Octane Q

[Red Rooster]

What is the minimum octane to run with 12.5-1 compression 12-1, 11.5-1, 11-1, 10.5-1 Thanks 4 the help in advance

[RideRed04]

at 11.1 you want to mix 104 race gas and 93 pump gas. Anything over, use race gas. Anything less, run 93.

[thorspapa]

Actually, it's more helpful to know the compression (psi) the motor has (like 150psi, 200psi, etc) when measured at the spark plug hole with a gauge. You can have a 12:1 compression piston, and still only have 170 psi, some banshees run 7:1 compression yet show 180psi on the gauge. The most common rule is : below 180psi, 92 octane pump gas, over 180 psi, start using 95, and by the time it climbs to 200 psi, 100 octane is recommended. You'll get the most power by running only the octane you need, just enough to keep detonation away. Going with much higher octane will actually decrease your acceleration, as higher octane takes more pressure to fully ignite, burns slower and cooler. That's one of the reasons for higher octane, cooler burning helps keep temps from getting too high, creating hot spots in the head, leading to detonation. Your motor runs more efficient and makes more power when operating at optimum temp, too cool and it'll make less power, ditto for too hot.

[FatBoy Redrider]

I have a 11.5:1 and mix octane booster with 93. THe problem is I never know what the octane level is. Is there a special mix that someone sells that gives a specific octane rating?

[Red Rooster]

very helpful. thanks for the help.

[thorspapa]

Hey FatBoy Redrider, I can't tell you much about how to find the actual octane you have, I think a chemist in this crowd may have a way, but it may not be simple. As for your piston, and using octane booster: do you know if you really need it? what's your tested compression?.
Too, if you really need higher octane than pump, I'd rely on a name-brand company's many types and many different levels of race gas, like Torco, Klotz, Cam2, VP, etc. If you REALLY need the high octane, any of these companies will be much more reliable and consistent in their fuels. Octane booster products aren't known for their reliability. Do you want to risk detonation over a few bucks?.
Also, in some private tests with our own bikes, I've found that different fuels with same octane rating, will make a motor respond different; not saying one is better than other, but if you have the time and availability, you can experiment to get the fuel brand/type that makes the most power in YOUR motor.
VP Fuels website has tables for each fuel, along with suggested use, and not by octane rating, as different types with the same octane are better at different aplications. Pro level/factory sponsored Drag racing, Supercross, Motocross, Karts, spend time testing their motors with different fuels each year. It does make a difference.

[01_300ex]

would i have to get a higher octane for my 11:1 piston, on a 300ex.
Also, what octane.

[EX 80]

I got a 10.8:1 compression JE 416 piston. I have been using 93 octane. I was thinking about trying higher octane, would it hurt my quad if i went to high? Should i be using higher octane, if so what number 100,105 114??? and what brand? Thanks

[macblaster]

Originally posted by FatBoy Redrider
I have a 11.5:1 and mix octane booster with 93. THe problem is I never know what the octane level is. Is there a special mix that someone sells that gives a specific octane rating? go to http://www.klotzlube.com/index.htmlklotz oil gas and octane boost

[thorspapa]

Hey guys, I think you didn't read ALL my post (hell I don't blame you, I talk too much).
EX 80, you can't hurt your engine by using too high an octane, but you will have less power if you use more than you need, and you'll spend more money buying it. Use only what you need.
01_300EX, I can't tell you what octane you'll need for your 11:1 piston, because that doesn't tell us what your compression is. You need to run a compression check with a gauge on your motor, then go from there.
As I said in previous post, a good rule is that 180 psi and less will run fine on 92 octane, 180-200 you'll need 95-100 octane, over 200 psi, your riding starts to get expensive, and you'll need the 105 and up race gas. By the way, literally all motor and parts builders for bikes agree on this: av gas is not a good idea.:blah

[crday98]

you are wrong thorspapa,if i run 115 octane in my stock 400 it will give me alot more power and it will burn alot faster and cooler.also,av gas will give my quad more power too,"i definitely noticed the power gain when i started running av gas".

:D i just had to be silly:D it is nice to finally see someone that has knowledge of octane ratings and such.i am no professor at it but i have some knowledge.i get into the octane/av gas arguement with many people i know and they still swear by it.:rolleyes: "if a stock bike is rated for 93 octane and you are running 115 octane,how could the race gas burn faster than 93 if it requires a higher compression to burn????????hell,let them waste their money.:blah

I've read numerous times from respected engine builders and articles out of mags that race fuel in a stock bike does absolutely nothing for the bike,,,I've never used it or had experience with it but I guess you could go faster with a lighter wallet...:huh

I've not put my 416 10:8.1 JE piston in my bike yet but I plan on running 93 octane,,,if I wanted race gas I would have went with a 13.1 or something crazy like that..use race gas when necessary I think ,,not "just cuz it'll make me fast."

["BLAHH"300!!]

WHAT OCTANE SHOULD I RUN IN A 96' 300EX
WITH STOCK MOTOR- OTHER MODS LISTED BELOW??

whatever your manual suggests you run,,,which is probably 92 octane or close to it,,,,,once you go with a different piston,,,mainly a high compression piston that's when the octane you use should change,,that should be the only time really. Pipes, filters changes,,rejetting,,mild motor add on's normally dont' require a gas change..

[EX 80]

How much does a compression gauge cost? What is a good brand to buy? Where is a good place to buy one? Are they easy to use correctly?







I bought a compression tester at sears for 24.99.

[thorspapa]

I like RICO's advice: if you spend money on race gas, you'll go faster due to the power to weight ratio being improved by the lighter wallet, (sigh)...how true.
crday98, thanks, I'm glad someone else understands this stuff.
EX 80, compression gauges cost anywhere from $20-$100, depends on what you need. You can get them at any auto parts store, OR if I was you (and I am, you know) I'd look at the Motion Pro offerings, made for bikes. You'll need the correct coupling for your spark plug thread size, so it pays to get one that's universal, or has several METRIC couplings with it.
Once you have one, you'll use it many times, because it's the best way to tell when you have piston ring wear or valve wear, without taking the motor apart or waiting 'till it's trashed and won't start.
Take a reading when the motor is fresh, then when it drops 10psi or more, you'll know it's time to rebuild, before it's too late.
Oh yeah, and the Sears one you bought is probably fine, as long as it will hold the reading steady enough for you to read.

[R-Crazy]

the highest my local pump goes to is 91. i use it in my stock 300 othen than the basics listed below. will I be okay?

dave