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Why does no one make a Flex Fuel kit?

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Old 01-04-2018, 12:24 PM
  #21  
Podium
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Originally Posted by Drewstein View Post

No reason to have flex fuel without big power, it's not worth the investment, especially NA.

That's not true at all.
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Old 01-04-2018, 06:10 PM
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For older N54 turbo BMWs a piggyback computer was used (I think common for subies in the old days also)... basically intercepted various parameters including crank/cam position altering it and fudged the data back to the stock ECU to keep it happy... easily could add an E sensor. But only reason piggybacks were used is cause the ECU was so difficult to hack initially.
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Old 01-04-2018, 06:31 PM
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Originally Posted by Joshboody View Post
For older N54 turbo BMWs a piggyback computer was used (I think common for subies in the old days also)... basically intercepted various parameters including crank/cam position altering it and fudged the data back to the stock ECU to keep it happy... easily could add an E sensor. But only reason piggybacks were used is cause the ECU was so difficult to hack initially.
I'm pretty sure that's how the FF kit on my STi worked. It intercepted the signal between the MAF sensor and ECU. When it saw there was more ethanol in the fuel, it would fudge the numbers to make the engine think more air was coming in, so it would dump more fuel. There was no direct interface with the ECU.

I don't know if there would be a way to advance timing based off ethanol content with this sort of setup though. I don't know how much use it would be NA.
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Old 01-05-2018, 12:18 PM
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You'd really only have to intercept crank position to raise global timing based on E and rpm... easy peasy. I'm ok with planning my fill ups and keeping gas cans at the house though

With NA just E35 does a LOT... so even if have to resort to 91 map with some E in the tank, not a big deal. And 10% swings either way in your mix, also not a big deal.
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Old 01-05-2018, 01:17 PM
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Originally Posted by Joshboody View Post
You'd really only have to intercept crank position to raise global timing based on E and rpm... easy peasy. I'm ok with planning my fill ups and keeping gas cans at the house though

With NA just E35 does a LOT... so even if have to resort to 91 map with some E in the tank, not a big deal. And 10% swings either way in your mix, also not a big deal.

Cam sensor, you would need to read the cam sensor for timing changes. I'm working on this now with an Arduino Nano. I have a working 2-step setup with it, but it can't do timing retard.
It seems the easiest way is to send the cam sensor through the arduino and either speed up or delay the signal to the PCM. I haven't tried it yet, but it shouldn't be too hard to do.


You can use a GM flex fuel sensor. I believe the GM sensor does a 5v square wave signal so that it can do ethanol content and fuel temperature on a single signal wire. With a little programming how-to, it wouldn't be too hard to read the flex fuel signal and adjust the cam sensor based on this. Probably easier than the cam sensor would be tricking the IAT sensor to do timing adjustments and supplemental fueling.
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Old 01-05-2018, 01:22 PM
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Originally Posted by JoeNova View Post
Cam sensor, you would need to read the cam sensor for timing changes. I'm working on this now with an Arduino Nano. I have a working 2-step setup with it, but it can't do timing retard.
It seems the easiest way is to send the cam sensor through the arduino and either speed up or delay the signal to the PCM. I haven't tried it yet, but it shouldn't be too hard to do.


You can use a GM flex fuel sensor. I believe the GM sensor does a 5v square wave signal so that it can do ethanol content and fuel temperature on a single signal wire. With a little programming how-to, it wouldn't be too hard to read the flex fuel signal and adjust the cam sensor based on this. Probably easier than the cam sensor would be tricking the IAT sensor to do timing adjustments and supplemental fueling.
Yeah, I thought about the IAT sensor option. (Again, I have no tuning experience, just some basic theoretical knowledge) It seems like you might run into issues when it gets really cold in the winter though.
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Old 01-05-2018, 01:37 PM
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I spoke too soon... you also need to change PW for accurate fueling. This can be global since a basic % diff.

IAT for 2 maps would work, but scaling based on E seems little complicated. And for SD peeps it would alter the fueling.

I know nothing of 2 step, but couldn't you use park vs in gear cutoff tables... AFAIK ECU only references clutch and mph.
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Old 01-05-2018, 01:43 PM
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I'm way out of my depth here, but feel free to carry on. Maybe something constructive will come from it. haha
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Old 01-05-2018, 01:46 PM
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Originally Posted by NSFW View Post
Related question - are there hobbyists involved in reverse-engineering C5 ECUs/PCMs and adding new features? If so, where do they hang out?
Not that I know of, only companies like EFI Live, HP Tuners have decoded the ecu. Most people just jump to an aftermarket ECU rather than continue to hack the stock one. The aftermarket ecus gain you so much it seems like a waste of time / money to try hacking the stock ECU after a certain point.
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Old 01-05-2018, 01:59 PM
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Originally Posted by Joshboody View Post
I know nothing of 2 step, but couldn't you use park vs in gear cutoff tables... AFAIK ECU only references clutch and mph.


Any method of using the PCM for 2 step is going to be fuel cut only (and lazy). The easiest method is the Bad VSS limit. You pass the VSS signal through a relay on the NC circuit and then use a momentary to ground the VSS signal. You end up with an artificial limiter. Works, but not very well. If you want a very responsive setup that isn't going to destroy everything, spark cut is the way to go.


Originally Posted by NSFW View Post
Related question - are there hobbyists involved in reverse-engineering C5 ECUs/PCMs and adding new features? If so, where do they hang out?

Several, it depends VERY specifically on what features you're looking for.
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Old 01-06-2018, 02:36 AM
  #31  
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Originally Posted by JoeNova View Post
Several, it depends VERY specifically on what features you're looking for.
I am just finishing up a project with my Subaru and it now does rev-matching for downshifts: https://github.com/LegacyNsfw/EcuHacks

I haven't got a Corvette yet, but I'm going to go look at another one tomorrow... If/when I get one I'll be wanting to do something similar. And I don't know if I could gotten as far I did with my Subaru without the help from the rest of the people in the community.
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Old 01-06-2018, 07:00 PM
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Old 03-20-2018, 03:29 AM
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yes!

So i got around to trying this out. I got my P59 from a 04 tahoe, i took the red covers off the connector and swapped on the green. I had to move the wire from green 52 to green 75 for the alternator f terminal. I did a segment swap with a 04 z06 and brought over my injector data, idle settings, ve, maf and spark stuff over to the p59 pcm. I deleted all the o2 heater and sensor 2 DTCs and did a pcm / bcm relink. The car starts, idles and everything with the TB seems to be working fine. I didnt do all of this at once it took some time and trial and error to figure out what it wanted but thats all i had to do. I also havnt driven the car so if something different happens during driving i wouldnt know yet. I also have not hooked up a flex fuel sensor yet, it should be here in a couple days. Hopefully everything will work with that. Honestly even if it dont work swapping to the p59 is worth it to me because the newer faster pcm controls the idle of my big cam much better.


this sounds very doable. I have an 04 z06 that needs a new engine wiring harness and I have most of the parts

anyone know of some folks with expertise in doing this, willing to pay for the right hands with HP tuners, and e85 experience. sounds like a solid opportunity here!
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Old 03-21-2018, 06:33 PM
  #34  
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Last edited by TastyBacon; 03-21-2018 at 06:33 PM.
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Old 03-21-2018, 06:43 PM
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Originally Posted by Rkreigh View Post
yes!

So i got around to trying this out. I got my P59 from a 04 tahoe, i took the red covers off the connector and swapped on the green. I had to move the wire from green 52 to green 75 for the alternator f terminal. I did a segment swap with a 04 z06 and brought over my injector data, idle settings, ve, maf and spark stuff over to the p59 pcm. I deleted all the o2 heater and sensor 2 DTCs and did a pcm / bcm relink. The car starts, idles and everything with the TB seems to be working fine. I didnt do all of this at once it took some time and trial and error to figure out what it wanted but thats all i had to do. I also havnt driven the car so if something different happens during driving i wouldnt know yet. I also have not hooked up a flex fuel sensor yet, it should be here in a couple days. Hopefully everything will work with that. Honestly even if it dont work swapping to the p59 is worth it to me because the newer faster pcm controls the idle of my big cam much better.


this sounds very doable. I have an 04 z06 that needs a new engine wiring harness and I have most of the parts

anyone know of some folks with expertise in doing this, willing to pay for the right hands with HP tuners, and e85 experience. sounds like a solid opportunity here!
Well, that doesn't sound overly complicated. Definitely keep us posted.
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Old 03-21-2018, 08:49 PM
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Are there flex-fuel vehicles that use the 0411 PCM? Or did that PCM get the retired before flex-fuel became a thing?
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Old 03-25-2018, 09:21 PM
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So that is my post from ls1tech. The PCM swap is very easy and im still tuning but so far it is coming along great. Problem is i have the flex fuel sensor plumbed, wired into the pcm and flex fuel is turned on in the tune but it is not reading alcohol percent. I have not messed with the flex fuel part any more yet but when i get the 93 tune down solid i will start messing with it again. I have been talking with james short from shortuning about this and he has figured it out by adding parameters with the user defined parameters in hp tuners but i havnt messed with it much after. He is offering this swap with flex fuel through is shop so if you are around ky then you should get in touch with him.
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Old 03-25-2018, 09:25 PM
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Well I'm about a stone's throw away from Kentucky actually, but not that part. That would be a good 4 hours drive at least.
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Old 04-16-2018, 07:51 AM
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Originally Posted by hodge9386 View Post
So that is my post from ls1tech. The PCM swap is very easy and im still tuning but so far it is coming along great. Problem is i have the flex fuel sensor plumbed, wired into the pcm and flex fuel is turned on in the tune but it is not reading alcohol percent. I have not messed with the flex fuel part any more yet but when i get the 93 tune down solid i will start messing with it again. I have been talking with james short from shortuning about this and he has figured it out by adding parameters with the user defined parameters in hp tuners but i havnt messed with it much after. He is offering this swap with flex fuel through is shop so if you are around ky then you should get in touch with him.
I have a TTiX TT Z06 and so the E85 flex fuel conversion is hot on my to do list.

If I can repin the ecm and swap in a truck ecm that already has the OS and provisions for flex fuel, and drive the gauges and get the car to run I'm in.

Can you put us in touch with Mr. Short? I'm going down to Bowling Green in mid may and could leave the car with himr to get er done.

This is a very cool approach and while not nearly as savvy as the aftermakret stuff, with a solid wide band monhitoring and a bit of talent with HP tuning the car I think I can get it to do what I want!!!

Last edited by Rkreigh; 04-16-2018 at 07:52 AM.
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Old 04-17-2018, 05:19 PM
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