How to mix a fuel for mpg?
 

Let me explain,

Oh hi, I am new here. I've lurked and read here and there for a few years but finally signed up today as I have an experiment I want to try.

I have a Honda Super Cub with a 90cc (84) motor. On hypermiling trips 25 mph "cruise" I have managed to get it up to 350 mpg. The bike is bone stock and has about 179k miles on it (so it's getting very old).

Now I'm interested in mixing a fuel that has a little more BTU and also one that would allow me to run leaner without overcooking anything. I'm toying around with the idea of mixing some petrol and diesel together but am wondering if anyone has tried that, and also if it's possible to try mixing a tiny amount of meth/water in with the petrol to create a possible detonation suppressant so I can run the bike leaner than normal. I know it's risky, but I am interested PURELY for the fun aspect of things and seeing how high I can get the mpg figure.

P.S. I know that to gain a greater efficiency out of the bike I need to mechanically change things like the compression ratio, intake manifold and ports, exhaust baffles, etc. I am looking for a "pour and play" solution. Thanks!

Diesel will make your bike stink to anyone that's behind. It also may make your engine knock. It will also make it run leans since the viscosity is higher than gas, less will flow through the carburator jets. A fairing would help your mpg, if it doesn't have one already. Maybe a front sprocket with another tooth or riding with a big tail wind or pushing it up hills.

http://craigvetter.com/pages/470MPG/470MPG%20Main.html

I would suggest looking into adding a specific type of ash-less two stroke oil ("TC-W3") as a gasoline additive. The ratio varies from 1oz TC-W3 to 4 gallons of gasoline to 1oz TC-W3 to 5 gallons of gasoline; I use the 1 to 5 ratio (a 1 to 640 ratio). This will not increase BTU (it will probably reduce it very, very slightly), but it will increase lubricity and act as a top end lubricant. I use this in my own car, and yes -- I have seen increases in mileage.

methanol does have a relatively high octane rating, however it's energy content is also pretty low, along with a REALLY low stoich AFR are not going to help at all.... without rejetting, you would be running dangerously lean.

Directory:Acetone:Rumbolt's 2-Stroke - PESWiki

This corresponds to 3oz/10 gal.

The first thing I noticed was an immediate increase in idle rpm by 1000rpm! I had to reset the idle screw. I also noticed that the mixture screw had to be reset for max rpm. I had to close it a bit.

I have now had a half dozen flights with acetone in the fuel. Further, the fuel has been allowed to sit in the plastic tank for 3 weeks with no apparent degradation.

My paramotor typically uses about 1 gal of fuel per hour of flight. Last night I flew for 0.9 hr and used only 1/2 gal of fuel! (90% gain?) I have also noticed a 1000rpm increase in max rpm while flying. This means more power!

Usually after a flight, I have to wipe the oil off the prop. (The unburned exhaust goes thru the prop.) I have seen a dramatic decrease in oil on the prop, indicating better burning of the fuel.

The spark plug is showing a good brown coloring, and I have seen no carbon buildup on the piston. Carbon buildup is typical of these engines.

In short, I have found acetone to be beneficial in small 2 stroke engines too!



GP-7 2-stroke racing oil

GP7 has PIB which has been documented to increase mpg for 2 strokes. Not cheap though.

PIB = polyisobutylene?

....

Thanks for the replies so far,

I've tried 2 stroke oil at a 1:100 ratio and have seen a small increase (10% ish) due to the the fuel mixture leaning out. I am not entirely convinced it's due to it being a top end lube though, seems how the mixed in oil only comes in contact with the piston crown and the tops of the valves and everything else is lube via the oil pump. Smells great though!

The bike runs a bit too hot though so I that's why I was looking for a detonation suppressant and something to cool the operating temps in general so I could run it a bit leaner and get a gain that way.

Oh, and I already have a taller ratio setup on the bike, and it's kind of a pig now to be honest. Gears are way too far apart for the measly 7 bhp motor.

Just don't cheap out and use too little oil or borrow your parents regular motor oil. If you try the acetone...find a Sally's Beauty Supply and buy a quart there...even KleanStrip acetone may be adulterated.

Try the 1 to 640 ratio I mentioned; it works very well.

I still have yet to burn off the current tank..:D I'll give it a shot when I run out of petrol.

Petrol and diesel together.

I have tried it in my engine and found that the timing needs to be retarded a bit and the diesel will settle to bottom of the tank and get picked up first.
I did also notice that after running it for a short time there was a bit of carbon build up on the pistons eg it permanently raised the compression when I went back to straight fuel.

Acetone belongs at the unicorn corral.

To make a fuel that improves MPG you have to increase the heat content. As a rule, heat content goes up as one moved down the distillate column. Kerosene and diesel have more heating value than gasoline, but they reduce the octane of the gas.

Now a Super Cub does not have all that high a compression, so you probably can lower the octane a bit and still run.

I'd suggest removing the fuel hose from your tank and try mixes of kerosene and gasoline. Use regular unleaded as a base. Regular has (slightly) higher heating value than premium.

Kerosene won't stink like diesel. at one time U-boats ran on spark ignition engines that were fueled by kerosene.

Start with a 5% kerosene/95% RUG by volume mix. Rig up a temporary test tank to hold a cup or so of the mix. You don't want to mix up a lot until you figure what your final mix will be. Once its in the carburetor, start it up,and see how it runs.

If it runs make up some 10% kerosene mix. Repeat until the engine won't run on the mix. Clean out your carb and back down to the last mix that ran.

Make a gallon of mix and put it in the gas tank and ride the bike around, to see how it runs under load. If it knocks, back down some more.

Kerosene will make it harder to start as the vapor pressure is much lower than that of gasoline. In the cylinder, the gasoline flame is blow-torching the kerosene into combustion. You might want to go to a hotter spark plug.

You'll undoubtedly need a "leaner" mixture to have enough air for combustion. If it makes black smoke, you're too rich.

My guess is you can probably run 25% kerosene.

Heat value for kerosene is about 135,000 BTU/gal.
Heat value for RUG is about 120,000 BTU/gal.

So the heating value of a 25% kero mix would be about 124,000 BTU/lb or about 3% higher than for RUG.

^^ Good idea, I never thought of this. I think I'll give it a try, although unfortunately for me, it's a little harder to find kerosene. I don't mind the smell, a lot of things really stink over here anyway so I think I'll give the mixing process a try with diesel oil.

As for other suggestions, I tried the 640:1 mix for 1 liter but my mpg stayed exactly the same as with straight petrol, about 220 mpg. I can see how it's possible how it might help out a diesel like my Hyundai though.

With a 200:1 mix it goes to about 235, and a 100:1 mix I am around 240-50. 2 stroke oil that is. I have the same commute everyday so it's easy to compare mileages.


Another question, since the kerosene/diesel takes energy from the petrol's flame front to combust, is it same to say that it can act as a detonation suppressant? Or would the diesel, since being a "lower octane fuel" create a condition more prone to detonation?

Thanks all so far!

diesel does not combust / at all in gas engines
 

You could always try adding nitroglycerin to gasoline like Jerry Lewis's character in "The Nutty Professor" ;)

As the hydrogen content goes UP so does the energy content.

I just read about the octane rating of diesel and am going to pass on mixing it or even trying. Sure, high flash point, but I am not willing to drop my octane rating that low, even in a very low compression engine like my Honda.

I think serious that I am just going to keep adding 2 stroke oil to keep it leaning out and then occasionally blast it with some water up the intake to decarbonize it. :) Then when I figure a more sophisticated way to do an experiment, I'll give it a go.

Saint LaPointe sez....
 

There is an important chore by the fuel in preventing combustion from becoming too fast during the early first stage after the spark has started the burn or after the diesel fuel is injected. Gasoline is designed to not burn too quickly while diesel fuel is designed to ignite as soon as possible without lag or with a very short lag time. When gasoline burns too easily, there is knock near TDC. When diesel fuel burns too slowly, there is knock near TDC. Knock is the general category for abnormal combustion, such as detonation (with gasoline) and fuel knock with diesel fuel. When fuel burns uncontrollably, pressure piles up on top of the piston near TDC where the excess pressure cannot do much to turn the crank and make torque. Plus this condition causes damage to engine parts and is inefficient as well. It seems the engine gets the longest life from its parts when it runs most efficiently and yields the best mileage. Runaway combustion happens from a bad combination of fuel components for the application. BTW there is a weird spark plug being promoted in Detroit that claims to ignite all the fuel and air in the chamber in a single (instantaneous) burst at TDC thereby creating enormous efficiency and economy. Yeah, right.

With gasoline we seek a gradual flame propagation from spark ignition in first stage and rapid propagation in second stage. With a diesel we seek rapid flame propagation in both first and second stage. The diesel fuel is supposed to ignite immediately as it gets squirted into the hot cylinder. That is what we mean by compression ignition. The combustion is regulated by the rate of injection from the pump and injectors while the piston is moving down. With gasoline the rate of combustion is regulated by a kind of "peeling the banana" effect whereby outer layers of more stable ions are stripped from the rather large original fuel particles by the violent collision process. These initial particles combust somewhat gently even at the high temperature and pressure near TDC. The burn is controlled by peeling the banana and uncovering faster burning fragments under the top skin. Then more peeling reveals very fast burning Freds that urgently seek any Opel to mate with in the scarce condition part way down the cylinder where fewer and fewer free Freds and free Opels can be found. Any aid that could assist combustion in that part of second stage will be very welcome indeed because that is where many engines and fuels go wrong. That is where they allow combustion to peter out, even well before the exhaust valve opens. In gasoline engines, we need to get maximum pressure to occur at about 15-20 degrees past TDC. In diesels, we will see a "constant" pressure from about 15 to 75 degrees after TDC. Gasoline combustion is termed "constant" volume while diesel combustion is termed "constant" pressure. The quotes mean it is ideally constant, not actually.

You can appreciate that diesel fuel is not as complex as gasoline which consists of hundreds of ingredients that contribute to a very carefully designed layered burn scenario that we commonly find available in three different grades of octane rating. Too much octane rating and the burn may be slow while too little octane rating and the burn may proceed too quickly from lack of tolerance for heat and pressure. Altitudes affect the rate of burning as atmospheric pressure drops and we need a lesser octane rating in the mountains. Superchargers raise the demand for higher octane because of the higher intake pressures from the blower. To protect engines from knock, electron absorbers are put into gasoline--such as metals or fuel additives with a lot of methyl ions such as xylene, toluene, acetone, neopentane or neohexane--my choices. These additives and methyl ions add a great deal of vaporization to the fuel and that in turn can create cooling due to the latent heat of evaporation. IOW evaporation and vaporization cool the mixture as larger Fred fragments are allowed to form into many small fragments and improve efficiency. It takes energy to force the breakup. That energy comes from the linear and spin kinetic motions of the particles in the furnace. So cooling occurs and the mix is less likely to detonate and will in fact allow a smoother operating, more efficient engine.

Octane and speed of combustion are only superficially related. Octane rating is best seen as the tolerance for heat and pressure of a fuel. Octane rating is NOT a simple reference to the speed at which fuel propagates a burn because that speed is never a constant but always very different and random.

When good fuel layering exists and combustion progresses nicely, most if not all of the fuel in the cylinder gets burned and the specific fuel consumption rate is the lowest possible--perhaps below .400. Average good gasoline is .500. When fuel layering is poor and combustion falters part way through the burn, the specific fuel consumption rate is very high--perhaps over .700 as may be the case with ethanol blends. When atomic hydrogen or CH particles are peeled or released too soon, an explosion could be triggered and the engine might ping like the old cliche--an ashcan full of marbles. Hydrogen gas burns 8-10 times faster than gasoline which makes for many headaches of engine design. Each hydrogen molecule or H2 has absolutely no layering and resembles a naked stick of dynamite with a microscopic fuse. Hydrogen is an ideal fuel for fuel cells and rockets rather than internal combustion engines.

There was a temptation to employ large and heavy fuel molecules as mileage fodder. Heavy molecules yield more BTU when they burn and can give a longer range. However they might be sensitive to cracking in the chamber and might produce undesirable products (such as heavy alkanes that refuse to disassociate) during the peeling, may cause detonation and/or create sludge and varnish problems in the engine. They are okay for asphalt. The fuel student must know his stocks intimately and have tested the components carefully in the lab before selling the stuff. During the fuel crisis of 1973, many bad gasolines were thrown out into the street.

A mix that might work?
 

Notice that this uses BOTH diesel and acetone...etc...

.66 oz SI-1, 2.5oz acetone, 1oz xylene, 1oz #2 diesel fuel, and 1/2 oz of synthetic motor oil, per ten gallons of gasoline.

Red Line 60103 SI-1 Fuel System Cleaner

Amazon.com: Red Line 60103 SI-1 Fuel System Cleaner - 15 oz.: Automotive


Almost the same thing?

Chevron 67740 Techron Concentrate Plus Fuel System Cleaner - 12 oz. : Amazon.com : Automotive

I can buy this locally for $4 when on sale....