Thursday, October 30, 2008

Tank #23

I filled up at Meijer again. Once again, I only filled up with 87 Octane gas.

14.736 gallons of regular. My tank is now at a little over 10% ethanol, octane is a little over 87.

It feels like the throttle response is sluggish (not much different from when I had 50% ethanol in there). I've got the ignition advance on the scangauge, and it looks like it is significantly retarded from when I was running lots of ethanol, like 4 or 5 degrees of timing.

I actually wanted to fill up with premium, but I was on autopilot when I was filling up (after 4 hours of overtime) and hit 87 without thinking about it.

Meijer changes their price spread!

Just as the price spread at Meijer starts to become fair, they go and change it.

It used to be that they charged 50 cents per gallon less for E85 than regular gas.

As of yesterday, the spread was 40 cents.

Regular was $2.51, E85 was $2.11.

That's just sad. But understandable. RFG is going for $1.47 on the NYMEX, ethanol is going for $1.71 on the CBOT. So E85 has lost much of its cost advantage over the last few weeks. If it wasn't for the subsidies, E85 would cost more than regular.

Monday, October 27, 2008

Long Term Fuel Trim update

I estimate that I've got about 15% ethanol in the tank.

I'm getting LTFT at cruise of 3 or so, which is EXACTLY where my regression equation says that it should be.


LTFT is an amazing thing.

What should E85 cost? 10/27 edition

Meijer has E85 at $2.15 today. It's been there for a few days.

They have maintained their 50 cent spread to regular even as prices have plunged over the last month.

As prices drop, E85 actually becomes a much better deal as long as Meijer maintains the 50 cent spread.

I reran my spreadsheet, and it says that E85 should cost anywhere from $1.95 to $2.10, so the amount Meijer is gouging us is also much less.

I think that I'm going to run another tank of E10, this time premium. Then back to mixing E85.

Wednesday, October 22, 2008

tank #22

I filled up at Meijer on Monday.

I bought NO E85, despite it only consting $2.30 a gallon.

I bought 14.1 gallons of regular, which cost $2.80 a gallon.

My ethanol content is 15.29%.

I got 22.8 mpg at 32 mph avergage speed on tank #21.

Dialing back on ethanol

Since I got to roughly 50% ethanol per tank, I've found that drivability has suffered (much more hesitation), cold start is an issue (even at 55 degrees, the open loop portion of startup is rough, the car almost stalled once), and mileage isn't great.

So I've decided to run a couple of tanks of regular. This will allow me to get some good data on mileage and LTFT with low ethanol content. It's been a long time since I've run regular, and I don't have this data.

I'll probably run a couple of tanks ot premium as well, just to compare.

Then, more than likely, I'll run E30 through the winter.

Thursday, October 16, 2008

Tuesday, October 14, 2008

More observations on LTFT

I've really been pushing the fuel injection hard as I've approached 50% ethanol.

It looks like my long term fuel trim at cruise is 24.

It also looks like LTFT is incapable of going over 25. Thus, there seems to be a risk of running lean, and pushing the ethanol content much further might not be a good idea.

It's hard to tell what the O2 sensor is going, the Scangauge scales the output from 0 to 100. I'm not exactly sure how to read it. It does bounce around alot. It will be 8 one second, and 72 the next. So I'm guessing that I'm not consistantly lean.

Tank #21

I filled up at Meijer on Sunday afternoon.

Gallons E85: 8.507
Price E85: $2.68

Gallons 87: 5.137
Price 87: $3.18

Gallons from tank #20: 3.179 (@ 46.62% ethanol)

Ethanol content of tank #21 (with E85 @ 74% ethanol): 49.35%

On tank #20, I got 22.8 mpg at 33 mph average speed.

Saturday, October 11, 2008

What should E85 cost? 10/11 edition

Bulk ethanol futures on the Chicago BOT are running at $1.67 a gallon. That is quite a drop.

Updating my spreadsheet, E85 should cost anywhere from $2.02 to $2.40 a gallon.

Meijer had it for $2.85 last night.

Monday, October 6, 2008

Does ethanol decrease mileage?

I've got a good amount of data now regarding how much ethanol relates to mileage. I've tracked ethanol content, average mileage, and average speed for almost every tank I've driven.

I threw this data into Excel and ran a multiple regression. I wanted to see how these two factors (average speed and tank ethanol content) influence mileage.

Now, I'm a little weak in statistics, but my reading is that these two variables can explain about 60% of the variation in mileage. Average speed is a very strong factor in controling mileage. Ethanol content is not. In fact, we can pretty much throw ethanol content out, it is not a significant factor (95% confidence). But it is borderline at about 6%.

Interesting stuff. If I had to guess, if I could collect data on, say, average temperature at start, to capture the decrease in mileage due to cold starting, or average temp while driving, to capture when I use the AC, I'd be able to explain a lot more of the mileage.

The people I meet while buying E85 at Meijer.

I met a crazy black man at the E85 pump. I suspect that he lives out of his car, based on his unkempt appearance and all the shit he had in the car. He was quite talkative, in an ADHD sort of way. Like I said, he was crazy.

He was driving a late ninetees Ford Escort, which quite obviously is not a FFV. So I took the opportunity to talk to the guy and find out what the deal was (with the car, not with him).

He said that he always fills up with straight E85. He said that he's been doing it for over a year, and he's had no problems with the car while doing it.

That Escort was either the last OBDI year or an early OBDII year. Maybe they're more flexible than later implementations?

Anyway, I was glad to see that the fraternity of crazy people running E85 in non-flex fuel vehicles included... someone certifiably crazy!

Tank #20

I filled up at Meijer on Saturday.

I decided to keep increasing the ethanol content, despite the CEL. I want to see if I can get LTFT over 25. If so, I'll keep going higher, if not I'll back off to something that doesn't light a CEL.

Gallons E85: 8.003
Gallons 87 octane: 5.571

Price E85: $3.05
Price 87 Octane: $3.54

Ethanol content of tank #20 (@ 74% ethanol in E85): 46.62%

I finished up tank #19 with 22.1 mpg at an average speed of 31 mph.

Thursday, October 2, 2008

CEL is back

Despite clearing the code, it was back within about 60 miles.

I'm going to just run with it lit. I'm still deciding whether my next tank should go higher on the ethanol (to see if LTFT can go beyond 25) or just go back down to an ethanol level that just doesn't light a CEL, to see if there are any cold start issues. It's starting to get really cold around here, it was in the low forties on the way to work today.

Wednesday, October 1, 2008


Well, I got a CEL on the drive home yesterday. Not too surprising, seeing as that I was getting long term fuel trims of 25.

I cleared the code (P0171), but unfortunately, that also reset the LTFT.

I was worried that I'd have a hard time starting the car with LTFT at 0, but it started normally this morning. By the time I got to work, LTFT was back to the 17 to 23 range, and STFT was around 0. So the ECU adapted in about 20 miles or so.

Also, interestingly, as soon as I cleared the code, the idle smoothed out noticably. I also though the throttle response improved.