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hambone71
Samba Member
Joined: November 12, 2006
Posts: 52
Location: North Carolina
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 Posted: Wed Aug 21, 2019 11:00 am Post subject: Ethanol free gas question |
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I have a 71 Bus with a 1776. I tried to run some ethanol free gas a couple years ago and the bus wouldn’t run on it. I drained the tank and put regular octane fuel in it and it ran. Do I just need to rejet the carb -German 34 pict 3- or just re- tune the carb? If I remember correctly, I am running a 127.5 main jet and a 55 idle jet. Thanks.
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Last edited by hambone71 on Wed Aug 21, 2019 11:57 am; edited 1 time in total |
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cmonSTART
Samba Member
Joined: July 15, 2014
Posts: 1915
Location: NH
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| Posted: Wed Aug 21, 2019 11:10 am Post subject: Re: Octane free gas question |
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.....ethanol free?
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52366
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| Posted: Wed Aug 21, 2019 6:49 pm Post subject: Re: Ethanol free gas question |
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| I have jetted all my old rigs a jet size richer since ethanol laced fuel showed up at the pumps. This would make then run rich should I go back to ethanol free fuel. |
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cdennisg
Samba Member
Joined: November 02, 2004
Posts: 20829
Location: Sandpoint, ID
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| Posted: Wed Aug 21, 2019 9:00 pm Post subject: Re: Ethanol free gas question |
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| hambone71 wrote: |
| I have a 71 Bus with a 1776. I tried to run some ethanol free gas a couple years ago and the bus wouldn’t run on it. I drained the tank and put regular octane fuel in it and it ran. Do I just need to rejet the carb -German 34 pict 3- or just re- tune the carb? If I remember correctly, I am running a 127.5 main jet and a 55 idle jet. Thanks. |
Do you mean it wouldn't run at all? Or just wasn't running as well as before?
If the former, there are other issues, if the latter, then some jetting changes may be in order. Switching to a non-ethanol blended fuel should, in theory, make your bus run slightly better, especially in hot weather under heavy loads.
My old 70 Riviera always liked non-ethanol fuel in the hot summer months when highway driving and climbing mountain passes. Helped with engine run-on and hot start issues, too.
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cdennisg
Samba Member
Joined: November 02, 2004
Posts: 20829
Location: Sandpoint, ID
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| Posted: Wed Aug 21, 2019 9:01 pm Post subject: Re: Ethanol free gas question |
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| Wildthings wrote: |
| I have jetted all my old rigs a jet size richer since ethanol laced fuel showed up at the pumps. This would make then run rich should I go back to ethanol free fuel. |
I do the same. But have never run into an issue when running a few tanks of pure gas in the summer months.
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SGKent 
Samba Member
Joined: October 30, 2007
Posts: 42591
Location: at the beach
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| Posted: Wed Aug 21, 2019 9:06 pm Post subject: Re: Ethanol free gas question |
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ethanol carries oxygen in the chemical structure. That makes the mixture leaner for any given amount of ethanol fuel. Mike went up a main jet size to compensate for that. Usually 3 air correction jets equal one main so maybe he could have tried one or two air correction jets smaller first. A wide band 02 sensor would get it near dead on. Regardless I see what he did and it is quite logical.
Summer is usually hotter and more humid which means less dense air. A mixture that is perfect in winter will be richer when hot and humid. If adding ethanol made the bus run better that likely means it is a bit rich. We used to see it at the track. Someone would do the oppisite. They would jet during the afternoon practice laps when it was hotter and more humid. In the morning their engines would be run racing and the extra lean they would detonate and destroy the engine. Same kind of problem was true if they jetted in cold dry morning practice laps but didn't run until afternoon when it was hotter and more humid. They would stumble around the track a little too rich. The trick was knowing what the weather would be like when you actually raced so you could jet for that. Before 02 sensors came along, reading the weather, cold fronts, afternoon temps, humidity was part of winning or not.
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Spike0180
Samba Member
Joined: June 06, 2015
Posts: 2269
Location: Detroit, Michigan
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| Posted: Thu Aug 22, 2019 4:22 am Post subject: Re: Ethanol free gas question |
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| hambone71 wrote: |
| I have a 71 Bus with a 1776. I tried to run some ethanol free gas a couple years ago and the bus wouldn’t run on it. I drained the tank and put regular octane fuel in it and it ran. Do I just need to rejet the carb -German 34 pict 3- or just re- tune the carb? If I remember correctly, I am running a 127.5 main jet and a 55 idle jet. Thanks. |
Just run the gas your van runs on.
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Brutis Patches Izabich: 1970 VW Transporter - 1776cc DP
Current State: Projects never truly end...
Location: Grosse Pointe, Michigan
Other cars: 2003 F150, 2003 Jetta GLI vr6-6sp
Sambastic: adj; the quality of being nit picky, elitist, expecting everyone to do things the way they believe is best with no regard to situation, "sambastic" |
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hambone71
Samba Member
Joined: November 12, 2006
Posts: 52
Location: North Carolina
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| Posted: Thu Aug 22, 2019 6:43 am Post subject: Re: Ethanol free gas question |
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That’s what I’ll probably do. Just curious to see how it would run on real gas.
I may re jet sometime and let you know.
Thanks
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Abscate
Samba Member
Joined: October 05, 2014
Posts: 23891
Location: NYC/Upstate/ROW
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| Posted: Thu Aug 22, 2019 7:09 am Post subject: Re: Ethanol free gas question |
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Lets do the math
Ill pretend cars run on a 14:1 mass ratio of air to fuel
Air is only 20% oxygen, so that means about 3:1 oxygen to fuel mass ratio.
Ill pretend fuel is mostly octane, C8H18, molecular mass is 114 g mol
Ethanol is C2H6O, molecular mass 46 g per mole, 16 of which is Oxygen
So Gas with 10% ethanol by weight adds...
100g of Gas/ethanol has 90g of octane, and 10g of ethanol
That 10g of ethanol contains 10g *( 16/46) or 3 g of Oxygen, rounding a bit
That same 100g of fuel needs 300g of oxygen (contained in 1400g air)
And so 10% ethanol is adding 1%, or 3g/300g of available oxygen to the burn equation.
How does that look?
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WhirledTraveller
Samba Member
Joined: January 09, 2008
Posts: 1414
Location: Cambridge, MA
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| Posted: Thu Aug 22, 2019 7:21 am Post subject: Re: Ethanol free gas question |
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| Abscate wrote: |
Lets do the math.....
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Ethanol doesn't just add oxygen, it subtracts carbon from a given volume of fuel. No need to reinvent the wheel, the math has been done. Stoichiometric on "pure gas" is 14.7 Air to Fuel ratio on a mass basis. Stoichiometric on 10% ethanol is 14.1. There is a minor variation in density between the fuel, but it's pretty inconsequential, so doesn't really affect our calculation much between mass and volume. Point being the engine needs to be tuned to inject approximately 4% more fuel to achieve a stoichiometric mixture compared to "regular" gas.
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hambone71
Samba Member
Joined: November 12, 2006
Posts: 52
Location: North Carolina
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| Posted: Thu Aug 22, 2019 7:39 am Post subject: Re: Ethanol free gas question |
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🤯 Too technical for me 😂
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cmonSTART
Samba Member
Joined: July 15, 2014
Posts: 1915
Location: NH
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| Posted: Thu Aug 22, 2019 7:46 am Post subject: Re: Ethanol free gas question |
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+10 Samba points for the use of "Stoichiometric."
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AlmostHeavenWV_VW
Samba Member
Joined: October 12, 2017
Posts: 1968
Location: WV
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| Posted: Thu Aug 22, 2019 9:31 am Post subject: Re: Ethanol free gas question |
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Ethanol blends vary between brands did to additives and the denaturant used. Also ethanol produces 33% less energy per gallon vs pure gas.
I take this to mean, find a station/brand who you wish to use and stick with them for consistency in the gas you receive( whether you buy E10, or non ethanol)
| Quote: |
The energy content of ethanol is about 33% less than pure gasoline. The impact of fuel ethanol on vehicle fuel economy varies depending on the amount of denaturant that is added to the ethanol. The energy content of denaturant is about equal to the energy content of pure gasoline. In general, vehicle fuel economy may decrease by about 3% when using E10 relative to gasoline that does not contain fuel ethanol |
https://www.eia.gov/tools/faqs/faq.php?id=27&t=10
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 42591
Location: at the beach
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| Posted: Thu Aug 22, 2019 9:37 am Post subject: Re: Ethanol free gas question |
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| AlmostHeavenWV_VW wrote: |
Ethanol blends vary between brands did to additives and the denaturant used. Also ethanol produces 33% less energy per gallon vs pure gas.
I take this to mean, find a station/brand who you wish to use and stick with them for consistency in the gas you receive( whether you buy E10, or non ethanol)
| Quote: |
The energy content of ethanol is about 33% less than pure gasoline. The impact of fuel ethanol on vehicle fuel economy varies depending on the amount of denaturant that is added to the ethanol. The energy content of denaturant is about equal to the energy content of pure gasoline. In general, vehicle fuel economy may decrease by about 3% when using E10 relative to gasoline that does not contain fuel ethanol |
https://www.eia.gov/tools/faqs/faq.php?id=27&t=10 |
from white papers, many progressive states, and environmental groups are pushing for E15 instead of E10. It cannot be burned in cars older than 2001 without damaging the cars according to fuel & auto industry specialists, and air board analysts. I already have to drain many of my lawn type items because of the damage E10 does to them if it is left in them after each use. I got tired of replacing diaphragms and gaskets annually in their carbs. It absolutely would destroy my fuel hoses in a Mercury outboard annually until I sold it. let the next guy deal with it. My neighbor across the street had the same problem with his boat, even though it was only a couple years old.
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Abscate
Samba Member
Joined: October 05, 2014
Posts: 23891
Location: NYC/Upstate/ROW
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| Posted: Thu Aug 22, 2019 9:55 am Post subject: Re: Ethanol free gas question |
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| Quote: |
| Ethanol blends vary between brands did to additives and the denaturant used. Also ethanol produces 33% less energy per gallon vs pure gas. |
Thats the key. The loss of energy content in ethanol is where you lose efficiency, for a 10% mix, you lose 10% of 33% or 3% total loss. That comes from the fact the ethanol is already partially oxidized (or burned) vs an alkane.
A C-O-H bond is easier to break than a C-H so less energy is recovered
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cdennisg
Samba Member
Joined: November 02, 2004
Posts: 20829
Location: Sandpoint, ID
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| Posted: Thu Aug 22, 2019 3:10 pm Post subject: Re: Ethanol free gas question |
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| Abscate wrote: |
| Quote: |
| Ethanol blends vary between brands did to additives and the denaturant used. Also ethanol produces 33% less energy per gallon vs pure gas. |
Thats the key. The loss of energy content in ethanol is where you lose efficiency, for a 10% mix, you lose 10% of 33% or 3% total loss. That comes from the fact the ethanol is already partially oxidized (or burned) vs an alkane.
A C-O-H bond is easier to break than a C-H so less energy is recovered |
For the record, the fuel efficiency in my daily driver (1987 Toyota pickup with 22R carbed) dropped by 8-10% with the switch to ethanol blended fuel. Still not enough gain/loss to justify burning the outrageous and not-justified high cost of pure gas.
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Daisy71Kombi
Samba Member
Joined: July 21, 2011
Posts: 141
Location: post falls ID
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| Posted: Fri Aug 23, 2019 4:05 am Post subject: Re: Ethanol free gas question |
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I've heard stories about ethanol gas hurting the vehicles while they sit. They would take them apart and noticed problems that if it had been sitting for years with non ethanol gas there wasn't this problem. I think the carburetors would have the most issues.
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Spike0180
Samba Member
Joined: June 06, 2015
Posts: 2269
Location: Detroit, Michigan
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| Posted: Fri Aug 23, 2019 10:23 am Post subject: Re: Ethanol free gas question |
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Don't mind me.
https://www.haltech.com/how-flex-fuel-control-works/
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Brutis Patches Izabich: 1970 VW Transporter - 1776cc DP
Current State: Projects never truly end...
Location: Grosse Pointe, Michigan
Other cars: 2003 F150, 2003 Jetta GLI vr6-6sp
Sambastic: adj; the quality of being nit picky, elitist, expecting everyone to do things the way they believe is best with no regard to situation, "sambastic" |
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