Race gas=run hotter??

[mxpimp2000]

ive been running 110 striaght because i have 13:1 piston and i started mixing my gas with 93 and it seems like my fan dosent kick on half as much as it did before because it use to kick on if i just cruise to the garage

[quadracer55]

race gas runs cooler

[coryatver]

Cooler

[Ride1Rob]

From the way it was explained to me if you have the piston to burn the race gas it runs cooler. If someone with a low compression piston runs race fuel it can cause the bike to run hotter. Not sure, but like I said this is the way that it was explained to me.

[mxpimp2000]

well i paid for a 13:1 piston wen it got rebuilt and ive ran race gas in it since then and the guy could be a crook and lied to me. however mine is a 06 so the 13:1 makes it a 12 5:1 right? would that still mean race gas or what?

[Ride1Rob]

No, a 13.5 to 1 on yours means just that.

[mxpimp2000]

Originally posted by Ride1Rob
No, a 13.5 to 1 on yours means just that.

ive been told on the 06+ the compression is diff but on the 04-05 what u buy is what ur getting. even the piston kits on ebay say this

12.5:1 = 12:1
13:1 = 12.5:1
13.5:1 = 13:1
14:1 = 13.5:1

[quadboy-55]

huh, well, thats interesting.

anyways, i heard 12.5-1 or lower you dont need to run race gas. however 13-1 is 50/50 pump and VP-c-12, im not sure what octane c-12 is, but its oxygenated race gas. and 13.5 is the same ratio, 14+ is straight c-12, again, not sure what the octane rating is for oxygenated c-12 racegas, thats just what i was told.

[Ride1Rob]

Pimp, you have it backwards. The 04's and 05's have a shorter stroke. This makes those bikes have less compression throughout the piston cycle.

[mxpimp2000]

heres why i thought that. and i provided the link from ebay as well


http://cgi.ebay.com/ebaymotors/Yamaha-YFZ450-Wiseco-Hi-Comp-Piston-YFZ-450-2004-2008_W0QQcmdZViewItemQQ_trksidZp3286Q2ec0Q2em14QQh ashZitem2ea7331a35QQitemZ200373639733QQptZMotorsQ5 fATVQ5fPartsQ5fAccessories



You are looking at a Brand New Wiseco Hi-Compression Piston Kit for years 2004-2008 Yamaha YFZ450 (part #4835M09500). This kit includes one (1) (95.00mm) .Std bore piston, rings, wrist pin, and circlips. For years 2004-2005 this piston will be 13:1 Hi-Compression, and years 2006-2008 it will be 12.4:1 Hi-Compression. Wiseco Pistons are Forged from high silicon, low expansion aluminum alloy which offers superior strength, reduced weight, improved heat transfer and longer life.

[atvlifestyle]

04 and 05 have a shorter stroke but do so higher in the cylinder. When it hits top dead center it is closer to the head making more compresion by .5 than the 06 and up.

[usp4u]

Originally posted by quadboy-55
huh, well, thats interesting.

anyways, i heard 12.5-1 or lower you dont need to run race gas. however 13-1 is 50/50 pump and VP-c-12, im not sure what octane c-12 is, but its oxygenated race gas. and 13.5 is the same ratio, 14+ is straight c-12, again, not sure what the octane rating is for oxygenated c-12 racegas, thats just what i was told.
c-12 is 108 octane

[Ride1Rob]

Originally posted by atvlifestyle
04 and 05 have a shorter stroke but do so higher in the cylinder. When it hits top dead center it is closer to the head making more compresion by .5 than the 06 and up.

Gotcha... But because of the shorter stoke of the 04's and 05's is why I was thinking there would be less compression because it's farther away from the dome/head. How could it be closer if the stroke is shorter? Now I'm confused lol.

[atvlifestyle]

The 04 / 05 had problems if the valves were out of spec the piston could hit the valves pretty easily, when they bumped it up to a true 450 they made a crank with a stroke starting lower in the cylinder and keeping the piston farther from the valves and. This took care of that problem but bumped the compresion down.

[Ride1Rob]

Hmmm... now I understand ;) . Well that explains why Pimps bike is running hot.

[mxpimp2000]

so my bike is actually a 12.5:1?? if the guy actually put a 13:1 in mine like he said

[yamahahaha]

Gas is ignited by heat which is made by spark and or compression. If the compression is high the gas will b ignited faster because of more heat, normal gas will ignite to fast in a high compression motor. Which will do damage to the motor... If u put race gas in a low compression motor it will not ignite fast enough.

There for race gas runs cooler

[atvlifestyle]

So chances are your compresion works out to 12.5:1 which means running 110 race gas would cause preignition which would also cause your motor to run hot. So when you are half and half your motor is happy because it is almost high compresion.

[Toadz400]

Race gas burns cooler because it is a slower burning fuel. Running it in a lower compression engine will result in fuel not being ignited which results in lower temperatures. If you ran normal octane fuel in a high compression engine the fuel would burn too quickly and therefore at an increased temperature and predetonation.

atvlifestyle - Running race gas would not result in predetonation. Not all of the fuel would be able to be completely burned because of the lower compression which would result in lower temperatures.