| Author |
Message |
    
Eicas
| | Posted on Wednesday, October 01, 2008 - 09:46 pm: | 
|
XB9ser is correct. Octane is there to protect the engine from "detonation", it does not give any more power by itself.
Detonation is what kills engines, no detonation, no kill.
If your engine does not detonate, no damage will occur.
Be careful though, air cooled engines are more critical than liquid cooled engines since liquid is a more predictable cooling agent than air.
Retarded ignition, cooler days, rainy day, richer mixture, driving habits can all help to reduce detonation.
Many cars will run safely on lower than recommended octane since they have "knock sensors" that will automatically retard the ignition and protect it, although you will lose some performance.
Manufacturers pick octane rating based on engine operating conditions, if you do not meet those conditions, you may safely be able to run your engine with a lower octane rating and not burn a hole in your pistons. |
Mattl
| | Posted on Thursday, October 02, 2008 - 01:45 pm: |
|
Sloppy, fair enough. I guess someone did mention doing it to save money. And fine, I could take public transportation, but come on. That would be so un-American. I mean, come on. Isn't it our duty to country to use as much resources as possible in order to maintain our consumption based economy?
WOA! There I go hijacking my own thread into a political rant! Sorry!
For now, riding easy with 87 octane will work fine for me. |
Jlnance
| | Posted on Thursday, October 02, 2008 - 02:05 pm: |
|
I had to use 87 last night. It worked fine. It's been fairly cool here though. I'm sure it would ping if it was 100 outside, but it was down in the 60s last night. |
Mikef5000
| | Posted on Thursday, October 02, 2008 - 06:41 pm: |
|
87 will not hurt your eng unless you are running 10.5:1+ comp NOT AT ALL..
There are more factors than just compression ratio that are effected by octanes. Playing with your timing like others have mentioned here is one way to see this. Saying something like NOT AT ALL is not an accurate statement. |
Ripdog28
| | Posted on Friday, October 03, 2008 - 10:45 am: |
|
True, but for this eng it will not hurt it. Timing will make a little diffrence for these bikes it is not going to. Now most of my eng exp is on SBC and BBC.you can change to a thicker head gasket if you want to run 87 also. If you are worried about throwing a valve(knocking noise mentioned)then you have more problems then running 87. I do still think that 87 will not hurt this eng. I usually say stuff like generally it will not...... most of the time it will not.... but here the reason Buell says run 91 is because there specs are all on 91+ so if you run 87 then it will not be to there specs. |
Sloppy
| | Posted on Friday, October 03, 2008 - 03:40 pm: |
|
Not sure about the knocking and valve comment, but the knocking noise of "detonation" is the sonic explosion of two combustion wave fronts colliding with each other due to the self ignition of the fuel. Pre-ignition and detonation are two different things, but the results can be similar. Normal combustion is a controlled burn / expansion process. Detonation is an uncontrolled explosion.
The wave front (I think it's sonic!) elminates an insulating boundary layer of gas that protect the piston from the heat of combustion. Once this insulating layer has been removed, the Aluminum piston is fully subjected to the temperature of combustion which exceeds the melting temperature of Aluminum. Hence, you melt pieces of Aluminum and if bad enough, you will put a hole in your pistion. If the knocking is brief and of low intensity, you will likley only weaken the piston.
So to say that knocking won't hurt the engine is incorrect. It does -- do a search via SAE, Hot Rod Mag or other reputable sources (not just a personal opinion page!). But how badly it hurts it is dependent upon how you ride it. For extremely light knocking for commuting, it likley won't significantly reduce the lifecycle of the vehicle. If you ride WOT you can hole a piston within a quarter mile. Visit your local drag racer and have him show you his Wall of Shame. 
Since you save so little money on low octane fuels and it limits the flexibility of driving the bike I would stick to high octane fuels. But YMMV.
If you do use low octane fuels, you can prevent from having detonation by driving it at partial load. Note -- you can have detonation WITHOUT hearing it. Ask any two-stroker to show you their wall of shame...
(Message edited by sloppy on October 03, 2008) |
|
