Octane? Regular? Super? : V-Twin Forum: Harley Davidson Forums

Rickstar321 · 10-25-2012, 09:13 AM

I pulled up to the pump and the "tanker" driver was there filling up the gas stations tank, walked over and asked me if I use octane boost... I was filling up with 87 and he said he always uses premium in his HD, with octane boost...

The 87 is what is recommended for my Yammy but didn't even consider that I'd need to put premium in my custom?

I have an Evo 80 CI, with S&S Super shorty...

Thanks,

Rick

Ok, I know I'm answering my own question but this is a very good explanation of the combustion process... (Clicky Here)

any4xx · 10-25-2012, 10:04 AM

Good article. But regarding which octane to use, I have always let my vehicles tell me what they need. Most of my HD's have been quite happy with regular gas. My current EG wants premium or it will ping under load. My V-Rod also asks for premium or it will talk to me. The thing that a lot of folks fail to consider is that there's more power stored up in a gallon of regular than there is in a gallon of premium. You will always be better off, both financially and in power-production, with the lowest octane your bike will drink without pinging.

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webco2 · 10-25-2012, 03:30 PM

Quote:

Originally Posted by any4xx

Good article. But regarding which octane to use, I have always let my vehicles tell me what they need. Most of my HD's have been quite happy with regular gas. My current EG wants premium or it will ping under load. My V-Rod also asks for premium or it will talk to me. The thing that a lot of folks fail to consider is that there's more power stored up in a gallon of regular than there is in a gallon of premium. You will always be better off, both financially and in power-production, with the lowest octane your bike will drink without pinging.

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Don't ya just hate it when your bike drinks without you...

mistert · 10-25-2012, 03:42 PM

Over the years (25-30+), I have found that engines will perform better with quality fuel, Harley's, hot rods, whatever.. That doesn't necessarily mean higher octane but, with the ethanol being added, the "quality" has gone way down. You may get away with low grade fuels but I strongly recommend at least 89 octane in any Harley...and...if it is modified in any way I'd jump it to at least 91 octane. I run 91 if I can't get 93 and will get better milage, no popping or backfire and a smoother-quicker throttle response. for the past 10 years or so I've added "rocket fuel" (octane booster) to any tank of fuel that was undr 91 octane and have had most of my customers do the same. We used to burn the cheapest gas we could find and ping....all the was home. Feed you rides good fuel and they will reward you whether you realize it or not.
note: there is a limit...I'd suggest not running over 93-94 octane. Most stock and moderately modified engines do not need that high an octane in fact you'll prpbably encounter some problems doing so i.e. valve buring, pre-ignition etc..

YankeeBob · 10-25-2012, 04:44 PM

Quote:

Originally Posted by mistert

Over the years (25-30+), I have found that engines will perform better with quality fuel, Harley's, hot rods, whatever.. That doesn't necessarily mean higher octane but, with the ethanol being added, the "quality" has gone way down. You may get away with low grade fuels but I strongly recommend at least 89 octane in any Harley...and...if it is modified in any way I'd jump it to at least 91 octane. I run 91 if I can't get 93 and will get better milage, no popping or backfire and a smoother-quicker throttle response. for the past 10 years or so I've added "rocket fuel" (octane booster) to any tank of fuel that was undr 91 octane and have had most of my customers do the same. We used to burn the cheapest gas we could find and ping....all the was home. Feed you rides good fuel and they will reward you whether you realize it or not.
note: there is a limit...I'd suggest not running over 93-94 octane. Most stock and moderately modified engines do not need that high an octane in fact you'll prpbably encounter some problems doing so i.e. valve buring, pre-ignition etc..

gretsch58 · 10-25-2012, 06:19 PM

My FXR manual says 87 octane for my 93 EVO. That's what I've always run. I don't get pinging.

lucille · 10-25-2012, 06:44 PM

Quote:

Originally Posted by mistert

...I'd suggest not running over 93-94 octane. Most stock and moderately modified engines do not need that high an octane in fact you'll probably encounter some problems doing so i.e. valve burning, pre-ignition etc..

Isn't valve burning, hotspots, knock, etc., a result of pre-ignition (pinging)? How is a higher than adequate octane going to cause the problem (pinging/pre-ignition) it was ment to control?

gretsch58 · 10-26-2012, 03:26 PM

Correct me if i'm wrong, but I don't think this question should be in the chopper section.

Rickstar321 · 11-03-2012, 12:49 AM

Quote:

Originally Posted by gretsch58

Correct me if i'm wrong, but I don't think this question should be in the chopper section.

I wasn't sure about that because I'm not riding a "store bought" Harley, it's a custom built bike... so that's why I put it here because it's a little different animal... :-)

petew · 11-03-2012, 07:51 AM

I read an artical about race fuel vs. ethanol tainted 91 octane gas in one of the sport bike magazines and the difference measured via a Dyno.
On a 1000 cc motorcycle it made like 7hp and 9tq more on 110 octane vs. the 91 ethanol mixed gasoline.
Now I tried a tank full of the 110 and I sure can tell the difference in my HD. No pings, just roll on at 50 mph in 6th gear and it doesn't buck or shudder, it just pulls much harder.
Now I am not gonna run it as my normal fuel, the cost is like 9 bucks a gallon...