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Messages - DesertDragon

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1
General Motorcycle Discussion / Re: What are those ODOMETERS up to?
« on: September 22, 2017, 09:55:17 AM »
Also a '96 I bought in 2006 from the second owner with 15K on the Odo.
I just bounced over 29K, so I'm nearly responsible for half the bike's mileage...
 bkr3

2
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 22, 2017, 09:51:17 AM »
Weather is definitely a factor, especially temperature on a "cold blooded" engine.
It's difficult to ascribe mileage to a fuel when riding conditions can be very different from one tank to another..
Big difference between rolling along at 35 vs. stop and go in heavy traffic, or riding in the flat vs steep hill canyon carving.
Speed is also a big factor as more fuel is required to overcome wind resistance, and strong head winds will also make a difference in mileage reduction.

Keeping all of the above in mind, and with 11 years of mpg calculations performed on every fill up, I'm still noticing an improvement by using super.
My rides to town went from an average of 45 to over 50, but this was when driven at the low end of the tach. - 25 mph dirt roads and 35 mph paved.
In all my years of riding, I'd never got 50 mpg out of a tank.

My last fill included a lot of traffic thanks to a major freeway overhaul, with high winds and trucks being passed @ 80 mph+along the way.
(High wind + truck wake @ 75 = Buffet City)
 fans1
Historically, using regular, these conditions would net ~ 40 ~ 42 mpg, vs the 47 I got..

The super I used was Mobil Synergy Premium, and it's the only super I've tried.
I am considering going back to regular for comparison, but my bike is running so well now, I'm not sure I want to.

3
General Motorcycle Discussion / Re: Don't wrap your pipes
« on: September 18, 2017, 08:45:52 AM »
Alan,
I've met lots of folks who will ride in the rain if they have to, but never...
Wow !  Look !  It's RAINING... Let's go for a ride!
 haphap
With the right gear it's tolerable, but compared to a nice sunny day that's 70~ish...

In my case, it's also that rain = mud which "ain't no fun" with a 500 lb street bike..

BTW - In case it DOES rain, it's nice to have a good set of "wet" capable tires.
I really like the Avon Storms.. I've got the Storm 3D-XM's and they don't mind wet one bit.

4
So, my YELLOW '96 is named.... Amber... and Amber wasn't feeling too pretty after riding home in the mud when we were surprised by a monsoon storm..
It's strange how when the Weather Service says there is a 10% chance, it rains, and with an 80% chance, it doesn't.. But I digress...

So Amber was a muddy mess and I gave her a bath and did a WD40 clean on her x-ring chain followed up with her favorite silicone lube.
Protects from corrosion and doesn't attract dirt like chain wax...  After 700 miles the tension adjustment was still perfect...

I also discovered that the boot that protects the wires going into the left side rotor cover was a bit loose, so I added a bit of waterproof grease to seal the rubber connector in case rain decides to intrude.

Years ago I bought a cleanable stock size Uni Air Filter, and it doesn't take too many trips down my dirt road to clog, so I did Amber a favor and cleaned that for her as well.  She does need to breathe after all..
 
Now she's "lookin' good and feelin' good"...
nice1


5
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 14, 2017, 04:42:39 PM »
DD - that is great.  If I got your results, I'd run Unicorn Gravy through my bike.  When I had a '96 750, I would usually get 45-47 mpg, on RARE occasion, 49-50 (55 mph stroll through the back country).
Where are you located?  If high altitude, was your bike re-jetted for that?
Unicorn Gravy retailers must be regional...
 yaaaah3
I'm not far from the Grand Canyon ~ a mile up.  Was never rejetted by me - prior owner was in Phoenix, AZ.
Based on my last look at my plugs, the bike was happy with the jetting it had (a nice even realtor approved light brown ;)
I'll check them again before too long to see what difference the super is making, but based on the mpg performance, it can't be too far to the rich side, or my mpgs would be worse, rather than better...

As to why it's running so well.... I can't explain it either.

6
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 14, 2017, 09:33:10 AM »
Once again I got a nice surprise on filling up with super yesterday - My last tank netted 53 mpg...
Amazing to me, as was I expected a significant drop because I was stuck in a huge semi-truck traffic jam on the interstate.
At this point, after 5 tanks, an error related to fill differences is very unlikely, not that I thought it was a contributing factor in the first place...

Since my switch to super I have yet to get less than 50 mpg, when previously 45 was the best I did (nothing to sneeze at either IMHO).
The bike continues to run great, so I'm a happy camper...

If it hadn't been for Rubo, and his "Placebo or Real? 87 or 92 octane" thread, I probably would have never tried super gas.

So, Rubo - Thanks for the "hot tip" - For me the fuel change has been great. 
My scooter is running better than ever and the modest increase in fuel cost is actually saving me money in increased mileage.

BTW - It turns out I have been using Mobil Synergy premium all along - It took the station awhile to post their stickers on the pumps....
 

7
Your Honda Nighthawk / Re: My First
« on: September 13, 2017, 09:04:14 AM »
Thanks, I hope the yellow makes me just that little bit more visible on the road. Even so, I ride as though I'm invisible.
Welcome aboard!
Nice choice! 
My '96 is also in Yellow... btw...It's been scientifically proven that Yellow is the fastest color available...
 scheet2
Your riding strategy is good... I also ride assuming that I'm invisible.....except to the drivers that are trying to kill me!!!
 fans1
Seriously, a little bit of paranoia goes a long way.

8
Here in blighty we get more of this. Bad and ignorant styles on the roads have escalated to a point that aggressive behaviour is rife. Our government has cut back too much on traffic cops,  relying on the good will of the people.... There isn't any. I discussed this in a meeting with the road safety team. U was told not enough money for cops.  I said the police are not doing the job they're paid for and they're welcome to come out for a drive with me after the meeting.....I could make a cops wage in one hour if they got out of their car ( then 39 hours pure profit) and enforced the law with fines....guess what? They refused. Excuse??
That's pretty sad, but of course if you tried to take any action yourself, I'm sure they would be right there to arrest you.
Myself, I wouldn't ride in a big city anymore. 
Take care my friend...

9
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 12, 2017, 09:47:43 AM »
I think you've hit the nail on the head, DD!  :gavel:
Thank You Mr. sg... 
Sometimes it doesn't hurt to state the obvious...
Unless you ARE the nail...
claugh1
For Mr. Fine... "I expect, at some point, to revert to the premium again to see if there is a discernible difference when going in that direction.."
I will do the same and revert back to regular and see if I notice a difference going that way.

10
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 11, 2017, 09:35:21 AM »
More good comments.  I did find it interesting that Larry Fine has the same year bike (96), was using super and went to regular and discovered he's been wasting money because his bike runs as well or better on regular.  In my case, I went from regular to super and found some advantages.
Some others did, and other's did not.  Some swear by super, others swear at it.

I guess the basic problem to getting an "answer" is there are too many variables, the biggest one being that all fuel is not created equal.
While octane is measured, there can be a huge difference in nearly every other aspect of a given fuel's ingredients.
In my case, I am convinced that it has a lot to do with ethanol, or that the super I'm using doesn't contain it, where the regular did...

Since this discussion is about fuel, and there is no way to effectively compare fuel chemistry (correct me if I wrong here), along with all of the other variables, e.g. temperature, humidity, atmospheric pressure, specific engine's compression, jetting, etc, etc, etc..., let alone significant differences that are possible even between two bikes of the same make and model, at the end of the day, I doubt a definitive answer is possible, beyond "if your bike likes a certain fuel, use it, and if it doesn't care, use the best price fuel you can find"..

11
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 09, 2017, 10:08:35 AM »
Test ride #2: Not really an experimental ride, just normal usage: leisure rides, chores and stores, going to work, etc.

So far, I have noticed zero difference on my second tank of regular grade, though still the same brand, Amoco..

Again, no difference so far, and even my local, privately owned-and-operated bike shop mechanic said he recommends regular. I had been using the reasoning that an air-cooled engine runs hotter (which it does) requires a premium-grade gas (which apparently it doesn't). I will keep all y'all (plural of y'all) posted on any future developments. Ciao for now!
Interesting... So you went from Super to regular and I went from regular to Super...
I should point out that my bike still ran well on regular, but with super, quicker warm-up (cold-blooded reduction), no stumble near redline and improved mpg was what I noticed.
When you say "zero difference" I'm wondering what (or if) you are measuring...
I guess the major thing for me is the mpg...
Do you check your MPG when you fill up?
If so, what are you getting?

 

12
Your Honda Nighthawk / Re: My '96 CB750 "Dragon Bike"
« on: September 07, 2017, 10:50:47 AM »
Beautiful bike! For a ridden Honda it sure is impeccably clean, Bravo Sir!!
Thank You!
Thank You Very Much...
A hunka hunka burnin' Thank You!
 haphap

13
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 07, 2017, 08:27:08 AM »
Quick update - another fill up with a tank of super, another 50 mpg..
This one included a 50 mile interstate ride @ 75 mph...

14
General Motorcycle Discussion / Re: New Bike Hauler
« on: September 06, 2017, 08:51:40 AM »
Just yesterday I picked up an 09 Ram 1500.  In Yellow of course.

A wise choice.... 
haphap

15
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 03, 2017, 03:16:12 PM »
Lotsa "ifs", oh slayer of the rodents 
heya2

I don't know that it is running richer, but if it is, if that could be attributable to the difference in octane rating.
The consensus opinion says no, and if the engine doesn't knock, more octane or actually, a higher octane rating isn't necessary.
On premium fuel, it just seems to be running better, and is running better by the several measures I noted..

Again, not sure why that is. I do find it interesting that the more research I do, the more information I get that says don't use super.
Of course, most of these statements are made "theoretically" and with caveats.. In MOST engines... GENERALLY speaking, etc...
Like you said, If it runs better, use it -  is probably a lot more useful advice, as it is at least based on observation.

An "octane rating" is, strictly speaking, used as a measure of a fuel's ability to resist 'knock' (pre-ignition) like you said.
If you research further, it is derived from the measure of a fuel's burn characteristic when compared to a defined quantity of the combustion of a standard mixture, the result of which can be reported on several different scales.
RON (Research Octane number) and MON (Motor Octane Number) are combined and averaged ((RON+MON)/2) = AKI (Anti-knock Index)
The AKI is what you see on the pump here in the USA as (typically) 87 for regular.
If you want to read about it, Wikipedia has a pretty decent explanation:
https://en.wikipedia.org/wiki/Octane_rating
I also learned in the article that a diesel only compresses air, and not the air/fuel mixture..
I learn something new every day... 
But I digress...

Anyway, you are right, octane or octane rating doesn't compensate for anything else, other than as an assist to prevent knock.

But - The octane component of a fuel is a relatively small part, and there can be (and are) many other differences between fuel compositions among producers and distributors, as well as between fuel grades (regular / mid / super).
It may be possible (likely?) that the basic composition or specific included ingredients is making the difference. 
Again - I don't know, but something made a difference.

If you are familiar with the "placebo" effect - (some people can be cured of illness with a sugar pill) a similar thing can happen with humans interacting with machines, like a motorcycle, for instance, where the thrill of a new fuel changes their perception of how "well" the engine runs, and it suddenly runs "smoother" and has more power.  This is usually based on an expectation that the new brand is better, and then the rider "discovers" what was anticipated. 
In my case I wasn't expecting anything, so it would be like I'm about to be cured of cancer with a new drug being tested, but they tell me it's only a sugar pill... Result - No placebo effect, because I "know" it won't do anything.

Dang... Again I've managed to digress...

Anyway, at this point I've spent too much of my remaining time on this planet discussing the relative benefits of fuel, and I'll post anything that looks significant, either way....
 (sudden drop in mileage / return to long warm up / top end burble when switching back to regular / engine EXPLODES due to octane overdose)
 yaaaah3
... but at this point I'm not thinking it's worth the effort to find out, or even if that is possible regardless of the effort.
That's it - I'm goin' for a ride!

16
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 03, 2017, 09:17:23 AM »
I can say I've never tried it.  Thought there was no point.  I would bet though that premium where I live would still have ethanol in it.  But for the sake of an experiment I'll try it.  I am confused about your use of the word octane.  Most of what you are describing would be accomplished by jetting.  Elevation, air temperature, anything that changes the air density will change the air/fuel ratio.  I've never heard of someone compensating for altitude changes with different octanes.  You would use different jets.  I'm curious about your bike DD.  Is it completely stock? Any jet changes or shims under the needles?  The late hawk is said to be lean from the factory.  Is the super somehow compensating for the lean A/F mix?  That would explain it.  If an engine was running lean and all of the sudden was running right you would get everything you describe.  I don't know if thats possible and you guys are diving deeper into this topic than I'm capable of.  Up until now my only thought of premium was some engines like it, some engines don't care.  Figure out what your engine likes and run that. 
You make some good points, and like you, I had never tried super either because I "knew" it wouldn't make a difference.
It was actually a guy on this forum that used it and seemed to have noticed results, so I tried it myself as an experiment.

"Octane" as used to describe a fuel rating, is actually an anti-knock index. It just happens to be one of the only easily identifiable qualifiers on fuel.  Ethanol is another, but you typically don't have a choice - Most metro areas use it ubiquitously.  I'm not sure if that also allies to super.
I live in a rural area, which doesn't have the same mandates as most cities do.
 
My bike is internally stock.  The air cleaner is stock in dimension, but a cleanable UNI which is likely breathing better than the stock paper.
That might cause the mix to be a bit leaner.. No other engine mods.  Carbs were rebuilt (gummed up from sitting - won't do THAT again) but they were reset to how they were. 
I didn't notice a difference afterwards.  I had not heard about the "lean 'Hawk"... Could be a factor. 
That might make sense if super "acts" like a "richer" fuel.  Maybe somebody can comment on that...
While perhaps the same results could be had with jet mods, there is no way I'm going to open up a "golden goose" to find out.
My scooter is running sweet, and since it "ain't broke"... 
 ridn2
I have always sought to understand things that I can't readily explain, but maybe this is one of those that prefers not to be known. 
I can live with that, and in any case, I'm happy with how the bike is running, especially my 51 mpg!

I like your last line, and that may be as close as I can get to an answer.. At least it's pragmatic.
I guess my engine "likes" super, some others like it, and still some others will find that their's don't care..

I'll be looking for your result, or not result...
 bkr3


17
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 02, 2017, 06:25:27 PM »
Larry - Good post...
I had an 82 GS 750EZ with TSCC - I loved that bike.
As far as the fuel....
I'm trying to understand, by thinking out loud, reading replies, and reading LOTS of other stuff with varying opinions, what is going on in my engine. 
I started all of this with an expectation that changing fuel grades would result in a big NADA - The exception being the cost difference between super and regular... 
But that's not what happened.
I know how an engine works, but I liked your explanation of the combustion phase.

For most folks I would agree that regular is a better choice. 
I wouldn't consider it for my car, but then it also water cooled, has a computer controlling it, has relatively low compression and runs fine on regular.
My bike is pretty much opposite of that, and although I didn't know it, or anticipate it at the time, they way it acts with super has been better.
It warms up faster, I can take off sooner without stumbling at low RPMs, I can run it all the way through to red-line without a burble like I had before, and to boot, I got better mpg than with regular. 

Regardless of the specific reason(s) for this, something is going on. 
My rifle vs cylinder example was an attempt at a possible explanation, because something is happening. 
Maybe it's a lot of somethings.

While both the too fast and too slow fuel burn phenomena are possible, all other things being equal, something caused my rpm at idle to increase. 
You would not expect to have waste cause an improvement, and I don't see that as being likely in my engine.

Could it be possible that it's ONLY my engine... Anything is possible, but several other folks have commented with similar results so I doubt it.
That's why I thought it might be interesting to find out results from other folks experiments.

Mechanically, my bike was and is in great shape. I went through a recent major tune, and have a newly cleaned air filter.
It has like new compression, and I was getting a consistent 45 mpg until I switched to super.  Now the mpg is over 50.
That's an 11 percent increase...  Will others see this.. Maybe.. Maybe not...

I would think an inexpensive and very easy test, by grabbing the "other" pump handle would be worth the possibility of having a machine that "worked" better with the more expensive fuel.  To me, it isn't even more expensive as the fuel cost and mileage are a wash.
The difference in how the bike runs makes it worthwhile for me.  For someone else, maybe not.  Maybe it would be worse.
I don't know, but I also never claimed that everyone would notice the improvements that I did - I just suggested they try it.

Apparently, fuel and oil and tires and just about everything else on a bike are topics where strong opinions are held.
Everyone is entitled to their own opinion, but if that opinion prevents them from trying something that might be good...

Anyway, whether or not you notice a difference in the positive, negative or none at all, please do post it.

18
General Motorcycle Discussion / Re: Exxon Mobil SYNERGY Gas
« on: September 02, 2017, 11:31:23 AM »
I have used this gas in my cage and my CTX700 with no issues. I find this gas is a bit better than the other gasses offered in the area where I live. I think it also comes down to the amount of ethanol the put into to gas when it is prepared to go into the tanker truck for delivery to the gas station.  Once I get my Night Hawk back in working order, I will definitely give this gas a chance to see how well it performs. 
I tend to agree as far as ethanol goes - Look at the "fun with fuel" thread...

19
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 02, 2017, 10:08:34 AM »
Larry, you make some good points, especially the "dilution" factor...
As far as a faster burn = more power.... Here's another take, from an optimized shooting perspective.
Different gunpowders, like gasoline grades, have different burn rates.
Very fast burning powders (like regular in your post) improves performance in a short barrel where there is a relatively short run to accelerate the projectile.
In a longer barrel, the same fast burning powder will not produce as much thrust as a slower burning powder, and although the differences would seem to be relatively minor, there are major measurable results between the two.
The reason the slower burn results in a faster projectile in a longer barrel, is that the bullet is being accelerated down the entire length of the barrel.
If the "burn" stops before the bullet exits, the gas pressure begins to lower and the remaining length of the barrel is actually serving to slow down the bullet through the remainder of its travel.
If you think about it, a gun and a motorcycle cylinder are not all that different, in regards to both being powered by a controlled explosion driving an object through a sealed space.
While the faster burn may have more initial pop - It is the total force applied over the length of the barrel (gun or cylinder) that results in power.
When you mention "smoother", and I've noticed this as well, it may well be that the bike "likes" a slower burn fuel, and rather than a quicker "pop", it is getting a longer "push"...  If the engine is taking advantage of this difference, it well could be a major component of reason I noticed a mpg increase.
It would also seem to explain why several people, myself included, noticed an idle speed increase with super.
If the same amount of fuel is delivered to the same engine and it begins running faster (increased RPM), it MUST have gained some efficiency.
I would be interested to hear an alternative explanation for this observation, but I doubt it would be one that made sense.  It's just physics.
Your comment made me think of one other fuel related item... 
When the Nighthawks were originally produced, ethanol was a much less common ingredient in regular grade fuel than it is today.
While the regular "octane rating" may be the same (~87) the addition of ethanol, which effectively increases the "octane number" may have changed the characteristics of the fuel burn rate enough that the engine is not operating effectively with the "regular/ethanol" fuel mix...
Thanks for getting me thinking... The ethanol/not difference may well be what's going on here...



20
Your Honda Nighthawk / Re: First time rider!
« on: September 01, 2017, 07:10:15 PM »
Wow - First time rider and you managed to select the best motorcycle ever made!
Good job.
I've had my 96 for 11 years and it's never left me stranded.
You also found a great forum - There are some very knowledgeable and helpful folks on here.

Enjoy the ride!

21
General Motorcycle Discussion / Re: More Fun with Fuel....
« on: September 01, 2017, 06:55:12 PM »
Pretty good post. I've done this several times over the years in my VFR and seen ZERO difference. BUT ... Just for gits and shiggles I'll try it next fill up in the Nighthawk and let you know.
As the Captain said... EFI - Keyword there is electronic. 
Don't know specifics of the ECM (engine control module) in your VFR, but you have one, and it likely will automatically alter timing to ensure that it is doing what its designer intended. With enough data (and you already added some) my hypothesis is that the more intelligent the machine, the less benefit from a higher grade fuel, except for those that NEED it..
But - In a dinosaur, like I am proud to ride, the upgrade makes a difference (well, I've convinced myself already based on observation).
Take note before you dump some super in there, how long it takes to warm up. and how it takes off from idle when "cold" (relatively).
Compare that to the next day with super in the tank.  That's the first thing that struck me.

Enjoy the ride...

22
General Motorcycle Discussion / More Fun with Fuel....
« on: September 01, 2017, 11:31:06 AM »
Howdy..
After a member's thread on "real or placebo" for a fuel switch prompted a lot of conversation, it got me to try super in my bike.
I noticed some positive differences in the fuel switch for my 96 750 from Mobil regular to Mobil super...
Quicker warm up, increase in idle speed, elimination of "stumble" near redline, and an improvement in mpg was what I noticed.
Some of this can be explained, and some seems to be a mystery and/or flys in the face of "consensus" opinion.
 
Between rides, I've been doing a lot of research, and it is amazing just how much controversy there is on the regular/super topic beyond this forum.

I did learn a few things.  Read on if you're interested.

Octane rating:
One of the few things you can tell about a fuel by looking at the gas pump.
Also one of the things that is tested, that must conform with reality.
A surprise to me, is that "octane rating" is NOT equivalent to, or a measure of "octane content".. e.g. super grade with a rating of 93 does not (necessarily) mean that it contains more octane than the fuel from the next pump displaying 87. 
What it DOES mean is that the super/premium rated at 93 "acts" like it has a higher octane content when measured.
This can be due to actual octane content in the fuel, one or more of a large number of base stock combinations, additive additions, displayed components (typically ethanol / mtbe) mandated for emission purposes, or substances included for engine improvement/advertising (Techroline?)
So, the "octane" rating is really not an "octane number" at all - It is called an anti-knock index (in the fine print), because that's what it is.
Octane or "octane acting" components act to slow down the combustion process... (more push, less BANG)
It assists in prevention of premature ignition (knock) which can destroy an engine over time.
The "consensus" opinion with regards to "octane rating" therefore, is if you don't have knock from a given fuel, you don't "need" a higher rated fuel to prevent knock. 

Fuel formulation:
Although the octane index is not an octane measure, and more isn't necessarily better (unless you need it to prevent knock), the way that the fuels get to that number can be very different by fuel grade.  One of the major differences, is in the addition of alcohol (ethanol) to the fuel.
Although alcohol has less measured energy than "gasoline" (BTU/unit of measure) it will provide the fuel to which it is added a relatively higher octane rating.
Alcohol also burns hotter, absorbs water more readily, and evaporates more quickly at the same temperature than does "gasoline".

Ethanol is a very common regular unleaded additive, but NOT a universal premium fuel ingredient. 
Therefore, in addition to the higher rating, that extra 20 or 30 cents per gallon for super may be buying you more "actual" gasoline, rather than an alcohol/gasoline mix.

Engine Control:
One of the primary cited reasons that "premium fuel" is a "waste" is because modern engines have computer controlled, multi-sensor systems that monitor both external environmental conditions and internal engine performance, and then dynamically modify engine operation based on sensor input to optimize for desired programmed factors (e.g. fuel economy/performance/emissions/etc). 
These systems can also allow an engine that would otherwise "knock" itself to death, run well, or at least acceptably well, with the same grade of fuel.

Engine types:
There is a considerable difference between an air cooled and water cooled engine in terms of their operational temperature, yep - air cooled engines run much hotter.  There is also more operational variation in them, as they don't have the mitigating factor of a water jacket surrounding them.
If you look at what's available out there - Lots more water cooled engines - Their operating temperatures can be modified (kick on the radiator fan) which is something an air cooled motor can't do.

How does this relate to using a "higher grade" fuel in the CB 750, and any actual or perceived improvement in performance....
While there is some pure opinion which follows, at this point, I think the following may be factors that align with my improvement observations...

Fuel Formulation:
Since the super I used didn't have ethanol in it, but the regular grade did, my Nighthawk, without any vapor recovery capability would lose more fuel to evaporation because the ethanol more easily evaporates.  Over time, this would mean there would be less fuel left to burn.
Alcohol also "loves" to absorb water, and the resulting regular fuel solution would contain more water (and less energy per unit volume) over time.
These factors may or may not be significant, but in my case, since I go on a large number of short trips (gas tank heated up each time) over an extended period of time (weeks), even small differences will add up.  All else being equal, these factors would serve to increase measured mpg.

Engine:
My CB 750, being air cooled, and therefore running hotter, especially in my high desert, high temperature environment, has an increased need for for a slower combustion process to run optimally.  The bike is not equipped to dynamically alter any performance characteristics beyond spark advance.
As temperatures increase, equivalent performance requires improved "octane" to maintain optimum performance. 
(this appears to be generally accepted, and is used in racing prep design calculations)
With regular fuel, the bike may not be knocking, but that doesn't mean it's running ideally either.
I did find an interesting fact for recommended fuel grade for The Harley.
With a lower compression ratio than the 'Hawk, but also equipped with an air cooled engine, their minimum recommendation is 91 (super).
The manufacturer rating requirement for a fuel grade cannot possibly address all possible conditions, but in my case, based on some performance curve calculations, the recommended fuel rating is apparently not sufficient for my engine's needs.  If it were, there could be no improvement.
Improvement was obvious to me, and apparently some others, and although I agree that "runs better" is a subjective assessment likely to be impacted by "placebo bias", when a significant change is measured, it's no longer subjective.
The most obvious change in performance for me, was near redline, which tends to require more help from the fuel in prevention of pre-ignition. 
I cannot think of any other reason why just a change in fuel eliminated a stumble if the lower grade was adequate....

Still interested? 
If you are willing to gamble a small wager (~$1 - $1.50) on a tank of fuel, see if it makes a difference for you.
Whatever you can measure, I'm interested to know your results, good, bad or no difference.

On the "placebo or real" thread, I mentioned that it might be an interesting experiment to capture results.
I'm thinking that brand, grade, octane rating and additive (ethanol and/or mtbe) of the fuel and your bike type would be a good start.

One benefit of participation...
 ridn2
You need to ride to find out if there's a difference!





 


23
General Motorcycle Discussion / Re: Placebo or Real? 87 or 92 octane
« on: August 30, 2017, 07:25:27 PM »
Sorry for my continued verbosity, and for any prior offense - especially to you Pants Man - I shouldn't be so passionate.. But I am..
 haphap
There is a lot more chaff than seed out there, but here are a few factors with some consensus I've been able to sift out so far...

Factors which increase engine fuel octane requirements:

* Compression: Higher engine compression ratios increase the engine's octane requirement (91-03 'hawks are 9.3 to 1)
* Temperature: Hotter air increases the engine's octane requirements
* Humidity: Drier air increases the engine's octane requirements
* As engine spark timing is increased, the octane requirement increases
* Driving method: Rapid acceleration and heavy loading increase the engine's octane requirement

Factors which decrease octane requirements:
* Altitude: Higher altitudes decrease your engine's octane requirements (and reduces effective compression)
* Modern Engine Control systems: Automatically compensate for nearly every factor

Looking at some very complex interactions, it appears that there is data to support the case why MY CB750 Nighthawk runs better on high octane fuel:

* Bike designed with (relatively) high compression engine
* My observed (adjusted) compression (see post in Engine Tab - Your bike's compression is better than you think) is close to factory spec ~ 185 +/- 5
* I ride in a very warm, dry environment (during testing period) > 90 F 10% RH
* Higher octane fuel performs better in full advance / high RPM situations - High speed full throttle performance improvement was noted
* My bike is carburated without engine control systems

I do live at altitude ~ 5000' which is a mitigation factor for octane need. 
My hypothesis is the other factors overcome this, to some extent.  (note: I'm NOT driving down into the heat to test this)

Based on these in totality, an effective octane rating for maximum performance for my bike in my environment is estimated between 91 and 93 - NOT 87.
Super (higher octane generally) fuel actually burns slower, but more effectively in the right cylinder, which may be a factor improving low rpm performance.
More effective burn will improve mileage through less fuel needed for a given rpm and cylinder charge.

I'm pretty sure another mystery - for me - Has been solved.

If you are driving a 'Hawk with good compression, in a warm environment "robustly", and especially if you are at relatively low altitude and humidity,
your ride may well benefit from an increase in octane that will be "noticed"....

If no factors apply, probably not (especially bikes with engine control systems).

There may well be other factors involved in fuel formulation components (or lack therof) / additive packages / alternative components (ethenol / MTBE) Etc... Etc... Etc....

This would be a candidate for a lot more input if there is an interest in experimentation.
In the meantime, it's summer, the weather is nice so go for a ride, check it out for yourself and see if you notice a difference...
It will cost you nearly a whole dollar for a tank.... Or don't.

Regards to All

24
General Motorcycle Discussion / Re: Placebo or Real? 87 or 92 octane
« on: August 30, 2017, 05:23:45 PM »
I'm too cool (i.e., lazy) to keep records, but I am willing to try a tank or few of BP/Amoco regular grade and report any noticeable changes. I figure changing grade and nothing else should point to octane reduction only, presuming otherwise-equal formulation.
Thanks for the offer to step up, and yes - See what happens. 
So, you already use super in your bike.... If so a single tank won't hurt and maybe save you a $1..
Please try to be aware that there is a possibility of bias..
Based on what you've read here, you may "expect" (or not) to see differences in performance.  But yes, please do and post!

The facts of octane rating of a particular grade of fuel may or may not be a relevant factor in this equation..
The consensus opinion (okay -the world being flat was also a consensus opinion at one point) for which there is a good deal of testing on and for, is that primarily, a higher octane rating in a fuel provides a benefit to reduce knock (pre-ignition) in typically high compression engines.
The official evidence says that an octane increase alone won't make a difference to an engine that doesn't knock, so it's a waste.
(If your engine STARTS knocking - Go back to super because you NEED it!)

I would point out that most of the testing evidence I've seen addresses power performance.. Tested on a dyno - BUT..
Has anyone seen test results pointed towards comparisons between fuel grades based on fuel economy, or engine performance at the opposite ends of the performance curve (i.e. startup / warmup / redline performance) ?  These are the areas where I noticed a difference.  Not in power output.

At this point, can anyone can say with authority (impassioned opinions aside) exactly what is happening, and what is causing any performance change?
My contention is that I did notice unexpected changes, and think it worthy of further investigation.
Maybe that investigation has already been done.
Maybe any potential benefit may be isolated to specific cases.
Maybe not.
If so, maybe we need to do the testing ourselves...

25
General Motorcycle Discussion / Re: Placebo or Real? 87 or 92 octane
« on: August 30, 2017, 11:29:43 AM »
Interesting, far more interesting and valuable than one or two random members tracking partial data. Mods?
Aye Captain!
By Mods, I'm thinking you meant bike modifications?  Like a 4 into one / velocity stacks / cams ...
I'm thinking logistically, a home on the forum would be good if there is serious interest in pursuing this..
Does anyone know the forum moderators and perhaps have a conversation with him/her/them ?


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