Running E85

I'm really curious which parts are not designed for high alcohol levels. Remember flex fuel gas tanks are also normally different. I don't think this would make them much more expensive.

Compression is mechanically a max of 9:1 because of late valve closure, expansion ratio is what goes to 13:1. Without modifying the stroke or adding forced induction the compression will stay the same.

Are you getting that from calculating fill ups from the pump? It seems magical since there is less energy per gallon of fuel. Something must be wrong with your vue tuning for gasoline. It may be running overly rich.

That makes perfect sense. You also will get less peak power and torque. How did you modify the view? I would think that at a minimum you would modify or trick the computer into understanding the correct open loop mix.

What are the stock injectors? Stoich on gas is 14.7, but only 9.76 on E85. That means around 50% more fuel than stock.

 

Adding to this comment, the Prius engine simulates an Atkinson cycle engine by varying the valve timing. Late closure of the intake valve relieves some of the pressure that would otherwise make for the 13:1 compression ratio. The actual compression ratio can be as low as 6.5:1. The average effective compression ratio is 8:1. The following article provides more detail:

MOTOR Magazine Article | MOTOR Information Systems

Tom

 

I cant say for other states, but in ND, the state and federal tax for all gasoline and E blends is the same per gallon.

The price spread between gasoline, E10-E20-E30-E85 depends on the price of gasoline and Ethanol at the time the station purchased it, along with where they think they can price it and still have it sell.

 

Ethyl alcohol contains 21.1 Mj/l.
Straight gasoline contains 32 Mj/l.
So if you remove 10% of the 32 and substitute it with 21.1 you will end up with less energy total.
Depending on how the car uses the fuel (we have to assume the Prius is as efficient with this as it is overall) you should -always- get poorer mileage when ethyl alcohol is added to the gasoline. The more ethyl alcohol the lower the energy content and the poorer the mileage.

Couldn't find the compression data in the manual you posted. Thanks btw. I have to assume the new engine is about the same as the old, but it -could- be different. Technology marches on!

At any rate, the compression ratio shouldn't make any difference. The energy is or is not in the fuel, nothing to do with compression ratio. Now -some- designs may be able to recover and use the energy better at higher compression ratios. Don't just assume the Prius is one of them. Pearl gets poorer mileage with "up to 10% ethyl alcohol fuel". It's almost exactly what you'd expect doing the calculations with the energy posted above.

 

My Gen 3 Prius makes best mpg on my perfered brand of E10. I have checked it very carefully using 5 tanks each of their 87 octane gasoline VS their 90 octane E10, calculating actual miles travled VS gallons consumed.

How can this be ?? E10 has 3% less heat energy, and other qualified folks have stated that their Prius difinatly gets less mpg on E10.

What some do not realize is that BTU content and conversion of heat to power is not a 1/1 deal, it depends on engine design and quality of the fuel.
An engine like the Prius 1.8 can adjust its cylinder pressure and spark advance to suite the antiknock qualitys of the fuel. The Prius 1.8 can increase cylinder pressure by changing intake valve timing and ignition advance to run the avalible fuel right to the edge of detonation, which causes the most expansion and highest cylinder pressure, producing the best possible fuel economy.

Another thing to consider, is that all E10 blends are not the same.
You have a much better chance of getting a quality E10 with the best gasoline stock from a blender pump in a non Ethanol mandate state.

A blender pump will have 2 tanks of fuel connected to it.
1 tank of 87 octane,100% gasoline, and another tank of E85 (15% gasoline/ 85% Ethanol.)
The blender pump will draw the correct ratio of gasoline and E85, mixed in the right perportions of Gasoline and Ethanol to produce your choice of 100% Gasoline-E10-E20-E30-E50-E85.

The thing is, a blender pump will be connected to a good 87 octane gasoline supply, which when blended with 10% Ethanol will produce a good quality 90 octane fuel like what gives my Prius it's best mpg (love to see the thing indicate 60 mpg under ideal conditions, never less than mid 50's in warm weather

If your not buying E10 from a blender pump, or are from a state where Ethanol is mandated in all gasoline (my state does not mandate Ethanol), then the fuel blender can substitute a really crappy low energy / low octane gasoline stock and "spike" it with sometimes more than 10% Ethanol to meet the minimum 87 octane required, thats the stuff that will cause a mpg drop in a gen 3 Prius.

 

Yes, you are correct on the lower chemical energy in ethanol vs gasoline, but what you are forgetting to consider that ethanol combustion provides higher engine efficiency, especially if compression ratio is increased as it can be easily done as pure ethanol is over 100 octanes.

Engine designed for ONLY ethanol consumption would be more efficient and MPG on ethanol would be higher. The only problem is such engine would be destroyed by using regular gasoline.

 

Modern fuel lines are made from nitril rubber or other synthetic rubbers and that is resistant to ethanol, no matter if 10% or 85%. I do not know why Toyota opposes E15. Probably they didn't test their cars with E15. Plenty of people tested E85 in non-FFVs and I haven"t heard a single problem, except for LT trim engine light.

Do you you have a link to that Motoweek? Thanks!

 

One thing to consider is that the government considers Methanol to be an alternate fuel.
I suspect the warnings on non FFV and FFV cars are in part, a move to CYA by the car co to protect themselves if a dishonest blender substitutes cheap but nasty corrosive Methanol for much less nasty, but more expensive Ethanol to add oxygen to their fuel.

In 30 years use with E10, I have not seen any parts failures with Ethanol. The limited experience I have with Methanol burning sprint car engines, showed how nasty it can be to unplated steel and aluminum.
I suspect the warnings are to protect them from a worst case situation where someone gets a Gasoline / Methanol blend in the tank and messes up the fuel system.

 

Thank you. I was going to have a another look at this price data to see if it was quoting wholesale price. I am curious if tax is different.

Looks like the assumed E85 hit is about 25% in the "adjusted" price.
The implication is certain engines can do better or worse but 25% is probably a good average.

Go AAA (member here).

 

I would think the cooled egr of the gen III would take some of this advantage away. I did find the study on the older generation prius and e85

http://www.greenenergynetwork.com/media/studies/prius-e85.PDF

 

Great info. The increase in torque is mind boggling (>30%!).
That itself could increase MPG by decreasing RPM to provide the torque needed at constant MPH.

 

Alternative Fuels and Advanced Vehicles Data Center: MotorWeek Explores Differences in Conventional and E85-Capable Vehicles

I'd posted it at http://priuschat.com/forums/gen-iii...cussion/103934-running-e85-4.html#post1477475, way back.

As I posted earlier, there are Toyota FFVs. Prius isn't one of them nor are any of their cars, only "light trucks". See http://www.e85fuel.com/flexible-fuel-vehicles/.