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Yes 35.7 mpg.  But, I recently returned from running a few errands (three stops in 12 miles) around this small town of 15,000 and my mileage dropped to 31.9.  It iwll likely drop further in the week with my short commute of less than 6 miles.  Yes, it is ok to ask a few questions when one post about high mileage results with their vehicle.  Some of these folks will cherry pick their routes to obtain impressive figures.

 

The old Opel vehicle was modified to run on gas vapors- at least from what I read.  I do not know what test track/route was utilized.  Am I correct that atomizing/vaporizing ethanol can/will also improve efficiency?  How do you do this?-Increase fuel pressure?- but does the engine control module (computer) compensate in other ways to minimize the changes?  Oh well, I'm getting out of my "area" and better let others with more mechanical and engineering knowledge take over.

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How to vaporize the fuel changes with the application. Some vehicles lend themselves to it, others dont. Everyone touts direct injection as the holy grail, but the results are less impressive on ethanol. With the properties of ethanol it makes more sense to run a wet manifold so you can take advantage of them. More time to get a complete vaporization is allowed when the fuel has to travel down the intake port rather than being shot directly into the chamber just before ignition. DI ethanol engines are leaving some efficiency on the table unless the fuel is heated considerably to maximize the vaporization.

 

To visualize the difference between vaporization and atomization, compare steam coming off a pot of boiling water and water sprayed from a windex bottle. The windex bottle is atomization, relatively large droplets in a spray. Vaporization is more like steam, its a vapor, very fine drops, much finer than a mist. You could also compare fog to rain, rain being the atomization.

 

If you can get the fuel to boil as it leaves the injector it will burn much more efficiently with less waste heat.  Heat itself isnt power.  Heat does little on its own to create work. It needs to be utilized to do work. Heat wont move something on its own, you need to channel it. Excess heat is a waste, and heating the engine beyond what it needs to run efficiently is waste. Far too much of gasoline's energy goes into heating the engine and water jacket only to be released into the air via the cooling system. When you utilize the engines heat to vaporize the fuel for a more complete combustion event, you are harnessing the heat and not as much goes to waste.

 

That is only one way to increase mileage and efficiency. There are others that have decent gains. Moving less mass, aerodynamic improvements, rolling resistance reductions, gearing, compression ratios, and sufficient torque production in the cruise RPM range with a low cruise RPM will also improve mileage. Build a light easy to move car with good aerodynamic properties, a high compression ethanol engine utilizing fuel vaporization, and you will achieve very good mileage even with a larger engine.

 

Have you noticed that even small engined cars of today seem to be mired in the 20s and low 30s in mpg despite very efficient engines using roller valvetrain, light reciprocating components, EFI, and overdrive transmissions with lock up converters? There were some cars in the 60s that got 25-30 mpg with a carb, not everything was a 8mpg hog. So why arent the new cars getting the same mileage? Check the curb weight. All that wiring for the bells and whistles adds up. Power this, heated that all add weight and mass to the vehicle. 250hp with 3600lbs to move is going to use more fuel than 350hp and 2500lbs to move. People want all the power accessories and the nice ride, plus there are safety concerns and strength requirements for the body itself. The weight makes a bigger difference than most people realize.

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Thumpin makes a good point about carb vs DI on ethanol. I will word it a bit different. Heat's real value in an IC a supporting role of the required fuel/air/ignition triangle for combustion (by assisting with fuel vaporization) and most importantly to cause the combustion mass to expand and push the piston down- period. The carb will likely get more air in because the charge is cooler and more compact even though the fuel must also come in thru the manifold and past the intake valve. We also get a bit more time to vaporize the fuel with a carb- though the DI may initially have finer mist but less time to finish full vaporization. The problem with DI and perhaps ethanol (IF) being less beneficial may indeed come from the DI's compression limit and injection timing being idealized for gas- ethanol would want even more compression or earlier injection to get the charge ready for ideal combustion.

 

Just my theory ;)

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It doesnt have to be a carb, it can be relocating the injectors farther up the intake tract. Something similar to a throttle body that doesnt have the blades in the way, or the blades above the injectors would be ideal. Sort of like the injector hat on a Top Fuel dragster engine, it dumps the fuel in above and below the blower rotors so the blower doesnt run dry and so they can get enough nitromethane in the engine.

 

Port injection works well on gasoline, and DI is intended for gasoline because of its limitations that are a reason for the requirement of more ethanol in the same configuration. The thing is the short length between the injector and the back of the valve doesnt leave much room for ethanol to do its thing with latent heat of vaporization, and DI would severely impact that too. Gasoline doesnt have that quality and adding more heat and length with gasoline creates new problems, such as puddles and fuel sticking to the port walls, distribution problems etc. That is why EFI injectors have been moved to right behind the valves and now inside the chamber. Its not about ethanol, its about gasoline.

 

Sure I am not an engineer, but I understand how the engines work, and what certain changes would do or might do. This is my opinion since I simply cant afford to buy a vehicle with DI and start testing with it. To me its like leaving something on the table that is a huge benefit with ethanol, and that is because it isnt a benefit with gasoline it is a detriment. When you switch the fuel and all the properties with it, you change the parameters and benefits. What works well with one doesnt work as well with the other if at all, and the one that isnt optimized will end up using more fuel even if it makes more power. Its the same thing that makes any engine that will run gasoline use more fuel with ethanol.

 

Until we can run ethanol on its own, I doubt any OEM will ever build a truly dedicated ethanol engine, they will just be capable of burning it and they just accept the lower mileage with ethanol. How many FFVs do you see that have never had E85 run in them? Until that changes the ideas will remain, turbos, DI, and keeping the heat out of the chamber and intake tract.

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Ron's Flying Toilet works pretty good for a few folks on E85 in the Bracket race world too. It injects very high above the manifold also. You ever mess with those Thumpin?

Are they not as "streetable" as a carb?

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Consider a small plate to plate heat exchanger at exhaust port heating intake air by traveling past exhaust heat. May port style injectors be utilized to spray this zone of hot intake? Fuel injectors more accurate and responsive as compared to carb.....but only if being able to vaporize the liquid fuel. If not advantage to carb sitting further away.

 

Now consider the advantage of DI as compared, per my best knowledge to date.....

 

1. No throttle plate, no hp wasted upon vaccum generation

 

2. The gas mix within combustion chamber does not have to meet critical proportions to combust or minimize pollution. IOW, when a diesel squirts the fuel the fuel mixes with first available oxygen and at some point combusts when proper ratio and heat arrive. Some of the air never mixes with the fuel. Thats ok. But, with aspirated fueled engines the mix has to be premeasured . All the air has to be within proper ratio. So, for instance low hp idling wastes lots of fuel with gas engine. The diesel needs only squirt the desired energy to the combustion zone to turn engine over. 

 

Burning ethanol DI has the nasty habit of greatly reducing chamber heat. Diesels rely on heat ignition, not a good thing for ignition. So, ethanol only reliable upon diesel cycle with incredible high compression rates and ultra high compression temperatures. Lots of mechanical waste (friction) with such high compression rates of 28:1 for instance. The mechanical waste more than offsets the efficiency gain of higher compression. Scandia, ethanol fueled bus engines run at very poor mpgs with diesel operation cycle.

 

Now, heating the liquid ethanol fuel and creating high psi vapor pressure with heat instead of mechanical injector pump a good thing for DI ignition efficiency. Also, heating the intake air maintains high chamber temps without high compression.

 

The high vapor pressure created much like a steam engine does with boiling water for high pressure only were using ethanol. Critical steam pressures of 2,000 psi common with modern steam engines. Refer to power utility turbine engines or the "Revolution" piston engine technology. 

 

Having a small cubic inch ethanol boiler feed by high pressure injector of ethanol not complicated or heavy if heated by hot exhaust gas. The fuel pressurized by vapor but still liquid for DI injector. Yes, the fuel would explode into vapor once released. 

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Oh, my reference to "critical" should instead refer to "super critical". This mentioned by Corey very interesting. At minimum pressure of close to 1,000 psi and temps of 241 C, ethanol has density of liquid but all vapor. This would appear easy to accomplish with such hot exhaust temps. Upon super critical conditions the fuel really takes on personality of another fuel. It would give the combustion engineers plenty of new frontiers.  Under hot conditions the exhaust could support super critical steam, 650 C and 35 MPA, somewhere 4,900 psi?

 

So, I guessing the SC ethanol would react with high energy with air upon the diesel cycle. Super critical steam, may be used as a thermal regulator for hot engines under max power to push thermal efficiency's higher?  In other words SC ethanol and SC steam DI.

 

Ford engineers did say their Ecco-Boost engine could run under diesel operation under some conditions. The DI is E85 fuel.

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The properties that make ethanol work very well for ignition engines are the ones that make it difficult to use in a compression ignition (diesel) engine. It resists ignition from just heat, ethanol needs a spark or at the very least a hot glow plug to ignite. The compression ratios used in diesels are preferable for an ethanol engine, so is the robust build of the blocks and other parts, but the ignition method isnt preferred as ethanol resists it. Although a converted diesel with the capability to run either ethanol or diesel with the addition of a part time spark ignition would be a good compromise and would benefit greatly from heating the fuel.

 

Diesels dont have a throttle plate, but ignition engines will due to the cycle they run. I mainly work with ignition engines, so that is mainly what I refer to. I havent delved into the diesels on ethanol much as yet, mostly because I dont own one right now.

 

The very high fuel pressures of DI allows very high fuel temperatures, but unless it has a significant impact on mileage, efficiency, and power, the expense and complexity of a DI engine will outweigh the relative simple method of shoving the fuel in a bit more upstream of the valves in an ignition engine and its benefits of cooling the engine itself along with the intake charge. In other words is the cost of DI and all the resultant high pressure plumbing worth the return compared to a 60 psi system that utilizes latent heat of vaporization? The other issue of needing to be flex fuel still remains, the limitations of gasoline and diesel fuel hold the engine back when its run on ethanol.

 

I like Ron's system, but its more of a race piece, the tuning is changing a jet/pill until it gets enough fuel for the air, and it isnt designed for part throttle or low rpm, high vacuum cruise conditions. They are kick butt in a race application with how easy they are to tune, but from a mileage standpoint it would have some limitations with it due to the simple nature.

 

Something similar with EFI for the low speed and lean cruise conditions would work. There are a few on the market for about $1300-$2000 that are TBI systems that will bolt to a carb manifold. Some are self learning, others require a laptop, I want to try one of each type in the near future, but the cost is a bit high for me all at once. Its very simple to retrofit one of these to older engines compared to the relative complexity of port injection. As yet none of the manufacturers of these systems wants to help me out with the testing.

 

I have a couple other ideas I would like to try using port injection with a higher injector placement. Such as on this engine, placing them right under the throttle body and firing into the plenum rather than into each port to maximize the effects I want. Imagine a throttle body instead of a carb with two large injectors per side, or four on the right and left, near the base of the carb. It would make for a much shorter fuel rail and they could be batch fire rather than sequential simplifying things further. The intake would not have to be that tall, I just use this one for illustration purposes. The injectors could also be under the intake firing upwards into the plenum on this particular engine design.

 

Again I am referring to ignition engines running only ethanol, not a flex fuel engine.

 

Uglyengineporn.jpg

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When talking economy, I always have to go back and look at combustion efficiency.

 

If you look at it by the numbers, this article http://www.epa.gov/otaq/consumer/12-miles.pdf  indicates in 1950’s typical cars were emitting 13 grams HC per mile.  Wiki a 50’s Chevy Bel Air and it gets about 17 mpg.  So 1 gallon gas ~ 2850 grams, and 2850 / 17 miles = 168 grams of HC used per mile and 13 out the tail pipe.  13/168 = about 8% unburned hydrocarbons.  So even in the 50’s combustion efficiency was about 92%+

 

By the 70’s the epa regulated .41 gram HC per mile, requiring the same 17mpg vehicle to have a combustion efficiency of about 99.8%  Car makers got close to that spec with a variety of design changes, Chryslers ‘electronic lean burn’ and Honda’s CVCC reportedly even met the initial spec without a catalyst.  I would wager 40 additional years of engineering has only bumped that efficiency upward from 99.8%.

 

In short, modern engines are very efficient in combustion.  Even with 70’s technology you have a system where 99.8% of the fuel is burned in the cylinder.  Of that energy, about 1/3 goes out the tail pipe, 1/3 out the radiator and 1/3 to overcome friction and move the car. 

 

From a personal ‘economy’ standpoint, it simply makes no sense to attempt to better the combustion efficiency.  Why attack the one point in the chain which is already 99.8% efficient?  Water, magic pellets, snake oil, fuel additives, HHO, magnets, vapor, fairy dust – even if they worked and worked perfectly, you’d go from 99.8% to 100% combustion efficiency... and still loose 1/3 of the energy out the tail pipe, 1/3 in the radiator and 1/3 in friction.

 

Also consider even in a 9:1 compression engine, working out the old gas law equations, you find under compression, the temperature of 70 degree inlet air has risen to a little over 800 degrees once compressed. About that same time, a supersonic jet of gas squirts out of the squish areas between the piston and cylinder head to create turbulence.  So 800 degrees in a supersonic jet of gas – I would say any ethanol is substantially vaporized at that point.

 

There can be a small benefit to keeping the intake warm with a carburetor – mainly eliminating fuel puddling in the intake.  IRIC, the old slant 6’s actually had a section of the exhaust manifold mating to the intake right under the carb to help in this respect.  But that is not a true ‘vapor’ injection.

 

 

On a side note, (Thumpin) I’m curious what effects you’re looking to maximize by moving the fuel injection just after the throttle body?  If it’s top secret, you don’t have to let the cat out of the bag :)  But general research has been pushing injectors the opposite way:  closer to – and even inside the combustion chamber.  Sequential injection (as opposed to carbs and batch fire) to allows cylinder to cylinder fueling to deliver a precise amount of fuel to each individual cylinder.  The multiport injection (to some extent) and direct injection (specifically) allows for optimal valve timing and overlap without worry of the injected fuel slipping out the exhaust during the valve overlap period.  With carbs, TBI, batch fire, etc - you have the whole intake charged with fuel/air, some of the mix will sneak out during valve overlap and scavenging. OK for performance, but terrible for economy and emissions.  You could then attempt to minimize the overlap and scavenging, but that increases pumping losses and hurts economy once again.

 

 

Re: earlier Opel T1 post,

 

It seems no internet fuel efficiency discussion is complete without someone posting the ‘Opel T1’ as an example of what mileage should be attainable if these technologies were just put in a normal car.  But that ‘car’ was barely a car as we know it.

 

By most accounts I’ve read, it was completely stripped and gutted of all extra weight and amenities (no power anything, no radio, seat belts, carpet, no heater, a/c, roll up windows, air bags, etc)  The driver sat in a single fiberglass seat.  The car had no suspension, no transmission – it was chain drive.  Rear axle was removed and rock hard tires were placed a few inches apart in the center of the car with a solid steel bar leading to a chain sprocket.  It had a top speed of 30 mph on flat level ground and no power to climb a hill or drive in stop and go traffic.

 

I haven’t seen anything specifically indicating it used a ‘vapor’ carb – only mention of a tillotson lawnmower carb, but it could be a possibility.  One thing is for certain – the vast majority of the fuel savings is from stripping/gutting the car, taking away friction of the driveline and reducing friction and rolling resistance, not from the carb.

 

The most complete set of pics and documentation I have seen so far:

http://www.opel-p1.nl/custom/testcar/Shell%20Opel.htm

 

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