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Octane??

  • Thread starter Thread starter opiewontaylor
  • Start date Start date
My machine doesn't like low-octane fuel. It pings on 87, I can get by with the 89 octane 'plus' gas. I HAVE checked the timing, it was actually a little retarded so I left it that way. Maybe I have carbon buildup, dunno .. it has 21k miles, shouldnt be too bad. :shrug: ..
 
Euro and US octanes are different in tersm of how they are presented, so don't try and compare them. In a civilised country like Australia we also use RON. There are a few websites that explain the differences.

Here, standard ULP is 91 RON. Premium is 95 RON. Higher density fuels are 98RON. In Japan I believe that over 100RON is common, as a few of their second hand performance cars make it over here that need the high octane stuff.
 
Gas

Gas

I use the highest octane that Union 76 has, I also use it in my 5.0 mustang, and in my car is where I do my experimenting, because with a helmet on and loud pipes it covers up any minor pinging or detoation that my be occuring, so I have used my car as a test bed, I have noted that the BP, Chevron and Shell gas stations all take delivery for the same supplyer, but that union 76 has its own trucks for delivery, Union 76 also Claims, (but who knows for sure that its true) that they don't have MTBE's in there gas, I know this for sure, my comp. ratio is 9 to 1, with 76 gas I can run a Total of 32 degrees of total advance, but with the others 27 is about max, my bike at 3.5 gals means I have to pay about 65 cents, more a fill up so there is no big deal there, I do on occasion use the others if Iam stuck, but I have at least proven to my self witch I prefer, I also use it in my full race 650 BSA with cam, pipes , big carbs and a whooping 12.5 to 1 comp. ratio that is what it likes, I dont scrimp on money for my bikes I do that on the wifes car!!!!
 
This is an old thread, but FWIW, I switched to 87 octane last week on my un-modified '83 GS850G. Well, OK, it's a frankenbike, but everything engine-performance-wise is generally stock, including carburation and timing, except for Dyna coils.

Four tanks so far, and no pinging or problems at all. Even deliberately lugging it in 90 degree weather caused no strange noises or running problems. Plus I'm about $2.00 richer, so I can get that extra cheese on my burrito.

Looks like Nick was right again!

With a modified bike, I would definitely run premium. But stock, they are designed to run fine on regular unleaded.
 
1981 cylinder head, 1983 block, and 1980 bottom end. It's a long story...

Well, bwringer, it's time to tell that story. Start a thread in the GS Stories section.

Nick
 
Well, Nick, I guess maybe someone could learn from my sad story. In fact, you played the role of the last-minute calvary. Remember selling me that GS850 cylinder head a few years back? It's still going strong more than 15,000 miles later!

I'll sit down and post the story soon. It's got suspense, crime, intrigue, a few cliffhangers, and a shocking twist near the end just when you think everything is all OK. No sex, though.
 
OK here is an update on octane usage. Mind you I am used to my modified GS so putting gas in this stock little Kaw 550 I was thinking old school and was just putting the same stuff in it.

Well here is the break down of an experiment I started last week and have done enough now to post on.

I have been running the 94 in my 550 like I am used to running in my 1000 and it runs fine on it as expected. So I thought about the stock factor having not run a stock bike in almost 20 years and I put a tank full of 87 in it to see what it would run like. I run the tank down well into the reserve first to make sure it was a good octane switch then filled it up with Sunoco 87.

I ran that tank through it and by the end of the tank I noticed a real loud knock and oil spraying out all over the place. Now it will start but if you rev it above 4k oil sprays out and it sounds like a jackhammer.
I have been forced to junk it as a result.























No no no no no I am full of crap but had to snap a girdle or two before I gave you the real scoop :twisted: After I run that tank out I noticed two things right off the first tank full.

1. It seemed to pull better in the midrange than before, I always had to tack it up really high to get it moving. I swear it pulls better from 4.5 to 7k now than it did on higher octane gas.

2. This is back-wards to what a lot of you have said but I never had an issue with this one either way so it didn't matter but my top end was always a little rattly noising in this bike once it gets good and hot. Right around 4 to 6k it will rattle until you get the revs up. Sounds like a chain more than valves though? But with 87 in it it does this a lot less and I mean a lot! It almost stopped it. SO now I can save 12 cents per tank full! WooHoo :) No it isn't about money obviously as it is only 12 cents a tank difference for me but it's about using the right fuel for the engine.

So to sum this up I have run two more tank fulls through it of Sunoco 87 since the first (I am on the third tank right now) and I can say for sure it is actually running better than it did on higher octane. This in my past experience is the opposite of what happens in my 1000 on it's previous build. It runs better on higher grades for sure without a doubt. We'll see when I get it done this time. I am going to test it.

So I am slowly being converted over to a low octane man after a life time of doing the high grade because I now have a stock bike that definitely runs better on it and a new car that does not need high octane.

My wifes car is a rattle trap on low grade and requires the good stuff to mask the impending doom syndrome but my other engines are now running low grade gas.

I will be doing more and more testing on this as time goes. If you know my history on gas grades then you will appreciate this entry even more.
 
Wow Mark, how long till Nick replies to that.

Anyway, as has been stated, bikes were designed for specific octanes and that is what you are finding out.

that 12 cents can add up though..

say I fill the cycle tank every 2 days of riding (just to and from work) that is .60 every two weeks.. Or a can (or two if you get the generic stuff) of soda you can treat yourself to every other week..

:D :D :D :D :D

Amos

(or every 4 weeks, I could get myself some Snapple Elements Moon tea...)
 
Right on Amos. One thing (if you know my take on this subject) that you will notice I didn't comment on as I am not done testing it yet is fuel economy.

I "think" it may be better or the same. It is my experience regardless what anyone says that when your running a grade of fuel that your engine runs noticeably better on that you get better fuel economy. It is running better on this stuff for sure so I am expecting it to get better economy or at a minimum stay the same. So far, it looks like it may be better but I don't use two tank fulls as a positive test. I am going to post on that later when I know for sure.
 
opiewontaylor said:
basaraj said:
1. Octane does not increase HP.
2. Use what is specified for your machine.
3. If your bike pings on 87 octane, you can usually retard the timing slightly (with subsequent loss in performance) and eliminate pre-detonation.
4. Use of high octane fuels may cause poor idling when cold and unexplained stalling.
5. Using premium in a low to mid compression engine is a waste of money!
Click to expand...
Interesting. But what is considered high compression? 9 to 1? 10 to 1? More?
Click to expand...

In auto circles, 10.1 is the general 'mark'...

My Z28 is 10.5.1 stock -> GM says 91 or higher octane only...

Of course, in a modern car, pinging/detonation is less of a threat because the ECM automatically retards the timing when this is detected... So running cheaper gas -> worse perfromance and fuel economy (due to timing retard), more than engine damage...

The thing is, old bikes do not have ECM units... So if you use too low an octane & get detonation, you can screw your motor royally as noted above...

GS450 -> recommends 89, I use 93 because it's not that much of a difference here (big diff is betwen regular and the others)...
 
I have got to say, Nick is right on this one, for the modified bikes, yes, higher octane may be what it needs, but if your stock motor is just that-stock, 87 is all you need. If you have pinging issues on 87, there is another problem such as carbon build up, mal-adjusted valves or something like that. Higher octane gas is more resistant to start burning, and in alot of cases, with a stock 'GS compression, will not effectively start burning untill the piston is at or past TDC. this solves the 'ping', and may give the false impression that it 'runs better'. This is due to the fact that when an engine pings, it tries to force the piston back down the opposite way of rotation. this lowers power, of course. when you stop the pinging, you restore that power. I believe this is why one poster on here said his bike actually ran better on 87 that 92. Ideally, an engine should use the lowest octane that it can without detonation. Higher compression engines, of course, offset the slower buring properties of high octane by it's higher compression. This brings the fuel properties to the point that it propagates combustion 'sooner'. and even higher compression will limit the 92's fuel properties and the cycle repeats.
Use of an octane rationg higher than needed can actually increase the deposit of carbon due to it's 'slower' burn properties. This in turn loweres actual combustion temps, causing the carbon build up. over time, this will cause the engine to require a higher octane fuel due to the carbon build-up induced higher compression. Alot of people who run high octane gas for long periods of time in an engine will sometimes find thier machine suddenly pings or detonates when they fill up with 87. :twisted:
 
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