ethanol

[Crazcnuk]

I see a whole bunch of misconceptions about gas, alcohol and Octane ratings here, as usual

Octane is a measure of how easily/quickly the fuel will explode. The lower the octane the more violent the explosion. Diesel produces more power/volume than gas and is lower octane. Bunker sea oil is even lower and produces even more power.

High octane fuel does NOT give you more power, by itself. High octane fuel was designed for the high performance 'muscle cars' of the 1960's. It was desinged to overcome the technology of the day that was having trouble with high compression engines and poor designs causing the fuel to preignite in the cylinders (detonation). Because Premium, or high octane fuel burns slower, it actually produces less horesepower.

The reason that the muscle cars engines used high octane, to produce more power, was that it allowed more timing to be used. and it was this tunability that added the horespower.

With modern engines most of this is a non-issue. However, the engine mfgs, specify high octane for 2 reasons, 1) they own lots of shares in the gas companies, and 2) Why not? anything to make absolutely sure there is no knock. ( and people think they are getting a 'performance' motor

I have one of the first 502/502 premium crate engines from GM Performance. It specifies premium fuel, and yet it is only 9.6:1 compression. I have used regular pump fuel in it for the last 9 years, on and off the drag strip with no problems.

Another issue with premium fuel is that all gasolines lose octane the longer they sit in the tank in the ground. Most stations sell very little premium fuel, so often the premium coming out at the pump is not the octane you are paying for. If you insist on using premium ask around your local dragstrip. You'll find that there will be one station that they all use as it has the 'freshest' premium fuel.

This is not usually a problem with regular as it is usually used up much quicker.

Alcohol: Ethanol produces less horsepower by volume than gas does, as mentioned, however, alcohol is a partially self-oxygenating fuel meaning you can burn more of it in the same volume of air. If you want to burn pure alcohol you can rejet and run @2.5 times as much alcohol in the engine as you could gas, at around double the horsepower. Thus Top alcohol funny cars at 2500+ horsepower. You would, of course, get serioulsy bad fuel mileage doing this.

This is why Formula One had to mandate fuel stops when they went back to gasoline from alcohol. With alcohol there was no choice, you had to stop somewhere in the race, w/gas they can do a whole race on one tank.

Alcohol burns a LOT cooler. If you ever watch the monster trucks or alcohol dragsters, you'll notice they idle them a lot before a match, this is to get some heat in the engine or the engine won't provide as much power.

Just as a note Nitro-methane can be run with @9x the fuel/air ratio. Nitro methane produces even less power/volume than gas or alcohol, yet top fuelers are 5000+ horespower.

Another note on premium fuel, mfgs may use any number of combinations to make thier fuel as cheap as possible. However, in U.S., Canada, etc. There are rules as to how much of these additives the can use. Most mfgs stipulate no more than 10% alcohol by volume for warranty purposes. So unless otherwise marked gas will have that or less. If your using fuel within these guidelines you shoul have no trouble with it.

MTBFE is a valve lubricant that replaced lead in gas. It has nothing to do with octane.

Alcohol absorbs water, which is what can cause corrosion in the fuel system. If you use up your gas fairly often this is not a problem, but it's not a good idea to let high ( more than 10%) alcohol fuels sit in the tank for months at a time. However, in the cold climates you will never need gasline antifreeze!

[HobbyMan]

MTBFE is a valve lubricant that replaced lead in gas. It has nothing to do with octane

MTBE, not MTBFE, will raise your octane. It was outlawed recently by the epa. .mtbe page
You are correct, just raising the octane will not in fact increase power. But, using a chemical that has a higher energy content than gasoline to raise your octane will increase power. Forgetting octane for a second, if you add a substance with a higher energy content in your gas(nothing to do with octane), more energy will be released through the engine, thus a higher mileage.(as long as it is compatable with gasoline) I am just talking about raising the average energy content of a substance by mixing two chemicals together. The only reason that I mentioned octane originally was that my side cover says that 91 leaded gasoline is recommended. SO I decided to buy regular gas and raise the octane to the recommended level. By adding toluene(which has a higher btu and octane rating), I was increasing the energy level and octane at the same time. Just treat the btu and octane as 2 different subjects. This is what I think has been confusing some people.

The reason that the muscle cars engines used high octane, to produce more power, was that it allowed more timing to be used. and it was this tunability that added the horespower

ACtually as I understand, some of the cars had something of an 11:1 compression ratio, so it isn't jsut a timing issue (although it may be a major part).
.

The 428 Cobra Jet engines were replaced in 1970 by new 429 Cobra Jet engines. The 429 Cobra Jet was rated at 370bhp while the Super Cobra Jet had 11.3:1 compression and was rated at 375bhp.

muscle cars
Look at radial engines of WWII running 145 octane. So I think that we are all in understanding that just raising your octane will not increase power.
My experiment did yield evidence that my assumptions were correct. My mileage did go up without even adjusting my timing. My engine did perform differently under a load also. I decided that it isn't worth it unless you are racing or doing things that required a really high performance. Besides, I love to travel. How would I bring extra chemicals along with me? So my friend in Auto class works with a lot of fuel injected cars so he will be helping me. I plan on building an EFI system from scratch. I have a car to cannibalize for fuel injection parts
for all you computer gurus:

boolean experiment_concluded=true;
boolean information_gained=true;
boolean Hobby_done_experimenting=false;

[Crazcnuk]

Corrected on the MTBE!

As for your energy content, the energy content of the fuel, as far as just burning has little or no effect on the power an engine produces, it's how 'quickly' the energy can be released. Octane, as I understand it actually measures this factor, and if your fuel is too low an octane value it explodes at times when you don't want it to. High octane fuels were developed to keep this from happening.

For race cars you do NOT want to use high octane fuel unless you absolutely have to. You only use premium or better in order to overcome problems with detonation in the engine that can cause serious engine damage. If you have no ping you don't use higher octane fuels, or additives.

The fact that the cars had 11:1 or better compression ratios and a few design issues in cylinder head and pistion design was what caused the engines to ignite the fuel too soon. As this can be catastophic to an engine, higher octane fuels were designed to make the fuel less likely to ignite before the spark plug told it to.

This can also be caused by built up carbon, but that is another story.

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The 428 Cobra Jet engines were replaced in 1970 by new 429 Cobra Jet engines. The 429 Cobra Jet was rated at 370bhp while the Super Cobra Jet had 11.3:1 compression and was rated at 375bhp.
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People look at numbers like these and think that these engines are something special. In fact they are not. In a 1954 white paper, the designer of Chevrolet's modern small block engine stated that any gasoline engine SHOULD produce at least 1hp/cuin.

If you look at any performance engine you will find numbers actually much better than this. The XS1100, for example is @65cu in and 95hp. Far better than 1hp/cuin.

So the above cobra jets should be at least 425hp or better.

My 502cuin is rated at 502hp and moves my unstripped 83 Monte Carlo (3800lbs) through the 1/4mile in 12.23secs at 112mph with no problem. GM does not advertise this as a 'racing' engine, it is a truck replacement engine.

At 9.6:1 compression with just a Cam change it will put out 640hp! As it is only 9.6:1 compression it could easily go to 10 or even 11:1.

I have never used premium or high octane fuel/additives in this
engine.

How this all relates top fuel economy is that the more efficient your engine burns it's fuel, the more power it will produce, the more work it can do from a given amount of gas.

Then you get into the efficiency range of the cam, gearing, wind resistance and a few other factors that affect mileage.

Theoretically if yout take a 265cu/in engine, in a P/U truck, producing 250-300hp, it should drive just as they do now with much larger engines, but be in the 30+mpg range if not close to 40, provided they are geared correctly.

As an example we took a 1991 Dakota Ext Cab 4x4 with a 318 V8 that got between 12-14Mpg highway. Jumped the compression from 8.2:1 to 9.5:1 and changed the cam. Rergeared the front and back diffs to 3:55:1 from 3.90 and the truck now avgs 25mpg highway.

[HobbyMan]

So the moral of the story is, don't change the gass that you burn, but the way you burn it.

also, with more energy in the gas you are burning, you can lean down the mix and produce close to the same result. This is the same principal as said about engines running straight alcohol. Since my carbs were tuned for gas without ethanol in it, they are actually running a slight bit lean. This is from, as said before, the extra Oxygen on the molecular formula. So in fact you could burn more ethanol gas with the same amount of air, but you mpg suffers. by raising your energy level, you burn less amount of gas per the same volume of air, increasing mpg. thats all I am getting at.

[Crazcnuk]

Exactly. I think, If I remember right as inmy first post, you can burn up to 2 and half times as much alcohol in the same volume of air.

You can effectively double the horsepower of your engine on pure ethanol.

Always wanted to do this to my 3.5hp briggs and stratton lawnmower!

[HobbyMan]

Actually, I fly RC airplanes. They burn nitromethane. For my .45 in^3 engine, I burn about 8oz in 10 minutes running 7k rpm. They burn up the fuel quickly, but they have loads of power. It was idling at around 500 - 600 rpm and I accidentaly got my hand caught in the prop. Not only did it continue to run, but it almost cut through the bone. It did take the skin off the top of my pointer and middle finger. It felt like my had was in a blender. Esentially it was. I know that it is nasty picture, but that is a testament to running alcohol type fuels. The really bad part was that I had to write with that hand a week later for finals. I have 2 B&S 2.5 hp motors and before I got my XS, I was going to weld a bicycle frame to mount them on. WEll, I think the XS is a better first mororcycle anyway

[Crazcnuk]

Right, Nitro-methane has even more oxygen in it than ethanol. If I remember right you can burn 9 times as much NM in the same volume of air, so although it produces less power/volume, you can still get 4 or 5 times the hp out of the same engine over using gas, provided the engine will hold together, at 1/9 the fuel economy!

[LoserShoes]

Actually most model airplane fuel is methanol with somewhere around 5 to 30% nitro added, depending on how much you want to pay for a gallon of fuel.

More nitro -- more $$$

Steve

[HobbyMan]

I pay about $11 for %10 nitro. The rest is castrol and some other junk(maby some alcohols) That is why I would never run it in a automobile engine. I don't even know if the rubber parts are compatable.

[Crazcnuk]

I am not sure what ratio the Top fuel dragsters burn, but you don't want to be standing anywhere near when they fire them up! Talk about 'feeling the burn'

High ratio NM is awful stuff to breathe

[TADracer]

Originally posted by Crazcnuk
I am not sure what ratio the Top fuel dragsters burn, but you don't want to be standing anywhere near when they fire them up! Talk about 'feeling the burn'

High ratio NM is awful stuff to breathe

Nah! It smells great....only burns your eyes alittle.

NHRA requires no more than 85% nitromethane in the top fuel and funny car classes and the balance must be methanol. Actually, gasoline is a much more efficient fuel than either nitro or alcohol. Takes only 1 part gas to 13 parts air while Methanol takes 1 part for 4 parts air and nitromethane takes about a 1 to 1 ratio. Not sure what a/f ratio pure ethanol would take. What makes methanol and nitro so powerful is that it carries much of its own oxidizer into the combustion process without the addition of very much outside oxygen. So you can inject alot more fuel into the cylinder and still have combustion than you can get with gasoline/air. A nitromethane engine can be flooded with so much fuel that it almost goes into a hydraulic situation on compression and you will still get combustion. That is why a good running top fuel engine will burn about 15 gallons of 85% nitro in a quarter mile run.

[Crazcnuk]

And why sometimes the top of the engine comes off in one big bang!

The other fun one one is standing a ways behind one of those jet turbine powered funny cars, when they flood it to get those big clouds of vapor!