Better Performance on E85?

[Agent WD-40]

I'm on my second tank of gas in my 12 Denali. First tank was from the dealer and I'm assuming was regular 87 octane. I decided to try E85 for my second tank.

The engine definitely feels stronger on my second tank. Do these 6.2's make more power on E85 like the 2015 V8's do? Or is this just the difference between the power running regular 87 and premium 91/93 octane (E85 is ~105 octane)?

I know the 6.2L in these is a premium recommended motor which means it won't make the advertised 403 HP without premium (the manual even says you may notice reduced acceleration with 87).

 

[TowGMC]

In my 6.2 I've tried E85 and while it made a slight bit more power my fuel economy was off more than 2mpg. And I tried E85 once when pulling my 7000# trailer on one long pull and sure it felt a slight bit more responsive but my fuel economy dropped from my typical 8-8.5 mpg (on premium) to 6 with E85

 

[okfoz]

Stoichemetric in a nutshell is the ratio of air to fuel to get the optimum power/economy etc...

Keep in mind that you might get better power because of the fact you have to use more fuel to get to stoich. On pure Regular Gasoline engine stoich is 14.7: 1 Pure Ethanol is something like 9:1, Methanol is 4:1 or something silly. As odd as this sounds, the higher the octane the lower the Stoich... IIRC the octane of Ethanol E85 is something like 100, pure Ethanol is around 110, and pure methanol I think is like 120 or so. What confuses people is ounce by ounce the higher the octane the less the energy. BUT (this is where it confuses people) The higher the octane, the more power you can create because you can put more into the cylinder at one time...

The Methanol cars IE dragsters and Sprint Cars (Not nascar sprint series, look up Extreme Sprints or Outlaw Sprints) use Methanol/Nitro to power the cars, They can put so much fuel in comparison to Air into the engine that it creates gobbs of power. Now if you tried to put this much Gasoline into that same engine, it would just spit out the unburnt fuel and it would smell really rich (it would kind of burn your eyes)...

So by using E85 1) you would see more power 2) you would see lower fuel mileage.

I hope that makes sense

 

[okfoz]

To Further my thought process, this ONLY works on engines designed to use E85. If you used E85 in a regular carburetor gasoline engine or FI Engine (not equipped to use E85) you would see a drop in power because the engine would not compensate for the loss in power from the less potent energy source. However, if you recalibrate your carburetor for the higher octane/more fuel scenario then you would get more power.

There are other things that go along with calibrating for a higher octane, 1) you can advance your timing to ignite the fuel earlier, which gets you more power through more of the stroke of the piston. 2) You can increase the compression, again You can reduce spark knock, again, because of the higher octane rating, slower burning of the fuel.

What happens if you ignite fuel too soon is you get spark knock (also called pre-ignition), That ticking noise is actually the combustion of the fuel exploding too early and it hitting the top of your piston like a hammer on the up stroke, or at the very top... This is potentially a bad thing and it can burn a hole in the top of the piston.

With the advent of spark knock sensors, 02 sensors, and other sensors like MAF & MAP, TPS, etc, in combination of the computers, this opened up a myriad of opportunities to use several different fuels without having to manually change the settings on your carburetor every time you wanted to change fuel...

In short, when you see an article in the media or some "news" organization touting how E85 is so much better than gasoline because you can get more "power" That is all a guise to push their agenda, because it takes more fuel to get that power.

Hope that makes sense

 

[JennaBear]

Better HP, worse MPG.

 

[okfoz]

Correct.

Is that Richard Dean Anderson in your Avatar?