Octane on bigger engines?

[davidon]

Is it required to run 92 or 93 octane in 1500 engines or can you get away with midgrade (89)?

 

[satariel666]

Required octane number depends from compression ratio.

 

[one2dmax]

87 is fine on most street engines. Some higher comp ratios (over 11-12) need more.

Sean

 

[RagingMain]

I am running 87 on my high comp piston 1300 just fine.

 

[EvilD]

octane is more mis understood than exhaust back pressure. timing and cylinder pressure are what determine you octane needs

 

[davidon]

Sean I believe mine are above 11..I guess I should try 89 and see how it reacts?

 

[mattness]

i ride with my gf and I on the bike so i run premium just to be safe. i aint bickering over 50 cents.

 

[one2dmax]

Nope, the higher the octane when not needed means an incomplete fuel burn which will lead to carbon build up and loss in power. Run only the octane you need. 99% of most of these bikes will not need more then 87.

Sean

 

[davidon]

Actually I would recommend you use 87 on non-mod engines..higher will leave more carbon deposits..as a found out on my original engine

 

[Rick52]

Since the question was on the 1500 motors I can can say I use 89 or 90 with no problem. My bike is 11:1 and 160 HP plus on any given day. I think PCW sign off okay on either the 87 or 89, But,,,, If I had a 12:1 I would definitely ask the engine builder.

rick

 

[davidon]

What will be the consequences if I try to use 87 and it's not the proper octane? Rough running? Rick.. PCW did my 1570 and he mentioned that he test rode the bike on premium so I was just wondering if I could drop down to 89 or 87.

 

[one2dmax]

An engine that large and probably with larger cams I would stick with the 89 minimum and maybe even the premium. You can take a look at your plugs to get an idea if you are getting complete fuel burn as well as if you are getting any detonation. There are plug pics online I am sure to show the various things to look for.

Sean

 

[davidon]

Sean..good point..I'll check the plugs and then try the 89.

 

[EvilD]

remember the good ole days when you could hear pining/knocking in your engine and know you had a problem. now with all the computer retards and sensors and stuff, you have no idea.

 

[davidon]

Sean plugs look good... the right side ones look slightly moist compared with the left side which look dry. Don't know if adjustment is necessary, runs fine, maybe just a touch rich on the right?

 

[one2dmax]

Might be able to simply adjust the a/f screw on that carb. Otherwise I wouldn't change it.

Sean