Tuesday, September 30, 2008

Saw the magic "25" LTFT

Driving home yesterday, sitting in light traffic, I saw LTFT of 25 under light acceleration.

25 is supposedly when the CEL will light. Not sure how long LTFT has to be 25 before the CEL lights. I guess we'll see.

I'm seeing 21 or so at cruise.

Monday, September 29, 2008

Fuel rail and fuel line metalurgy

I had the hood open this weekend, and inspected my fuel rail and fuel lines closely.

They're all stainless steel. Very nice and shiny!

I'm pretty sure that there are no metalurgical issues with running E85 in this non-flex-fuel vehicle.

Friday, September 26, 2008

Tank #19

I filled up this afternoon at Meijer. The god damn display on the pump was broken, so I didn't know exactly how much I had filled. I had to estimate, and I was a little short of where I wanted to be (7.5 gallons).

Price of E85: $3.29 Gallons: 7.307
Price of regular: $3.79 Gallons: 6.650

Gallons left from tank #18 (@42.81% ethanol): 2.243

Ethanol content of tank #19 (@ E74): 43.40%

I got 23.5 mpg at 28 mph average speed on tank #18.

Thursday, September 25, 2008

Vapor recovery is not an issue for running E85 in a non-FFV

One of the claims against running E85 in a non-flex-fuel vehicle is that ethanol has a higher vapor pressure than gasoline, and thus you will get a check-engine-light when the vapor recovery system is overwhelmed.

As you can see from the graph above, that is not quite true. In fact, E10 has a higher vapor pressure than just about any mixture of E85 and gas that you could come up with.

From the graph (which is from an SAE paper), I would say that even running straight E85 will not throw a code from the vapor recovery system.

Wednesday, September 24, 2008

How to improve cold starting on E85

A university paper on the subject is here.

This has got me worried. This paper was kicked off from the experience of a university team that converted a car to E85 in '98. They had cold start difficulties at 50°F! They doubled the fueling on cold start. Not sure how I would do that!

Tuesday, September 23, 2008

Considering upsized injectors

I'm seriously considering getting higher flow injectors to be able to run straight E85 with no CELs.

Figuring out what the injectors are, and what higher flow injectors are compatible, is no easy thing.

It seems that the stock injectors are Siemens part number 12790827. I've seen them quoted at 355cc/min, 32#/hr, 34#/hr, and 36#/hr. Not sure which they are, and I'm just going to assume 36#/hr.

These injectors are also used in the supercharger Cobalt SS.

Just doing the calculation, at 210 hp, with a .5 BSFC and 80% of capacity, you need 33#/hr injectors, so 36 seems right to me.

Now I need to figure out a compatible higher flow injector. Just comparing air-fuel ratios between gas and E85, I need about a 55# injector. Maybe a little less, since we know that the Saab injector is optimized for E10, not gas.

Monday, September 22, 2008

What's different about the Ecotec FFVs?

Found this:

Hardware changes for flex-fuel operation are limited to the injectors. Because ethanol has fewer BTUs (less energy) than the same volume of gasoline, more fuel is required to produce the same horsepower at wide-open throttle. Flex fuel engines use unique stainless injectors with a greater cone angle and higher maximum fuel-flow rate. The fuel rail matches the injectors, but it’s manufactured of the same stainless steel used for all 2.2L I-4 fuel rails.

The flex-fuel 2.2L doesn’t require a special fuel sensor. The first flex-fuel engines used a light-reactive sensor to measure fuel composition from 100 percent gasoline to 85 percent ethanol. The 2.2L has a virtual sensor—software programmed in the E37 ECM with no separate physical sensor whatsoever. Based on readings from the oxygen (O2) sensors, fuel level sensor and vehicle speed sensors, the ECM adjusts the length of time the fuel injectors open for the type of fuel used. Within a few miles after filling up, the E37 controller determines what fuel is powering the 2.2L I-4 and manages the engine accordingly.

I'm really beginning to thing that flex fuel vehicles are just regular cars with higher flow rate injectors!

Saturday, September 20, 2008


Check this out, from a GM corporate website no less!

A new virtual fuel sensor reduces the cost and complexity of adding E85 capability to the fuel system. The ECM samples the exhaust at the oxygen sensor, and an algorithm determines whether E85 is used, as well as its mixture percentage with gasoline. It’s a much simpler, less costly system than previous systems that relied on fuel composition sensors. In fact, the entire system on the engine is simple: only the fuel rail and fuel injectors are different between E85 versions and non-E85 versions.

Did ya get that? The only difference between a flex fuel vehicle and a non flex fuel one is basically the fuel injectors. They probably flow a little more than the non-flex fuel ones.

I'm looking into the availability of higher flow injectors for the Saab.

Thursday, September 18, 2008

Good resource regarding converting to E85

Evidently, there was a conference in Minnesota about converting non-flex-fuel vehicles to E85.

Here is the powerpoint presentation.

There is a LOT of good information in there. I especially liked the presentations from the Ford and GM folks about the changes they've made in their FFVs to survive E85.

I wonder how many of the issues they bring up are really a big deal.

Wednesday, September 17, 2008

I drove a REAL flex-fuel vehicle...

...but not on E85.

I had to go to Tulsa on business, and because of the hurricane, there was literally only one rental car left, a Lincoln Town Car.

Lo and behold, it had a yellow gas cap indicating that it was a flex fuel vehicle.

Sadly, I couldn't find an E85 station in Tulsa, and the car had a full tank anyway.

But if you're in the market for a FFV, maybe a used Towncar is the way to go. There aren't that many FFV cars, they're mostly SUVs.

Tuesday, September 16, 2008

Tank #18

Well, it took me 2 hours to get home and an hour and a half to get back to work this morning, because of all the flooding and closed roads. So I decided to fill up so I don't get caught in traffic and run out of gas.

Gallons E85: 6.997
Gallons E10: 4.414

Gallons from last tank (@ 31.39% ethanol): 4.989

Ethanol content of tank: 42.81% (assuming E85 was 74% ethanol). Could be as high as 47.65% if it was 83% ethanol.

I was getting some funky STFT before I filled up. I saw -15! Kind of indicates that tank 17 was really low in ethanol.

I just ran up to O'Hare, and STFT looked much better. LTFT was around 17 or so.

Monday, September 15, 2008

Disaster! Then tank #17.

Well, we got 9 inches of rain since Friday. Needless to say, there's flooding all over the place...

...including Meijer's E85 tanks! They're totally shut down. Gas City is in Hammond very near the Little Calumet River, which is totally flooded as well.

And, of course, I'm at empty.

And gas is going for $4.26 a gallon. It was $3.79 on Thursday.

I put in 5.126 gallons of E10. No E85.

Unfortunately, because I didn't fill up, I don't know exactly what was left from tank #16. The display said 49 miles to empty, and the average mileage for tank 16 was 23.2. I'll just divide one by the other to estimate the gallons left.

So, tank #17 is 31.39% ethanol. So far that large decrease in ethanol (from near 40% to near 30%) hasn't kicked off a check engine light. I was getting short term fuel trims on the order of -5.

Wednesday, September 10, 2008

Funky stuff with my LTFT

My long term fuel trims are all over the place on this tank. It seems like they're fairly steady at 19% on the highway once I'm up to speed, but accelerating there I saw numbers as high as 24. Yikes!

And the LTFT is not as steady on this tank as the last tank. They go as low as 18, and as high as 21, and seem to fluctuate more, with 19 probably being the average.

I wonder if this is the behavior you'd expect when you're reaching the limit of the fuel injector system's ability to deal with ethanol.

I think the mileage is a bit worse as well. I'm sitting right at 23 mpg, with an average speed of 30.

Monday, September 8, 2008

What should E85 Cost? 9/9/08 edition

I'm calculating between $2.65 and $2.90 a gallon. That's for 74% ethanol, which is what we're supposed to be getting in Illinois and Indiana this month.

Meijer had it at $3.38 this morning.

Sunday, September 7, 2008

9-3 doesn't increase timing advance with increasing ethanol content

This plot is of the timing advance, which was in all three data file Alcohol gave me. Essentially, it's not showing any more advance with more ethanol.

Now, I don't know jack about timing advance, if ~32 degrees of advance is a lot, if you should expect a lot of advance on the highway, etc. But I was hoping to see the Saab Trionic ECU be able to increase advance, since higher ethanol means higher octane, and less detonation.

Thursday, September 4, 2008

How high can a Saab 9-3 go?

I've made a lot of progress in the last couple of days.

First, I found the Saab trouble code list that shows that if LTFT goes over 25, a CEL is thrown. So 25 is the upper limit for this car.

And I now know the relationship between LTFT and ethanol content. Is is y = 0.54x - 4.6. y is LTFT, x is ethanol content.

With these two pieces of info, I now know that I'll get a CEL at 54.8% ethanol!

LTFT vs. Ethanol Content

Well, the E30 data wasn't at a 70 mph cruise, so there was a lot of crap in it. Not usable for the analysis I want to do.

I plotted long term fuel trim vs. ethanol content for the data that I have (Alcohol's two data files, and my Scangauge reading from my last tank), and lo and behold, not only is there a linear relationship, it is a very stron relationship (R^2 of 1!!!!!!)

Pretty frickin cool.

And now I have a nice equation that I can use to predict LTFT based on tank ethanol content.

LTFT on E10 at 70mph

This is AWESOME data. You can see that LTFT on E10 is a mere 0.8, confirming my hypothesis that cars are "tuned" for E10, and that LTFT is essentially zero on E10.

I think Alcohol gave me a run on E30. Will do same analysis if I can.

BTW, this analysis required cutting the data from a word file, pasting it to excel, parsing the data to separate the text from the numerical data, and doing a halacious amount of cutting and pasting to get it all into tabular form. No shit, it's like half an hour of cutting and pasting per file! And it's only 45 data points!

Woe is me, I complain worse than an Obama voter.

LTFT on E20 at 70 mph

Alcohol sent me some data from his car. This is a graph from one of the data files, where he had the cruise set at 70 while running E20.

LTFT is pegged at 6.2. Interestingly enough, if LTFT is zero on E10 (do they design them that way), then it should be about 18 at E40. That's more or less where I am.

Alcohol sent me something similar for E10, I need to look at that for comparison.

LTFT on tank #16

It doesn't look like I'm getting any higher LTFT with the new tank. Still seems to be 17 on the highway.

This kind of indicates to me that the E85 I bought in August was 79%+ alcohol, and the tank I just bought was 74% or so. In that case, the ethanol content of my latest tank is no different than the last tank, despite adding half a gallon more E85.

Tank #16

I filled up at Meijer last night. Here are the stats:

Price E85: $3.29
Price 87 Octane gas: $3.79 a gallon

So much for Hurrican Gustav! That's cheaper than what I paid two weeks ago!

Gallons E85: 6.518
Gallons 87 Octane: 8.022
Gallons left from tank #15 (@~37.15%% ethanol): 1.86

I'm assuming that the E85 is 74% ethanol, 100 octane.

Ethanol content of tank #16: 38.52%
Octane of tank #16: 94.27

I got 23.7 mpg at 27 average mpg on tank 15.

Wednesday, September 3, 2008

Comprehensive list of GM trouble codes


I now know that you get the CEL for the lean condition(P0171) when long term fuel trim goes over 25. Good to know.

Being that LTFT at 40% ethanol is 17, the upper end of ethanol for the 9-3 is 58%. Also good to know.

Tuesday, September 2, 2008

What does it take to convert a late model car to E85

Here's an SAE paper about converting a '99 Silverado to E85.

They're not trivial changes! The changes to the fuel system were significant:

1) fuel pump
2) fuel lines
3) fuel rail
4) injectors

The paper says that +25 LTFT indicated a "severe lean condition". I wonder if it was lean, or just an idication that the injectors were being pushed realy hard.