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Thread: Anyone running e85 with oem merc direct injection? m278 e550

  1. #1
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    Anyone running e85 with oem merc direct injection? m278 e550

    Safe to run full e85 or like some DI cars a max of e30?

    11 e550 m278, has flex fuel tables but does anyone know if it has a flex sensor?

    Thank you

    med17.7.1

  2. #2
    E550s got the M278 beginning in 2012 - is that what you meant?

    Haven't seen anyone running full E85, but the fuel system seems able to flow E50 okay.

    I could be wrong, but I don't think there's an actual ethanol sensor.. rather the PCM may calculate fuel type based on fuel flow vs wideband feedback, or fuel flow vs air load, or something along those lines. Also IIRC, the "2nd Fuel" table has the same lambda values as the regular fuel table, but the stoich air/fuel ratios are defined for regular gas and for E85. So I think the PCM calculates actual stoich and then applies that to the fuel tables as 1 lambda. This is all just a theory.

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    I have the M278 and wondered if anything became of this? I would assume everyone would have at least some interest in easy power...
    I'm interested now because I recently saw my first E85 gas station and can't stop thinking about how much I can mix in. Trail and error would likely take months so I was hoping for some insight. I would assume 40% alcohol would be easy, maybe 50 but just don't know. Of course all based on how far the eng is pushed but I'm sure someone has tried to some degree using the oem injectors?

    I read a scary article where they tried to test E85 in a car, only to discover it was a lie and it was actually 40% ethanol. Say one of us finds our mix limit, but it was a dirty stinkin lie and really E40. Then unwittingly we mix in real E85 from an honest station and cook the eng.

    Meanwhile, I'd assume whatever is on the lambda chart for gas is fine for ethanol? I'd assume the same lambda would actually end up a bit cooler? So same chart settings and you simply watch for when you max out your injectors or fuel pump. Right?

    Not sure what the second fuel chart is for, or what triggers it into action. With wide band what fuel would need such a chart? My guess is it's there in case it's used on engines that don't have wide band. Maybe someone who knows can share?
    '16 E550 Coupe RWD - C207.373 / M278.922 / MED17.7.3 / 722.909

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    First you have to get ethanol content tester to test the ethanol from the gas station to get the actual alcohol % , keep in mind as weather changes the stations change the % of alcohol.

    You can run e85 and the car will run fine with no issues but ofcourse tune is required.
    In the long run you will damage the fuel pump, lines, HPFP, and injectors so I would recommend running a mix and get the additional power better than running e85 with stock fuel system.

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    Good to know that outlaw_50
    I was reading about this subject and you gave a great info.
    thank you
    Abdulaziz T Hadi - E-mail: [email protected]

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    Quote Originally Posted by Abdulaziz T Hadi View Post
    Good to know that outlaw_50
    I was reading about this subject and you gave a great info.
    thank you
    your welcome bro, anytime
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    I put some E85 in, and if it's really 85% then I had a tank of 28% pure ethanol in there. It did make more power and I had no timing retard, but it was weird.
    Cold idle was a disaster, either stalling or revving too high. Once past that and into closed loop, it still idled weird and the O2 sensors were reading richer than commanded the whole time.
    Fuel trims were +10-30% despite my adding the appropriate 10% Inj pw. I even bumped it all the way to 40% pw which only lowered trim by ~10. Despite the math saying how much more fuel it was adding, it was actually adding ~10%, as predicted and my mpg dropped ~10% to match.
    So while it seemed to run fine at anything above 1500rpm, I didn't seem to able to handle idle well at all.

    I just topped off with 8.2 gal of gas, which leaves me with ~13% ethanol, and apparently I had forgotten how smooth and quiet it can idle, I had to check the tach to verify the eng was still running. I guess I'll find out tomorrow how it starts.
    '16 E550 Coupe RWD - C207.373 / M278.922 / MED17.7.3 / 722.909

  8. #8
    Quote Originally Posted by chevota View Post
    I put some E85 in, and if it's really 85% then I had a tank of 28% pure ethanol in there. It did make more power and I had no timing retard, but it was weird.
    Cold idle was a disaster, either stalling or revving too high. Once past that and into closed loop, it still idled weird and the O2 sensors were reading richer than commanded the whole time.
    Fuel trims were +10-30% despite my adding the appropriate 10% Inj pw. I even bumped it all the way to 40% pw which only lowered trim by ~10. Despite the math saying how much more fuel it was adding, it was actually adding ~10%, as predicted and my mpg dropped ~10% to match.
    So while it seemed to run fine at anything above 1500rpm, I didn't seem to able to handle idle well at all.

    I just topped off with 8.2 gal of gas, which leaves me with ~13% ethanol, and apparently I had forgotten how smooth and quiet it can idle, I had to check the tach to verify the eng was still running. I guess I'll find out tomorrow how it starts.
    Where did you increase injector pw? The inj slope value or the inj pw table? Could you post a screenshot?

    This response to ethanol could help diagnose your original problem. What did your rail pressure look like in the logs?

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    Inj pw table. Never tried the slope. ~1750psi at idle and ~2450 above

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    Speaking of clues, I made yet another tune in an attempt to tame the idle issue. The oem file idles fine on gasoline so I've been trying to figure out what in my tunes is causing it, which E85 made much worse. So this latest tune had what I thought would still make full power but with minimal mods to hopefully fix the idle. My power was less than half! I floored it on the freeway and it was holding throttle at 30, which is ~25% open. It's never pulled throttle like that. At 5500rpm my MAP was 12.5. I floored it several times and 30 was the limit.
    Note my min turbo duty cycle is 52%, so I think it would've pulled boost instead, which is what it did before with the oem tune but now it couldn't. So I think whatever is limiting the oem tune I managed to find again, but it went too far in pulling power with the throttle, like 30 is a safety default or something. Just an assumption but makes sense.

    My main suspect is temps, like Airflow/General/Overheat Prevention/Load Limits, because I've never set that to oem, that I can recall. Or maybe Exhaust temps, but it's made more power than this with the oem temps and the turbo duty cycle at 52...
    I suspect temps because the water temp was 208F when this power loss happened, but in the am when the eng was only 180F, the throttle was only limited to ~62% and MAP was 23.8, which of course made double the power. AIT was ~100, and on the am it was 75. Other than that I can't think of anything different between the AM drive vs the lower power PM drive, so my guess is a temp limiter.

    That minimal tune did nothing for the idle btw, it pegged the 1400rpm rev limiter until I put it in drive to tame it. I can then put it right back into park and the rpms are what I have programmed in. It's like I'm breaking the cycle or maybe something is outside its limits and doesn't know what to do and that brings it back. I dunno...
    I normally have the P/N rev limit at 2500, for the inevitable scenario just like this since I have no actual control over the throttle. It was just a matter time and didn't take long at all... 2500 is obnoxious at 5am, probably not good for it, and most importantly it won't allow me to put it in drive. So 1400 works but still high enough to show a normal start once I it figure it out.
    '16 E550 Coupe RWD - C207.373 / M278.922 / MED17.7.3 / 722.909

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    Quote Originally Posted by chevota View Post
    I put some E85 in, and if it's really 85% then I had a tank of 28% pure ethanol in there. It did make more power and I had no timing retard, but it was weird.
    Cold idle was a disaster, either stalling or revving too high. Once past that and into closed loop, it still idled weird and the O2 sensors were reading richer than commanded the whole time.
    Fuel trims were +10-30% despite my adding the appropriate 10% Inj pw. I even bumped it all the way to 40% pw which only lowered trim by ~10. Despite the math saying how much more fuel it was adding, it was actually adding ~10%, as predicted and my mpg dropped ~10% to match.
    So while it seemed to run fine at anything above 1500rpm, I didn't seem to able to handle idle well at all.

    I just topped off with 8.2 gal of gas, which leaves me with ~13% ethanol, and apparently I had forgotten how smooth and quiet it can idle, I had to check the tach to verify the eng was still running. I guess I'll find out tomorrow how it starts.
    E85 usually takes longer to cold start, also needs more fuel to idle cold. Which leads me to think possibly your ecu is leaning out at cold start, which is causing the rpms to idle higher when cold for more fuel, maybe.

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    When you add alcohol %. Your idle will suffer, right? You have to add more fuel, because of lean condition ?

    Wrong.. The alcohol has more air in it. So, you need to restrict air flow. Airflow->Electric throttle body and restrict air flow while idling. Like -20%, -15%, -10% and finetune. You are welcome .
    If there is too much air in the system and you add fuel, you will add more rpm. The ECU can't compensate that and start to revup. Now it should start to make sense -> why it start to raise rpm or the STFT is all over the place.
    Last edited by Makeclick; 06-17-2022 at 01:26 AM. Reason: LTFT->STFT

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    So youre suggesting it needs less fuel at idle, but more everywhere else? Ethanol has a less energy than gas which is why you have to richen it up, including idle. Idle mix is less important than elsewhere but I would never set it leaner than pure gas. At my ethanol ratio itll still idle on the same qty of fuel as it would on gas, but its lean and once it sees that it richens it up.
    Like many things in the HP program, adjusting start throttle position does nothing, it does what it wants regardless. Idle speed adj works but not when it loses control like its been doing. Eg this am, as usual, it bounced against the rev limiter until I put it in drive then right back to Park and idle followed the programming just fine. If I dont do that it takes about a minute for idle to slooowly come down.
    What also doesnt make sense is why the fuel trims dont match what is actually happening. Eg my open loop Inj pw fo idle is .32, once closed loop kicks in it sees its lean and bumps trims +30. Then pw is .35. I didnt do the math but .32 +30% does not = .35.

  14. #14
    Advanced Tuner outlaw_50's Avatar
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    Quote Originally Posted by Makeclick View Post
    When you add alcohol %. Your idle will suffer, right? You have to add more fuel, because of lean condition ?

    Wrong.. The alcohol has more air in it. So, you need to restrict air flow. Airflow->Electric throttle body and restrict air flow while idling. Like -20%, -15%, -10% and finetune. You are welcome .
    If there is too much air in the system and you add fuel, you will add more rpm. The ECU can't compensate that and start to revup. Now it should start to make sense -> why it start to raise rpm or the STFT is all over the place.
    Nice way of thinking
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    I believe we're thinking of two different things. My Inj pw adjustment doesn't actually add more fuel and I have zero control over the throttle. If the throttle didn't open then yes that would solve my problem, but nothing I can do about that. And when I say I bump the Inj pw up and things get worse, I'm just changing a # in the program. Like telling my cat to come here, he doesn't actually do it. So from cold start to closed loop to when I shut it off, the only thing my Inj pw setting does is change is the # on the screen for fuel trims. Actual fuel delivered is the same. When it transitions from open to closed loop it'll change, but it's not my doing and again my Inj pw setting only changes the fuel trim #'s. The moment the O2's start working it'll say ~1.25 lambda, so it richens it up. I can set the pw to whatever and this happens each time. Despite my pw change not physically adding more fuel, it does somehow upset the ecu at start. Just like adding ethanol should not cause this problem, changing a # that doesn't actually do anything shouldn't either, but it does.
    I can also lean the pw and while it still looses control of idle, it did recover sooner. Still not soon enough but somehow it made a difference in the ecu.
    I suspect, at least I would assume, the open loop control is based on previous data. So maybe it needs to run on ethanol for xx number of cold cycles before it works right? I rekon I have ~20 cold starts on it and it's no better than day one, and I'm not interested in testing my theory so I'm done playing with it.

    I can change the Open Loop Lambda, which does work and change fuel qty during open loop, but only after the ecu freaks out so it's no help.
    Once it's in closed loop and you give it a minute to settle, it idles with the throttle at 12.7%, same as with gas, and inj pw is ~10% more than with gas as it should be. Not less air or less fuel. So with the same qty of air it needs ~10% more fuel, there is no way around this. If ethanol had "more air" in it then I suppose the throttle could close a teeny bit, maybe. It has O2, but that's not air, and more O2 means it needs more fuel not less air. It's not a carburetor which could get away with that to some extent.

    That throttle position setting you mentioned, that I said doesn't work, is mostly true. It does work but only when the Ign is On but eng is Off, so it doesn't actually work. I've had it set substantially lower than stock for months, I think about half the oem setting, but it never changed anything. I did change it back to oem along with most all my settings to see if would fix my issue, but nothing.
    So it'll sit at whatever it's programmed at until I touch the start button, then the throttle does what it wants. Not sure why that function even exists but my guess is it simply had to have a chart because otherwise the throttle didn't know what to do. Then HP saw it and thought it was useful? Or maybe they just add any chart they can figure out so it looks like we have more to play with, but don't care if it actually does anything. I haven't counted but lots of things do nothing or don't do what it claims. That is if you can decipher what it's supposed to do by their cryptic description. When people are cryptic with me they either have no time or interest to explain, or they don't actually know the answer and are trying to avoid getting cornered. Mostly the latter.

    This ethanol thing too much of a pita to deal with right now, but maybe I'll try again at a later date, or if I get a different car. I do like octane and power boost but everything with a computer or electronics comes with a price and I'm broke. I miss my carburetor and I fantasize about this car with mechanical fuel injection and throttle. Or maybe just all the bs programming removed so it simply does what you ask. That would be a tune worth paying for...
    '16 E550 Coupe RWD - C207.373 / M278.922 / MED17.7.3 / 722.909

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    Quote Originally Posted by chevota View Post
    I believe we're thinking of two different things. My Inj pw adjustment doesn't actually add more fuel and I have zero control over the throttle. If the throttle didn't open then yes that would solve my problem, but nothing I can do about that. And when I say I bump the Inj pw up and things get worse, I'm just changing a # in the program. Like telling my cat to come here, he doesn't actually do it. So from cold start to closed loop to when I shut it off, the only thing my Inj pw setting does is change is the # on the screen for fuel trims. Actual fuel delivered is the same. When it transitions from open to closed loop it'll change, but it's not my doing and again my Inj pw setting only changes the fuel trim #'s. The moment the O2's start working it'll say ~1.25 lambda, so it richens it up. I can set the pw to whatever and this happens each time. Despite my pw change not physically adding more fuel, it does somehow upset the ecu at start. Just like adding ethanol should not cause this problem, changing a # that doesn't actually do anything shouldn't either, but it does.
    I can also lean the pw and while it still looses control of idle, it did recover sooner. Still not soon enough but somehow it made a difference in the ecu.
    I suspect, at least I would assume, the open loop control is based on previous data. So maybe it needs to run on ethanol for xx number of cold cycles before it works right? I rekon I have ~20 cold starts on it and it's no better than day one, and I'm not interested in testing my theory so I'm done playing with it.

    I can change the Open Loop Lambda, which does work and change fuel qty during open loop, but only after the ecu freaks out so it's no help.
    Once it's in closed loop and you give it a minute to settle, it idles with the throttle at 12.7%, same as with gas, and inj pw is ~10% more than with gas as it should be. Not less air or less fuel. So with the same qty of air it needs ~10% more fuel, there is no way around this. If ethanol had "more air" in it then I suppose the throttle could close a teeny bit, maybe. It has O2, but that's not air, and more O2 means it needs more fuel not less air. It's not a carburetor which could get away with that to some extent.

    That throttle position setting you mentioned, that I said doesn't work, is mostly true. It does work but only when the Ign is On but eng is Off, so it doesn't actually work. I've had it set substantially lower than stock for months, I think about half the oem setting, but it never changed anything. I did change it back to oem along with most all my settings to see if would fix my issue, but nothing.
    So it'll sit at whatever it's programmed at until I touch the start button, then the throttle does what it wants. Not sure why that function even exists but my guess is it simply had to have a chart because otherwise the throttle didn't know what to do. Then HP saw it and thought it was useful? Or maybe they just add any chart they can figure out so it looks like we have more to play with, but don't care if it actually does anything. I haven't counted but lots of things do nothing or don't do what it claims. That is if you can decipher what it's supposed to do by their cryptic description. When people are cryptic with me they either have no time or interest to explain, or they don't actually know the answer and are trying to avoid getting cornered. Mostly the latter.

    This ethanol thing too much of a pita to deal with right now, but maybe I'll try again at a later date, or if I get a different car. I do like octane and power boost but everything with a computer or electronics comes with a price and I'm broke. I miss my carburetor and I fantasize about this car with mechanical fuel injection and throttle. Or maybe just all the bs programming removed so it simply does what you ask. That would be a tune worth paying for...
    This is odd I?ve been running e25-e40 mix in my car since before Hptuners and never had that issue I?m now using a e30 mix with my 93 tune I didn?t change any values yet and I?m still having no issues. Maybe something or a sensor is going bad causing this problem

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    There's no doubt my car has issues, but it's weird how it acted. How it revs out of control or the trim math not adding up, or how it won't idle right most of the time. Not sure if I mentioned that but it won't stay on target. If the idle is set to say 600 in neutral it'll go from ~550 to 650, back n forth over n over. The data is too slow to see what is driving it so I don't have a clue.
    I put 14gal of gas in it and it started fine.... I was looking fwd to noting the power difference but it's rather hot out today which killed it. Not sure about other people but the heat has a drastic effect on mine.

    I'm guessing you never looked at your fuel on cold start if it never gave you trouble, but I was curious if it just feeds the usual gas amount or does it add more? And when the O2s kick on, what's the lambda before it adjusts and what's the fuel trim before and after it adjusts?
    I did learn one thing, the LTFT pegs out at 30 and STFT at 25. Before this mess I had no clue what the limits were.

    Do you run ethanol for power or? In my area they made sure the price of the E85 was set so your miles per $ are about the same.
    What about your fuel maps? Are they oem? I've also always wondered about the "second fuel" maps and what could possibly trigger it to switch to that map? E85 is really the only thing I could think of but what triggers it? Or maybe it's an actual E85 map for a flex fuel car but redundant for us?
    '16 E550 Coupe RWD - C207.373 / M278.922 / MED17.7.3 / 722.909

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    Quote Originally Posted by chevota View Post
    There's no doubt my car has issues, but it's weird how it acted. How it revs out of control or the trim math not adding up, or how it won't idle right most of the time. Not sure if I mentioned that but it won't stay on target. If the idle is set to say 600 in neutral it'll go from ~550 to 650, back n forth over n over. The data is too slow to see what is driving it so I don't have a clue.
    I put 14gal of gas in it and it started fine.... I was looking fwd to noting the power difference but it's rather hot out today which killed it. Not sure about other people but the heat has a drastic effect on mine.

    I'm guessing you never looked at your fuel on cold start if it never gave you trouble, but I was curious if it just feeds the usual gas amount or does it add more? And when the O2s kick on, what's the lambda before it adjusts and what's the fuel trim before and after it adjusts?
    I did learn one thing, the LTFT pegs out at 30 and STFT at 25. Before this mess I had no clue what the limits were.

    Do you run ethanol for power or? In my area they made sure the price of the E85 was set so your miles per $ are about the same.
    What about your fuel maps? Are they oem? I've also always wondered about the "second fuel" maps and what could possibly trigger it to switch to that map? E85 is really the only thing I could think of but what triggers it? Or maybe it's an actual E85 map for a flex fuel car but redundant for us?
    Maybe your O2 sensor/s are going bad causing the fuel trims to go crazy
    I have not data logged cold starts. I can next time I cold start and share them with you
    My fuel maps are changed but the car is running a little rich with this tune, as it?s my 93 tune I can definitely lean out more during the WOT
    My second fuel tables are the same I have not touched those but from my lambda values while @wot doesn?t seem like 2nd fuel tables are touched not sure how much alcohol the ecu needs to see to trigger those tables

    If you want to share your tune file and data logging file I can look it over and try to make some corrections

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    My O2's are the original and seem to be ok, but I have new ones, just haven't installed them yet. It has 52k on it now.

    Here's the tune I have in it now. I change them a lot but I'm not really getting anywhere. The only way to fix the idle issue is to load the oem tune.
    E550 77x (Don't use!).hpt
    The "Don't use" is a warning to other people because I'm not sure what it would do in a normal car

    Here's a few from my commute. I haven't had any good ones in a while, where I could floor it for long, but see if these are of any value:
    22 Jun '22 pm.hpl
    21 Jun '22 pm.hpl
    20 Jun '22 pm.hpl

    Thanks
    '16 E550 Coupe RWD - C207.373 / M278.922 / MED17.7.3 / 722.909

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    Here's a couple where I got to floor it for than a couple seconds. The 8 June is the fastest I've ever gone in this car. Extremely rare opportunity.
    23 Jun '22 am.hpl
    8 Jun '22 pm.hpl
    '16 E550 Coupe RWD - C207.373 / M278.922 / MED17.7.3 / 722.909