3.5 V6 Atkinson Cycle engine and the gas grade parade extravaganza...

For those who are getting prepared to nit-pick, what I mean by effective compression ratio is this: normally compression ratio refers to the number of times smaller the combustion chamber becomes during travel from bottom dead center to top dead center during the compression stroke. It literally means the amount of air that normally fills the combustion chamber is compressed in this case 11.8 times as much as it would be at BDC when the motor is at TDC during the compression stroke. Due to the fact that the modified atkinson cycle means the intake valves remain open for a small portion of the compression cycle, no compression happens until the valves are fully closed. This means that during this portion of the cycle the 'effective compression ratio' drops to 10.2 because the valves are allowing some of the air in the cylinder to 'leak' back into the intake tract for lack of a better way of putting it. This gives the motor much better fuel economy without any risk of creating an overly-lean running condition, or a significant drop in power.
Coincidentally, this phenomenon also means that forced induction should, in theory, be particularly effective as it will force all of that intake charge into the intake without adding any extra fuel using the air pressure of the compressor to overcome the atkinsons tendency to allow leak down into the intake tract during that gap in the compression cycle.

 

I would love to be able to run ethanol free in yard equipment, chainsaw nd boat but it is 50 miles to nearest station that has it. Even when I pass the station with the boat I do not get gas there. I am running milled heads in the boat and and need 92-93 octane. The station with ethanol free only carries it in 87. I lost at least 200 rpms at WOT in the boat when they went ethanol in DFW area.

 

Please post where you found this information. Less horsepower is absolutely correct, but better gas mileage?

 

I've done a lot of high altitude driving and it's just something I noticed. Possible reasons:
- Less air resistance due to thinner air
- Tire pressure increases as you drive up

The better gas mileage is just something I noticed, and it was not backed by something I read. I've done several full tanks of gas on the highways in New Mexico, and several full tanks of gas near sea level. I was driving around the same speed (highway speeds), and my MPG is New Mexico beat all of my previous records.