Octane Boost
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,022
Likes: 7,547
From: Poolville
I'll Jump.. *** Octane levels increase so does the flashpoint temp of the fuel. This alone will not add power.. What this does is cool the combustion chamber more effectively allowing the addition of more ignition timing to be put into the tune to produce more power without producing detonation. With ION sensing spark knock control you can set your parameters to whatever you want to decrease or even eliminate the amount of ignition timing reduction. Is Octane booster a power adder? NO.. but will increase the efficiency of the motor.
And yes you probably will need at least a 12-16% mixture increase to really notice a difference. I like the Idea of a Dyno shootout on the subject but I don't think we will see any significant gains unless changing the tune.
And yes you probably will need at least a 12-16% mixture increase to really notice a difference. I like the Idea of a Dyno shootout on the subject but I don't think we will see any significant gains unless changing the tune.
Last edited by 98hotrodfatboy; Jun 1, 2025 at 07:30 AM.
Grand HDF Member
Joined: Sep 2022
Posts: 4,253
Likes: 3,670
From: Florida
I ran almost 12:1 mechanical compression in my Shovel… in Florida heat.. with 93 pump gas. To do that I had to nerd out in machining the combustion chamber. I had to remove areas where carbon could build up (top of fire ring) I had to gap at over 50 thou… lots and lots of little tricks. I ran 27 degrees timing and used the Dyna S advance weights to play with curve at the top end.
My 127 is right at 10.6:1 mechanical. I also run 27 degrees in it and have just the dip switches used with my 2000i. No knock or detonation. I use 93 octang
My 113 I didn’t CC when I rebuilt it. Math wise it should be around 10.7:1. Now it will detonate on hot days.. I have to watch it like a Hawk. I use 93 octang I also am only able to run 25 degrees when hot out. A lot of it is probably corrected compression and cam timing. Some could be motor seal. It can also somewhat be carb.. the 113 really needs the 127’s bored out G and the 127 really needs my D to be installed.
If I buy another bike I’ve been circling I’ll put the Springers 127 in it and I’ll finish my 131 and go 12.5:1 and run 101 octang and save it for just hot Rodding in the Springer.
My 127 is right at 10.6:1 mechanical. I also run 27 degrees in it and have just the dip switches used with my 2000i. No knock or detonation. I use 93 octang
My 113 I didn’t CC when I rebuilt it. Math wise it should be around 10.7:1. Now it will detonate on hot days.. I have to watch it like a Hawk. I use 93 octang I also am only able to run 25 degrees when hot out. A lot of it is probably corrected compression and cam timing. Some could be motor seal. It can also somewhat be carb.. the 113 really needs the 127’s bored out G and the 127 really needs my D to be installed.
If I buy another bike I’ve been circling I’ll put the Springers 127 in it and I’ll finish my 131 and go 12.5:1 and run 101 octang and save it for just hot Rodding in the Springer.
Last edited by Rains2much; Jun 1, 2025 at 07:48 AM.
Seasoned HDF Member
Joined: Apr 2014
Posts: 5,420
Likes: 2,484
From: Lititz Pa
I put some in my tour pack on a trip I was going to a area that hit or miss with a least 91 octane. That was two years ago and some leaked out because I didn't put the cap on right, and I still get the smell out.
Road Master
Joined: Feb 2021
Posts: 1,054
Likes: 469
From: Phoenix Arizona
All Data is information. Some is useful. This has been a very good discussion.
FACTS are hard to come by.
I do like the idea of doing dyno shoot out.
1. Stock bike, set up on dyno with no changes (pipes, AC, exhaust, etc), 83 gas Get read out.
2. Drain all fuel, refill with 87 and repeat run. NOT redo a dyno run, just do a power run in 3rd, 4th and 5th gears. Get read out
3. Drain again, refill with 91 and repeat.
4. Drain again, 83 with "BEST" octane booster. This is where the problem lies. With so many different brands out there, how is the "BEST" decided? There might be some data out there to look at to separate TOP TIER brands.
Run power pull again, 3rd, 4th, 5th
5. Repeat 87 with octane
6. Repeat with 91 and octane.
That's a $hit load of work. To prove what? The proof is in the results. Except, air temp, humidity, quality of gas on that day. Too many variables. The results might not be definitive, however, it might show some change or no change? The BUTT dyno is connected to preconceived notion of expected results. Like which brand of oil, which brand of gas, which battery, which tire. All subjective.
TBT, I do acknowledge that octane boost DOES have some benefit, such as higher compression engines. I was glad to read how many do acknowledge that higher octane does NOT increase power just because of the gas. IT HELPS ON DETONATION , WHICH can allow the engine to run better.
Back in mid 70's , I did drag racing. Fully built engines. Just from experience, race car would not run on 83 or 87. It would start, idle, but under hard acceleration would knock bad. 91 would stop the detonation.
What are you thoughts about AV gas ? Not for bikes.
FACTS are hard to come by.
I do like the idea of doing dyno shoot out.
1. Stock bike, set up on dyno with no changes (pipes, AC, exhaust, etc), 83 gas Get read out.
2. Drain all fuel, refill with 87 and repeat run. NOT redo a dyno run, just do a power run in 3rd, 4th and 5th gears. Get read out
3. Drain again, refill with 91 and repeat.
4. Drain again, 83 with "BEST" octane booster. This is where the problem lies. With so many different brands out there, how is the "BEST" decided? There might be some data out there to look at to separate TOP TIER brands.
Run power pull again, 3rd, 4th, 5th
5. Repeat 87 with octane
6. Repeat with 91 and octane.
That's a $hit load of work. To prove what? The proof is in the results. Except, air temp, humidity, quality of gas on that day. Too many variables. The results might not be definitive, however, it might show some change or no change? The BUTT dyno is connected to preconceived notion of expected results. Like which brand of oil, which brand of gas, which battery, which tire. All subjective.
TBT, I do acknowledge that octane boost DOES have some benefit, such as higher compression engines. I was glad to read how many do acknowledge that higher octane does NOT increase power just because of the gas. IT HELPS ON DETONATION , WHICH can allow the engine to run better.
Back in mid 70's , I did drag racing. Fully built engines. Just from experience, race car would not run on 83 or 87. It would start, idle, but under hard acceleration would knock bad. 91 would stop the detonation.
What are you thoughts about AV gas ? Not for bikes.
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