Octane ?

[Passx]

Hi All,



With the escalating gas prices I was thinking of going to a lower octane in my 81. I have always run either premium or mid-grade with no side effects. On my 80 it says to use 91 octane or better meaning it needs premium but I don't have the manual for my 81 (school bike,, anybody have a manual ?) so I'm not sure of what Honda spec's for it. Now the confusing part,, On my 76 GL1000's they say they have a cranking compression of 171psi which is the same as both X's but it is spec'd as requiring only 86 octane. So you can see why I ask,, I do realize that cam timing and rpm has an effect on this and I have yet to see an X or GL meet the 171psi cranking spec most are in the 135-145 psi range a substantial difference. So anyway can I get someone to tell me what the manual says is needed for my 81 before I do something stupid and hole a piston. Thx in advance , Steve P.

[cbxdragbike]

Steve



First it is very difficult to do serious damage by running lower octane with normal street use. You should hear pinging (knock) long before you have any damage at all.



Detonation (pinging) is caused by a combination of high compression and spark advance. The stock spark advance on a CBX (any year) is not very aggressive. I normally run mid-octane in my street cbx but some times mess up and put in regular by mistake. It has never done any knocking that I have noticed. Run your tank as empty as you dare, fill it half full of regular then try to accelerate hard up a hill. If you hear any knock. go fill the tank up with premium. If you don't, go back and fill it up with regular.



Mark

[KEYSMAN]

Down here in west central Florida I have found that I can only use premium in the summer in my '81 that has a stage 3 kit, ported heads, and performance exhaust. It pings on any other octane but will run on mid-grade in the winter. Considering what it costs to fill up my van, I can't gripe about the 4-5 gals of gas for the bike.

[joeduc996]

To answer at least part of the question, the recommended octane from my '82 owners manual states "...octane number (R+M/2) of 86 or higher, or a research octane number of 91 or higher may be used. If knocking or pinging occurs, try a different brand...or higher octane grade."

I use 87 here in the midwest with no issues.

Joe in WI

[CBXRoger]

We experienced better run times at the drag strip with lower octane gasoline here in Hawaii.

Roger

[EMS]

We experienced better run times at the drag strip with lower octane gasoline here in Hawaii.

Roger

That doesn't surprise me too much. Unless the motor NEEDS high octane gas because of a high compression ratio (the CBX with 9.3:1, does not) running higher octane gas will give you less energy to turn into performance. High octane gas carries more ignition retarders which means it burns less efficient in a lower compression motor and will make less power.

[Don]

Not knowing any better, I always ran premium in my first '79 . . . . thinking that a 'high performance' motor (especially one designed in the '70's) surely must need the 'good stuff'

Dave McMunn straightened me out when he delivered tthe Katrina bike to me - Stick with regular 87 ocatane he told me and you'll never have any problems. I pointed out that it gets pretty darned hot down here on the Gulf Coast in the summertime but he told me not to worry

He's right (of course) - A stock or slightly modified CBX runs just fine on 87 octane . . . . actually better as some of the guys are saying

Buy the cheap stuff - Do your bike and your pocketbook a favor all at the same time ;)

Don

[alimey4u2]

Run high enough octane ( technically the term octane on regular pump gas is a misnomer, it should be RON) to prevent pre ignition. Any higher "octane" will reduce the calorific value (less bang) of the fuel as Mike said...

[joeduc996]

Run high enough octane ( technically the term octane on regular pump gas is a misnomer, it should be RON) to prevent pre ignition. Any higher "octane" will reduce the calorific value (less bang) of the fuel as Mike said...

Soooo. I take it RON is Euro and R+M/2 is U.S.?

[alimey4u2]

Run high enough octane ( technically the term octane on regular pump gas is a misnomer, it should be RON) to prevent pre ignition. Any higher "octane" will reduce the calorific value (less bang) of the fuel as Mike said...

Soooo. I take it RON is Euro and R+M/2 is U.S.?

All here Joe....

http://en.wikipedia.org/wiki/Octane_rating

[daves79x]

Not to hijack the thread, but it is fantastic to see so many newcomers posting here on the site. Welcome all, and I think I may have met a lot of you at Mid-Ohio this summer.

Dave

[George R. Garrison #0857]

If you crash in Knox is it the location of "HARD KNOX"?

Where the heck is Knox Pa?

I've always tried to use the good stuff, premium in most of my big bikes,, are you saying it is not justified?

By the way,, the Marine Stabil Blue has better ratings that the red stabil regular.. Seems it covers a broader range of problems.

The new fuel is like Frog Pxss and it seems a crime that we have to buy the crap that ruins things.

And just what was the occasion for Obama to win the Nobel Prize. I don't see any evidence that the award is a honest item,,it is obviously and item that can be purchased by the hightest bidder.

Woops, here I go again... Sorry guys,,, the devil made me do it.

[EMS]

I've always tried to use the good stuff, premium in most of my big bikes,, are you saying it is not justified?

.

I think that this is a common wrong perception, that premium is "good" or better than other fuel. All it is, is gasoline enhanced with additives to prevent self-ignition at higher pressures. Many people think that premium makes more horsepower than regular gas, which is nonsense, of course.
The potential energy in fuel is defined by the amount of combustible CmHnmolecules, which means the more dense a fuel, the more performance, more non-combustible additives taking space of CmHn strings equals less potential energy.

[EMS]

If you crash in Knox is it the location of "HARD KNOX"?

Where the heck is Knox Pa?

.

If you draw a line from Los Angeles to New York and a line from the North Pole to the South Pole, excatly where these lines intersect, is Knox, PA which means, Knox, PA is the center of the United States.

[harvey]

I am not so sure those lines will cross depending on how they are drawn but I am sure the Dave feels that Knox, PA is the center of his universe. All I know is that there are some great roads to ride in that area.

Regarding octane, I have run 87, regular, in my 81 CBX since I got it back in the 1990's. I have never experienced pinging. But it is also worth noting that I don't push it to the extremes either.