Myself I do not use 87 in mmy cars and have not for years. I use 89 during cooler months and 93 is hot summer. Even my wife 4cyl Cherokee picked up a few MPG with better gas. It is possible to use 87 in a higher CR than 8 to 1 with spark control but efficency is lost but I would also say that 87 is good to about 8.5 to one without knock control in most engines. If you use 93, 11 to 1 it quite doable. Propane can work up to about 13 to 1.

 

It's not just the compression you have that determines octane requirements. It's the dynamic compression. Say it with me, dynamic compression!

Static compression ratio, which is what has been discussed thus far, is simply displaced volume over combustion volume. However, there is more to it than that. Dynamic compression is the amount of compression that the motor sees under actual operating conditions. It will always be lower than static compression. A motor will not start building compression until the intake valve closes. At lower RPM's, some of the fuel / air mixture is pumped back out into the intake until the intake valve closes. At higher RPM's, the ram effect somewhat negates this, however then the fuel / air has less time to ping / detonate.

This has some interesting effects. It allows us to build an 11:1 motor, that runs on 87 octane! Keep the dynamic compression down around 8:1, and you'll get by on 87 octane pump gas.

An interesting effect of alcohol, is that it will withstand extremely high dynamic compression ratios without pinging. 15.5:1 is not unheard of. This will get your fuel efficiency back and then some! Ethanol blended E85 will, of course, be a little less.

See here for an article:
http://www.kb-silvolite.com/article....n=read&A_id=36

 

[QUOTE=jim henderson]Manufacture of ethanol costs more engery going in than we get out. It is a politically correct solution but energy efficiency wise, you loose. Several South American states have been doing this for decades. They import less oil but they get less energy for the energy put in than they would get if they used gas.

When you take into account the cost of farming the land(tractors use fuel), growing the corn(fertilizer etc), making the alcohol etc, you wind up using more energy like gasoline, electricity etc to make the ethanol than it costs us to get gasoline. Someday, if oil becomes expensive enough the equation will tilt in favor of ethanol, but even at $3/g gas, it is still too energy wasteful to use alcohol.

About the only advantage of using ethanol for now is that 1) farmers love it, it is essentially a huge subsidy and 2)At least it is locally produced 3) treehuggers love it.





Sorry, but this all is not true. Ethanol has a 33% increase in energy output, which is less than gasoline, but not at a net loss.

Last time I checked, it took less fuel per acre to farm, and this only gets better every year. Secondly, the byproducts are sold as a more efficient feedstuff for livestock production, thus reducing waste.

The liberals in Berkely and the oil companies are doing their part to shut E-85 down with poor science. I use it in my minivan. Yes, the mileage went down to 16 mpg, but I still burn less gasoline I would be at the normal 20 mpg. The cost of using E-85 is equal and/or better than gasoline depending on the price.

 

An interesting fact for all you guys who are tuning E85 engines. In Iowa, unsure about other states, you are actually buying a lower percentage of ethanol at the pump in winter months. At lowest, it's about 70%. Thus, your vehicle will run better in the cold.

We race an E85 powered formula car at Iowa State, and do our tuning in the winter. However, we do our racing in the summer. This is our third year running on E85, but the first year we knew about the ethanol difference from summer to winter.

 

If we could get a supply of E85, we'd run it in our formula car here at NC State too. It would be great with the turbo!

 

Dad runs it in his 74 Cuda and has expereince great results. He has lobbied for a rules change in his racing org to allow the running of E85.

 

Is your dad's Baracuda orange by chance? I've seen one sitting on Knapp before.

 

BTW, I attended a lecture given by one of the IRL safety engineers this fall, and he informed us that all cars will be running on 90% methanol, 10% ethanol during the 2006 season. By 2007, all cars will be running 100% ethanol.

 

No, it is a 74 that is IROC Z-blue and runs in the NMCA all over the Mid West and East Coast.

 

Actually, that was bought in Sioux Falls, SD, as there were no E85 pumps available to me at that time. The cold start was near Huron,SD.

 

if you really wanted to you can get a free federal permit to operate a still as long as you denature the ethanol . stills are remarkably easy to build (if you wanted to you can build one out of a teapot, a milk jug, and 8 ft of copper tubing)
the operating price for a 40 gallon still will run about 90 cents per gallon if you include your time spent making it