high octane

[quadsport_rider]

my buddy was ridin his dirt bike with high octane and he had no mods. done to his bike and it blew up,....when they opend up the engine at the shop it was all white...it got cooked...was it something eles that made it bloew up...or can i run high octane thro my z with no mods.??

[LT250RMan]

when you run higher octance gas than normal you have to re jet your carb, and if you guys didnt jet the bike for the high octane gas thats why it blew up, if it was all white that means he had way to small of a jet for the gas he was running.

[quadsport_rider]

alright...so ur sayin all i would need to do is jet my quad..does any one know wat size jet i woudl use if i have a pipe and air box lid off and high octane fuel...??....thanks for ur reply lt250rman

[LT250RMan]

Just keep checking your spark plug, and just keep trying diffrent jets start with a rich jet and if the plugs black go down a size, a good jetting job the spark plug should be a nice chocolate brown never a white color or never a yellow color.

[quadsport_rider]

alright sweet.:) thanks for ur help replying hopfuly i dont fry my z beast up..haha

[400exrules]

dude, stop drinking paint.........you dont have to re-jet with higher octane unless its oxgenated

[LT250RMan]

Originally posted by 400exrules
dude, stop drinking paint.........you dont have to re-jet with higher octane unless its oxgenated

what are you talking about, when you run diffrent octane gas it burns hotter making it leaner or it burns cooler making it richer,.,,,, ok then if i'm wrong explain to me why my jet chart for my snowmobile tells me to jet my sled diffrent when i go from 92 to 110 octane gas with the same cylinder head and a timing switch.:huh

[fastbanshee4u]

To run high octane in a stock motor is a waste of cash.It will not be any faster,High octane is only needed whan timing is advanced alot ,or if you have high compression.Most people have a misunderstanding about race fuel,it takes more compression pressure before it will ignite with out spark than 87 octane.Run the gas your engine needs,not what you think it should have.

[Wheelie]

I ran 110LL aviation fuel in my quad, when the engine was stock for more than three years every time I went to the dunes. Straight Avy fuel, not mixed. When I tore the engine down for the stroker, the piston, cyl, etc. looked great--no adverse wear whatsoever.

I never rejeted, just poured the fuel in and ran it. Supposedly avvy gas blows up engines too.:eek2: :rolleyes:

[LT250RMan]

what is that guy talking about oxgenated gas????:huh

[GooseZ400]

higher octane fuel actually burns cooler than regular unleaded. It has less additives in it. As long as it isn't oxygenated youll be ok. If your jetting was good w/ regular it should be fine w/ 110. Check your plug to see if it is jetted right to begin w/ anyway.

If there is no need to run the race fuel dont run it, youre just wasting your money

[400exrules]

Originally posted by LT250RMan
what is that guy talking about oxgenated gas????:huh

just leave, you have no idea what you are talking about

[LT250RMan]

Originally posted by 400exrules
just leave, you have no idea what you are talking about


whatever man,,

[GPracer2500]

There is nothing set in stone that I'm aware of indicating that switching fuels always WILL or WON'T require a jetting change. It just depends on the particular fuels, fuel types, carb, engine, etc.

Oxygenated fuels like VP MRX01, VP MR10 and others (there are a bunch) are fortified with oxygen molecules in a way normal pump or racing fuels aren't. 5% increases in HP are not unusual (after jetting for the fuel) with no other changes other than the fuel. HP = is as simple as $$, in this case.

Octane rating is independent of whether a fuel is "oxygenated" or not. Some oxygenated fuels have octanes as low as 87 MON.

Oxygenated fuels DO normally require richer jetting. The extra oxygen carried by the fuel will lean out your fueling unless more fuel is metered in to compensate. In a way, oxygenated fuels are like running a tiny dose of nitrous oxide or nitropropane in you air/fuel mixture.

Can you run whatever adaquately octaned fuel you want and never rejet without blowing up your engine? In most cases--sure (although a small bore two stroke will be more sensitive to jetting than some others). Most of us can't tell the difference between a 2% or 3% rich or lean condition anyway. But if you want "perfect" jetting than you should always be on the look-out for minor rich/lean conditions anytime you change anything to do with air and fuel moving through an engine.

[boricua]

thats true.....
also, ive heard that race/higher octane fuel burn a little faster, and needs to be ran a little richer because of it. it just may be 2-3% difference. but every little bit counts, right?

[GPracer2500]

I'm certainly not advocating ignoring jetting that is a few percent off. In that part of my post I was just pointing out that it's hard to detect such small differences.

[deathman53]

race gas tends to burn slower and cleaner, on a stock motor, all you will notice is less money in your wallet. The cooler temperature is very minimuim to ever notice. Higher octane gas is used when far advanced timing and/or high high compression. You use race gas on a air cooled motor over 11:1 compression or a air cooled with advanced timing and you can safely use pump gas(93+) on a liquid cooled up to about 12:1, but race gas will run signifigantly cooler and better. I use race gas in my crf450r hyrbid and it has a stock compression piston(but 488,not 450).

[boricua]

really? ive know guys(racers) who have mix race with pump gas, and they always compensate some carb adjustments. by the way, this is one a jetski(stand-up) motor. much like the banshee.
he has higher compression, but not too high cause he still runs pump gas with no problems all day.
as its been explained to me....the race gas burns quicker and needs more to compensate, same as alcohol fuel. the fuel has a higher flash point and when it does flash/ignite, it does so at a quicker rate than pump gas. i dont want to argue. there's enough of that on here already. if you or anyone knows different, and care to explain, by all means please do so....

[ohsobad_chevy]

Originally posted by fastbanshee4u
To run high octane in a stock motor is a waste of cash.It will not be any faster,High octane is only needed whan timing is advanced alot ,or if you have high compression.Most people have a misunderstanding about race fuel,it takes more compression pressure before it will ignite with out spark than 87 octane.Run the gas your engine needs,not what you think it should have.

^^^^^^^^^^^^^This is very, very true.

[boricua]

i do agree that its a waste of money if your engine doesnt need it.
but i guess" to each his own"....
:ermm:

[GPracer2500]

Boricua, do you ride a ski? I've got a 95' 750SXi.

[boricua]

Originally posted by GPracer2500
Boricua, do you ride a ski? I've got a 95' 750SXi.

yes sir!!!!!
i got a 94 yamaha superjet.
701cc, factory B pipe, msd ignition, pro-tec ride plate, worx scoop intake grate, skat trak S.S. prop(dont remember the pitch...a little on the low side), 0 degree bars, umi "straight" throttle.
it moves pretty damn good for me
i ride mostly at lake mead, parker strip...big bend, emerald cove and once in havasu.

[honda460ex]

Unless a motor needs race gas, don't run it. Like the others have said, it's a waste in all honesty. It is a good idea from every experience I've ever known to up the jetting when running race gas though. Race gas does cause a leaner burn, lean means not enough fuel, one of the main purposes of fuel that most overlook and never think about is to keep a cylinder cool... If you are running lean, your cylinder will get hotter, therefore you need to rejet to a larger jet to get more fuel to that cylinder and help in keeping it cooled down. Rejet...

[400exstud]

^^^ Can you explain why race gas would require a change in jetting? From my chemistry class I have learned that octain number is only a relative figure assigned to a hydrocarbon's resistence to detonation. If this holds true, the only change that race fuel would bring about is a decrease in the likelyhood of detonation.

Unless the fuel is oxygenated I cannon see how it would affect jetting.

[GPracer2500]

Originally posted by boricua
yes sir!!!!!
i got a 94 yamaha superjet.
701cc, factory B pipe, msd ignition, pro-tec ride plate, worx scoop intake grate, skat trak S.S. prop(dont remember the pitch...a little on the low side), 0 degree bars, umi "straight" throttle.
it moves pretty damn good for me
i ride mostly at lake mead, parker strip...big bend, emerald cove and once in havasu.

{sorry for the off topic stuff, folks}

Nice!

I ride most of the lakes in central AZ (Saguaro, Canyon, Apache, and Bartlett mostly). If your ever in the area, let me know--I'm always looking others to ride with.

Keep the stand-up alive!!

[bwamos]

Originally posted by 400exstud
^^^ Can you explain why race gas would require a change in jetting? From my chemistry class I have learned that octain number is only a relative figure assigned to a hydrocarbon's resistence to detonation. If this holds true, the only change that race fuel would bring about is a decrease in the likelyhood of detonation.

Unless the fuel is oxygenated I cannon see how it would affect jetting.

Ahh.. but what if the ratio of gasoline to additives & detergents was different in the race fuel, than what you get at the pump.

If you had less pure gasoline per gallon, then wouldn't you hypothetically need a larger jet to compensate for that? ;)

[400exstud]

AAhhh.... I wasn't takeing that into account. I was only looking as straight up numbers.

[boricua]

Originally posted by GPracer2500
{sorry for the off topic stuff, folks}

Nice!

I ride most of the lakes in central AZ (Saguaro, Canyon, Apache, and Bartlett mostly). If your ever in the area, let me know--I'm always looking others to ride with.

Keep the stand-up alive!!

absolutely! STAND UP AND RIDE!:blah:

[boricua]

race gas starts off as what they called, bendable stock. which is pure, unblended gasoline. what you get before any additives are added by different companys, chevron, mobil, etc.....
so from there, for example, VP will add their blend of additives that they feel are best for a given application. some claims are made saying you can run faster using "brand X" race fuel. all of their gas is held to very strict tolerances allowing each batch to be extrememly consistant, unlike the gas we get at the pump....which is mass produced to turn a quick profit. race gas is formulated for different jobs, like high compressions, nitrous, forced induction....
and according to my sources you can go too high on octane. if you dont need race gas, using it will not yield enough benefits to justify its use. you might run a bit cooler on normally warm days, and can add a little protection over pre detonation, pre igniting on really hot days.

[†2005 400ex†]

dont run high boctane, it wont do that much for you on a stock motor

[MarkyNark]

The only thing I'll add to this thread is the following ...

1) Run at LEAST the octance that your engine or aftermarket piston recommends.

2) Always jet accordingly. If you dont know how to jet, let a pro do it. There are ways to consider jetting. Jetting becomes more critical when you add more performance mods. High performance mods tend to narrow the range of tunability between too rich and too lean. When you get very modified, an Air Fuel gauge or sniffer can be helpful.

3) Octane. The higher the compression engine, the more octane is required. As the piston moves up, its the octane the keeps it from burning too soon. The heat of the compression can spark ignition before the spark plug does it - usually when there isnt enough octane. When this happens, the crank is forcing the piston up, while the pre-ignition tries to force it the other way. Small pre-ignition is pinging, big pre-ignition will break things.

3) Oxygen, jetting and octane. Things get more complex when you add variables such as elevation. The lower the elevation, the more oxygen there is available to burn - If you dont add more fuel, you run the risk of running lean. This also happens if the temperature drops dramatically. A 40 degree temperature drop can equate to a 3000 foot drop in elevation.

4) So, to be safe, I always run at LEAST the octane that the engine or aftermarket piston recommends.

5) Aviation fuel and race gas. There is a big difference. If you NEED more octane, you'll get better results if you run race gas instead of aviation fuel. Av gas is meant to burn slow - Believe it or not, they add slow burning additives so that when the plane crashes all the passengers can have a better chance of getting out faster without burning up! It does burn slower, and causes engines to rev slower - But, there arent a lot of quick rev changes in aircraft - there is with quads.

I've run pistons in my DS as high as 14:1. On my EX I've run them as high as 13:1. I currently run a 12:1 piston on my 460EX and the fuel I use is VP C12 - It keeps the motor very cool when I add a 25hp shot of nitrous. C12 is rated at 108 octane. I could probably get a way with 105 at my elevation of 5000 feet.

[LT250RMan]

Originally posted by MarkyNark
It does burn slower, and causes engines to rev slower -

.

I have never heard of Av Gas making a engine rev slower:confused: My dad has a snowmobile that he runs Av gas in and it did not make his engine rev slower when he switched from 110 VP race gas to 100LL Av gas, it works just fine and it still revs the same as it did when he ran the VP race fuel.

[GPracer2500]

Originally posted by MarkyNark
...As the piston moves up, its the octane the keeps it from burning too soon. The heat of the compression can spark ignition before the spark plug does it - usually when there isnt enough octane. When this happens, the crank is forcing the piston up, while the pre-ignition tries to force it the other way. Small pre-ignition is pinging, big pre-ignition will break things...

This isn't quite right.

Octane is a measure of a fuels resistance to detonation. Detonation is an abnormal combustion phenomenon and it ALWAYS occurs AFTER the spark plug fires. It is when the air/fuel mixture at the edges of the combustion chamber "detonates" (i.e. explodes) before the flame front reaches that part of the combustion chamber. Detonation creates an audible "knock" or "ping" when it is occuring.

Pre-ignition is the other abnormal combustion phenomenon. It ALWAYS occurs BEFORE the spark plug fires. It is caused by an ignition source other than the spark plug. It is silent other than your engine destroying itself. Pre-ignition is not normally related to octane.

I can elaborate if needed.

[GPracer2500]

Originally posted by MarkyNark
...Believe it or not, they add slow burning additives so that when the plane crashes all the passengers can have a better chance of getting out faster without burning up!...

I'll choose NOT, unless you can provide some evidence to support this statement. I'm a GA pilot and have never heard such a thing.

[MarkyNark]

Originally posted by GPracer2500
This isn't quite right.

Octane is a measure of a fuels resistance to detonation. Detonation is an abnormal combustion phenomenon and it ALWAYS occurs AFTER the spark plug fires. It is when the air/fuel mixture at the edges of the combustion chamber "detonates" (i.e. explodes) before the flame front reaches that part of the combustion chamber. Detonation creates an audible "knock" or "ping" when it is occuring.

Pre-ignition is the other abnormal combustion phenomenon. It ALWAYS occurs BEFORE the spark plug fires. It is caused by an ignition source other than the spark plug. It is silent other than your engine destroying itself. Pre-ignition is not normally related to octane.

I can elaborate if needed.

Thank you on clarifying det and pre-ignition. There are things I am still learning! :D

[MarkyNark]

Originally posted by GPracer2500
I'll choose NOT, unless you can provide some evidence to support this statement. I'm a GA pilot and have never heard such a thing.

I'll be happy to try and google something for you.

[MarkyNark]

Originally posted by MarkyNark
I'll be happy to try and google something for you.

Here you go -

"We asked Sunoco's Wurth about using aviation fuel in an automobile engine. He was emphatic when he said, "Don't do it. Even though Sunoco is a major producer of aviation fuel, this fuel is specifically blended for aircraft engines. Aircraft operate under very different conditions than automobiles, and the fuel requirements are quite different as well. Aircraft engines generally.... run within a very narrow rpm range. There's no need for transient throttle response in an airplane because after the pilot does the initial engine run-up, the throttle is set in one position and the rpm doesn't normally change until landing. Also, airplanes fly where the air is cold and thin, and the atmospheric pressure is low. These are not even close to the conditions your street machine will see on the ground. Also, since most piston-driven aircraft cruise at 3,000 rpm or so, the burn rate of aviation gas is much too slow for any high performance automotive applications."

Found here (http://www.nsxprime.com/FAQ/Miscellaneous/FuelAdditives.htm)

There's probably a lot more, but thats a result of my first search.

[MarkyNark]

More info on the differences between Pre-Ignition and Detonation. My point here is that pre-ignition can indeed lead to detonation.

Check it out (http://www.misterfixit.com/deton.htm)

[MarkyNark]

Volitility of aviation fuel:

"Aviation Gasoline Aviation gasoline, or Avgas, is the fuel used in aircraft powered by reciprocating, rather than turbo-jet or turbo-prop engines. Avgas is similar to conventional motor gasoline; however, there are several important differences. Avgas is generally less volatile and has a lower freezing point than conventional gasoline. Common additives to Avgas include alkyl-lead anti-knock additives, metal deactivators, color dyes, oxidation inhibitors, corrosion inhibitors, icing inhibitors, and static dissipaters. Three grades of Avgas are currently available in the U.S. and are characterized by their anti-knock characteristics. American Society for Testing and Materials (ASTM) Grades 100 and 100LL Avgas have octane ratings of 100 and are the most widely available. These grades contain about 1.0 and 0.5 grams per liter of tetra ethyl lead, respectively, considerably more than automotive gasolines currently in use. ASTM Grade 80 Avgas has an octane rating of 80, is declining in use, and contains about 0.14 grams per liter of lead. "

found here (http://www.afcee.brooks.af.mil/PRO-ACT/fact/petfuels.asp)

What is fuel volitility?

"Reducing fuel flammability involves limiting the volatility of fuel and the rate at which it vaporizes. Liquid fuel can burn only when enough fuel vapor is mixed with air. If the fuel cannot vaporize, a fire cannot occur. This principle is behind the development of higher-flashpoint fuel, whose use can decrease the likelihood of a fuel tank explosion. The flash point is the lowest temperature at which a liquid fuel produces enough vapor to ignite in the presence of a source of ignition--the lower the flash point, the greater the risk of fire. If the fuel is volatile enough, however, and air is sucked into the fuel tank area upon crash impact, limiting the fuel's vaporization can prevent a burnable mixture from forming. This principle supports the use of additives that modify the viscosity of fuel to limit postcrash fires; for example, antimisting kerosene contains such additives. According to FAA and NASA, however, these additives do nothing to prevent fuel tank explosions."

Found from a site on the web reporting efforts to further decrease fuel volitility in aircraft for passenger safety:

right here (http://www.gao.gov/atext/d0433.txt)

From everything I've read, fuel volitility in aircraft has not exactly where it should be, but clearly they understand that fuel volitility is directly related to passenger safety.

[GPracer2500]

Originally posted by MarkyNark
Here you go -

"We asked Sunoco's Wurth about using aviation fuel in an automobile engine. He was emphatic when he said, "Don't do it. Even though Sunoco is a major producer of aviation fuel, this fuel is specifically blended for aircraft engines. Aircraft operate under very different conditions than automobiles, and the fuel requirements are quite different as well. Aircraft engines generally.... run within a very narrow rpm range. There's no need for transient throttle response in an airplane because after the pilot does the initial engine run-up, the throttle is set in one position and the rpm doesn't normally change until landing. Also, airplanes fly where the air is cold and thin, and the atmospheric pressure is low. These are not even close to the conditions your street machine will see on the ground. Also, since most piston-driven aircraft cruise at 3,000 rpm or so, the burn rate of aviation gas is much too slow for any high performance automotive applications."

Found here (http://www.nsxprime.com/FAQ/Miscellaneous/FuelAdditives.htm)

There's probably a lot more, but thats a result of my first search.

Hey, no worries. :) Deto and pre-ign are commonly missunderstood. I went a long time without really understanding it myself.

But the part I was questioning about Avgas is not burn rates. Rather, it's the part about Avgas's formulation having anything to do with protecting pilots and passengers in a crash.

[GPracer2500]

Originally posted by MarkyNark
Volitility of aviation fuel:

"Aviation Gasoline Aviation gasoline, or Avgas, is the fuel used in aircraft powered by reciprocating, rather than turbo-jet or turbo-prop engines. Avgas is similar to conventional motor gasoline; however, there are several important differences. Avgas is generally less volatile and has a lower freezing point than conventional gasoline. Common additives to Avgas include alkyl-lead anti-knock additives, metal deactivators, color dyes, oxidation inhibitors, corrosion inhibitors, icing inhibitors, and static dissipaters. Three grades of Avgas are currently available in the U.S. and are characterized by their anti-knock characteristics. American Society for Testing and Materials (ASTM) Grades 100 and 100LL Avgas have octane ratings of 100 and are the most widely available. These grades contain about 1.0 and 0.5 grams per liter of tetra ethyl lead, respectively, considerably more than automotive gasolines currently in use. ASTM Grade 80 Avgas has an octane rating of 80, is declining in use, and contains about 0.14 grams per liter of lead. "

found here (http://www.afcee.brooks.af.mil/PRO-ACT/fact/petfuels.asp)

What is fuel volitility?

"Reducing fuel flammability involves limiting the volatility of fuel and the rate at which it vaporizes. Liquid fuel can burn only when enough fuel vapor is mixed with air. If the fuel cannot vaporize, a fire cannot occur. This principle is behind the development of higher-flashpoint fuel, whose use can decrease the likelihood of a fuel tank explosion. The flash point is the lowest temperature at which a liquid fuel produces enough vapor to ignite in the presence of a source of ignition--the lower the flash point, the greater the risk of fire. If the fuel is volatile enough, however, and air is sucked into the fuel tank area upon crash impact, limiting the fuel's vaporization can prevent a burnable mixture from forming. This principle supports the use of additives that modify the viscosity of fuel to limit postcrash fires; for example, antimisting kerosene contains such additives. According to FAA and NASA, however, these additives do nothing to prevent fuel tank explosions."

Found from a site on the web reporting efforts to further decrease fuel volitility in aircraft for passenger safety:

right here (http://www.gao.gov/atext/d0433.txt)

From everything I've read, fuel volitility in aircraft has not exactly where it should be, but clearly they understand that fuel volitility is directly related to passenger safety.

Gotcha. But, none of that relates to Avgas as was implied in your original post.

[GPracer2500]

Originally posted by MarkyNark
...My point here is that pre-ignition can indeed lead to detonation...

I didn't understand that was what you were getting at.

:)

[MarkyNark]

It is a stretch, but my point is that AV Gas is less volitile, burns slower and as a natural result, has a higher safety factor. However I will concede that the reduced volitility and limited safety benefits are more of an indirect result rather than a direct result of fuel additives to AVgas. Clearly, the brains of the government are looking to capitalize on further increasing passenger safety of all aviation fuels by further reducing volitility even more. If given the choice of standing in a pool of AVgas or race gas, Id choose AVgas. But I wouldnt put it in my quad.

My main point in my original thread, is that AV gas burns slower. As a result, does decrease the performance of gasoline burning engines.

[GPracer2500]

From the site you linked:


...Fire-safe fuels are not currently available and are in the early stages
of research and development...

And I don't believe they are talking about Avgas (which is for reciprocating engines only) but jetfuel which is an alltogether different animal.

[GPracer2500]

Originally posted by MarkyNark
...My main point in my original thread, is that AV gas burns slower...

I think we're on the same page. I wasn't trying to be argumentative...it's all good.

:)

[MarkyNark]

No prob! We all learned something. Open minds are the only way to learn.

[GPracer2500]

It's hard to debate when we're posting simultaneously!

From the Sunoco guy:

...the burn rate of aviation gas is much too slow for any high performance automotive applications...

Nonetheless, people seem to use it with sucess. I'm not implying an indorsment of Avgas in lieu of race fuel, but I wonder if the burn rate of Avgas is as significant as the Sunoco fellow suggests?? I really don't know.

Gosh, I wish I had my own dyno. There's soooo many things I'd have fun testing for myself in the engine applications we're discussing.

[MarkyNark]

In sleds, our friend that posted that his dad didn’t notice the difference is because of clutching. It may have taken just a bit longer for his clutch to engage, but once the revs reached the point to where the clutch engaged, there would have been little or no difference. So it would be less noticeable in a sled than a quad. Because quads rely on a gear box and require dramatic rev changes often, the dyno results will have been more dramatic than on a sled.

Everyone is looking to save money on fuel. Since sleds are so much more expensive on fuel, it makes sense that someone might want to compromise the slow burn aspects on a CVT transmission engine.

However, in quad, I think performance would skew any price difference in the fuels. At least it would for me. I doubt any sled races have been won with AV gas; Certainly not very many quads that run AV Gas.

[Wheelie]

I ran 100LL in my quad last weekend during my trip to Sand Lake OR. The quad ran great, I noticed no ill effects from running this fuel.

The quad had great throttle response, revved quick, and ran very strong.

[MarkyNark]

Originally posted by Wheelie
I ran 100LL in my quad last weekend during my trip to Sand Lake OR. The quad ran great, I noticed no ill effects from running this fuel.

The quad had great throttle response, revved quick, and ran very strong.

Just running around I doubt that many would notice. If you race and times are important, then it will be a different deal altogether. As mentioned before, by guys that are a lot smarter than me or you, you will get better results with race gas. The best way to tell is not 'seat of the pants' testing, but on a dyno in controlled conditions.

Im not saying you'll have any detromental ill affects of running AV gas, but I would like to nix the general conception in the quad world that AV gas is somehow better than race gas. Its not. While it may hold the proper octane to control the burn in your application, better results in horsepower will occur with actual race gas.

You can run whatever you want, but I have some pretty healthy evidence that its not better from a horsepower perspective than race gas.

[Wheelie]

I wasn't running it for an improvement in horsepower, I'm just looking to bump up the octane to help stave off detonation.

Octane booster is not an option.

[MarkyNark]

Then it will do exactly what you expect it to - stave off det.

[trick250r]

http://www.eric-gorr.com/twostktech/carbtuning.html


check this site out, it has the basics of fuel. such as the octane isnt what you want to look for, the ignition time of the fuel is more important. that, and never run a higher octane in your engine than it needs. it should have all of the formulas on the site.



if you want to run down the pre-detonation, put a wet cloth over your bikes gas tank, cooler fuel has much less pre-detonation.

[GPracer2500]

BTW, pre-detonation is not a term. The two abnormal combustion phenomenon are detonation and pre-ignition.

[zeppelin]

Originally posted by trick250r
http://www.eric-gorr.com/twostktech/carbtuning.html


check this site out, it has the basics of fuel. such as the octane isnt what you want to look for, the ignition time of the fuel is more important. that, and never run a higher octane in your engine than it needs. it should have all of the formulas on the site.



if you want to run down the pre-detonation, put a wet cloth over your bikes gas tank, cooler fuel has much less pre-detonation.

if you ever notice on factory mx bikes they put insulation on the bottom of their gas tanks, and some even put their tanks in an ice box before the race because cooler and denser gas means more power :)

[MarkyNark]

Originally posted by trick250r
http://www.eric-gorr.com/twostktech/carbtuning.html


check this site out, it has the basics of fuel. such as the octane isnt what you want to look for, the ignition time of the fuel is more important. that, and never run a higher octane in your engine than it needs. it should have all of the formulas on the site.



if you want to run down the pre-detonation, put a wet cloth over your bikes gas tank, cooler fuel has much less pre-detonation.


I will just add one thing to your post, never run more octane than you need - but only if you are able to tell exactly WHAT you need.

Who in here has an air/fuel gauge or CO sniffer to determine that?

Its better to run slightly more octane than you need if you are in situations when you cant tell exactly what you need. Its always better to run more octane than you need because its safer than running less than you need. Nobody caused engine damage by running more octane, but only less.

What are things that affect jetting .... ?

Outside Temperature
Elevation
Humidity
high flow mods (cams, exhaust etc)

What are things that determine octane?

Piston compression
Ignition Timing
Engine cooling demands - Nitrous, Type of cooling on motor.

So the word NEVER, is probably a bit presumptuous. Im totally comfortable with running higher 3pts higher octane in my motor with a cooling fuel because I am running a 60hp total and using nitrous with an air/oil cooled engine. Plus, I run variable temperatures from 40 degrees to 90 degrees.

Yes, I have a sniffer as well - fine tuned to the max.

Never is a bit absolute - but if you want to play rocket scientist, and run on the edge, the perfect otance level will indeed get you the most horsepower. But if your engine is very high performance, you better have it tuned like a piano all the time - at lower octane levels otherwise you run the risk of damage.

[LT250RMan]

Originally posted by MarkyNark
In sleds, our friend that posted that his dad didn’t notice the difference is because of clutching. It may have taken just a bit longer for his clutch to engage, but once the revs reached the point to where the clutch engaged, there would have been little or no difference. So it would be less noticeable in a sled than a quad. Because quads rely on a gear box and require dramatic rev changes often, the dyno results will have been more dramatic than on a sled.

Everyone is looking to save money on fuel. Since sleds are so much more expensive on fuel, it makes sense that someone might want to compromise the slow burn aspects on a CVT transmission engine.

However, in quad, I think performance would skew any price difference in the fuels. At least it would for me. I doubt any sled races have been won with AV gas; Certainly not very many quads that run AV Gas.

The clutch cut in at the same time as it did with the 110 VP fuel

[MarkyNark]

So you are telling me that you had a stop watch and made several runs between the two to make that determination? Were you actually thinking there would be a difference, or merely ran without being aware that there is good documentation pointing out the actual slow burning aspects of AV Gas.

You wont know what to test if you are not aware of what to test for. Recollection can be faulty, especially when you may not have been aware of the actual differences.

Open minds..... and facts .... are a good thing :eek2: