Why do we need 91 or higher octane?
Seasoned HDF Member
Joined: Oct 2012
Posts: 13,104
Likes: 13,047
From: Texas, USA
[QUOTE=brakeless;19700687]
It may be a good idea to refrain from using this word. It is likely to offend a millennial or two
Maybe use "octane challenged engine" instead.
Maybe use "octane challenged engine" instead.
Stellar HDF Member
Joined: Jun 2018
Posts: 2,235
Likes: 1,210
From: AZ
Yea I never understood this either. My SV1000S is an 11:1 ratio & only requires 87. Maybe its the fact its water cooled?
I've run 89 octane in my 103 TC in the winter with no troubles but wouldn't do it mid summer. Can only get 91 octane here but thats always been adequate.
I've run 89 octane in my 103 TC in the winter with no troubles but wouldn't do it mid summer. Can only get 91 octane here but thats always been adequate.
Thread Starter
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Tourer
Joined: Apr 2020
Posts: 490
Likes: 271
From: PNW
Wow, this turned into quite a conversation. While I understand engines, tuning, compression, and octane performance, I'm wondering why our "low performance" engines are so "hi-tech" they require high octane. From the various responses, I surmise that it's due to the "low-tech" (i.e., lack of sensors, cooling, etc.) paired with "high-performance" engineering whereas the high octane covers the lack of technology required. Thanks.
Stellar HDF Member
Joined: Nov 2005
Posts: 3,183
Likes: 837
From: KMHT KFMY
My Kawi ZRX took 87 octane. TheZZR1200 with the same bottom end with slightly higher compression, a better head, and different timing needed 91+ or it would ping
My current rice bike,a Kawi C14 is a premium fuel motor, very aggressive timing and fuel maps
Octane has zero to do with power, the guys running E85 are making sick HP with the right set up.
The Octane Rating is a numerical representation of the resistance to the stuff popping off without spark, aka pre-detination or pinging.
I can assure you when the gasoline mixture lights off before it is supposed to, it can destroy pistons, rods, bearings, cranks... you name it
I filled the C14 last night and premium fuel was almost 3 bucks a gallon, while 87 octane was in the 2.30 range.
That is the price of ownership, and an extra $4.00 a fill up is still cheaper than splitting the cases and replacing bent or melted parts.
All 3 of my bikes use premium fuel, as does the wife's Porsche,,, I know it costs more,,,, but it is still cheaper than the 100LL I have to buy when flying.... and the burn rate is about 10 gallons an hour... I flew in and out of Key West the other day and it was $6.80 a gallon and I needed 20 gallons.... do the math
My current rice bike,a Kawi C14 is a premium fuel motor, very aggressive timing and fuel maps
Octane has zero to do with power, the guys running E85 are making sick HP with the right set up.
The Octane Rating is a numerical representation of the resistance to the stuff popping off without spark, aka pre-detination or pinging.
I can assure you when the gasoline mixture lights off before it is supposed to, it can destroy pistons, rods, bearings, cranks... you name it
I filled the C14 last night and premium fuel was almost 3 bucks a gallon, while 87 octane was in the 2.30 range.
That is the price of ownership, and an extra $4.00 a fill up is still cheaper than splitting the cases and replacing bent or melted parts.
All 3 of my bikes use premium fuel, as does the wife's Porsche,,, I know it costs more,,,, but it is still cheaper than the 100LL I have to buy when flying.... and the burn rate is about 10 gallons an hour... I flew in and out of Key West the other day and it was $6.80 a gallon and I needed 20 gallons.... do the math
Seasoned HDF Member
Joined: May 2012
Posts: 32,934
Likes: 36,032
From: Carlsbad, CA
Wow, this turned into quite a conversation. While I understand engines, tuning, compression, and octane performance, I'm wondering why our "low performance" engines are so "hi-tech" they require high octane. From the various responses, I surmise that it's due to the "low-tech" (i.e., lack of sensors, cooling, etc.) paired with "high-performance" engineering whereas the high octane covers the lack of technology required. Thanks.
Thread Starter
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Tourer
Joined: Apr 2020
Posts: 490
Likes: 271
From: PNW
You must have me confused with another "dude." I never said anything about performance related to octane or knock. You should double check who you are quoting.
Thread Starter
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Tourer
Joined: Apr 2020
Posts: 490
Likes: 271
From: PNW
Nope, as I said, I own two very new Harleys. It comes down to the actual REASON we need high octane when true performance bikes can get away with low octane. Either Harley can't engineer proper tuning for regular gasoline or they don't want to. The tech has been around since the 80s in the automotive world.
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Club Member
Joined: Feb 2013
Posts: 9,833
Likes: 8,739
From: Edmonton, Alberta
Huh. My 17 Ford Fusion Sport 2.7L V-6 twin turbo comes with a 91 octane recommendation from Ford.
