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I have converted my '88 Firebird (the build is in my sig) to run Flex Fuel. For the uninitiated, thats any mix of pure gasoline to E85. This is made possible by EBL's 8 calibration banks. Each bank is calibrated for a different percentage of ethanol, in 12% increments.
Actually, it's not a full conversion yet. When I fill the tank, I must do some math to calculate how much ethanol is in the mix, then switch the EBL to the appropriate bank using my laptop.
Next stage is to tie a GM Fuel Composition sensor to EBL, so I can read the percentage from the data stream, rather than do the math. I'll still have to switch banks.
BobR is working on a bank switch so you can swith banks without a laptop. That will help.
I'm trying to convince BobR to add logic for the Fuel Composition Sensor and Flex Fuel capability. He has agreed it won't be too hard and there's room in the firmware and calibrations to do it.
I have created an Excel spreadsheet that gives the adjustments to 7 settings and tables in EBL to handle high mixtures of ethanol. I have a modification to make to it. Then I'll post it here.
All that is needed is to change these entries--
Closed Loop - Stoich AFR
Closed Loop - Idle Lean Limit
Closed Loop - Max Lean AFR
PE AFR Commanded table
Open Loop AFR vs RPM vs VAC
Hwy AFR vs MAP
Open Loop - AFR Multiplier vs CTS
My results so far, with my build--
Lowered MPG, but....
Lowered "cost per mile"
Significant increase in power output
Problems I'm still working on--
"Open Loop - AFR Multiplier vs CTS" settings. But I didn't have this right for pure gas yet, anyway. It's too lean until engine temp gets up to about 100 F.
Found out I need a higher-volume fuel pump and larger injectors. Those will come over the winter.
Could use higher compression, noticeable at lower RPMs. I'll solve this by increasing the dynamic compression ratio with Rhoads lifters.
And a "by the way" to any naysayers about ethanol conversion-- No corrosion or seal deterioration has been observed. Don't mistake "ethanol" for "methanol." They are related, but also way different. I've had several tanks of pure E85 through it now. All I can say is, it's running sweet!
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__________________ '88 WS6 Formula 400 "SR-71 Black 'Bird"
Copy & Paste "pure gas" values from TunerPro tables into the BLUE cells.
Enter the percent of Ethanol in your fuel to cell B6.
Enter a value for "AFR Change per % Ethanol" into cell E6. A suggested range and a default value are supplied. I believe this will vary depending on your build. Mine prefers a "leaner" setting.
Copy the new values from the gold cells to TunerPro.
The "AFR Change per % Ethanol" is a constant calculated from the stoich / best power / best economy AFRs for pure gas and pure ethanol. The spreadsheet uses this value and the percent ethanol value entered to calculate the new values.
On my build, it appears that the "Hwy AFR vs MAP" calculation may need some adjustment. This morning at steady cruise, my O2 sensor was reading toward the rich end of the scale, even though it was in "Lean Cruise" mode.
Experience (of others, not mine) seems to show that ethanol mixes are happy with the same spark advance settings as pure gas at part throttle. At full throttle, only a small increase in spark advance is needed.
Since ethanol cools the intake charge more than gasoline does, and E85 octane is usually 105, it's very easy to over-advance the ignition timing. You can advance the timing to the point that the force of the burn actually pushes against the rising piston, with no knock. The result is a power loss.
Apparently the ThirdGen.org file system doesn't allow spreadsheets, even in ZIP format. The attachment is broken. This link will download the spreadsheet from my own web site.
Well this is an interesting conversion. What static compression are you running? Have you dyno'ed the engine? That would be some very valuable information.
Keep going!
Static compression is 9.3. No dyno available in my area, at least not that I have found that is affordable. The "feel" of the engine says it matches very closely what I "built" in Dyno2000. That's about 370 horses and 460 ft-lbs. As my sig says, I built it for torque, not max horses. My "feel" is based on driving a lot of machines over a lot of years. For lack of a dyno, the strip will tell the tale, but it needs a new transmission first.
Winter upgrades will be a "stage 3" 700R4 build (will take up to 900 horses), Rhoads lifters (will raise the dynamic compression from 7.8 to 8.9 in the lower RPMs), possibly a roller cam with the same specs as the flat-tappet that's in there now.
Also, the spreadsheet I uploaded has now been upgraded again. There is no need to adjust the "Open Loop - AFR Multiplier vs CTS" table for ethanol. So, if anybody has already downloaded it, go to the link and get it again.
If anyone is still following this thread, I have greatly improved the math in my spreadsheet for calculating AFR for varying gas/ethanol blends. The "AFR Change per % Ethanol" constant has been removed. The non-editable constant is now calculated from real chemistry and physics.
To reiterate, I build 8 calibrations for my EBL, in ethanol-mix steps of 12%. I switch calibrations manually when I fill up, to match the actual percent ethanol in the tank. This doesn't happen very often, as I usually run E85 tank after tank 9 months of the year.
The values from the spreadsheet produce very good starting points for tuning ethanol blends. As is normal, some tweaking will improve individual cars' results.
To make my 406 happier when cold starting with E85 in cold weather, and to make more power and mpg, I will be installing thinner head gaskets to up the static compression ratio from 9.14 to 9.5. Also a set of Rhoads V-Max variable lifters to raise the dynamic compression from its present constant value of 8.1, to varying from 9.1 (at idle) to 8.5 (3500 rpm and up). Should be a very noticeable power increase.
I have been able to get the mpg reduction from gas to E85 down to less than 15%. Since E85 in my area sells for around 25% less than pure gasoline, I get the best of all worlds. The power increase of ethanol AND lower cost per mile.
And a "by the way" to any naysayers about ethanol conversion-- No corrosion or seal deterioration has been observed. Don't mistake "ethanol" for "methanol." They are related, but also way different. I've had several tanks of pure E85 through it now. All I can say is, it's running sweet!
The only thing you need to be aware of is that E85 has an affinity for water since it has ethanol in it. Over time, it can lead to rust formation in the fuel system.
The only thing you need to be aware of is that E85 has an affinity for water since it has ethanol in it. Over time, it can lead to rust formation in the fuel system.
Actually, I haven't found that to be a problem, either. If the water in the fuel is "tied up" with the ethanol, it can't corrode surrounding pieces. Yes, ethanol blends will attract water. However, in my experience, that's more of a problem with E10 (which most everybody gets nowadays) than it is with E85.
For example, I got some bad E10 fuel in my boat. Mix 2-stroke oil with "wet" E10, and the water drops out. That will stop a carbureted 2-stroke outboard in its tracks! To get rid of the bad fuel, I drained the boat tank into my '03 Tahoe's tank of E85. No problems. The high ethanol level soaked up the water and all was well. The Tahoe was perfectly happy.
If you're going to have your vehicle parked long enough to develop fuel system rust, then you need to 1) fill the tank FULL with gas, and 2) put in a fuel stabilizer. Or drain the fuel system completely.
Fuel system rust can happen with straight gas, if you buy off-brand gas or keep a vehicle parked long-term in a relatively high humidity area (say, in eastern Texas as opposed to western Arizona).
It takes a LOT of water to cause problems with E85. The first problem you get with water in E85 is a drop in mpg and power, yet it still "runs" just fine. This happens long before rust can become an issue.
The ONLY problem I have ever had with ethanol happened when my Mallory fuel pressure regulator was brand new. E10 fuel literally melted its diaphragm. Mallory said, "Oops! Our bad!", and sent me a replacement diaphragm free of charge. No problems of any kind since then.
Still have some cold start issues to address and i guess your new spreadsheet will help me.
I've found the toughest thing to tune for, E85 or gas, is cold starting and warmup. I'm still working on it. The trouble as I see it, is that you can't keep the engine cold long enough to really determine what is happening. The silly things insist on getting warm.
Also, cold start with E85 is best helped with higher compression. Part of the reason for the adjustments I'm making to my build with head gaskets and lifters.
I've found the toughest thing to tune for, E85 or gas, is cold starting and warmup. I'm still working on it. The trouble as I see it, is that you can't keep the engine cold long enough to really determine what is happening. The silly things insist on getting warm.
I know what you are talking about, i have it cold starting good enough so far, but the outside temp is still around 8-10 C and it will get lower.. but E85 goes to E75 during winter here in Sweden, just because FlexFuel vehicles have cold start problems.
Anyone heard from SR-71 lately?
I may have some questions about the project.
First thing I'd ask is how in the world you get 9.3:1 compression with 416 heads on a 406cid engine ??
