An Exercise, Silly cpt it Confirms Literature

A few months back I had experimented with e85/gas ratios ranging from 1/8-1/1 with varying results; basically the mpg ran a little higher to no change at the smaller end to power issues and stalling at the 1/1. I dropped it for the time being but ran out of gas a week ago and decided to use a gallon of ethanol to get to the station where I topped it off with 10 gallons of e85. The pump guarantees a 70% minimum ethanol in the mix, and I met with some interesting/annoying results. Immediately I noticed that equivalent power was to be found at substantially higher rpm, 4200 vs. 2900, and soon thereafter I found that it took two to three starts on cold mornings to get it to stick. Additionally, I found that after the engine warmed, a little higher than normal, the system has serious power issues based on how much I was pushing and at what rpm; basically, an acceleration of no more than ~2miles/hr/s could be got below 4000 rpm and a persistent chugging/shaking of the whole vehicle could be temporarily remedied by an in-transit shutdown/clutch pop without pedal depression to high rpm (popping it in 3rd gear at 65 mph without pressing the gas pedal) or by stopping and shutting down for 5-15 minutes. My cousin hypothesized I needed more air, via a cold-air intake, one house mate thought I needed more fuel and should replace the fuel filter, another said I needed more compression and that the higher rpm performance showed this. Personally, I am thinking that it seemed like engine flooding/incomplete combustion since the engine definitely had more power and less chugging at higher rpm.

After my first experiences of power loss etc. I thought to put a couple of gallons of 91 octane gas in to see if that made difference, which it didn't. I included this in the mpg calculation, 379.4 miles/(11 gal. e85 + 2 gal 91O) = 29 mpg, a 22% decrease from my usual 37 mpg. This is consistent with the ~29% lower energy density of e85 vs. gas (http://www.epa.gov/air/caaac/mstrs/2006_10_dunham.pdf). At $2.14/gal and $2.850/gal for the e85/91 octane mix and regular gas respectively, 0.074$/mile vs. 0.077$/mile. Whatever the case, normal operation was restored after refilling with reg. unleaded.