If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Volatility Question about Mixing Fuels
My understanding is that 100LL has a relatively low volatility to reduce the
chance of vapor lock. Whereas Mogas often has a higher volatility. With this in mind, what happens to the volatility if I mix 50% 100LL with 50% Mogas? Is the volatility of the mix the straight average of the two fuels, or is the net volatility higher than the straight average? Why do I ask? I'm considering running a "mix" in the RV-6 to save a few bucks. The FBO at my home field charges about $2.00/gallon more for 100ll than the nearby station charges for 93 octane, so a couple of 5 gallon tanks worth of fuel will save me $20 bucks. |
#2
|
|||
|
|||
Volatility Question about Mixing Fuels
My experience suggests that the volitility of 100LL is not always less then
mogas. I have seen 100LL 'fizz' like champagne in a drain test container when mogas from an airplane parked next to mine showed no volitility at all. This as at Albuquerque on a 100+ degree afternoon. He departed with no problems. My fizzing 100LL scared me enough that I stayed overnight and left in the early morning with cool fuel. Bill Daniels "Kyle Boatright" wrote in message . .. My understanding is that 100LL has a relatively low volatility to reduce the chance of vapor lock. Whereas Mogas often has a higher volatility. With this in mind, what happens to the volatility if I mix 50% 100LL with 50% Mogas? Is the volatility of the mix the straight average of the two fuels, or is the net volatility higher than the straight average? Why do I ask? I'm considering running a "mix" in the RV-6 to save a few bucks. The FBO at my home field charges about $2.00/gallon more for 100ll than the nearby station charges for 93 octane, so a couple of 5 gallon tanks worth of fuel will save me $20 bucks. |
#3
|
|||
|
|||
Volatility Question about Mixing Fuels
In article ,
"Kyle Boatright" wrote: My understanding is that 100LL has a relatively low volatility to reduce the chance of vapor lock. Whereas Mogas often has a higher volatility. With this in mind, what happens to the volatility if I mix 50% 100LL with 50% Mogas? Is the volatility of the mix the straight average of the two fuels, or is the net volatility higher than the straight average? Why do I ask? I'm considering running a "mix" in the RV-6 to save a few bucks. The FBO at my home field charges about $2.00/gallon more for 100ll than the nearby station charges for 93 octane, so a couple of 5 gallon tanks worth of fuel will save me $20 bucks. The volatility should be the average of the two. That said, the octane of the mix should be significantly higher than the average of the two, due to the fact that TEL boosts octane nonlinearly -- i.e. small amounts of TEL boost unleaded fuel, but large amounts do not boost it proportionately. |
#4
|
|||
|
|||
Volatility Question about Mixing Fuels
On Wed, 04 Apr 2007 03:37:54 GMT, Orval Fairbairn
wrote: In article , "Kyle Boatright" wrote: My understanding is that 100LL has a relatively low volatility to reduce the chance of vapor lock. Whereas Mogas often has a higher volatility. With this in mind, what happens to the volatility if I mix 50% 100LL with 50% Mogas? Is the volatility of the mix the straight average of the two fuels, or is the net volatility higher than the straight average? Why do I ask? I'm considering running a "mix" in the RV-6 to save a few bucks. The FBO at my home field charges about $2.00/gallon more for 100ll than the nearby station charges for 93 octane, so a couple of 5 gallon tanks worth of fuel will save me $20 bucks. The volatility should be the average of the two. That said, the octane of the mix should be significantly higher than the average of the two, due to the fact that TEL boosts octane nonlinearly -- i.e. small amounts of TEL boost unleaded fuel, but large amounts do not boost it proportionately. So does that mean that it would be OK to use 87 octane mogas because the octane would be raised by the 100LL? Steve in Michigan |
#5
|
|||
|
|||
Volatility Question about Mixing Fuels
Earl wrote:
So does that mean that it would be OK to use 87 octane mogas because the octane would be raised by the 100LL? Other than the fact that it would put you in violation of the regulations. The STC's don't have any provision for "custom blending". You can mix avgas and the minimum octane mogas (as indicated by your STC) in any ratio you want however. |
#6
|
|||
|
|||
Volatility Question about Mixing Fuels
Ron Natalie wrote:
Earl wrote: So does that mean that it would be OK to use 87 octane mogas because the octane would be raised by the 100LL? Other than the fact that it would put you in violation of the regulations. The STC's don't have any provision for "custom blending". You can mix avgas and the minimum octane mogas (as indicated by your STC) in any ratio you want however. Oops...forgot we are talking homebuilts here. |
#7
|
|||
|
|||
Volatility Question about Mixing Fuels
In article ,
Earl wrote: On Wed, 04 Apr 2007 03:37:54 GMT, Orval Fairbairn wrote: In article , "Kyle Boatright" wrote: My understanding is that 100LL has a relatively low volatility to reduce the chance of vapor lock. Whereas Mogas often has a higher volatility. With this in mind, what happens to the volatility if I mix 50% 100LL with 50% Mogas? Is the volatility of the mix the straight average of the two fuels, or is the net volatility higher than the straight average? Why do I ask? I'm considering running a "mix" in the RV-6 to save a few bucks. The FBO at my home field charges about $2.00/gallon more for 100ll than the nearby station charges for 93 octane, so a couple of 5 gallon tanks worth of fuel will save me $20 bucks. The volatility should be the average of the two. That said, the octane of the mix should be significantly higher than the average of the two, due to the fact that TEL boosts octane nonlinearly -- i.e. small amounts of TEL boost unleaded fuel, but large amounts do not boost it proportionately. So does that mean that it would be OK to use 87 octane mogas because the octane would be raised by the 100LL? Steve in Michigan The answer depends on the minimum octane requirements for your engine. |
#8
|
|||
|
|||
Volatility Question about Mixing Fuels
"Earl" wrote So does that mean that it would be OK to use 87 octane mogas because the octane would be raised by the 100LL? I would think you would want to find how to figure the reslulting blend's exact octane rating. Otherwise, if it were not high enough, you could end up creatings some pistons with special "flow through ports" in the piston's crowns. :-o Detonation would be a nasty price to pay for saving a couple bucks per tank. -- Jim in NC |
#9
|
|||
|
|||
Volatility Question about Mixing Fuels
"Orval Fairbairn" wrote in message
news In article , "Kyle Boatright" wrote: My understanding is that 100LL has a relatively low volatility to reduce the chance of vapor lock. Whereas Mogas often has a higher volatility. ... The volatility should be the average of the two. I don't know that I would assume that - vapor pressure can have some non-linear behavior. Example: When you add ethanol, the vapor pressure with 10% is higher than the vapor pressure at either 0% or 85%... That said, the octane of the mix should be significantly higher than the average of the two, due to the fact that TEL boosts octane nonlinearly -- i.e. small amounts of TEL boost unleaded fuel, but large amounts do not boost it proportionately. Yup. -- Geoff The Sea Hawk at Wow Way d0t Com remove spaces and make the obvious substitutions to reply by mail When immigration is outlawed, only outlaws will immigrate. |
#10
|
|||
|
|||
Volatility Question about Mixing Fuels
Bill Daniels wrote:
My experience suggests that the volitility of 100LL is not always less then mogas. I have seen 100LL 'fizz' like champagne in a drain test container when mogas from an airplane parked next to mine showed no volitility at all. This as at Albuquerque on a 100+ degree afternoon. He departed with no problems. My fizzing 100LL scared me enough that I stayed overnight and left in the early morning with cool fuel. Bill Daniels The volatility-(vapor pressure) of mogas changes with the season,locatiom & altitude--the plane with the straight mogas probably resided at Albuq. Whereas avgas keeps pretty much the same volatility, since it is designed for longer storage times,etc. "Kyle Boatright" wrote in message . .. My understanding is that 100LL has a relatively low volatility to reduce the chance of vapor lock. Whereas Mogas often has a higher volatility. With this in mind, what happens to the volatility if I mix 50% 100LL with 50% Mogas? Is the volatility of the mix the straight average of the two fuels, or is the net volatility higher than the straight average? Why do I ask? I'm considering running a "mix" in the RV-6 to save a few bucks. The FBO at my home field charges about $2.00/gallon more for 100ll than the nearby station charges for 93 octane, so a couple of 5 gallon tanks worth of fuel will save me $20 bucks. |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Alternate Fuels | john smith | Piloting | 0 | September 25th 05 03:10 AM |
Mixing PPG delta and PPG Durathane.....??? | Randall Shimizu | Home Built | 3 | November 5th 04 05:07 AM |
U-2 fuels ? | Lynn Coffelt | Military Aviation | 2 | May 29th 04 04:48 PM |
mixing 80 and 100 and autogas...? | R. Wubben | Owning | 5 | March 15th 04 03:28 AM |
Mixing construction materials | Neal Fulco | Home Built | 3 | October 7th 03 01:55 PM |