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Thread: Injection vs E85

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2009-06-05 19:40:18
Injection vs E85
Each unit of heat can be referred to in calories. The amount of energy (heat) required to raise the temp of one Kg of water by one degree C at 1 bar of atmospheric pressure.

The latent heat of vaporization for water is 539 calories per gram. This is an endothermic reaction, meaning it absorbs heat. Water can reach up to its boiling point but not any higher. The process of vaporization (boiling) is a cooling process. In the process of cooling, the water boils as the vaporized water absorbs energy during the change of phase. Higher pressure means more energy is required to make this change happen.
So we know that vaporization of water absorbs a lot of heat. This is more than any other easily available liquid. Here are some comparisons:

Water 539 cal for enthalpy of vaporization
Ethanol about 201 cal for enthalpy of vaporization
Methanol 264 cal for enthalpy of vaporization

So you can see that the Water absorbs 2x the heat energy from the surrounding air/surfaces during this change of phase. This gives water extremely high anti-detonation properties when injected into the internal combustion engine because it is able to absorb a lot of heat. Under higher pressures, the energy required is even higher. In a typical forced induction application, the water can absorb more than 2x as much energy as water under atmospheric pressure.

A calorie: The energy needed to increase the temperature of a gram of water by 1 °C"

"Water is also commonly expressed as 539.423 calories per gram.

So the amount of energy absorbed by one gram of water during a change of phase is the same amount that it takes to raise the temperature of that same amount 539.4 °C. Of course, water will vaporize at 100°C but that just goes to show... The amount of energy absorbed is extremely high.
2009-06-05 19:40:58
Water injection can allow for more aggressive timing/boost/compression because of the detonation suppressing qualities that it has. It has few inherent drawbacks: plumbing, weight, reliability, and it may slightly suppress flame travel.

Although water injection may increase the engine’s ability to suppress knock, it doesn’t actually increase the octane of the fuel. This is why methanol is mixed in with water in different ratios. Methanol has a higher octane rating, and when it burns it releases less energy than gasoline. By adding methanol to water, octane levels of 116 have been reached. Though I am somewhat skeptical of this high of an octane, somewhere around 110 sounds more reasonable on pump gas.

So let’s take a look at Ethanol. Octane rating of ethanol is around 115, and E85 (85% ethanol 15% gasoline) is between 100-105 octane. Ethanol is oxygenated, and requires 9.765:1 afr for stoichiometric ratio and around 7:1 for best power in a boosted engine. This means it requires a lot more fuel to reach a ratio where good power can be made. The other issue is that E85 doesn’t pack the punch of gasoline. By the stoichiometric ratio, E85 produces between 70-75% of the power that gasoline does. This means that E85 not only requires more fuel to get the right ratio, but would require about 25% more just to get the same power out of gasoline. Luckily, some of the lack of boom can be solved with different AFRs and a more aggressive timing map. Generally, cars will lose power when changing to E85 unless timing is adjusted to take advantage of the higher octane it provides.

So you can expect to use about 30% more fuel, and gain in 5% of power with the switch (NA), more gains can be had depending on setup. There is also the hidden power-adder that works behind the scenes: vaporization. When gasoline vaporizes it absorbs is around 180-190 calories. Compared to the straight ethanol (201 cal) I would expect these two to perform about the same, except the E85 is using a lot more fuel. This means a 30% increase in cooling ability since 30% more fuel is being used. The more fuel used, the cooler the combustion temps will be. This is why E85 can be so potent.

Overall though, I would like to see a comparison of a 91-93 octane gas engine with water/meth injection compared to an E85 setup. I am putting my money on the pump gas and the injection. I think a gas setup with a scramble boost setting would work perfect for water/meth injection. This would prevent draining the reservoir quickly, but you would get a much better range between fill-ups and have all the benefits of E85.

Your thoughts?
2009-06-05 20:32:19
E85 is the ideal solution. It has higher octane than gas with water/meth.

In general with e85 you can advance the ignition more, run more boost, and run leaner. The problem with e85 is availability and the additional fueling requirements.

When I tried to run 21psi with e85 the walbro couldn't keep up and I was running as lean as 13.5 with no detonation.

Water/meth is potent too. I ran over 26psi on this set-up.

If I could have e85 everywhere and had the system for it, I would choose to run it over gas+water/meth. And wouldn't hesitate to throw 35psi at it.
2009-06-05 21:05:10

I was thinking about this a couple hours ago. There's only 1 E85 even remotely close to me, that I heard of.

That's a great selling point on methanol injection for me.
2009-06-05 21:11:36
Originally Posted by danmartin
E85 is the ideal solution. It has higher octane than gas with water/meth.


Water-meth injection on pump gas has seen AKI as high as 116 octane. E85 is around 105 AKI.

Here's an ad from a popular site. I would like to know what just water would be. I have heard from users that it is around 100 octane or so. Notice though, that the octane is not increased, just the anti-knock index.

2009-06-05 21:30:13
Originally Posted by mirrortints

I was thinking about this a couple hours ago. There's only 1 E85 even remotely close to me, that I heard of.

That's a great selling point on methanol injection for me.

how's is there 1 for you and like 5 for me? we live like 8 miles from each other.

the only problem I have with E85 is that you would have to drive it everyday, i have to many cars to do that.
2009-06-05 21:43:45
The biggest shortfall for E85 is mileage for sure. With using 30% more fuel, you can expect 150 miles or less from a full tank of fuel.

Good read.


As previouisly mentioned already, water methanol injection has become a tried-and-true proven way for users to effectively increase their 87-93 octane pump gas. Depending on the amount injected and the type of mix used (pure water, pure methanol or a mix of the two), gains up to 10-25+ points in octane can be achieved. Thus making 91 octane pump gas act like 105-116 octane racing fuel in their engines. Thereby eliminating our dependency for notoriously expensive racing fuels, which can cost upwards of $8.00-$12.00 per gallon as so many of us have reluctantly had to use in the past. Costing only pennies to operate when using 100% water, its also a far more effective, affordable and convenient to those expensive octane booster fuel additives as well.

While once believed impossible several years ago. It is now possible and becoming quite common to find individuals using 91-93 octane combined with water methanol injection to support engines well over 1000+ horsepower. One top engine builder, Steve Morris of New Era Performance, has already made upwards of 1700+ horsepower with a non-intercooled carbureted big block Chevy ProCharged engine on 93-pump gas using only 100% water injection .

2009-06-05 22:08:01
Here are some popular places selling kits:

Water Injection, Methanol Injection, Alcohol Injection Systems | Coolingmist
Snow Performance: Home
Water injection : alcohol-methanol injection | DevilsOwn
AEM UEGO Wideband O2, Water/Meth Injection, EMS, V2, Cold Air Intakes, Brute Force Intakes, AEM Gauges and Electronics
Aquamist 1s Water / Methanol Injection System - Modern Automotive Performance

or DIY
Do It Yourself Water Alcohol Methanol Injection
DIY Water Injection
Water Injection By Robert Mann
2009-06-05 22:21:29
the octane rating on water/meth is dependant on the ratio of meth to water. Straight up meth is around 135 from what I have read. I would not want to run it straight up but that gives you a idea.
2009-06-05 22:22:51
A 50/50 mixture by the math is around 105 AKI. This is right on par with the E85, but doesn't consider how much you are injecting.
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