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Old Time Fuels


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Our local High School Auto Shop teacher would like to have me bring in my '31 Model A Roadster and run some emission tests on it using modern fuels and an approximation of the old time fuels used back in the twenties and thirties. About all I know is that they were pretty poor compared to todays blends and commonly referred to as "keroseney". I would suppose one could get pretty close by adding some amount of kerosene to a cheap unleaded fuel, but how to blend the mixture is a quandary. If anyone could supply a recipe, we would sure appreciate it.

Jim Uhl uhldwm@ak.net

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First of all....there is no such thing as "cheap unleaded fuel".

Let me give you a little background :

ALL gasoline contains roughly the same potential energy (which..incidentally, pount for pound, is more than most explosives !

The difference in fuels, is the flame-travel speed (what we call "octane rating"),. The slower the flame speed, the higher the octane. It does cost a trace more for the additive that slow the speed of the burn down (higher the compression ratio, the slower-burn the fuel you need to prevent "knock" or detonation - the harder you squeeze fuel, the closer you come to the point where it dosnt burn smoothly..it just goes "bang".... The SLOWER the burn and the higher the compression, the less energy is wasted as heat, more energy comes out in the form of mechanical energy.

Given our modern Federal/EPA fuel standards, ALL fuels sold in the United States MUST be manufactured to meet certain "clean burn" standards. You are not going to be able to find "old style" fuel. It simply does not exist in this country.

Another way modern fuel differs reduce pollution) is that its evaporation rate is much higher - so it is MUCH more prone to "vapor lock" than the old lower..ie..Ried Vapor Pressure fuels manufactured during the "carbuerator" era. This is why modern fuel systems MUST be completely sealed...so that the fuel dosn't "boil off" into the atmosphere.

The farther back in time you go, the lower the vapor pressure. As late as the mid 1920's, it was just about impossible to start a car on a cold day without some kind of "trick". For example, Packard had its "fuelizer" system (nothing more than an extra spark plug in the manifold...to give the fuel an extra "shot" before it got into the cylinders..

Modern cars have high pressure fuel pumps in their tanks, so the entire fuel line is under pressure, thus eliminating vapor lock (vapor lock occurs on the SUCTION side of a "diaphram" fuel pump...not the "pressure" side..always makes me laugh to see people with vapor locked cars....trying to cool the PRESSURE side of their fuel pumps...!

So - forget about trying to duplicate the fuels of other eras. Unless you want to build your own refinery, and hide it from the "feds"...aint gonna happen !

Pete Hartmann

Big Springs, AZ

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As Peter notes, you can't really remove additives from today's gasoline. So adding something like kerosene really won't allow you to duplicate the fuel of 70 years ago.

However, it should be possible to research and find out the typical composition of retail gasoline of the era of interest. Once you know what you are trying to make, you *might* be able to find the component parts. For example, I have heard that Coleman stove fuel is pretty much gasoline with out any additives. You might be able to use that as a base. I suspect that research will be the big problem for you, not the actual recreation of the fuel after you have done your research.

To learn more about gasoline you might want to check out the gasoline FAQ at:

http://www.faqs.org/faqs/autos/gasoline-faq/

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Some old( ~20 to 60) farm tractors were set up to use "distillate" fuel, kerosene really. The tractor would be started/warmed up on gasoline then valves switched to the distillate fuel. The real key to running on kero is a low compression engine. Your A has a sub 5 to 1 compression ratio correct?

Perhaps a posting on a old farm tractor site would produce some info. Another place would be a "hit and miss" engine site as these engines probably ran on similar fuel.

As for the emission test, will the engine be run under a load or just at idle? With a low compression the NOx will be pretty low. NOx Oxides of Nitrogen are formed when Nitrogen is subjected to high pressure and tempratures. Low compression, exhaust gas recirculation and/or less spark advance will reduce NOx formation. Unless the engine is under a load NOx should be low.

I suspect HC ( hydrocarbon, unburned fuel) to be pretty high with either fuel with kero being higher due to it's low vaporization. Also the lack of a power valve in the carb would tend to give a rich mixture during light throttle cruse.

As for CO ( Carbon Monoxide, half burned fuel) I'm unsure what the result would be.

The real problem with automotive emissions is that as the fuel mixture is changed to reduce one gas, another rises. There is a very narrow air fuel ratio ( 14.7 air to 1 gas) where these gasses are at their lowest point. This is fine for a pre catylic converter car, but a cat equiped car needs a slightly different mixture to keep the cats hot and active. The whole thing gets to be quite a control mess in short order. tongue.gif

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Hartman... how come you show up "unregistered"? Question to you... I add "lead' substitute to the gas I buy for the Model A, but have been told by a few folks it's not as good. I expected it wouldn't be the same as the old leaded fuels for the engines of this era but have you heard of the leaded gas called Ultra Blue? It supposedly is a high octane leaded fuel some race enthusiasts use. Too high an octane? Any other thoughts on lead additives? confused.gif

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Hi Pop !

First of all, my name is HARTMANN, not Hartman.

Secondly, you are asking the wrong guy - I am not educated enough in the mysteries of petrol chemistry to answer your question with any degree of competence. I can tell you this - and you may have seen the same reports, or summaries of these reports - while you can demonstrate in a laboratory, under extreme conditions, that NON leaded gas will cause valve and valve seat erosion. In the real world, unless you are operating your collector car continiously at very high power settings, the literature says we shouldn't have problems.

I have seen "octane inhancers" sold at my local auto parts store. Since modern "premium" is still over 92 octane, I would not expect significant detonation - pinging on even the highest compression cars, again, unless you are operating at extremely high power settings. ASo, I am not sure tha you need this kind of additive, nor, if you did (assuming some absurdly high compresson car with timing advanced too far) whether it does any good.

About the only "gas additive" I take seriously, is the "preservatives". Ordinary pump gasoline has a "shelf life" of about 7-9 months (somewhat longer if you can keep it very cold). The preservatives extend this somewhat.

Sorry...never heard of "Ultra Blue".

And I have NO clue why I occasionaly show up as an "anoym". ? ? ?

Pete Hartmann

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Heypop,

It seems like I read somewhere that there was no lead in gasoline during the Model A era. It was added at a later date. I wish I had more information on this. As far as octane rating goes, I don't believe you can hurt an engine by burning fuel with too high an octane rating. While a Model A certainly doesn't NEED high octane fuel, I understand your desire for the lead. I really don't think that is a cause for concern either.

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Thanks for the responses... I think what I'll do is post this as a thread on it's own and see what other kind of responses it will generate. Heck... if I don't need to keep getting can gas just to bring home and add 'lead' substitute to for use in the "A". I'll be happy as can be. It's better to be able to just pull into a station and "fill er' up" while watching the reaction of the folks at the pumps beside you anyway. smile.gif Most of my trips average 15-20 miles one way and maybe 2x a month, so I'm not over using her. I hope it lasts another 72 years and someone else can enjoy it. cool.gif

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