Octane question...

[450 Racer R]

How come with higher compression you need to run higher octane? like if I'm running a 13.1:1 piston, why can't I run pump gas? What's the difference in running 93 octane vs 106?

I run 86 now and it runs great. 93 is reccomended but there's nothing wrong with the regular.

[BSTURDIVANT]

With higher compression, the flame front that comes from ignition can travel uncontrollably across the piston causing a distinct "knock" and engine damage! Higher octane fuel tends to give a more controllable flame front across piston.

Octane rating is done by testing fuel in a special "engine" with a
adjustable compression device and compared to the test fuel (octane). The point of knock( in percent) such as 93 is the motor octane #. This number is added to the reaserch (calculated) # and devided by 2 giving the final pump octane rating.

Cam duration and timing also play a part in determining actual minimum octane you can run! The cam bleeds compression off on high duration cams enabling a lower octane fuel. YFZ's, 450R's and others with TPS adjust timing curves so you can run 91 octane with 10.5 - 12.0 to 1 compression.

[Jersey450R]

i dont know about all the gas crap. 450 racer r puts 86 in his 450 and that thing rips! so whatever, i dont know. i use sunoco94 and it works fine but the other day i was about to run out and put some of jeremiah's reg 86 octane in mine and it ran the rest of the day the same as with 94...

[450 Racer R]

I would think that if you just break in the piston with race gas then it should be fine to run the 93 or premium pump gas. Anyone have any thoughts on this? Once the rings are properly seated, then the lower octane shouldn't be a problem...

[BSTURDIVANT]

It will still run but the life of the piston, rod and bearings will be shortened!

[Jersey450R]

just put gas in and go, lol.

yo 450racerR, when you gonna be up and ready to go? sunday was awesome at the viz!

[450 Racer R]

not til like middle december maybe. I'm down to 3 weeks on friday. And doctor it'd be longer until i could ride cause I'd have to build the muscle back up. As soon as I can move my arm though you can bet I'll be working on it.

[ThumPIN_450R]

you should run enough octane to keep it from knocking and no more high octane does not equal higher horse power

[RedRacer44]

If i'm correct, running that low of octane is going to cause a lot of carbon deposits to build up....thats one reason why they say to run the 91 or 93 octane. Your motor will probably start having a "ping" or "knock" before too long if you keep running that cheap gas. It might run about the same but its not too healthy for the engine. These 450R motors arent like the ol' 400EX, need to run some good gas in it. Not saying you have to run race gas but at least throw some 91 or 93 octane in it.

Higher octane burns cleaner too, means less carbon build up. If you dont run race gas in the motor w/ high comp pistons....you are going to have issues. Need to run at least a 50/50 mix with 93 octane fuel.

[RedRacer44]

Heh, you're going to love that broken collarbone. I broke mine in August of 2003 and i missed the end of the MX season. I was sooo mad. I also missed the fall dune season. Have to wear that gay-*** brace that felt like a bra...at least thats what I had to wear. It really sucks....

I was down for quite a while, but i took my time in healing. I went to a sports doctor and he gave me a lot of exercises to do to build up the muscle again. The 1st few rides I took on the quad were somewhat painful....vibration was the main issue. I would be sore for a while after riding.

I got back to full speed pretty quickly though after the doc released me to ride. I've landed hard on my left shoulder a few times over this summer and it didnt hurt one bit. I got a huge calcium deposit too all around where it broke so its got some "gusset work" haha!

[450 Racer R]

Nah they just put me in a sling. It's broke way out by my shoulder. He said it was a "good place" for a break. whatever that means. I kinda wish they put me in that figure 8 though. Took an xray last week and the bone isn't lined up at all. said it would heal back curved. that should cool

Anyway about this... How about running a hotter spark plug? that would ensure a complete combustion. I'm just being stubborn, I'd never run pump gas with a 13:1 piston. Maybe on a low 12:1 though.

[RedRacer44]

Yeah, when I broke mine.....I sat in the emergency room for a while before they put me in the figure 8 brace. I did it riding my quad too so I was covered in dirt and I know I had to stink to high heaven! Nurse came in and went "dear god young man did they just dig you out of the ground??"

Heh, they gave me some Demoral or whatever....everything was kinda weird after that:p Finally they came in and put the brace on me.....that was the greatest feeling in the world. When they pulled the straps back and pulled my shoulders back.....the bone popped and lined up SORT OF. It felt great.....i wanted to just die right there, heh!

Mine broke right in the middle, heh really sucked. It lined up somewhat...the 2 pieces just over-lapped each other and grew back together that way. Like I said, there's a huge calcium deposit all around it now. You can see it bulging through a t-shirt, heh. Its great. I tell everyone its where my collarbone is "gusseted" :D

[450 Racer R]

yeah I'm gonna have that huge deposit too. I did mine riding too. I was covered in sand. I just can't wait to be able to move my again.