AvGas Question ????

[Quad18star]

I was just wondering if running a mix of 93 Octane fuel and Aviation Fuel (115-120 Octane) would hurt my YFZ450 ?

I'd be running the mix 70/30 or 60/40 .

Anyone have any opinions or suggestions on this? My 450 is relatively stock with only my airbox lid removed and rejeted and my baffle taken out .

[dirtmomma]

WOW are you sure thats the octane for the AV gas??? Seems REALLY high, the AV gas we get is 100LL we run it straight w/ no problems,
the 450 my son is racing the owner runs about the same mix you are asking about & he's got a pipe w/ jetting I think thats about it. Actually he doesn't run AV gas but I think it's ELF?
The quad runs fine!! Not much of a solid answer though :o :p

[Toadz400]

I don't see why you would want to run the AV gas if your engine is stock. You won't see any gains out of it at all, but I don't think it will hurt anything.

[Quad18star]

I just got back from the airport to check the exact Octane of the fuel , and it's 115 Octane . The reason I was asking about it , is because my cousin's husband is a float plane pilot and was telling me about the fuel and that he can get it for not too much more than the price of 93 Octane . I know we used to run it in our Drag car and noticed quite a difference in performance , and he runs it in his old sled that he uses to groom his runway on the lake during the winter . He mixes his at 50/50 in his sled , and you can really notice the difference .... it seems to give the motor that little bit extra .

[red2004 TRX450R]

We use to run it on the drag car 15-20 years a go. best stuff then!

AV gas is not the same as it was then!! I would not run it in any thing.

run cam2 or turboblue!!! it cost a little more but not much!!!

most towns will have a pump of it hideing some where!!

[wilkin250r]

First off, do a search on the subject. I have posted lots of information, but I don't feel like re-typing all of it.

Second, you need to understand exactly what octane is, and what it is not. Octane is not power. Higher octane does not produce more power. Octane is a measure of stability under heat and pressure. Higher octane means more stability. Specifically, octane is a measurement of resistance to detonation (sort of like pre-ignition). The higher the octane number, the more you can compress it before it ignites.

So why is it such great stuff, this high-octane fuel? Because compression equals power. The more you compress your fuel/air mixture before you ignite it, the more power you will get out of it. With a higher octane fuel, you can compress it more, and thus get more power. The power comes from the compression, NOT the octane.

In your engine, you are not increasing the compression, because it is relatively stock. So you do not need higher octane. It's not giving you any performance advantage. But at the same time, the "it runs fine" arguement also works, because it won't do your engine any harm.

Will it hurt your engine? No. So it's safe.

Will it help your engine? No. So what's the point of doing it?

Will it cost more money? Yes indeed.

[DaleJrFan]

hey wilkin, what does the higher octane do as far as heat inside the chamber and disapating it through your exaust? what i mean to ask is how much more heat does higher octane actually generate when used on a stock engine and if there is more heat, can you control it through a better exaust or port and polished head?

[sampleez]

when i ran a 110/93 mix in my 300ex w/ a 11:1 piston and ported head, it ran a lot cooler than with 93.

[wilkin250r]

It's not a simple answer, since there are many ways and additives to increase octane, and they don't all have the same effect. In order to answer your question, many general assumptions need to be made, but those assumptions aren't always accurate.

Cooling effects: Generally, high octane fuels have a higher heat of vaporization. This means when the fuel hits a hot surface (like your piston) it will take more heat away as it evaporates, so it can actually cool your piston better.

Burn Rate: A slower burn rate will result in lower cylinder pressures, which results in less heat and less power output. Now, many people think higher octane fuel burns slower. Sometimes this is true, sometimes it's not. AV gas generally burns slower than pump gas, but that's about the only safe assumption you can make. Many race fuels actually burn faster than pump fuel, even though the race fuels have higher octane. It all depends on the blend.

So, as for your original question, a properly blended fuel can lower your engine tempurature, whether it is high-octane or not, but it's generally only a few degrees. This usually isn't important enough to justify the cost of a specialty-blended fuel. Most often, the goal of a specialty blend (like race fuel) is increasing octane but still maintaining or maximizing other factors like Burn Rate, Energy Content and Oxygenation (usually the addition of alcohols).

Valve timing is typically not adjusted for heat dissipation. A high-flowing exhaust will allow exhaust gases to escape faster, so it would theoretically lower the exposure time of hot exhaust gasses, and thus limit their transfer of heat, but I don't think you would actually see a decrease in engine tempurature. The jetting and mixture changes that rise from a change in backpressure will have much more effect.

[redrunner]

Hey quadstar ready to ride again are we? Getting the itch eh? How is the movement of that leg? I am waiting until I get my brace and or some asterisks.

[cletusEX]

Isn't there a difference between gas and fuel? Certain higher octanes are fuels and won't mix with regualar pump gas. Stuff like 113 octane VP are actually a fuel and will not mix in pump gas. I might be wrong but I don't know.

[dunedragger]

I am definately not a gas pro, but from my expierence I know a little. The higher the Octane the drier the fuel, which can create problems with gaskets drying out and so forth. Secondly in order for fuel to burn better there needs to be oxygen, the more oxygen the better it will burn, so from what I have been told, I run 50% 114, and 50% 94 Octane with Ethanol, because Ethanol has more oxygen to allow it to burn better. But I also have a 39 h.p. 416. vs a stock 400, tht mixture may be a little too much. Remember Ethanol has more Oxygen. Anyone can correct me if I was told wrong, I would never want to instruct somebody wrong especially on something as important as fuel.

[wilkin250r]

I don't know about "drier" fuel and gasket problems, but you are correct about oxygen.

Fuel needs oxygen to burn, but not all fuels have the same oxygen requirements. Alcohols (like Ethanol, Methanol) and other fuels like Nitromethane actually carry oxygen atoms with them, so they don't need as much oxygen to burn. They supply part of their own oxygen requirements.

Gasoline requires about 15 pounds of air for every pound of fuel. (this is weight, not volume) In contrast, pure Methanol only requires about 6 pounds of air, and pure nitromethane only requires about 1.7 pounds of air for each pound of fuel.

On the intake stroke, your engine pulls in a certain amount of fuel and air (forget the throttle position for now). That air has only so much oxygen in it. The amount of oxygen controls the amount of fuel you can burn. If your fuel needs lots of oxygen, you can only burn a small bit of fuel. But if your fuel supplies part of it's own oxygen, then you can add more fuel, which creates more power.

So, look at your quad, 400cc. This is about 490 milligrams (mg) of air, which means you can burn bout 32mg of gasoline. In contrast, with the same 400cc amount of air, you can burn about 82mg of Methanol, or about 288mg of Nitromethane. More fuel equals more power.

[dunedragger]

Very smart...or did you sleep at a Holiday Inn Express last night?

[wilkin250r]

Originally posted by dunedragger
Very smart...or did you sleep at a Holiday Inn Express last night?

Ask anybody, I'm the Official Thinker of Exriders ;)

[Cody_300ex]

I used to run 110 in my 300ex when it was stock and it seemed to give it a bit more umph. When i tore it down the piston looked to be in good shape for its first ever rebuild (note its a 96' :eek: ).

[Quad18star]

Originally posted by redrunner
Hey quadstar ready to ride again are we? Getting the itch eh? How is the movement of that leg? I am waiting until I get my brace and or some asterisks.

I got the itch to ride again , but that ain't gunna happen for a LONG time . I'm on crutches for atleast another 6months which really blows but what can ya do right??? Movement in my leg is getting a little bit better .... I'm do very small stretching excercises , so that when therapy comes around I have a bit of an advantage , instead of starting from scratch . I'm not sure what kind of devices I'll be able to buy for my leg ... I know some sort of knee brace will help cuz there was about 10 breaks around the knee area ... I'm just not sure what they can do about a leg brace .

[redrunner]

Yeah i know you had a long way to go but just reading it seems like you will be doing something... therapy is a good thing but them boys are really working me now. It has been 5 weeks and now the sessions are longer and harder. I swear I spend more time icing it down then working it but the muscles are coming back. ;)