And just to add to the fuel discussion, I run pure gas (ethanol free) whenever possible and get an extra 1-2mpg. Now who wants to be brave enough to try E85 and post their results?

 

What octane is the pure gas you're running? I might try that as it's plentiful (but expensive) around these parts.

Once again, If I see that much of a gain, I'll have to crunch some numbers to see if it's worth it.

Will these trucks even run E85 without mods?

 

Highest octane they sell. Usually 91-93
I thought about E85 but my Disco has been running terrific and really hate to take a chance. Co-worker of mine ran it in his Dodge van (think it was a 2002) and said it ran terrific but the CEL came on. (Don't know what the code was)

 

I've run pure E85 in lots of vehicles not designed for it. Contrary to popular belief, the rubber fuel lines won't melt, engine won't explode, etc. It burns a lot like gasoline, and the engine doesn't much care as long as it ignites.

The issue is that the stoichiometric ratio for ethanol is quite different than gasoline, at around 9:1 compared to 14.7:1. Mixing ethanol with gas (E85) bumps it up some. While running E85, the computer will use input from the O2 sensor tell it that there's a lean condition, and dump more fuel in to compensate. This shows up as a positive fuel trim if one were to use a scan tool, the ECU is simply adding fuel to maintain clean emissions (a stoichiometric ratio).

All ECU's have a predetermined fuel trim value, that if exceeded, will light the CEL. If the ECU is having to dump in too much fuel to maintain stoich (as will often be the case with straight E85), it will show a "lean mixture" code. This is because it thinks there's a wonky sensor, since in normal conditions it would never have to add that much fuel.

I've found the trigger in most non-flex fuel vehicles is about 60-70% ethanol. The computer will happily adjust to that point without a CEL, but go beyond that and it gets cranky. I've never seen any detrimental effects from running E85 on a vehicle not designed for it, but the loss in gas mileage makes it a wash, or more costly (than gas), with the E85 prices around here. Also ethanol's cold weather properties leave something to be desired-- Engine will take some extra cranking to start in very cold weather.

One thing to keep in mind is that some vehicles' fuel injectors will be running close to maximum duty cycle at full load when using E85. Most manufacturers add in a 20-30% (or more) extra capacity for injector size, as a margin for error, or for safety. Using E85 will run the injectors close to max on some vehicles. Flexible fuel vehicles have larger injectors for this reason.

Also, never run E85 on a carb'd vehicle or anything without O2 feedback as there's no way to compensate for the mixture or extra fuel requirements. Running lean over extended period of times, especially at high load is a good way to see your engine self-destruct.

 

Good info QuakerJ!! So you couuld run a 50/50 mix and the ECM will compensate for it? I also heard that E85 burns hotter than regular gas.... any truth to that?

 

That is interesting stuff, Quaker.

I thought there was some advantage to having your vehicle tuned to E85. I was told it burns like 100+ octane gas or something.

 

Well everyone is entitled to their opinion and I am happy paying a bit more at the pump for higher octane gas and I am fine with that. I am wondering if the OP goes to the supermarket and searches the marked down meats and vegetables or the dented cans of beans that are on sale. Hey if that reflects your financial situation I understand as I have been there and done that. NowI don't care a whole lot what the cost is, if I want a really tender steak I get the tenderloin or some really fresh Ahi tuna.

Go ahead and run the lowest octane cheapest gas you can find! Then tell us how much it costs to rebuild your engine down the line. If I got a LR Disco just to run in the mud I'd be spending the least amount on the fuel and putting the rest into off road stuff for the rig.

Funny thing about new LR owners wondering about how to increase their MPG by using cheap low octane fuel. You bought a beast of a vehicle that gets CRAPPY gas mileage for the most part so if you want to save at the pump go by a Prius or something that really saves you money.

Nuff said!

 

Not being a chemist, I can't tell you exactly what is going on as far as heat generation, but there is less energy per unit in ethanol compared to gasoline (34% less energy seems to be the most quoted number, hence the greater fuel consumption, when using E85). Whether that translates into "burning hotter," I can't be sure without further research. I have heard that burning ethanol will produce a higher exhaust moisture content which has the potential to dilute oil.

And yes, running a 50/50 mix, the ECM will compensate to a large degree. That said, there are limits however, as non-flex fuel vehicles will likely not extract all of the ethanol's (or perhaps more accurately, an engine's) potential for producing power, because there is no programming or provision in the ECM to take advantage of ethanol's anti-knock qualities.

Therein lies the advantage of tuning a vehicle to E85. This quality (octane, aka anti-knock) disproportionally benefits engines with forced induction, as they are able to readily take advantage of a higher octane fuel by increasing boost, advancing timing, and most often both. Tuners will set the ECM to parameters that would cause detonation or spark knock when using ordinary gasoline. There's a huge potential for power here. Flex-fuel vehicles will have timing curves / fuel maps best suited for use with ethanol, that adapts to the ethanol to gasoline ratio.

Keep in mind that ethanol's octane doesn't make it more efficient. Its energy density is still poor compared to gasoline. Just because an engine might have the potential to produce more power by using it (forced induction being the primary example), it still has to burn extra fuel for whatever extra unit of power produced.

Again, this just touches the surface of the differences I'm sure, and is no scientific explanation by any means. I'm not arguing the merits of running cheap fuel vs premium either. There are valid reasons for running Premium vs regular, but wasn't sure how that applied to the Rover V8, hence my original post. I suspect the ECM uses aggressive timing to extract all the power it can from the older design, so there's some loss in power associated with running regular is my suspicion.