How are you going to inject ethanol at the right time? 'Cuz the OEM injection system sure won't hold up to it, no way.
as you experienced it wasn't the motor that was effected by the gas it was the injection pump.
but we know about biodiesel's lubricity! -i've read studies with ball scratch tests where pressures of over 6000psi have been recorded before bio diesel fails and a small scratch can be made.
-and bio does mix with ethanol . it also improves the cetane(somewhere around 8 as apposed to diesel's 45) -cetane is just an expression of the auto-ignition temp.
i have read, and seen pics, that while ethanol and diesel don't mix if you add bio they will all mix together.
(another concern would be if there is any zinc in the system any water in the fuel would probably have some effect over time.)
i was thinking a blend of ethanol and bio diesel through the stock injection system. maybe start with a 50/50 blend and possibly go up to an 80/20 blend without modification.
While the majority of plants produce more sugar than fat, the fat is higher in energy-density than anything you can do with the sugar AFAIK, and algae is likely an exception to the ratio rule. I don't know about rapeseed/canola, but after oil extraction, the byproduct of soy oil is high-protein cake that is excellent for feeding cattle -- not that I'm wild about that idea either, but it does kind of shoot down the whole food-or-fuel argument.
you are absolutely correct on the algae exception
but i think they are still working on the oil extraction methods.
i think that if you first make ethanol with the starch in the algae that the oil seperates and rises to the top then make bio and you would still have the proteins left for animal feed.
the same is true of corn ethanol production -ferment the starch(which cows don't digest anyway) the oil rises to the top and is collected and the rest is a much higher quality animal feed. its called distiller's grains and is a commodity (DDGS) traded on the stock exchange. in fact here in ptown Pacific Ethanol sells wet what they have left over for more than what they purchased the dry corn for. again shooting down the whole food vs. fuel argument.
even beter than corn is cattails grown in waste water producing 5-6k gallons of ethanol per acre just from the starch as apposed to corn with all the petroleum assistance producing only at most 450gl/acre
as far as the energy density is concerned you are right as far as it concerns Btu's.
if you had a furnace under the hood that would be important.
but we are looking for other qualities in a fuel such as kinematic energy -how much work it produces not how much heat it produces
-and flame front speed -when it produces that work
-and how clean it burns -sulfur, heavy metals, HC, NOx, CO could all be reduced drastically with alcohol.
all this is just thinking i will always defer to experience -and any experimentation should probably be done in a shop with a dyno and a knock sensor/meter to avoid damage.
but during the '80s mercedes-benz did produce diesel buses running on straight alcohol by routing an extra lube oil line from the engine with appropriate filtration of course into the injection pump and a return line for excess oil.
but probably with a cetane improver and at least 1% biodiesel the extra lube could be eliminated.
volvo avoided the extra lube by using a dual injection system that first injects 20% diesel to get a good hot burn and then slightly after injecting alcohol (with as much as 50% water!) through a seperate injector loosing lest than 10% power. at low loads and idle they only injected diesel.
obviously this isn't an economically viable solution for retrofitting but it does provide some applicable data.
another option would be fumigation through the air intake after turning the ip down to only deliver maybe half -made easy by the throttle body on the SDxx. i figured someone would have some experience with some kit that was available in the '80's
i'm sure it would be similar to injecting propane or natural gas systems rapidly spreading through city bus companies. -since they are also high-octane/low-cetane fuels -
of course again a dyno would be useful in determining the optimum tuning.
i can imagine if just using the stock ip system and blending fuels the difference in viscosity with ethanol that more fuel would get through the injector at a given pressure though the increase in HP and torque might be worth the small increase in fuel usage .
again i know i'm young and inexperienced and will always defer to real world data i just read stuff and think a lot