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Discussion Starter #1
Just picking up on the comment AZGeek makes in his thread about fuels - I've been experimenting with different octanes on my 09 Custom; here in New Zealand, most gas stations sell 91 or 95 (BP also do a 98), and I find a noticeable difference with 91 - engine pings, rattles at lower revs, and generally doesn't sound as happy. First modern vehicle I've owned that behaves so differently depending on fuel.

Does anyone know how timing is controlled on Vulcans? I just assumed it was auto-magic, and would adjust for different octanes.
 

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Compression ratio is rather low for a motorcycle at 9.5:1. That being said, that's fairly high to be running crappy fuel. 91 is our Mid grade here. Its hard for me to believe you can tell a difference between that and 95 with this bike, but maybe if you have the big 3 you might detect a slight difference. What sort of elevation do you live at? Maybe that's the x factor.
 

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Discussion Starter #3
Compression ratio is rather low for a motorcycle at 9.5:1. That being said, that's fairly high to be running crappy fuel. 91 is our Mid grade here. Its hard for me to believe you can tell a difference between that and 95 with this bike, but maybe if you have the big 3 you might detect a slight difference. What sort of elevation do you live at? Maybe that's the x factor.
Yeah, I have the Baron BAK, V&H Big Radius pipes and Cobra PowerPro - living on the coast, so pretty much at sea level.

I guess the difference could be imagined, but it definitely runs at lower revs (assuming the Cobra tacho is accurate): 60 mph at 4000 rpm on 91, same speed on same stretch of road with 95 octane, bike makes 3800 rpm.
 

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Unless you have an automatic transmission how do rpms change for a given speed (in this case 60 mph, assuming you are in the same gear at that speed for each ride)?
 

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Unless you have an automatic transmission how do rpms change for a given speed (in this case 60 mph, assuming you are in the same gear at that speed for each ride)?
With all things (vehicle speed, rider, gear selection, choice of road) being equal, and the only difference being fuel, the engine must working harder on lower-octane gas to produce the same power.
 

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Sorry dude, that's impossible.

Same speed in the same gear = same RPM. That's a given.

We're assuming you haven't changed your rear tire size or your rear pulley in between tests.

You have 2 variables working against you - the accuracy of the tach, and the accuracy of the speedo.

Its hard to believe you could read those both wrong consistently.

I have a Kawi OEM tach on my Custom - and it wouldn't matter if I ran race gas or pump gas, or pulled the bike with a tow truck (with the rear wheel on the ground, spark plugs out, in gear) - the speed of the rear tire and the RPM of the engine would be exactly the same. The rear tire and the crankshaft of the engine are locked together by the transmission and the drive belt.
 

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Sorry dude, that's impossible.

Same speed in the same gear = same RPM. That's a given.

We're assuming you haven't changed your rear tire size or your rear pulley in between tests.

You have 2 variables working against you - the accuracy of the tach, and the accuracy of the speedo.

Its hard to believe you could read those both wrong consistently.

I have a Kawi OEM tach on my Custom - and it wouldn't matter if I ran race gas or pump gas, or pulled the bike with a tow truck (with the rear wheel on the ground, spark plugs out, in gear) - the speed of the rear tire and the RPM of the engine would be exactly the same. The rear tire and the crankshaft of the engine are locked together by the transmission and the drive belt.
Yeah, fair call - I guess I hadn't really thought my hypothesis though too well. :p But my earlier point is still valid; there seems to be a big difference, albeit subjective, between the different octanes.
 

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Well, you are running a Cobra Powerpro, so maybe its just happy with the higher-octane fuel. Its hard to know.

Over here in Canada, our pump "regular" is 87 ((R+M)/2) calculation method.

We have 87, 89, 91, and 94 ((R+M)/2) at the pump, at Chevron.

I would expect the PowerPro to keep feeding the cylinders fuel (longer injector cycle and/or longer pulse width) until the speed of the engine does not increase any further - that's from the Cobra literature.

It could be that your bike (and aftermarket goodies) likes the higher octane.

But, like I have said, this octane change will not change your engine RPM at any given speed.
 

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Yeah, fair call - I guess I hadn't really thought my hypothesis though too well. :p But my earlier point is still valid; there seems to be a big difference, albeit subjective, between the different octanes.
I wonder if your higher octane fuel has a different percentage of ethanol in it? That to me would make a big difference if that was the case. Also you should do a test where you put the lower octane fuel in, and pour in some octane boost to see if its really the octane or some other property like ethanol content giving you the better performance.
 

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Just picking up on the comment AZGeek makes in his thread about fuels - I've been experimenting with different octanes on my 09 Custom; here in New Zealand, most gas stations sell 91 or 95 (BP also do a 98), and I find a noticeable difference with 91 - engine pings, rattles at lower revs, and generally doesn't sound as happy. First modern vehicle I've owned that behaves so differently depending on fuel.

Does anyone know how timing is controlled on Vulcans? I just assumed it was auto-magic, and would adjust for different octanes.
What method are they using to get those octane numbers? Here in the states, we have 87,89,91 using the r+m/2 method as has been mentioned.

Depending on the method, your 91 could be equal to @84 using our method with the 95 being 87 and the 98 being 90 (I'm just guessing here.)

The real question is what does your owners manual say for New Zealand gas? That's what you should use.
 

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I found my VN runs best on 95. It runs ok on 98,But it takes longer to start on 98 though.
I try to stay away from the 91 E10 Ethanol blend stuff they are pushing onto us here.
Not too sure if it is just my imagination,But running 98 at 120kmh, I get more engine vibration through the floor boards.
 

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What method are they using to get those octane numbers? Here in the states, we have 87,89,91 using the r+m/2 method as has been mentioned.
All of this has been confusing the hell out of me LOL. When I go to pump gas we have Regular, Plus, and Premium in octane levels 87,89, and 93 respectively. I've never seen 91 octane fuel in the states...unless my local fuel stops and others in my travels have been lying to me!
 

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Iam pretty sure Australia and maybe New Zealand have a different rating. We have 91 which is the cheaper one blended with Ethanol most of the time. 95 is classed as a premium at some fuel stations. 98 is the most expensive. I have see 100 a while ago,but didn't use it at all. It was at a discount petrol station.
 

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All of this has been confusing the hell out of me LOL. When I go to pump gas we have Regular, Plus, and Premium in octane levels 87,89, and 93 respectively. I've never seen 91 octane fuel in the states...unless my local fuel stops and others in my travels have been lying to me!
Two stations off the interstate here. One is 87, 89, 91 the other is 87, 91, 93; same prices for "regular" "premium" and "super", so obviously the better value is at the higher octane place! In theory. There's a place near here that also sells 100 octane "offroad only" fuel and evidently some places to get 95 and 97. Those are all RON+MON/2 numbers. In other parts of the world, they simply use RON. So 91RON = 87 R+M/2. Sort of like metric and imperial. 88km/h=55mi/h. Two metrics describing the same thing.
 
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