Fuelology - Honda Shadow Forums : Shadow Motorcycle Forum
Reply
 
LinkBack Thread Tools
post #1 of 112 (permalink) Old 12-15-2008, 07:40 PM Thread Starter
Senior Member
 
Join Date: Mar 2004
Posts: 4,688
Fuelology

<< Originally posted by 'litnin' >>

Octane affects the flash point of gasoline, period.

The flash point is the point at which the vapors from the fuel will ignite by means of heat, instead of spark.
It's also known as 'dieseling'.

Just to help clarify some terms also:
Pre-ignition, detonation, pinging, are not interchangable terms.
Pre-ignition is when the vapors ignite from heat, not spark.
Detonation is what happens AFTER pre-igntion occurs.
Detonation is the result of two flame fronts (one by pre-ignition, the second by spark) colliding in a massive release of heat energy.
Pinging/Spark Knock is the noise you hear as a result of the two flame fronts colliding.

The amount of pressure present in the cylinder will actually surpress spark combustion. One of the many reasons that high boost engines require very small spark gaps and very high ignition voltage.
The more compression you have, the higher the electrical resistance is present and the harder the plug is to fire.
However, the more compression you have, the greater the change of pre-ignition there is... that's why high compression engines detonate so easily.
Ever see a Top Fuel motor? They run DUAL 44amp magnetos putting out about 70,000 volts, each... and spark plugs in the 10 and 11 heat range with a gap of only .015-0.017".

All you are doing by increasing octane, is increasing the point at which the gasoline vapors will ignite by heat. When you change the compression ratio, you change the heat level. High compression generally generates higher combustion temperatures.

Now, if you take a 12.0:1 compression engine at 90 degree ambient air temp, and run it on 87 gasoline... will it ping? Possibly.
Compression is NOT the only thing that makes an engine ping.
Take that same 12.0:1 compression engine and take it where it can run in 40 degree ambient air... Likely, it will not ping. You could likely even increase the compression ratio to 12.5:1 and still not have it ping.

Just another thing to throw in to the mix.
In general, the slower a fuel burns, the more power it can produce.
That is generally the case in most all fuels... even gun powder.

It's all a balancing act, really. You can't just say that high compression engines need higher octane gas. You HAVE to factor in the enviroment(termperature and altitude), the cylinder head design, etc.. There are MANY factors that determine whether or not an engine will detonate.

But, as it's been said, the Shadow's do not generally require high octane gasoline. However, if you live somewhere that has extreme heat (such as parts of California, Arizona, New Mexico, etc...) a higher octane gas may be needed as your outside air temp rises.

So, why do some people notice a difference in power when switching to high octane gas? Well, likely, they live in an environment that makes it necessary. If you have aftermarket exhaust on your ride, you may not hear the pinging.. Switching to a higher octane gas IF your engine is pinging can and most likely will result in better gas mileage and more power. Why? Well, let's look at the cycle of an engine.
On the intake stroke, the cylinder takes in an intake charge that consists of gasoline and air. As the piston moves up on the compression stroke, that mixture starts to heat up. If it gets too hot and flashes before the spark ignites the fuel at the appropriate time, the flash point flame starts burning bottom to top. Not the way you want the flame to burn. You want a downward expansion. Now, as the bottom flame is burning upwards, the spark plug ignites the mixture and starts burning top to bottom.
The two flame fronts collide and all that energy that would normally be used to push the piston down has exerted much of itself upwards and outwards as the flame rises and collides. This force is also trying to push the piston back down as it's trying to come up in the hole.
Now, switch to a higher octane gas and the gas is resistant to the heat generated by compression and outside air so that the plug ignites the mixture at the appropriate time. Now, the expansion of the exhaust gases are expanding correctly in time with the piston. As the piston travels over TDC, the expanding gas can push the piston back down in the hole with the majority of it's energy. So, does pre-ignition cause power loss? Absolutely. Will higher octane fuel help? Absolutely. Will you get more power by running higher octane fuel? Yes, in a case where pre-ignition is robbing the engine of power. Will it always give more power? Nope. If it's not detonating, the higher octane is not doing anything.

And no, higher octane doesn't burn any cleaner or dirtier than low octane gas.

Cbjr is offline  
Sponsored Links
Advertisement
 
post #2 of 112 (permalink) Old 04-26-2009, 11:13 AM
Member
 
Join Date: Nov 2008
Location: Harrison, Ohio
Posts: 375
There was a question on the General Discussion Forum about what octane to use. This is a good write up and says exactly what I was always told. Someone on the other forum said to go ahead and use high octane if you like, it will give you better gas mileage but I was told by the Honda Tech to stick with Regular in my Spirit that prolonged use of high octane wasn't good for the engine.


toolman1951 is offline  
post #3 of 112 (permalink) Old 04-26-2009, 12:20 PM Thread Starter
Senior Member
 
Join Date: Mar 2004
Posts: 4,688
Quote:
Originally Posted by toolman1951
Someone on the other forum said to go ahead and use high octane if you like, it will give you better gas mileage but I was told by the Honda Tech to stick with Regular in my Spirit that prolonged use of high octane wasn't good for the engine.
Both are wrong. Premium hurts nothing but your wallet and won't give better fuel mileage/power unless the engine is designed to use it.

There are occassions when running an up-grade could be beneficial, like in very hot conditions,if you start getting a little ping noise under load, or if you got a tank of below grade octane fuel at a fuel station that doesn't sell much fuel or sells off-branded fuel it would be nice to mix fuel back up to the correct octane, with a little mid-grade.

I run a timing advance that is a little hotter than stock so occasionally I will run a mid-grade.....but I doubt it's necessary.
Cbjr is offline  
 
post #4 of 112 (permalink) Old 06-13-2009, 07:55 PM
Member
 
Reverend Biker's Avatar
 
Join Date: Jun 2008
Location: Western Massachusetts
Posts: 197
Garage
Send a message via AIM to Reverend Biker Send a message via MSN to Reverend Biker
I think this is an appropriate place to bring up the question of ethanol in gasoline. I am attaching two links to this post for some additional background on my current concern.

Right now Massachusetts has had a 10% ethanol/90% Gasoline blend for between 18 months and two years. I have watched my mileage dwindle 7 mpg over that time, from 45.3 mgp at its best down to 38.4 at its worst this spring.

When running the 5% ethanol/95% blend in 2006 and 2007, I noticed a better throttle response and less carbon build-up at the mouth of my exhaust and an averaged 45.5 mpg.

My greatest disappointment has been the decrease in mpg after running my fuel additive through the system. Prior to treatment I was averaging 38.7 mpg. The next tank I added B-12 chemtool (the key ingredients pointed out to me by a chemist-friend was tolulene and methanol). I jumped back to 44.1 mpg for that tank. My friend indicated those two chemicals are also key ingredients in the 104 octane boost as well. They allow the fuel to burn hotter and clean the carbon deposits, inproving performance to some extent.

My disappointment came today when I calculated my mileage for the last additive-free tank I just ran and my mileage is back down to 38.3 mpg.

The crux of what I am saying is that with the evidence in hand, ethanol is significantly affecting performance and it would seem that the additives in the B-12 offset the detriment of the ethanol. Does anyone know to what extent ethanol is affecting our engines other than in loss of mileage?

Lastly, it hardly seems practical or healthy for the bike to be constantly adding fuel additives and octane boosters to regain that performance, but what other alternatives are there?

http://www.nytimes.com/2009/05/10/au...10ETHANOL.html

http://www.businessweek.com/technolo...519_225336.htm

The Rev

The Reverend
'01 Shadow Sabre VT1100C2
'83 XVZ12T Yamaha Venture Royale
Reverend Biker is offline  
post #5 of 112 (permalink) Old 06-26-2009, 03:41 PM
Junior Member
 
Join Date: Jun 2009
Location: Arlington, Texas
Posts: 7
Just a note on this subject, I am new to the whole cruiser scene having been riding and racing dirt bikes and crotch rockets since I was three. I am very much used to running high octane fuel in my bikes, so I naturally did the same with my recently acquired Shadow Spirit 1100. Today, I decided to try and put mid grade fuel in and it has never run so good....it smoothed out the engine vibration so that it is like a dream on the highway at 80.....Heck, tomorrow, I may try the cheap stuff considering I fill up almost every day. I cant say if it gave me anymore power or not, but it certainly seems to have made my butt better in the saddle!
Cheers,

Eagles may soar, but weasels don't get sucked into jet engines.

99' Shadow Spirit 1100
Arlington, Texas
Iamtheweasel is offline  
post #6 of 112 (permalink) Old 07-25-2009, 10:19 PM
Junior Member
 
Join Date: Jun 2008
Location: Massachusetts
Posts: 2
Quote:
Originally Posted by Reverend Biker
The crux of what I am saying is that with the evidence in hand, ethanol is significantly affecting performance and it would seem that the additives in the B-12 offset the detriment of the ethanol. Does anyone know to what extent ethanol is affecting our engines other than in loss of mileage?
My '03 Spirit started running poorly, I determined the fuel system needed cleaning, so I tried some fuel system cleaner. No luck. I take it to the local Honda dealer for a fuel system clean out and they told me the fuel system will get clogged more easily with the new ethanol gas blend then the previous MTBE blend. The tech didn't explain all the chemical reactions, but just boiled it down to the ethanol turning into a white substance similar to the aluminum oxides formed when aluminum corrodes. He stated that this stuff will clog the carbs and isn't as easy to burn off as "bad gas" clogging was in the past.

He stated that if the bike sits for more then a week or so, if one doesn't ride it that often, it will result in a dirty fuel system. He also said to keep the gas level as fill as possible if leaving the bike sitting for a while, and to put fuel stabilizer in it also.

The dealer's repair order states "Due to ethanol in todays (sic) gasoline fuel system cleaning is only warrantied for 14 days after completion of work! It is your responsability (sic) to keep fuel stabilized or drain the fuel from the unit per the manufactures recommendation."
margaret is offline  
post #7 of 112 (permalink) Old 08-11-2009, 11:49 PM
Member
 
Join Date: Aug 2009
Posts: 44
I tried reading through as much as I could, but I'm not understanding how to know the proper grade to use. I just filled up for the first time and put 87 in by habit. I could figure out a way to drain it if necessary.

What are the basics? Go by manufacturers recommendation for grade and avoid additives/ethanol?

I talked to my uncle today who told me ethanol will prevent rust in the tank... not sure what to make of that.
Netdewt is offline  
post #8 of 112 (permalink) Old 08-12-2009, 12:01 AM
Senior Member
 
litnin's Avatar
 
Join Date: May 2004
Location: Dallas, GA
Posts: 3,761
Quote:
Originally Posted by Netdewt
I tried reading through as much as I could. How do I find the proper grade to use? Is it guess and check? I just filled up for the first time and put 87 in by habit. I could figure out a way to drain it if necessary.

What are the basics of what you're saying? Go by manufacturers recommendation for grade and avoid additives/ethanol?

I talked to my uncle today who told me premium is best for motorcycles and ethanol will prevent rust in the tank... hmmm?
Your owners manual will tell you what minimum octane to use.
As long as the octane of the fuel you use is equal to or above, you're fine.
Yes, you can use premium if you want, but unless you're running one
of the older Shadow's, it's not doing anything except emptying your wallet faster.

Yes, unless you have your bike sitting for long periods of time or have
fuel system clogs, there is no reason to run fuel additives.
Most of the fuel additives are nothing more than a detergent with
an octane booster (which does nothing for you if your engine isn't pinging).
Avoiding ethanol is a personal choice.
Running ethanol is fine, it won't hurt a thing.
You will notice a drop in MPG and a little power loss simply because
ethanol doesn't contain the same amount of energy potential as gasoline.
It's not a super power loss, but in many cases it is noticeable.
In older vehicles, it can cause problems.
Older vehicles actually have "rubber" seals which the alcohol affects.
Vehicles made within the last 20 years have seals made from Nitrile,
which is resistant to harsh chemicals and isn't bother by them.

No offense, but what your uncle told you about premium being best for "motorcycles" in general is bologna.
In *some* motorcycles, premium is needed because they run high advance ignition or run high compression.
The older Shadows (80's) use premium.
Modern Shadows (early 90's and up), premium is a waste of money.
The early 90's and up Shadows are low compression engines
and are generally not prone to pinging.
If you want to run premium, it won't hurt anything.
People will tell you that it burns slower and burns dirtier in engines
that aren't built for it... but they are wrong. It doesn't.
Octane has nothing to do with the burn speed or cleanliness of the gasoline.
Octane is nothing more than a resistance to detonation by heat.

Gasoline is for washing parts, Alcohol is for drinking... NITRO is for racing!
litnin is offline  
post #9 of 112 (permalink) Old 08-12-2009, 12:18 AM
Member
 
Join Date: Aug 2009
Posts: 44
Okay cool. It looks like the 87 should be fine from what I can find on the net (I haven't gotten a manual yet, I've only had the bike for a week). Thanks.
Netdewt is offline  
post #10 of 112 (permalink) Old 03-18-2010, 11:58 AM
Member
 
Lonerider60's Avatar
 
Join Date: Mar 2010
Location: Gaylord, MI
Posts: 232
Garage
This write-up definitely has a lot of good info. The gas grade subject has generally been beaten to death on every forum I've been a member of, just like "what oil to use". Right now I'm riding a 2008 FZ1 that has 11.5:1 compression and a 1981 Goldwing which is about 9:1. I run regular grade fuel from whatever station is there when I need fuel. In my area all gasoline is 10% ethanol. I can ride at 25 degrees or 90 degrees, sometimes very hard and I've never had a problem. It may be that the ethanol is a positive when it comes to preignition, I'm not realy sure, but I also get about 41 MPG on the FZ1 and that's not bad for a 130 Horse 1 litre bike. I do think that combustion chamber shape is also an important factor is how well a bike burns fuel.


Riding is good for the soul. Be spiritual, ride a lot.

Lonerider60 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Honda Shadow Forums : Shadow Motorcycle Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
A question in addition to 'Fuelology' RidehardVT Technical Discussion 1 04-06-2009 01:23 PM
Fuelology, please. chopsawcycles Technical Discussion 7 12-16-2008 08:49 AM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome