Harley Qs

[old slider]

91 95 and 98 all work fine in my old 88ci motor. I cany tell any diference between any of them.

Pumped in some 95 today in the 2010 Fat Bob after doing about 25-30kms on the last 1/3 tank left of 91 , about 5 kms from leaving the station I noticed the popping greatly reduced on deceleration and a smoother running engine.

[Bass]

Depends entirely what the motor is tuned for. The compression ratio defines the volumetric efficency of any motor, hence drag motors run very high CR and produce enormous HP on Methanol fuel. Methanol however has a relatively low calorific value compared to petrol.

Sorta true but only part of the story.
The stoichiometric ratio for methanol means that you put nearly twice as much in compared with petrol. This more than overcomes the lower calorific value. The ratio is what controls the amount of fuel going in and so the total energy released.

A discussion on efficiency is a whole different topic and not really appropriate in this thread IMHO.

[AllanB]

I played with 91 and 95 on the Hornet 900 (book said 91 was fine) - there was zero noticeable difference in feel or fuel consumption between the two.

The Ducati states 95 or higher. 95 it is, the closest BP (seller of 98) is not on my usual travels but I may try a tank and see if I notice anything.

[Bass]

I played with 91 and 95 on the Hornet 900 (book said 91 was fine) - there was zero noticeable difference in feel or fuel consumption between the two.

The Ducati states 95 or higher. 95 it is, the closest BP (seller of 98) is not on my usual travels but I may try a tank and see if I notice anything.

That's normal.
The octane rating is a measure of the fuel's anti-knock properties, not it's calorific value.
The 2 fuels have much the same calorific value and so if the motor runs fine on 91, you are unlikely to get any extra benefit from 95.

There is an exception however.
Some modern motors may have knock sensors and moderately high compression ratios. They will run on both fuels but on 91, the ignition timing is retarded behind ideal. When fed 95, the motor is able to advance the ignition timing resulting in better all round performance.
The exception may well become the rule in this case.

[Flip]

Sorta true but only part of the story.
The stoichiometric ratio for methanol means that you put nearly twice as much in compared with petrol. This more than overcomes the lower calorific value. The ratio is what controls the amount of fuel going in and so the total energy released.

A discussion on efficiency is a whole different topic and not really appropriate in this thread IMHO.

F. Go back to engineering school.

[GrayWolf]

You're not exactly right there Crasher.

25 years in the fuel and lubricants industry here and I was on the industry panel that the MOE put together to establish the fuel specifications for the introduction of ULP. I'd say that Marsden UL91 was as good as any UL91 anywhere, Marsden Point being a somewhat MON limited refinery you tend to get RON give away and the fuel out of there is fairly free of olefins. Spec'd for NZ conditions too, vapour pressure changes to accommodate winter starting.

But then, Auckland gets only Marsden Point petrol down the pipeline, you poor folk south of the Bombays might be getting imported fuel - but it'll still have to meet the MOE specs and they're quite rigorous.

Did you have any particular area where UL91 falls short? And is that a shortfall against the actual MOE spec or just a shortfall in your expectations?

You do know of course that US engines have their octane requirement specified in a different way. Here we identify petrol by only its RON, either 91, 95 and 98 for certain brands. In the States they identify gasoline octane by (RON + MON)/2, an average octane. Therefore the States 91 is more like NZ 95 RON (95 + 85)/2.

I live in Welly, and any testing done on WMCC's old dyno, tended to point to our 91 down here being poos. But yeah, when I was in the States riding a Beull about, their 91 seemed to suit it just fine. Thanks for your reply...good reading! Cheers.

I went into this very thing with my MT-01.
NZ fuel is different in it's levels of aromatics and sulphur, compared to many other countries.
Nearly every other country, the bike ran 'rich' as standard, and the Yamaha 'stage 1' tune of Akropovich 'road legal' mufflers, and a free flow air filter was coped with by the factory fitted ECU/O2 loop.
My bike ran lean, I could smell the motor was hot, and the oil temp gauge was higher than normal besides obvious hesitation on throttle opening. It was a point of discussion as it was so 'out of the norm', until we researched the composition of NZ fuel compared to others... It's not just the RON/MON, but seems the level of constituents used to get there also effects 'quality'.
Even with a fueller added I couldnt run the bike properly on 91. Yamaha reccomended NOT using fuel with an ethanol blend, so 98 was out as an everyday fuel
When I stage 2'd the bike, without a fueller, the motor was completely naff. And that was WITH the Yamaha stage 2 ECU fitted which removes the O2 loop, and alters the F/A ratio. That ECU was designed to run with a 'free flow' air filter and larger diameter headers with 'race' mufflers.

[RDJ]

Since we are all individuals, personally I like subjectivity. What works best by my seat-of-the-pants dyno, is what I fill my tanks with. For the V2s, and the V8s.

[Crasherfromwayback]

Since we are all individuals, personally I like subjectivity. What works best by my seat-of-the-pants dyno, is what I fill my tanks with. For the V2s, and the V8s.

The thing with seat of the pants dynos is...you take some low end torque away (bad move) and the thing more often than not *feels* faster when it gets it's self out of that whole and *comes alive*.

It's a seat of the pants *illusion*.

[RDJ]

Not arguing with you... But:

...I do recall being taught many years ago "in the end, all illusions have some therapeutic value"

[Crasherfromwayback]

...I do recall being taught many years ago "in the end, all illusions have some therapeutic value"

If being beaten in a race of some form due to said *illusions* is therapeutic for you, knock yourself out!

[RDJ]

Nah I'm not racing on the road

Anyway actual dyno readings are the kiss of death to rated horsepower

[Crasherfromwayback]

Nah I'm not racing on the road

Anyway actual dyno readings are the kiss of death to rated horsepower

Me neither. Never!

[granstar]

So to find out about gas, look up a thread on Harleys

So a bad tank of gas from Challenge 91 just cost me a non running bike (Hornet 919) over my holiday (trip around S.I cancelled while waiting for a new filter to arrive from U.S. Filled up bike, rode 2k's home and it wouldn't start from there. Possibly station has a bad tank or been dumped with bad gas from tanker but word it has happened to another motorcylist recently and a group of classic car owners.

Checked over by bike shop to eliminate fault ($300), came down to a new filter, flush out tank, farking good whinge, and away we go. If yer bike stops out of the blue/ runs very rough out of ordinary after a fill, check for bad gas.

[Katman]

So to find out about gas, look up a thread on Harleys

So a bad tank of gas from Challenge 91 just cost me a non running bike (Hornet 919) over my holiday (trip around S.I cancelled while waiting for a new filter to arrive from U.S. Filled up bike, rode 2k's home and it wouldn't start from there. Possibly station has a bad tank or been dumped with bad gas from tanker but word it has happened to another motorcylist recently and a group of classic car owners.

Checked over by bike shop to eliminate fault ($300), came down to a new filter, flush out tank, farking good whinge, and away we go. If yer bike stops out of the blue/ runs very rough out of ordinary after a fill, check for bad gas.

A tip for future reference.

If you should ever pull into a gas station while a tanker is there filling up the tanks, ride/drive straight on through.

Any water or sediment sitting in the bottom of the tanks has now been stirred up throughout the tank.

[pritch]

A tip for future reference.

If you should ever pull into a gas station while a tanker is there filling up the tanks, ride/drive straight on through.

Any water or sediment sitting in the bottom of the tanks has now been stirred up throughout the tank.

Thanks. I will file that away.

Right now I can't even remember exactly when I had my BMW, but I distinctly recall that in the event of almost any problem with the way the bike was running, the manual advised replacing the fuel filter as the first step.