Necessary Octane For Your Bike?

[espitbullpup]

I'll check on that I could swear it said suggested 91

 

[cvlighthouse]

I guess I was one off... It's 86...

 

[F4yoshi]

So what counts as "heavily modified"? I've got a jet kit and Yoshi piping and exhaust (all from previous owner) on my F4. I've been running 91 octane, but if 87 will suffice, I'm all for saving $$.

 

[xgambit]

just throw a couple of shots of jack daniels in there. thats a sure 5-10hp increase.

 

[Joebar4000]

So what counts as "heavily modified"? I've got a jet kit and Yoshi piping and exhaust (all from previous owner) on my F4. I've been running 91 octane, but if 87 will suffice, I'm all for saving $$.

Changing the cam timing to increase the actual compression ratio will do it and - maybe, but highly unlikely so will porting work, and/or raising the static compression by skimming the head/fitting different pistons.

Increasing maximum flow usually has negligible effect (assuming the air/fuel ratio has been compensated to suit - you can make any motor pink with a lean mixture) because it only increases dynamic compression fairly high up the rpm scale - and detonation simply doesn't have time to take place - unless something is REALLY out to lunch.

I've seen a highly modified SV650 make 91hp on 91 octane, and then made nearly TEN horsepower less with 110 octane.

Higher octane ALLOWS you to run higher dynamic compression, ergo you can get more power. Calorifically, it doesn't have more energy.

Unless you put something like Nutec in, which is one of the very, very few ways you can literally add horsepower to a stock motor with just fuel. But it only lasts about 2 weeks, costs $15 a gallon and more and smells like death.

 

[michaeln]

Honda XR650L: 8.3:1

Runs on paint thinner or even fermented mule piss if neccessary.

 

[afm199]

BTW the owners manual for the 600rr says to use 87. Yup It does.

Pump fuel is crap. It's dirty and for that reason I dilute it with clean race fuel.

get less dirt that way huh?

 

[elskipador]

http://www.bayarearidersforum.com/f...7477&perpage=15&highlight=octane&pagenumber=1

 

[cvlighthouse]

get less dirt that way huh?

I'd say so.. But as Alanrider mentioned in the other post, make sure you never run leaded race gas in a bike with a catalytic converter on it

 

[mototireguy]

Interesting discussion on this topic over at...

http://www.sportbikes.ws/archive/index.php/t-8525.html

VP Racing Fuels website also has some great info.

http://www.vpracingfuels.com/vp_01_fuels.html

 

[nicebloke]

My old ZX7 used to be hard to start when running hot using 91. I the switched to 87 and never had the problem again when the bike was hot. Don't know if that has anything to do with this, but that was my experience.

 

[auntiebling]

Calorifically

is that actually a word doesn't matter i know what you mean. all gasoline has the same energy content

anyway, another discussion in the garage with interesting info.....

http://www.bayarearidersforum.com/forums/showthread.php?s=&threadid=114132

 

[mototireguy]

I think he meant to say Caloric.

The calorie may also be defined by expressing its value in some other energy units. The 15° calorie is equivalent to 4.185 joules (J), 1.162×10−6 kilowatt-hours, 3.968×10−3 British thermal units, and 3.087 foot-pounds; the 4° calorie equals 4.204 J; and the mean calorie equals 4.190 J. Two other calories sometimes used are the International Steam Table calorie, equal to 4.187 J, and the thermochemical calorie, equal to 4.184 J. When the calorie is used for precision measurement of heat energy, the particular calorie being used must be specified.

 

[Jakemate]

For me, anything under 91, (pump gas), and I ping like hell. I don't remember what the comp. ratio is on the 900, thinking 12:1. However, it's got jets, pipe, ign. adv, mod'd airbox, yadda-yadda-yadda; so I'm purdy well stuck.
I run the left over leaded fuel from my 125 in it, (not the premixed, the stuff that hasn't been mixed yet), and I swear it feels all around better. I don't remember what the book said a stock one should run. I go by the old school theory, fuel it, get on it hard, if it pings, use more octane.

 

[velowood]

How the hell would I know if it pings, with loud pipes and earplugs?

I don't really want an answer. I don't think you can tell if there's pinging going on. Unless it's super-bad, which means you're beating hell out of your motor.

So I just use 91, because even though I'd like to save $ I know how expensive motors are.

 

[Jakemate]

I don't really want an answer. I don't think you can tell if there's pinging going on. Unless it's super-bad, which means you're beating hell out of your motor.

If you FEEL there is no need for an answer, one will not be given.