Watch gas boil Fume cause?

[Magdave]

Thanks to spacetiger for the link. It show that gas starts to boil at ~160+ and could explain a lot about those of us with fumes and drips after shut down. I have measured my cap over 150 in the past looks like I will have to start checking it again.

 

[jaherbst]

Obviously, when the gas heats up over 100 degrees it creates fumes and expansion which have to escape through the purge valve and into the canister. That is where our gas fume smell begins and it escalates from there as the fuel gets increasingly hotter. IMO this is dangerous beyond belief. Thank you so much for this video and explanation.

 

[NancysToy]

The point at which gas boils is variable, depending a lot on the gasoline formulation. Gasoline is a mixture of substances, and different ratios cause the boiling point to change. Different octanes boil at different points, too, due to the way gasoline is refined. The degree to which ethanol and other additives are included also changes the game. Gasolines may boil anywhere from 100 to 400 degrees Farenheit.

 

[Magdave]

The point at which gas boils is variable, depending a lot on the gasoline formulation. Gasoline is a mixture of substances, and different ratios cause the boiling point to change. Different octanes boil at different points, too, due to the way gasoline is refined. The degree to which ethanol and other additives are included also changes the game. Gasolines may boil anywhere from 100 to 400 degrees Farenheit.

Well I am not duplicating that from gas in my tank. I do not want to be the human torch :yikes: Is it true the lower the octane the higher the boil temp?

 

[spacetiger]

Short answer:

Yes; the higher the octane the lower the boiling point, so the lower the octane the higher boiling point. If the bike runs on 87 (and it does), don't use 91 or 93.
​

Longer answer:
Final Boiling Point Decreases in the final boiling point increase fuel octane. Aviation gasolines have much lower final boiling points than automotive gasolines. Note that final boiling points are being reduced because the higher boiling fractions are responsible for disproportionate quantities of pollutants and toxins.

Link (There are many, its in the internet, so it must be true...):

http://www.repairfaq.org/filipg/AUTO/F_Gasoline6.html
​

If the filler cap is 150 degrees F, how hot do you think it is next to the exhaust pipe?

:yikes:

 

[Bob Denman]

Based upon what I've seen; I would guess that boiling fuel is not all that uncommon...
It may not even be all that much of an issue to the engineer who designed the system. :shocked:

2002 and 2003 Yamaha Grizzly 660s would boil their fuel,,, Yamaha aded some heat shielding under thank tank, and some ventilation slats in the bodywork as a result... :thumbup:

 

[bruiser]

[TABLE="class: small, width: 390"]
[TR]
[TH]Fuel[/TH]
[TH]Boiling Point ([SUP]o[/SUP]F)[/TH]
[/TR]
[TR]
[TD]Acetaldehyde[/TD]
[TD]70[/TD]
[/TR]
[TR]
[TD]Acetone[/TD]
[TD]134[/TD]
[/TR]
[TR]
[TD]Acetylene[/TD]
[TD]-119.2[/TD]
[/TR]
[TR]
[TD]Benzene[/TD]
[TD]176.2[/TD]
[/TR]
[TR]
[TD]Butylene[/TD]
[TD]21.2[/TD]
[/TR]
[TR]
[TD]Ethyl Alcohol[/TD]
[TD]172[/TD]
[/TR]
[TR]
[TD]Ethane[/TD]
[TD]-127.5[/TD]
[/TR]
[TR]
[TD]Ethylene[/TD]
[TD]-154.7[/TD]
[/TR]
[TR]
[TD]Fuels Oil No.1[/TD]
[TD]304 - 574[/TD]
[/TR]
[TR]
[TD]Gasoline[/TD]
[TD]100 - 400[/TD]
[/TR]
[TR]
[TD]IsoButane[/TD]
[TD]10.9[/TD]
[/TR]
[TR]
[TD]Isobutene[/TD]
[TD]19.6[/TD]
[/TR]
[TR]
[TD]Isopropyl alcohol[/TD]
[TD]181[/TD]
[/TR]
[TR]
[TD]Iso-Octane[/TD]
[TD]243.9[/TD]
[/TR]
[TR]
[TD]IsoPentane[/TD]
[TD]82.2[/TD]
[/TR]
[TR]
[TD]Kerosine[/TD]
[TD]304 - 574[/TD]
[/TR]
[TR]
[TD]Methane (Natural Gas)[/TD]
[TD]-258.7[/TD]
[/TR]
[TR]
[TD]Methyl Alcohol[/TD]
[TD]149[/TD]
[/TR]
[TR]
[TD]n-Butane[/TD]
[TD]31.1[/TD]
[/TR]
[TR]
[TD]n-Heptane[/TD]
[TD]209.1[/TD]
[/TR]
[TR]
[TD]n-Hexane[/TD]
[TD]155.7[/TD]
[/TR]
[TR]
[TD]n-Octane[/TD]
[TD]258.3[/TD]
[/TR]
[TR]
[TD]n-Pentane[/TD]
[TD]97.0[/TD]
[/TR]
[TR]
[TD]n-Pentene[/TD]
[TD]86.0[/TD]
[/TR]
[TR]
[TD]Naphthalene[/TD]
[TD]424.4[/TD]
[/TR]
[TR]
[TD]NeoPentane[/TD]
[TD]49.1[/TD]
[/TR]
[TR]
[TD]NeoHexane[/TD]
[TD]121.5[/TD]
[/TR]
[TR]
[TD]Propane[/TD]
[TD]-43.8[/TD]
[/TR]
[TR]
[TD]Propylene[/TD]
[TD]-53.9[/TD]
[/TR]
[TR]
[TD]Triptane[/TD]
[TD]177.6[/TD]
[/TR]
[TR]
[TD]Toluene[/TD]
[TD]231.1[/TD]
[/TR]
[TR]
[TD]Xylene[/TD]
[TD]281.1[/TD]
[/TR]
[/TABLE]


Ethanol boils at 173F

 

[NancysToy]

Based upon what I've seen; I would guess that boiling fuel is not all that uncommon...

It's really not. It happened on some of my Triumphs, including my Bonneville, and has happened on some of my Hondas. The old 305 Scrambler was reknowned for it. My BMW's seem pretty immune, probably due to the boxer engine design that keeps the heat producing components pretty far from the tank. It happens pretty easily on bikes with tight fairings...even more so if they have much of the exhaust enclosed or have been modified to flow less air through the fairing (when racing). It is disconcerting, and probably an emissions problem, but if the system is designed right I don't think it poses much of a hazard. The exception to this, in my opinion, would be when the boiling fuel or heat retained in the gas tank causes the fuel to flash off or spit back when trying to fill the tank. I would not be surprised if the new three cylinder becomes standard across the line, just to get the exhaust away from the tank, and to relocate the tank and emissions system. JMHO

 

[Chupaca]

Curious..!!

how much gas. If tank is full how long will it take to boil..?? If moving temps will be below boiling so keeping tank fairly full should keep it from boiling on normal rydes. So a bit more wrapping should help...:thumbup:

 

[spacetiger]

This was a very common problem in the car world before EFI became the norm. I'm sure many remember vapor lock. Once EFI came into place, the fuel under the hood (where is was the hottest) was always under high pressure so gas changes between seasons vs the odd warm day in winter (for example) were not troublesome. When carburetors were used, the fuel in many places under the hood were not under very much pressure - if at all. I think the only place that had any pressure was between the fuel pump and carb. Everywhere else it was exposed to atmospheric pressure. Heat was a problem when winter gas was in the car and it was a hot day in winter.

Jerry

 

[OJ UK]

I had my Norton cut out on several occasions due to the fuel boiling in the carb. bowls.
I had to use Paxolin spacing pieces half an inch thick to stop the problem.
It was a common occurrence back in the 60s and 70s when using high octane (100+) fuel to
wring out every last drop of perormance from these old motors.
I recall that they also used to go BANG!! with seemingly alarming regularity!!

 

[Magdave]

I had my Norton cut out on several occasions due to the fuel boiling in the carb. bowls.
I had to use Paxolin spacing pieces half an inch thick to stop the problem.
It was a common occurrence back in the 60s and 70s when using high octane (100+) fuel to
wring out every last drop of perormance from these old motors.
I recall that they also used to go BANG!! with seemingly alarming regularity!!

Norton Commando :thumbup:

 

[OJ UK]

Norton Commando :thumbup:

Actually no....it was an Atlas! The Commando frame was a nightmare.
The Atlas although still a 750cc retained the 'Featherbed' frame and magneto
ignition. And was also a 6volt system. I modified mine for 12volts quite early on.

 

[Bob Denman]

So; the electricals weren't by Lucas: the Prince of Darkness?? :shocked:

 

[OJ UK]

So; the electricals weren't by Lucas: the Prince of Darkness?? :shocked:

Yes they were indeed!...I have to be honest and say that despite their nasty cheap construction the Lucas stuff
seldom gave me any problems. Their spares prices were frightening! :yikes:

 

[Bob Denman]

I heard that Lucas also makes refrigerators... :shocked:







...and THAT'S why the British, don't drink their beer cold!! :cheers: :roflblack:



Okay; I'm done "Brit-Picking" ... we now return you to the arts...

 

[OJ UK]

I really, sincerely hope that you do not want me to justify that remark with a reply!!
I am a paid up member of CAMRA and I have just returned from my local REAL ALE Pub
with two pints of an extremely nice ale at 5.9ABV and two pints of even nicer Strawberry
Cider at around 7.1ABV (hic!!)
The only reason to drink beer at well below room temperature is because it tastes like....:shocked:!!
Ice cold Bud draft in a 'Sports Bar' on your side of the pond is around 2.8ABV....YECH!!

 

[3 Wheel Addict]

This was a very common problem in the car world before EFI became the norm. I'm sure many remember vapor lock. Once EFI came into place, the fuel under the hood (where is was the hottest) was always under high pressure so gas changes between seasons vs the odd warm day in winter (for example) were not troublesome. When carburetors were used, the fuel in many places under the hood were not under very much pressure - if at all. I think the only place that had any pressure was between the fuel pump and carb. Everywhere else it was exposed to atmospheric pressure. Heat was a problem when winter gas was in the car and it was a hot day in winter.

Jerry

Vapor lock in a car is a very different problem than boiling in the tank. Vapor lock is caused by heat AND gasoline under vacuum, the vacuum reduces the boiling point of gasoline and then it don't take very much ambient temp to cause it to boil in the suction line. Pumps can not pump vapor then you get the vapor lock. EFI did cure this by placing the pump in the cool fuel tank. Motorcycle EFI system still have issues with this "boiling fuel" in the lines. This is why when you turn the key on the pump cycles for a few seconds before you can start the motor. Sometimes when it's really hot and you listen close you can hear the vapor bubbles being pushed through the system back into the tank before you start up. My 2002 Goldwing had a problem with this on really hot days and sometimes would stall out requiring it to be restarted. Honda installed an update to the ECM causing the pump to cycle just a bit longer upon turning the key on and I was instructed to not crank the bike until I heard the pump stop cycling. Could be why we have the start delay built into the Spyders.

 

[NancysToy]

Vapor lock in a car is a very different problem than boiling in the tank. Vapor lock is caused by heat AND gasoline under vacuum, the vacuum reduces the boiling point of gasoline and then it don't take very much ambient temp to cause it to boil in the suction line. Pumps can not pump vapor then you get the vapor lock. EFI did cure this by placing the pump in the cool fuel tank. Motorcycle EFI system still have issues with this "boiling fuel" in the lines. This is why when you turn the key on the pump cycles for a few seconds before you can start the motor. Sometimes when it's really hot and you listen close you can hear the vapor bubbles being pushed through the system back into the tank before you start up. My 2002 Goldwing had a problem with this on really hot days and sometimes would stall out requiring it to be restarted. Honda installed an update to the ECM causing the pump to cycle just a bit longer upon turning the key on and I was instructed to not crank the bike until I heard the pump stop cycling. Could be why we have the start delay built into the Spyders.

I'm afraid I have to disagree to some extent. Although a vehicle with an engine mounted fuel pump can have gasoline subject to a vacuum, fuel injected (i.e. modern) vehicles have the fuel pumps in the gas tanks, so those fuel lines are under constant pressure. Vapor lock can occur on either side of the fuel pump...and is often very near the carburetor on some cars...a point normally under pressure. The fuel vaporization that causes vapor lock is actually the equivalent of "boiling" fuel...but it is not often caused by fuel boiling in the tank. It does, however, take a lot less heat to vaporize the fuel when it is already so hot that it is near the boiling point.

 

[jaherbst]

I'm afraid I have to disagree to some extent. Although a vehicle with an engine mounted fuel pump can have gasoline subject to a vacuum, fuel injected (i.e. modern) vehicles have the fuel pumps in the gas tanks, so those fuel lines are under constant pressure. Vapor lock can occur on either side of the fuel pump...and is often very near the carburetor on some cars...a point normally under pressure. The fuel vaporization that causes vapor lock is actually the equivalent of "boiling" fuel...but it is not often caused by fuel boiling in the tank. It does, however, take a lot less heat to vaporize the fuel when it is already so hot that it is near the boiling point.

That is correct and I would have to second that.