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Alcohol in gas affects mixture

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Bonnewagon
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Alcohol in gas affects mixture

Postby Bonnewagon on Fri Jun 21, 2013 7:05 am

1983 Pontiac Bonnewagon, 1979 Pontiac 301, 4 speed Saginaw, 1980 TA 301 Q-jet set to 1979 TA w/301 specs: #70 jets, #44 rods. I was getting some detonation on takeoff, as well as in high gear, for no good reason, driving me bonkers for several years now. Ignition timing was conservative, EGR working. I decided to rebuild the Q-jet and when I opened it, the gas was gone from just yesterday, evaporated away overnight,the bowl was just damp. I found nothing wrong but on a hunch I decided to richen up the primary jets by 3 numbers, to #73 jets, same rods. The change was dramatic. NO detonation, pulls like it grew 2 cylinders, idles better, runs cooler. Now, this set up is even richer than a Pontiac 400 would have normally needed , yet this little 301 eats it up. All I can deduce is that the alcohol in the gas has changed the density of the fuel, requiring a richer mixture for the same power as before. The rate of evaporation is increased, so yeah, after a couple of days, the bowl is dry, answering all those "hard to start" posts. I am amazed.
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Re: Alcohol in gas affects mixture

Postby pontiacgp on Fri Jun 21, 2013 7:31 am

Alcohol in fuel raises the octane so I don't think that was the cause of the detonation. I wonder if it could be a carbon buildup that raise the combustion temps.
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Re: Alcohol in gas affects mixture

Postby Chris Van on Fri Jun 21, 2013 10:48 am

Alcohol raising the octane is not necessarily a good thing. Ethanol in fuel will cause nothing but problems in the long run unless your car is set up for it. Try some ethanol free gas one time and let us know. I have tried straight pump 93 octane (with 10% ethanol) and tried everything from that to about a 50-50 mixture and I can tell ya that my car ran the best on ethanol free 93 octane. Even better than 110 racing fuel.
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Re: Alcohol in gas affects mixture

Postby Bonnewagon on Fri Jun 21, 2013 12:28 pm

While alcohol may raise the octane, it has about one half the thermal energy of gasoline. I remember reading that alcohol racers needed to re-jet their carbs to double the volume of what they ran for gas. This motor has no carbon build up at all. It was rebuilt to stock specs and has less than 10K on it and always has had synthetic oil in it. Plugs burn a nice tan color. There is NO alcohol free gas available here in NYC, so that's all it has seen. I should add that the secondary rods remain the stock CH models, as I have found that the stock 301 can only flow so much at WOT and the stock CH rods all 301's are equipped with are perfect. Any slight variation up or down results in crummy performance. I think the added richness in the primary circuit overlaps into the overall mixture so even with the same the secondary side I get no pinging at WOT with a load. Steve I too was reluctant to believe such a jet change could be so dramatic and expected it to be an over-rich dog. But it immediately went from annoying pinging to smooth strong power. I even try to force it to ping by lugging the motor, like starting out in second gear. None. I got OK mileage before and I am currently logging my odometer to see if it goes to better or worse.
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Re: Alcohol in gas affects mixture

Postby jrm81bu on Fri Jun 21, 2013 2:01 pm

Bonnewagon wrote:While alcohol may raise the octane, it has about one half the thermal energy of gasoline. I remember reading that alcohol racers needed to re-jet their carbs to double the volume of what they ran for gas. This motor has no carbon build up at all. It was rebuilt to stock specs and has less than 10K on it and always has had synthetic oil in it. Plugs burn a nice tan color. There is NO alcohol free gas available here in NYC, so that's all it has seen. I should add that the secondary rods remain the stock CH models, as I have found that the stock 301 can only flow so much at WOT and the stock CH rods all 301's are equipped with are perfect. Any slight variation up or down results in crummy performance. I think the added richness in the primary circuit overlaps into the overall mixture so even with the same the secondary side I get no pinging at WOT with a load. Steve I too was reluctant to believe such a jet change could be so dramatic and expected it to be an over-rich dog. But it immediately went from annoying pinging to smooth strong power. I even try to force it to ping by lugging the motor, like starting out in second gear. None. I got OK mileage before and I am currently logging my odometer to see if it goes to better or worse.


It only has as much as 30% less thermal energy than gas and that is e85, 85% ethanol. So 10% ethanol would have a very minimal reduction in thermal energy. Yes for e85 you need more fuel to make the same power, e10 not so much. And it definetly wouldn't cause detonation. Just for reference I need to run 92 pump gas with my blower, I just filled up with a 60/40 mix of 89 pump and e85. I made no changes, didn't have any detonation, and it makes just as much power.
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Re: Alcohol in gas affects mixture

Postby Chris Van on Fri Jun 21, 2013 2:24 pm

Well my car ran worse with a mixture of 93 and E85. I have no scientific formula for coming to this conclusion but what I do have are the time slips to prove it.
And to me these scientific formulas that some of the smart guys are quick to throw around are like comparing dyno numbers to real on track ET's. If said engine/fuel type makes more power on the dyno than racer Joe's engine/fuel combination, that doesn't mean that dyno man can outrun racer Joe. When it comes down to it, real world scenerios do not always match up with engineer Bob's outcome on paper.
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Re: Alcohol in gas affects mixture

Postby Bonnewagon on Fri Jun 21, 2013 7:58 pm

OK well I'm no genius nor an engineer nor a chemist. I'm just a guy who likes to play with Q-jets. So someone tell me why a bone stock motor with a stock 1980 TA 301 Q-jet set up to a much richer 1979 TA 301 specs detonated all the time and then richening up the jets by 3 more numbers cured it. No other changes were made to anything and there were no vacuum leaks. I was tempted to fool with the vacuum advance first, but to prove a point to myself, I didn't. And how stock is this 33 year old carb? It still has rivets on the choke housing. I'm pretty sure I didn't accidentally "fix" something else during the rebuild.
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Re: Alcohol in gas affects mixture

Postby 79wagonator on Fri Jun 21, 2013 8:53 pm

Well.. being the gas alcohol mixture has less thermal energy even by just a small amount
Being jetted the same as for running pure gas it would run slightly lean thereby causing more heat
which in turn = Detonation!
Makes perfect sense to me..
Good call Bonnewagon..
Everybody knows your gas mileage sucks with E10 as compared to straight gas..
Not a problem with newer injected motors as fuel, air and timing is automatically adjusted to compensate.
Sucks for older cars like ours..
E10 is even worse for boats with constant loads on motor and fuel sitting for longer periods evaporating and absorbing moisture from the air with vented fuel systems. :?
Now there pushing for e15 in some states... F&*k That!!
Is it really helping in any way? I don't think so..
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Re: Alcohol in gas affects mixture

Postby jrm81bu on Fri Jun 21, 2013 9:31 pm

Chris Van wrote:Well my car ran worse with a mixture of 93 and E85. I have no scientific formula for coming to this conclusion but what I do have are the time slips to prove it.


What did you do to your set up to take advantage of the change? If you're not pushing detonation with you're set-up there isn't a lot to gain.

Bonnewagon wrote:OK well I'm no genius nor an engineer nor a chemist. I'm just a guy who likes to play with Q-jets. So someone tell me why a bone stock motor with a stock 1980 TA 301 Q-jet set up to a much richer 1979 TA 301 specs detonated all the time and then richening up the jets by 3 more numbers cured it. No other changes were made to anything and there were no vacuum leaks. I was tempted to fool with the vacuum advance first, but to prove a point to myself, I didn't. And how stock is this 33 year old carb? It still has rivets on the choke housing. I'm pretty sure I didn't accidentally "fix" something else during the rebuild.


I have every bit of faith that you know what your doing. I have no reason why anything you did fixed anything you had a problem with, but i'm guessing you are inlcined to believe you think your need for running pig rich is because of a tiny % of thermal output? Your comparison of the alcohol(methanol) drag racers needing to double up has nothing to do with the alcohol(ethanol) in your pump gas. They are two very different creatures.

79wagonator wrote:Well.. being the gas alcohol mixture has less thermal energy even by just a small amount
Being jetted the same as for running pure gas it would run slightly lean thereby causing more heat
which in turn = Detonation!
Makes perfect sense to me..
Good call Bonnewagon..
Everybody knows your gas mileage sucks with E10 as compared to straight gas..
Not a problem with newer injected motors as fuel, air and timing is automatically adjusted to compensate.
Sucks for older cars like ours..
E10 is even worse for boats with constant loads on motor and fuel sitting for longer periods evaporating and absorbing moisture from the air with vented fuel systems. :?
Now there pushing for e15 in some states... F&*k That!!
Is it really helping in any way? I don't think so..


You need to do more research. On e10 not changing your jetting would have almost no effect on you mixture let alone enough to go lean enough to cause a pinging issue. Your mileage shouldn't see any more of change than any other naturally occurring events would make it vary(wind, other drivers, your mood). Why would the "newer injected motors" not see a drop in mileage? They are programmed to target a certain mixture ratio, and if by your reasoning it would take more gas with ethanol in it to make that same ratio then they would lose the same mileage that any other vehicle would. Why would it be worse for an engine that sees constant loads? Yes ethanol absorbs moisture, it also hols it in suspension. The only time that causes a problem is when it gets more moisture than it can hold then it drops out. However the more alcohol, the more moisture it can actually hold, so a higher level is actually better in that respect.
And yes if it's handled correctly it can definitely help, however there is way too much politics involved in that for discussion here.
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Re: Alcohol in gas affects mixture

Postby gp02a0083 on Fri Jun 21, 2013 11:50 pm

I did a thesis on effects of ethanol blends with gasoline for my chemistry degree. Ethanol now is used among other components blended in our gasoline as we know to help reduce pre-detonation or knock. MTBE used to be used to help with this, but has been deemed a hazardous material and has long been phased out of gasoline. I tested various blends from pure gasoline (0% Ethanol) to 20-25%. When you start going past 10% ethanol, the energy per unit due to the combustion starts to decrease rapidly to about 30% when you have 20% ethanol. It does not really make the combustion favorable, the only benefit of the ethanol at this point is the fact it burns colder. IIRC it will allow you to run more timing. If you look at a balanced combustion reaction, you will need a bit more ethanol and emissions would yield more water vapor. The comparison between ethanol and methanol is not correct. They both have different related enthalpies, basically even though they are alcohol's they are that much different.
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Re: Alcohol in gas affects mixture

Postby 79wagonator on Sat Jun 22, 2013 8:25 pm

jrm81bu wrote:
Chris Van wrote:Well my car ran worse with a mixture of 93 and E85. I have no scientific formula for coming to this conclusion but what I do have are the time slips to prove it.


What did you do to your set up to take advantage of the change? If you're not pushing detonation with you're set-up there isn't a lot to gain.

Bonnewagon wrote:OK well I'm no genius nor an engineer nor a chemist. I'm just a guy who likes to play with Q-jets. So someone tell me why a bone stock motor with a stock 1980 TA 301 Q-jet set up to a much richer 1979 TA 301 specs detonated all the time and then richening up the jets by 3 more numbers cured it. No other changes were made to anything and there were no vacuum leaks. I was tempted to fool with the vacuum advance first, but to prove a point to myself, I didn't. And how stock is this 33 year old carb? It still has rivets on the choke housing. I'm pretty sure I didn't accidentally "fix" something else during the rebuild.


I have every bit of faith that you know what your doing. I have no reason why anything you did fixed anything you had a problem with, but i'm guessing you are inlcined to believe you think your need for running pig rich is because of a tiny % of thermal output? Your comparison of the alcohol(methanol) drag racers needing to double up has nothing to do with the alcohol(ethanol) in your pump gas. They are two very different creatures.

79wagonator wrote:Well.. being the gas alcohol mixture has less thermal energy even by just a small amount
Being jetted the same as for running pure gas it would run slightly lean thereby causing more heat
which in turn = Detonation!
Makes perfect sense to me..
Good call Bonnewagon..
Everybody knows your gas mileage sucks with E10 as compared to straight gas..
Not a problem with newer injected motors as fuel, air and timing is automatically adjusted to compensate.
Sucks for older cars like ours..
E10 is even worse for boats with constant loads on motor and fuel sitting for longer periods evaporating and absorbing moisture from the air with vented fuel systems. :?
Now there pushing for e15 in some states... F&*k That!!
Is it really helping in any way? I don't think so..


You need to do more research. On e10 not changing your jetting would have almost no effect on you mixture let alone enough to go lean enough to cause a pinging issue. Your mileage shouldn't see any more of change than any other naturally occurring events would make it vary(wind, other drivers, your mood). Why would the "newer injected motors" not see a drop in mileage? They are programmed to target a certain mixture ratio, and if by your reasoning it would take more gas with ethanol in it to make that same ratio then they would lose the same mileage that any other vehicle would. Why would it be worse for an engine that sees constant loads? Yes ethanol absorbs moisture, it also hols it in suspension. The only time that causes a problem is when it gets more moisture than it can hold then it drops out. However the more alcohol, the more moisture it can actually hold, so a higher level is actually better in that respect.
And yes if it's handled correctly it can definitely help, however there is way too much politics involved in that for discussion here.

I guess I wrote it wrong, newer motors see a drop in mpg also is what I've heard from people in areas where pure gas and e10 is available
On LI only e10 is available.
As far as the high performance boating community, nobody likes the e10 which in my area is whats sold at the docks also.
And being able to absorb more moisture cant be a good thing..
I'm no scientist but Last I checked, water doesn't burn
I drain the fuel tank in the boat at the end of every season and burn it in my truck.
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Re: Alcohol in gas affects mixture

Postby CWPottenger on Sat Jun 22, 2013 8:44 pm

jrm81bu wrote:And yes if it's handled correctly it can definitely help, however there is way too much politics involved in that for discussion here.


Totally agree with that statement.

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Re: Alcohol in gas affects mixture

Postby Clone TIE Pilot on Sun Jun 23, 2013 12:26 am

It's pretty simple, a motor set up to burn gas won't have enough compression to properly burn ethanol. If it did, it would spark knock badly running on just gas. Cliff who is one of the top Qjet guys around says ethanol leans out the fuel mixture on older engines because they are not set up to burn it. It's just 10% inert filler to a gasoline engine, so you must enrich your mixture to make up for it. Ethanol has an -OH group in its chemical formula. That OH group is IN THE FUEL, you can not get rid of this -OH group. The only way to do so is to run straight gasoline. This extra oxygen IN THE FUEL, combined with the oxygen in the air (approximatley 21% O2, 78% N2) leans out your engine if you have a carbed motor. So basically you have extra oxygen in your fuel which changes the chemical equation from stoich and causes a lean burn, which results in higher flame temps. By having this leaner mixture, your jetting would need to be a size or two richer to compensate. A perfectly running engine uses 14 parts air to 1 part fuel. If that one part fuel is 100% fuel then your ratio is a perfect 14:1 When you introduce ethanol it uses up a percentage of the 1 part fuel. For example if you are running 15% ethanol then your new ratio is leaned out to 14:0.85. Ethanol burns at a different air/fuel ratio. It takes more ethanol for the same amount of air. An E10 combo is going to take slightly more fuel than straight gas for the same amount of air.
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Re: Alcohol in gas affects mixture

Postby Bonnewagon on Sun Jun 23, 2013 9:41 am

Now THAT is what I was thinking. ^^^^^^^^ Thank's Clone TIE Pilot for putting it in technical terms that make sense.
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Re: Alcohol in gas affects mixture

Postby jrm81bu on Sun Jun 23, 2013 5:30 pm

79wagonator wrote:And being able to absorb more moisture cant be a good thing..
I'm no scientist but Last I checked, water doesn't burn


Yes and no. Water in gas is a bad thing because they won't mix. The gas will float on the water and all you get out of the pickup is water. However since the alcohol in e10 will absorb the water it does get burnt because it gets all mixed together. Water is nothing more than hydrogen and oxygen, both of those elements burn when separated.
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