[scooter99]

I put 100 octane unleaded gas in my 450r cause I like the smell. When I would run hard into a corner and let off, it would seam to misfire on decel. I normally run Mobil 93 in it and it never does this. I have read on the forums that there is nothing wrong with running race gas. And the manual states run 93 or higher. What would cause this just out of couriosity. I am not going to run race fuel untill I bump up the compression. I was thinking that it could be the stock plug causing it.

 

[M3zy6]

I believe the manual says 91. I wouldnt run any more than 93 in it, waste of money, and loss of HP.
But as far as the misfiring, it might have something to do with the oxygenation of the fuel.

 

[450RRRR]

once you go to a higher comp .piston, you might want to check out V.P. -CMP it is good up to 13.1,it has a rateing of 104.5, with oxygenates. i ran it in a yoshed out drz 440. and it was perfect.it a little expensive in the 5 gal. but if you have the room you can get deals on drums. sorry i have no help with your current problem.but to tell you you are wasteing money putting it in a stock 450r.

 

[lukester720]

when you start running fuel like that you have to rejet, thats why its doing that on deceleration. you don't really stand to gain much by using high octane fuel without upping the compression. I hope this helps!

BTW welcome to the site!

 

[scooter99]

Thanks for all the feedback... I switched back to the mobil 93. No problems I am purchasing the hrc kit in the next couple of weeks is there anything that I should get with it to really bring out the full potential of the cam??? like a header pipe??? I am assuming that I shouldn't run any more than 93 without a higher comp rat.

 

[lukester720]

Originally posted by Scooter99@Jun 16 2004, 02:50 AM
I am assuming that I shouldn't run any more than 93 without a higher comp rat.

Yes, this is true, you are basically just throwing money away without a higher compression piston.

 

[buck naked]

Originally posted by M3zy6@Jun 15 2004, 08:08 PM
I believe the manual says 91. I wouldnt run any more than 93 in it, waste of money, and loss of HP.
But as far as the misfiring, it might have something to do with the oxygenation of the fuel.

[snapback]7320[/snapback]​

i heard this many times,but no one has given the reason why you would lose hp with race fuel on say 10.5 or 11.5 compression. :dunno:

 

[450RRR]

The reason you would lose HP if running too much octane on a low compression engine is because you will pushing un-burnt fuel out the exhaust before it has time to completely burn in the combustion chamber.....

everything from cam timing, to ignition timing and curve, to pipe flow and backpressure ALL have to do with this...

cramming as MUCH air/fuel into the combustion chamber as possible.....then, igniting that A/F mix at the precise moment in order for it to begin its burn rate and push the piston downward in the cylinder ....then, as soon as it is completed, leave the combustion chamber out the tail pipe so the next fresh A/F charge can enter......and it starts all over again...

with this in mind....if you are using TOO high of octane...which as we all know, the higher the octane, the slower the burn rate...(kinda like magnum gunpowder)....this fuel cannot COMPLETELY ignite and be consumed at the same rate as lower octane fuel.....so some of this fuel is going to be wasted.....or the timing of the burn rate is going to be off.... as you increase compression....then this fuel can burn at a faster rate due to increased pressure inside the cylinder......where a low octane/faster burning fuel, would cause detonation/preignition from burning TOO fast....

High octane fuel is great...but only if needed.....

does any of that make any sense?

Greg

 

[desratt]

race gas ignites slower then pump gas. the higher the octane rating the slower it burns. people think race gas is more explosive then pump gas but it is not. you only run race gas cause you have to to avoid detonation

race gas is more stable then pump gas. it will burn as it should. when under more heat or compression.

do I make any sense

 

[buck naked]

so because it burns slower on a piston that needs it to burn fast it slows things down and causes a power loss.. :dunno: :ermm: :dunno:

 

[450redrider]

a great gas for a stock bike is nitro RX-7..unleaded and works well on stock bikes... i run MR-9 but it sucks when the bike is stock, great when the bike is built...

 

[buck naked]

okay if its true that you lose power why do pro's use it in bikes with stock [read this in dirtwheels] piston...i've also read where they put it in the new ltr when they dyno'ed it

 

[T210DRVR]

If you use oxygenated (alcohol) enhanced race fuel and you up the jetting you may get a bit more power. The engine also needs to breath better so intake (airbox) mods are good along with a less restrictive exhaust system.

 

[griz]

Originally posted by buck naked@Mar 4 2006, 11:02 PM
okay if its true that you lose power why do pro's use it in bikes with stock [read this in dirtwheels]  piston...i've also read where they put it in the new ltr when they dyno'ed it

[snapback]204969[/snapback]​

What pros did they say were using stock pistons? I'd bet my third nut NONE of them are.

BTW, Dirt Wheels sucks harder than a turbocharged Dyson vacuum.

 

[450RRR]

First off....I dont do ANYTHING...just cuzz the 'pros' do it...

Second off.....I rarely believe what I read in a magazine....any magazine... (I like looking at the pictures tho.... :11doh: )

Dont confuse High Octane fuel...with Oxygenated fuel....

usually....Oxygenated fuel WILL perform better....due to its charactoristics....however, it is quite pricey for the average rec rider...

In My Opinion.......if your 12:1 or under in compression..... you shouldnt run High Octane fuel.....it simply costs you MORE...and COULD lose some power......but, if you like the smell....then go for it....

Greg

 

[buck naked]

Originally posted by 450RRR@Mar 5 2006, 10:39 AM
First off....I dont do ANYTHING...just cuzz the 'pros' do it...

Second off.....I rarely believe what I read in a magazine....any magazine... (I like looking at the pictures tho.... :11doh: )

Dont confuse High Octane fuel...with Oxygenated fuel....

usually....Oxygenated fuel WILL perform better....due to its charactoristics....however, it is quite pricey for the average rec rider...

In My Opinion.......if your 12:1 or under in compression..... you shouldnt run High Octane fuel.....it simply costs you MORE...and COULD lose some power......but, if you like the smell....then go for it....

Greg

[snapback]205102[/snapback]​

okay that makes sense......thats probably what there using the oxygenated fuel

chis biuge or whatever his name is has a stock engine with hrc cam.........and i couple more gncc racer........didn't hear of any mx racers with stock pistons.

thanks for the info 450rr.......think i was getting the to different race fuels mixxed up......i can't find any oxygenated fuel down here..
just cam 2 110 and 116

 

[BackSpace]

What is the best octane


the minimum required to keep it from detonating and pre ignition


:beatingdeadhorse:


lower octane burns faster

hight octane burns slower

but you have to keep in mind compression

more pressure/heat will make it burn faster

octane is sort of like

different gun powders

pistol cartridges has a small volume so it needs a faster powder to make the projectile exit he gun in a given time translated gas has to push the piston in a given time and burn completely to extract every pressure transformed gas molecule

but you have to think in the area of volume the same gas in in a larger area so it has to burn faster and also pressure adds to faster burning pressure translates into heat

compress some thing and it heats large volume lower pressure lower heat slower burning

now a large magnum my favorites are belted 257 and 30/378 weathersby's has to do the same but now have a larger volume of powder it must burn slower to keep from exploding translated gas in a smaller combustion area has to burn slower to keep from exploding

as much more powder translates in to a lot more

= pressure = heat= faster burning

as heat is increased with higher compression compressing a volume into a smaller area= increased pressure /heat=faster burning

take a look at diesels no spark is needed as the the compression of the mixture is all is needed to burn the fuel

we are dealing with controlled burning of fuel


think of the Goldy Lox and the three bears


cold porridge not good

hot not good

warm just right AAAAAHHHHH :drink:

FYI if you uncompress/expand some thing it looses heat how do you think you refrigerator and air conditioner works let air out of you tire it gets cooler to the point it in higher pressure MC tires will make a small chunk of ice thats what the little noise is like some thing just got spit out of it :slap:


also super high RPM motors sometimes use lower octane as it only has a small time to burn in also compare a 10,000 to 20,000 rpm motor it only has half to time to burn in

how about a 40,000 13 port 3HP nitro .21" RC engine :rock:


burn baby burn

 

[Mitco39]

From what everyones saying it does seem that the lowest octane you can run before detenation will give you the most complete burn...hmm. For me i have been running 87Octane in this bike now for 3 years, been running great. At the races it would pull ahead of people running the race fuel, and i guess because of the reasons stated earlier that would make sense.

 

[desratt]

also a 13:1 piston gives a compression of 13:1 but you have to look at when the valves open and close. that is when you get dynamic compression.

If said pro is running a stock piston. with a cam that closes the valves sooner. he may have a higher dynamic compression then stock.

but I seriously doubt that. 90% of cams have the valves open longer for more scavanging and a much better top end.

so what octane you need is not only the piston you have but also the cam and how well your engine flows air.

 

[450RRR]

thats correct...the cam design has a lot to do with octane requirements...so does altitude...for obvious reasons...

and yes...usually the STOCK cam produces the most static compression...especially at lower rpms...where detonation likes to occur... so, if your running high compression....but a Radical cam with a lot of duration....you may not need high octane fuel.........or at least less octane than the same bike running a stock or low end camshaft....

Greg