23 replies to this topic

[TEAM MEDICARE]

I've come up with a source for pump gas without ethanol. Is there any benefit to paying a little extra for this?

[Mike Collins]

no

[Chris Windsor]

Yes,
It will run cooler- the alcohol burns hotter
It will hold it's octane longer
It will not absorbs water from the air like E10


The Gov is trying to mandate E15, that will be worse yet

[Mike Collins]

While Chris is correct. The E10 will make more power and is GCR compliant. E15 would put you on the edge of compliant and you would go over if the fuel took on any moisture.

Tune your car to what you run and don't let gas just sit in your car and you will be fine wither way.

[TEAM MEDICARE]

Hey guys

Thanks for the response. I seem to remember this discussion in the past but my search didn't bring anything up. My thinking is that gasoline has more BTUs then alcohol. This would seem to equal more power. Am I missing something here?

If anyone's interested my source is a local marina. It seems they have a special permit to sell straight gas as the ethanol is really causing problems with marine engines.

[Keith Novak]

Hey guys

My thinking is that gasoline has more BTUs then alcohol. This would seem to equal more power. Am I missing something here?

You're not trying to generate the most heat (BTUs). The heat is just a byproduct of the explosion that causes a rapid of expansion of gas and pushes the piston. Pushing the piston = mechanical power.

[Jim Drago]

You're not trying to generate the most heat (BTUs). The heat is just a byproduct of the explosion that causes a rapid of expansion of gas and pushes the piston. Pushing the piston = mechanical power.

that makes sense, because scientifically ( when thinking BTU's) the ethanol argument holds no water. But I have seen slightly better numbers on well tuned e10 cars compared to properly tuned zero ethanol pump gas as well. I have always attributed it to other ingredients in the gas as ethanol just didn't make sense to me, but maybe Keith is right. The E10 gas does kill fuel pumps in the 99's.
Jim

[James York]

You're not trying to generate the most heat (BTUs). The heat is just a byproduct of the explosion that causes a rapid of expansion of gas and pushes the piston. Pushing the piston = mechanical power.

Heat is wasted work... there is more to it than just BTUs...... ETOH has something else in it that is useful. With unlimited air, the highest specific energy content gas would give you the most power.

[davecarama]

I know when I was doing HPDE track days with the Mazda Club of Washington a few years ago, the FD (3rd Gen) RX7s were having serious issues with the Ethanol fuel. The heat was causing the apex seals to fail. One weekend went through about 5+ cars/motors. Luckily those guys always trailered to the track. But that has nothing to do with this section on SM racing does it Lets see if I can make them connect...

I think that gas is somewhat of a lubricant on it's own. Ethanol, or alchohol, doesn't really have that same slippery feeling... and in fact can clean off that lube?

Dunno, I am not a scientist / engineer / or sleep in a holiday inn express, but I would imagine that not only would your explosion be cooler, but the friction of the motor might be less and your oil changes might last longer.

What do you think? Maybe?

[Mike Collins]

[font=arial, verdana, tahoma, sans-serif][size=2]

What do you think? Maybe?

I think that as of the this morning I have 129 dyno pulls on my '99 cars and I know what recipe my car likes.

[Tom Sager]

In order to get the most from each fuel, you will likely need to change ignition timing and fuel pressure. You can drive yourself (and your helper) nuts doing this for very little difference. Then you'll have to repeat the test again just to be sure you can trust the result. I agree e10 just slightly better. There is more to be gained or lost IMO by knowing in advance what to do if the temperature on race day is warmer or colder than average.

[GregA]

Here's some science for the discussion.

Attached Files

•  Effect of ethanol–unleaded gas blends on engine perf.pdf   236.16KB   34 downloads

[James York]

I think that as of the this morning I have 129 dyno pulls on my '99 cars and I know what recipe my car likes.

50-60 pulls here; does that mean I was twice as lucky or efficient???

[Mike Collins]

50-60 here; does that mean I was twice as lucky or efficient???

That means you haven't owned '99's for near as long as I have....

[Keith Novak]

Holy crap. People are supposed to read that? Here is my dumbed down version...

Why do we care about timing? Because it's not just about making an explosion in your engine, it's about that explosion happening in the sweet spot of the engine stroke. How big an explosion, how fast it happens, how much energy is lost to create the explosion, and how much energy gets wasted in other ways determines how much energy in the fuel gets converted to turning the engine over.

We want the fuel to burn completely rather than go out the tailpipe when the valves open so we're actually converting the fuel to HP. We want the fuel to burn at the right speed so it's pushing the piston and not burn so fast that it's just a bomb in the cylinder. We want to limit the amount of work required to compresss the air fuel mixture because that's not helping at the wheels. We want to keep the air fuel mixture cool so there's more air and fuel in it at the right mixture to go boom. We want the engergy in the fuel converted to pushing the piston rather than just heat. Ethanol changes those things.

That study was done at 3/4 throttle. For how it affects the HP at the wheels at WOT in a Miata, skip the thermodynamics class (horrible horrible stuff) and put the car on a dyno.

[James York]

That means you haven't owned '99's for near as long as I have....

That's probably true.

[Mike Collins]

That's probably true.

The '99 I am driving now is personally my 6th '99. Those Dyno pulls are over probably half of those cars. I think maybe only Drago has built himself more cars. I have also built 4 1.6's, 2 1.8's and 1 '01+ for myself. I would be scared to add up all the dyno pulls on all the cars in the shop.

[davecarama]

I think that as of the this morning I have 129 dyno pulls on my '99 cars and I know what recipe my car likes.

Hahaha! Better than me! I have zero dyno pulls on my cars and I could care less what fuel I put in my car, as long as it comes out of the pump and is convenient (and cheap).

Dyno pulls are going to do nothing for me but make me depressed on how crappy my car actually is... that said, I may consider trying that one day, once I have the loot to put a motor in my car, so I can see how much of an improvement the power-plant swap gives me.

[TEAM MEDICARE]

Here's some science for the discussion.

"The 20% ethanol fuel blend gave the best results of the engine performance and exhaust emissions."

I don't have a dyno. Couldn't I just add of a bottle of 100 proof vodka per tankfull?

[Tom Hampton]

"The 20% ethanol fuel blend gave the best results of the engine performance and exhaust emissions."

I don't have a dyno. Couldn't I just add of a bottle of 100 proof vodka per tankfull?

Note: 100 "proof" means 50%. The other 50% is water.

Questionable legality notwithstanding....everclear is essentially 200 proof / 100%.