octane.

If you don't have an rpm meter: Are you hearing a reduced noise level, and confusing that with reduced rpm?

It would be interesting to determine if you hit 4500 rpm, where I saw the really loud engine noise, and 'staggering' reduction.

What sound meter are you using?

 

[MrFixit]

If you don't have an rpm meter:

Just a reminder, you can easily get RPM's with a simple and low cost OBD2 adapter and one of several App's on your phone...
There are many to choose from... I have this one:
https://www.amazon.com/gp/product/B00PJPHEBO

 

[David Towle]

I did not see any reduction in RPM with higher octane.

If you don't have an rpm meter: Are you hearing a reduced noise level, and confusing that with reduced rpm?

It would be interesting to determine if you hit 4500 rpm, where I saw the really loud engine noise, and 'staggering' reduction.

What sound meter are you using?

The difference in sound was very slight so I really don't know what I was hearing. Since there was no change in volume at full throttle it seemed like a change in rpm had to be there but I certainly believe you if you say its not.

I have an OBD2 unit but its packed away in a warehouse with 90% of our stuff until we move to our new place and I don't want to buy another one.

The sound meter is just called dB meter.

Bill let us know when you do the full throttle test while going up your big hill at 75+ with the 2 different octanes.

 

[ClarityBill]

Bill let us know when you do the full throttle test while going up your big hill at 75+ with the 2 different octanes.

I probably will not do full throttle on that hill.

Full throttle does not guarantee 'peak' rpm. I have already achieved over 5K rpm, and I am not convinced you are reaching that. I have reported my results over 4500 rpm.

I am really wondering what your rpm experience is. I was planning to do full throttle on level terrain, to see what rpm I reach, and assume that is your experience.

At lower rpm levels, the sound differences are slight, but they are still there (as you have confirmed). The staggering difference is at higher rpm levels.

 

[Landshark]

With all this staggering, it is certainly a blessing that everyone will be seated while experiencing this event.

 

[ClarityBill]

I was planning to do full throttle on level terrain, to see what rpm I reach, and assume that is your experience.

I did full throttle on level terrain and hit 5K rpm with a full battery, and at zero EV range. Looks like David is doing tests at 'high' rpm.

I am running 93 octane. I did not use the sound meter during these tests, but the noise would not prohibit a conversation at reasonable voice levels. (db well below 80)

 

[Landshark]

I did full throttle on level terrain and hit 5K rpm with a full battery, and at zero EV range. Looks like David is doing tests at 'high' rpm.

I am running 93 octane. I did not use the sound meter during these tests, but the noise would not prohibit a conversation at reasonable voice levels. (db well below 80)

How is it possible to have a full battery and zero EV range?

How do you know the dB level without a meter?