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Old 05-31-2013, 09:40 PM   #1
imma_stocker
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Question Flex fuel possible?

Soooo is it possible yet to run a single map with E85, straight pump gas, and random mixtures?

Ran across some of hotrod's posts testing the ECU's ability to self-adjust for different mixtures. They were on his bugeye though and I think our ECU's have changed in recent years. Current 93+meth tune can adjust for +/- 25% fueling but I'm far from stock running 26psi.

Need bigger pump, injectors, underhood lines, and higher flowing rails before I can actually make the jump anyways. Just seeing what's new if anything in the E85 world.
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Old 06-09-2013, 11:33 PM   #2
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No. Well yes if you wanna buy a new motor.
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Old 06-10-2013, 12:12 PM   #3
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You'd need a standalone ECU and ethanol sensor. Relying on the factory ECU's closed loop adjustments is absolutely retarded.
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Old 06-10-2013, 01:04 PM   #4
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That's what I figured. Any piggy back controllers up to the task? Ideally a piggy back that simply sends altered MAF and AFR values to the ECU based on ethanol sensor readings. Guess that still wouldn't adjust boost and timing though.


All I've come up with so far is running either ProEFI or AEM standalone and an ethanol sensor. Just looking for a cheaper alternative and preferably non-standalone.
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Old 06-10-2013, 01:11 PM   #5
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Why would you alter the MAF readings? That's going to throw off the load calculation.

You'd need to modify the injector scaling, tip-in, and per inj fuel compensations to have it run correctly across the board, but if that's all you did E85 would be a complete waste, you'd gain nothing by putting any of it in your tank. If you actually wanted to take advantage of it, you'd also need to modify boost and timing.
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Old 06-10-2013, 01:36 PM   #6
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There's not a lot of demand for it given a netbook and tactrix that live in your glovebox gives you 90-95% of the capability for $500. Yep it's less convenient than a standalone, but when you include cost of the ECU plus boatloads of extra tuning involved in a flex fuel standalone, it's so much cheaper that people overlook the inconvenience of re-flashing at the pump when you switch.
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Old 06-10-2013, 01:52 PM   #7
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Dangit. I'm better with wrenches LOL so insight into how the ECU functions is always welcome. Thanks again Eggroll!

Yes we can switch maps all day long and flex fuel would still require at least 2 maps to "blend" and more likely a middle 50/50 blend map for smooth interpolation. Had to ask if anyone has solved an impossible puzzle, seems not yet.

Conclusion: upgrade the parts, get 2 tunes for straight gas and straight E85, work with what I got.
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Old 06-12-2013, 01:00 PM   #8
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I was on EVO M a while ago and I think they figured out how to wire a flex fuel sensor from a GM vehicle to the ECU and have the ECU adjust accordingly.
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Old 06-12-2013, 01:03 PM   #9
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I was on EVO M a while ago and I think they figured out how to wire a flex fuel sensor from a GM vehicle to the ECU and have the ECU adjust accordingly.
Link? Aren't the EVO computers very different from Subaru's?
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Old 06-12-2013, 01:09 PM   #10
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This is the link. I'm not sure if they ever finished it. And yes, the computers are very different.

http://forums.evolutionm.net/ecuflas...n-evo-ecu.html
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Old 06-12-2013, 03:10 PM   #11
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Seems their patch works by using the ethanol sensor to blend maps. That is exactly what I'm looking for.

Please correct me where I'm wrong but I heard their ECU's hold 2 maps: high octane and low octane. Typically it would default to the low octane map when something goes wrong (detonation). Then they went and made a patch that uses both maps to determine targets based on ethanol sensor readings. But I don't think our ECU has that kind of capability. Ours is designed to learn and apply its own functions to "auto-tune" a single map but theirs either runs on map 1 or map 2. How far off am I?
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Old 06-12-2013, 04:05 PM   #12
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Very few Subaru open source ROMs have more than one set of maps.

I guess it's something that none of the ROM developers have deemed important. The only one I'm aware of is the Carberry ROM for 16 bit ECUs

Carberry is the closest thing to the Tephra mod maps on the Evos. There just hasn't been anyone putting in the work on the Subaru side for 32 bit ROMs. Probably a lot of it has to do with their being relatively few EVO ROMs but every model year Subaru has a WRX ROM, an STi ROM, a Forester XT ROM... all for the Euro, Aus, JDM, and US market. There's like 8-16 ROMs for any given model year that are all a little different. On the Tephra ROM seems to work for several model years.

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Old 06-13-2013, 08:42 AM   #13
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Quote:
Originally Posted by imma_stocker View Post
Seems their patch works by using the ethanol sensor to blend maps. That is exactly what I'm looking for.

Please correct me where I'm wrong but I heard their ECU's hold 2 maps: high octane and low octane. Typically it would default to the low octane map when something goes wrong (detonation).
Subaru's have the same but it is more if a "limp mode" mapping.
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Old 06-13-2013, 04:11 PM   #14
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Yeah, so Tephra did the work to make those 'limp mode' maps work as two separate and switchable maps. He effectively disables the limp mod and provides that as an alternate map to use. Then there's also a version that works with the E85 sensor for blending.

IMO two separate and easily switchable maps is plenty convenient. The physics of it works out nicely.
When you switch to E85, you'll be slightly rich, which makes up for any octane loss, especially since the fuel is so knock resistant. It's plenty safe to be running E65 or E70 on an E85 map.

Switching back to 91/93 the small amount of E85 left makes it run a little lean, but the extra octane makes up for that so it's not a problem.

The only reason for the sensor and blending would be for giving the car to your wife or something. It's a lot of outlay for what is a pretty negligible convenience. Easily switchable maps provide 99% of the benefit. I wish there were more Subaru OS ROMs that were easily switchable though. Most require re-flashing, which I don't consider easily switchable.
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Old 06-13-2013, 07:12 PM   #15
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The only real reason I want to have true flex-fuel is for convenience. Say I do my normal routine of filling up for normal life.

Come Saturday night I still have half a tank of 93. Means I gotta race on 93 or drive til empty then fill up on E85. Guess its not that big a deal. Just no money runs with 93 in the tank
...... race at the track of course
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Old 06-14-2013, 08:49 AM   #16
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The same has been done for Subaru by using diagnostic mode or one of the transmission switches to enable the secondary mapping. Basicly a SPST switch activates it. The issue is you can only change the base timing and fueling map. Boost control and the tons of other tables are unchanged. It is floating around Romraider somewhere. I think it is only for the 04-05 WRX.

http://www.romraider.com/forum/viewt...=map+switching

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Old 08-10-2013, 12:17 AM   #17
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Any updates to this?^^^^
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Old 08-14-2013, 04:17 AM   #18
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I was looking into this a while back, and then... well... got injured, got married, moved, still doing hours of PT every day... excuses excuses.

Anyway: http://www.romraider.com/forum/viewt...hp?f=25&t=8024

Most 32-bit ROMs already have two sets of tables for fuel and spark and boost, and a map switch ratio (cruise / non-cruise). It should be straightforward to run an ethanol sensor into an unused TGV sensor input, scale it like any other sensor, and use it to modify the injector scaling and replace the existing map switch ratio.

Someone needs to tackle this project. I thought it was gonna be me, but now I'm not so sure. If anyone out there is handy with software and wants to do this...

http://www.romraider.com/forum/viewt...hp?f=25&t=6303
http://www.romraider.com/forum/viewt...hp?f=25&t=7680
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Old 08-14-2013, 06:03 PM   #19
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bump cause the Valero down the street has E85
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Old 08-17-2013, 11:21 AM   #20
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I tune GM engines to run flex fuel; however, that's because all 05+ Ford & GM vehicles have flex fuel capabilities within their ECU algorithm, EVEN if they are not sold as flex fuel. WE do not have this capability. I'd like to mention they also don't require a sensor to do this. It's quite an innovative method that involves exhaust sniffing & adjusting the fuel trims until a consistent point is found.

I was able to run the following conditions ON MY SUBARU, not the GMs.
E10-E50 on the same map after a dyno tune on E40. E85 did fine on this tune during CL, but would lean out when floored.

I then swapped to the opposite end of the spectrum with E40-E85. Once you get your starting compensations working, they can work for both fuels UNTIL it gets cold. E85 doesn't like to ignite below 55F, which is why we switch to a winter blend of E70.

I'll explain why I'm not concerned with a little leaning out on E85 at high load.
Burns 200F cooler, less chance of piston holes
Has an octane rating around 100, so it won't burn unpredictably when leaned out.
The charge cooling effect it has (latent heat of vaporization) absorbs a lot of heat that would normally lead to issues.

Now for my plug. All our cars should be able to run Methanol. Every single one. If we passed the Open Fuel Standard Act, the US automarket would require sales of GEM FFVs (Gas, Ethanol, Methanol). Driving on M60, I'm able to get the same gas mileage as my E85 tunes, yet it costs 35% LESS THAN GASOLINE TO DRIVE ON. If we all had this choice, that's $3-5,000 per year in savings per household. Stop the OPEC Monopoly.

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Old 08-17-2013, 08:30 PM   #21
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Quote:
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I tune GM engines to run flex fuel; however, that's because all 05+ Ford & GM vehicles have flex fuel capabilities within their ECU algorithm, EVEN if they are not sold as flex fuel. WE do not have this capability. I'd like to mention they also don't require a sensor to do this. It's quite an innovative method that involves exhaust sniffing & adjusting the fuel trims until a consistent point is found.

I was able to run the following conditions.
E10-E50 on the same map after a dyno tune on E40. E85 did fine on this tune during CL, but would lean out when floored.

I then swapped to the opposite end of the spectrum with E40-E85. Once you get your starting compensations working, they can work for both fuels UNTIL it gets cold. E85 doesn't like to ignite below 55F, which is why we switch to a winter blend of E70.

I'll explain why I'm not concerned with a little leaning out on E85 at high load.
Burns 200F cooler, less chance of piston holes
Has an octane rating around 100, so it won't burn unpredictably when leaned out.
The charge cooling effect it has (latent heat of vaporization) absorbs a lot of heat that would normally lead to issues.

Now for my plug. All our cars should be able to run Methanol. Every single one. If we passed the Open Fuel Standard Act, the US automarket would require sales of GEM FFVs (Gas, Ethanol, Methanol). Driving on M60, I'm able to get the same gas mileage as my E85 tunes, yet it costs 35% LESS THAN GASOLINE TO DRIVE ON. If we all had this choice, that's $3-5,000 per year in savings per household. Stop the OPEC Monopoly.
Being able to operate without damage on E85/gas mixes is a completely different ball of wax than actually taking advantage of each fuel. This is what bothers me about current advertised "flex fuel" vehicles. Sure they can operate without damage on different fuels, but is ANYTHING being done to actually take advantage of the E85? They're still running WOT AFR, timing, and boost levels for gas, and merely adjusting the IPW so the AFR is correct.

In fact, according to your post, it's not even using an ethanol content sensor. It's merely adjusting the CL correction range to be wide enough to handle the change in stoich on e85! You even said yourself that the engine would pull lean when going WOT. This is NO different than shoving E85 into the tank of ANY car and hoping for the best. In fact it sounds like all you've done is expand the CL correction range to cover E85. That is NOT true flex-fuel operation, and to be honest it's laughable that this is what GM calls "flex fuel".

If there's anything that has come out of your post, it's that I will absolutely never buy a GM "flex fuel" vehicle. Good god American motor companies scare me more and more each day...
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Old 08-18-2013, 12:08 AM   #22
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Quote:
Originally Posted by the suicidal eggroll View Post

Being able to operate without damage on E85/gas mixes is a completely different ball of wax than actually taking advantage of each fuel. This is what bothers me about current advertised "flex fuel" vehicles. Sure they can operate without damage on different fuels, but is ANYTHING being done to actually take advantage of the E85? They're still running WOT AFR, timing, and boost levels for gas, and merely adjusting the IPW so the AFR is correct.

In fact, according to your post, it's not even using an ethanol content sensor. It's merely adjusting the CL correction range to be wide enough to handle the change in stoich on e85! You even said yourself that the engine would pull lean when going WOT. This is NO different than shoving E85 into the tank of ANY car and hoping for the best. In fact it sounds like all you've done is expand the CL correction range to cover E85. That is NOT true flex-fuel operation, and to be honest it's laughable that this is what GM calls "flex fuel".

If there's anything that has come out of your post, it's that I will absolutely never buy a GM "flex fuel" vehicle. Good god American motor companies scare me more and more each day...
Gm PCMs are quite in depth. The simple explanation mentioned in this thread is grossly inaccurate at best.
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Old 08-18-2013, 12:43 PM   #23
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The simple explanation mentioned in this thread is grossly inaccurate at best.
I sure hope so.
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Old 08-19-2013, 11:05 AM   #24
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It's certainly quite over simplified. I also think you misread my results for the last 3/4 of the post as what the GMs do. Instead, I told you how I fooled my car into becoming FFV enough for my tastes.

Fill up more than 3 gallons
Drive for at least 10 minutes
As the new fuel displaces the old fuel in the line, the Oxygen/AFR sensor will read either rich or lean.
If it reads too rich, it will jump approximately halfway to stoichiometric, run for a few seconds more, then repeat. You wouldn't believe how many plots I have of this process.
Once it narrows within 10-20% of the correct fueling trims, the process stops.

Since the fuel is now dialed in, it will reference from around 26 tables (of >100) to come up with multipliers to apply to various compensation tables. I've been able to alter these tables so that flex fuel vehicles can run off any alcohol & gasoline blends, even up to 100% Methanol, which is $1.20/gallon and increases output at least 10-20%.

Imagine having a turbocharged, 15:1 CR, direct injection engine running off 100+ octane fuels... that's the future we need. We'll never get there with gasoline though, time to open the market to competition.
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Old 08-19-2013, 12:55 PM   #25
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Goodness, something tells me it would be cheaper to go with a ProEFI system and let the gizmo blend 2 maps. Or run a standalone ethanol sensor and keep several maps and laptop handy to suit several different ethanol blends.
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