Improving gas mileage?

[redliner1973]

<The only time octane makes any difference, is in performance. The higher the octane, the slower it burns. The longer the burn, the more pressure can be made to push the piston, wich results in more power. Jeff

Almost, but not quite: piston speed has all to do with power production. gas burns at the same speed regardless of how fast your going, the faster the piston goes, the less time the gas has to burn, in effect, it starts going out the exhaust the faster the engine goes. Timing advancement will overcome some of this, but not all. you can sometimes see this effect running a lawn mower at night, and watching the muffler actually glow at top engine RPM, and lessen when idling. If your above statement were true, everyone would be burning premium because 'longer burn would = more pressure which would inevitably = more power. More octane only comes into help when compression ratios are higher. Octane then is used only to 'resist' premature burning.

[DMPLATT]

For tyre pressures try 28 front 32 rear solo,30 front 35 rear with pillion

Now I've got a question about tire pressure. My manual says 28, but the tires I have say 40 psi. What should I use? They were both low and I just pumped them up to 38 - 40?

[Anonymous]

I have to laugh when I see people at the pumps throwing Super Unleaded in their average cars. They're paying more for no gain what so ever...unless they re-timed their cars to run on Super...

(p.s. it takes more refining to make Regular Unleaded then it does to make Super Unleaded. Yet they charge you less for the Regular).

I know the grade of gas has little to do with mileage as long as the engine runs well, no knocking or pinging. But I'm curious about brand. I'd been putting Kwik-Fill (local discount chain) regular in the bike until about two weeks ago, and that's where I was getting about 95 miles on a tank. Last week and again early this week I put Sunoco regular in it and got 110 miles on the same tank. That's about 2.5 gallons, so I'm up to about 44 mpg from 38.

Maybe my riding style's changed. I'm using 6th gear for pretty much everything now, where before I'd stay in 5th while in town where the speed limit is 30. I also have been taking the freeway to work more often since my favorite back road (which is still posted 55 but has more stops) is closed for construction.

Dave

[Nerobro]

Actually, he's right. Higher octane fuel burns slower. it's also more resistant to self ignition. it also has a lower energy content. (yes. 93 octane fuel has LESS energy than 87)

Unless you bike somehow has a knock sensor, your fuel economy will be unaffected by the fuel you run.

[redliner1973]

Not faster or slower.....
'The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting. "


"The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio. "

Taken from:

http://auto.howstuffworks.com/question90.htm

[Anonymous]

Yes gas will make a differance in fuel mileage. My 82 gs 1100 according to the factory service manuals requires 94 or above. Of course most places around here only carry 93 but that is within tolerance. However yours being a smaller bike you may only need 87. Always go with the fuel the engineers desingned the bike to use. I get about 32 MPG with my 1100 but that is due to my riding style. I am in stop and go and I ride hard. But the most notable factor in the poor MPG is my riding style. Braking has a lot to do with MPG. If you are a rider that is always on the brake or the gas then you will be eating into your fuel mileage. Coasting to a stop is not only safer but it wears less on you parts, bike and you. Of course apply the brakes to fully stop. That's what we would call a crucial point. But anyway anticipating stops and not accelerating hard to start up will help.
Mechanically check compression, spark plugs clean air filter, clean carbs.

[Anonymous]

Straight from the factory manual:

"Use only Unleaded or low-lead type gasoline of at least 85~95 pump octane ((R+M)/2 method) or 89 octane or higher rated by the Research method. If engine pinging is experienced, substitute another brand as there are differences between brands."

So, that's one heck of a range of octanes! What is one supposed to use?

My GS1000, when timed to spec, pings on 89 octane if its warm out, and I get on it hard in a high gear. I haven't tried 92 octane, I just try and keep the revs up instead if it wants to ping. False economy, really, as any money I save on 89 octane is just wasted on having to keep the engine at higher RPMs.

[Anonymous]

One has to take into consideration that these are old bikes and if they haven't been rebuilt, carbon build up on the piston could cause high octane to be helpful if not necessary. I've mainly used regular in my bike during the few thousand miles I've put on it, and I will say that unfortunately it idles better and pings less when accellerating from lower rpm's when high octane is in it. Recently I tried Shell's premium "V-power" and with no difference in riding style or type my mileage increased at least 4 mpg maybe 5-6 I forget. Maybe there is something wrong with my bike, (the jetting is not perfect yet) and it doesn't need high octane, (manual says 85 or higher low lead or unleaded) but does seem to work better with it.

[joeadams]

"The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio. "

Taken from:
http://auto.howstuffworks.com/question90.htm

I disagree with this. It is correct about the octal number of straight chain heptane being low. It is actually 0. The problem is that the other part of the mixture is not octane. It is 2,2,4-trimethylpentane that has an octal number of 100. The 0 and 100 are both arbitrary values. 2,2,4-trimethylpentane has 8 carbons but it is not octane.

[Anonymous]

[quote]

Thats pretty dismal for a 450. My 1150 gets 38 mpg at a steady 70-75 mph and 41 at 60-65. Do you have the stock toothed countershaft and rear sprocket? Do you have the stock exhaust and airbox? Does the bike have an electronic ignition or is it points? If electronic ignition, is it adjustable?
Have you checked compression. As compression goes down due to wear, gas milage decreases also. The first thing I would check is the compression.
The next thing to check is valve clearances. After that, ignition system and last, carburation.

Earl

I know this is an old topic, but I'll add some data on my 1982 450L for reference. All stock parts, commute at about 45mph average, some city driving, a few miles of 60mph: I average a bit over 50 mpg. I haven't hit reserve yet; I chicken out at about 95 miles and fill up anyway.

[BigMattyD]

I was searching for mpg threads, hoping to find a benchmark for my 1982 450 GA. Being an automatic, I don't have much control over rpm or shift points, obviously.

I have been riding this 23-year old bike for about a month now, and I have run a couple tankfuls of gas with carb cleaner through it, which has improved throttle response and power.

I am getting a solid, steady, 45 mpg, and I hit the reserve at about 100 miles. I thought I would get better mpg than this. I was hoping for 50 to 55 mpg.

I am planning to clean the carbs, check valve clearances, etc. I have pulled the spark plugs and it looks like the mixture is a little lean if anything.

I guess my weight (near 300 lbs) doesn't help anything. Also, I could ride more efficiently (less fun) by decreasing acceleration. I ride about 12 miles each way to work. About 1/2 the trip is steady 55-60 mph, and 1/2 is in-town at 30 mph stop-n-go. There is also a bit of hilliness to the terrain.

Matt
P.S. I started my diet today, that should help a little... Ha Ha

[Eran]

Air filter,

My gs650 "drink" 10 liter for 100Km. the reason for that was a clogged
air filter, after i chage it, the consumption was approx 22Km for 1Liter.

[Anonymous]

Re: Air filter,

My gs650 "drink" 10 liter for 100Km. the reason for that was a clogged
air filter, after i chage it, the consumption was approx 22Km for 1Liter.

Eran,
At Isreali prices, that 10km/L had to hurt your wallet! And we have the gall, in America, to complain about our gas prices.
For readers in America, that's an improvement from 23.5 mpg to 51.75 mpg.
For the rest of the world, may I say, as an American and as a physicist, I am profoundly embarrassed, , that my country still isn't on the metric system.
As another reader commented, I also found that a couple tankfuls with carb cleaner did wonders for my engine, too. Sure beats pulling carbs, and certainly something to try!

[mcycle-nut]

My 82 gs 1100 according to the factory service manuals requires 94 or above.

I've never seen this before. Can anybody else verify this?