Octane Booster for 440ex?

[06_hondatrx_400]

Does anyone know what a good octane booster is to run in my 440ex, Because i really dont have any idea what to run in my quad. Anyone have any sugestions thats would help out alot thanks.

[Scro]

You need to find out what the compression ratio of your piston is. If it's 12.5:1 or lower, there is no reason to run anything higher than 93 pump gas.

[06_hondatrx_400]

Well my piston is 11 to 1, and we dont have any pump gas that is 93 we only have 91.

[guenther]

Don't use octane booster. There is no 93 on tap in my area so I'm in the same boat as you. For my 11:1 416EX I use a 1/2 gallon of 110 race fuel to 4.5 gallons of 91. That will give you 92.9 which is right on the money.

[Trxracr]

the only 93 in my area has ethanol in it so i just run 91 in my yfz which has the stock 11.2:1 piston and it runs fine

[rooster300ex]

i have 11:1 and i run 87-91. Runs like **** on 110 or even mixed 50/50

[guenther]

Originally posted by rooster300ex
i have 11:1 and i run 87-91. Runs like **** on 110 or even mixed 50/50

I usually run 1 gal of 110 to 4 gals of 91 which would calculate to 94.8 octane. I can tell a huge difference between 94.8 and 91. The throttle response and the way it pulls is so much better with the higher octane. Maybe around 95 is threshold for gains from higher octane!?!?

[rooster300ex]

For some reason if i mix any high octane leaded fuel in mine its doesn't have the same throttle response. Could be jetting.

[06_hondatrx_400]

Thanks for the responses guys! Well I have been just running 91 in mine and it runs alot worse then with 91 mixed with octane booster. Im buying some 114 race fuel from a friend and im going to mix that with 91 and see how she runs.

[guenther]

Mix that 4:1 and I know you and your quad will be happy campers.

[Scro]

With only 11:1 compression, anything over 91 is a waste in my opinion. I used to run 93 on a 12.5:1 piston with no problems at all. It was harder to crank with any kind of race gas.

[fearlessfred]

u r right on the money with that comment anymore than needed to prevent detonation and u r hurting performance

[guenther]

Hey Dustin, what do you mean by harder to crank? The starter drags or it's harder to fire off? I'm haven't noticed any difference in either of those with approx 95 octane. I can tell performance improvements with the 95 over 91, especially on the low end.

[Scro]

Originally posted by guenther
Hey Dustin, what do you mean by harder to crank? The starter drags or it's harder to fire off? I'm haven't noticed any difference in either of those with approx 95 octane. I can tell performance improvements with the 95 over 91, especially on the low end.

Well, not necessarily harder to crank, but rather it didn't crank as fast. Racing XC, if you want the holeshot you have to know you're quad and when it's going to fire. With racing fuel, it seemed like it was hit or miss if it would fire on the first revolution. I never had that problem with 93.

[guenther]

I'm racing this year in XC so maybe I'll try taking it down to a 93 mix and see what's the difference (93 mix vs 95 mix). I can only get 91 on tap and the quad runs better on the 95. If I don't see any difference between the 93 and 95 I'll run the 93 and save a couple bucks.

[Scro]

It's all about testing. Whatever works best for you.