Motiv flex fuel erratic ethanol content under WOT

doublespaces

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Precisely. No return LINE..

Actually there is a return line, unless I'm misunderstanding the question.

It's just inside of your fuel tank and returns fuel from the regulator on the driver side back to the passenger side where the pumps are at. A return line is simply the waste fuel line after the regulator. In our cars the regulator is in the tank by default so it's pretty short.

We have a dead head fuel system but the pumps never stop running, there is always going to be waste fuel returning back to the pump side from the regulator side and that's what drives the venturis to ensure you don't run out of gas by getting all the fuel stuck on one side of the tank. At least, that's how my current fuel setup works(not pictured). I forget how the oem Venturi system operates.

20190809_175004.png
 

langsbr

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To be clear, can you connect the ethanol sensor to that in tank line? I would suspect not, and for all intents and purposes our cars are considered a "returnless" fuel system.

I think that, combined with the tone of how Milan came across is the root issue. Unless you've fully converted to a return style fuel system, there isn't a return.
 
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doublespaces

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I don't actually care, call it a waste fuel line if you prefer. One person was exercising knowledge and the other person didn't seem to understand what he was getting at so I'm just clarifying.
 

fmorelli

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Actually there is a return line, unless I'm misunderstanding the question.
Context matters. There is no return line in a traditional external return-to-tank ... where someone could install a sensor (e.g. flex fuel). Both "return" systems on the N54 are localized - inside the HPFP, and inside the tank for the LPFP. In the context of the original dialog, there is no external return line to which someone could have incorrectly installed a flex-fuel sensor (and to which the comment was, one might not have constant fuel flow).

Filippo
 

Threetirtyfive

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It's Milan trying to be a smartass but it actually backfiring as he clearly doesn't know what he's talking about.
There are no return lines from the engine back to the tank, so no chance of the eth sensor being on the wrong line. You would not mount the sensor inside the fuel tank and certainly not inside the high pressure fuel pump.
Further the return IN TANK (from the STOCK pressure regulator, in tank) as well as venturi returns is there for any HP build inc stock cars, where he was suggesting for all 'us early big power' builds you have a return. Absolute bs.

Milan is exercising a lack of knowledge.
 
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Milan

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It's Milan trying to be a smartass but it actually backfiring as he clearly doesn't know what he's talking about.
There are no return lines from the engine back to the tank, so no chance of the eth sensor being on the wrong line. You would not mount the sensor inside the fuel tank and certainly not inside the high pressure fuel pump.
Further the return IN TANK (from the STOCK pressure regulator, in tank) as well as venturi returns is there for any HP build inc stock cars, where he was suggesting for all 'us early big power' builds you have a return. Absolute bs.

Milan is exercising a lack of knowledge.

I don't know who you are but I think you are trolling just to troll, or maybe you have little to no experience building cars and your FBO 335 is the fastest thing you have owned.

If you are running a flex fuel sensor there is a high likelihood that you have a custom fuel setup, most likely port injection at the minimum. It's also likely that you are running 2 LPFPs. Now if you want to do this the right way, you need either a BPM4 or external regulator so the factory EKPM doesn't slow down your main pump once your Hobbs switch comes on, this is the correct way to do your fuel system. Now because you have lines running all over the place, it gives you a lot of places you could potentially mount the flex fuel sensor. If you mount it in the return line, which is actually very common on some other platforms, you can sometimes get air in the line and the sensor can no longer read accurately.

While I realize that this wasn't the case with the OP, he would have had the same symptoms with what I described.

On the other note, there is always a return line, period. It might be in tank, but there is no such thing as a returnless setup and the fact that the internet has made that a term is stupid to me. On many modern cars it's not even in tank it's just in the back of the vehicle.
 

langsbr

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I don't know who you are but I think you are trolling just to troll, or maybe you have little to no experience building cars and your FBO 335 is the fastest thing you have owned.

If you are running a flex fuel sensor there is a high likelihood that you have a custom fuel setup, most likely port injection at the minimum. It's also likely that you are running 2 LPFPs. Now if you want to do this the right way, you need either a BPM4 or external regulator so the factory EKPM doesn't slow down your main pump once your Hobbs switch comes on, this is the correct way to do your fuel system. Now because you have lines running all over the place, it gives you a lot of places you could potentially mount the flex fuel sensor. If you mount it in the return line, which is actually very common on some other platforms, you can sometimes get air in the line and the sensor can no longer read accurately.

While I realize that this wasn't the case with the OP, he would have had the same symptoms with what I described.

On the other note, there is always a return line, period. It might be in tank, but there is no such thing as a returnless setup and the fact that the internet has made that a term is stupid to me. On many modern cars it's not even in tank it's just in the back of the vehicle.

I think the problem is you came across really poorly in your initial response. It's been shown that while there is a "return," NEITHER is useable as a line to connect the flex fuel sensor to in an OEM configuration.

I would also disagree completely that if you're running flex fuel there's a high likelihood of having a custom fuel setup and PI. I'd wager it's the opposite and a vast majority of flex fuel users are NOT using PI or on bigger fuel systems. They even have MHD OTS maps for flex fuel. Also, the number of 600+ whp setups without custom return line setups is vastly more than those that have converted to a full return style fuel system.

Your final note is just you trying to backtrack on your initial troubleshooting and inability to simply admit it wasn't applicable. Instead you were a bit brash calling @Threetirtyfive's comment stupid. You're still just trying to save face because you cannot just admit that your suggestion didn't make much sense for the vast majority of use cases.
 

Threetirtyfive

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I don't know who you are but I think you are trolling just to troll, or maybe you have little to no experience building cars and your FBO 335 is the fastest thing you have owned.

If you are running a flex fuel sensor there is a high likelihood that you have a custom fuel setup, most likely port injection at the minimum. It's also likely that you are running 2 LPFPs. Now if you want to do this the right way, you need either a BPM4 or external regulator so the factory EKPM doesn't slow down your main pump once your Hobbs switch comes on, this is the correct way to do your fuel system. Now because you have lines running all over the place, it gives you a lot of places you could potentially mount the flex fuel sensor. If you mount it in the return line, which is actually very common on some other platforms, you can sometimes get air in the line and the sensor can no longer read accurately.

While I realize that this wasn't the case with the OP, he would have had the same symptoms with what I described.

On the other note, there is always a return line, period. It might be in tank, but there is no such thing as a returnless setup and the fact that the internet has made that a term is stupid to me. On many modern cars it's not even in tank it's just in the back of the vehicle.
I actually have a fully forged n54 with pi, I've also set up a pressure regulated pi system with aic6 on another built n54. Neither has a return line nor is it normal or necessary.
The oem regulator in tank isn't what you were implying by saying big power builds.
Both of these car are big power builds, neither has a return.

Pi from fuel tank is on the lpfp feed with no return and where you would mount the sensor.

Pi from a boot mounted tank has a return from the pressure regulator, to the tank in boot, but would be 100 percent eth {or meth} and not applicable to where you would mount an eth sensor.
Congratulations on being a bellend.
 
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doublespaces

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For what it's worth I've known more than one person to put the sensor on the return line back from the engine, yes a custom one. They did it because they thought it wouldn't impede fuel flow.

These were the things likely going through his head, there can be a return line with a sensor on it. I've seen it.

From there it turned into squabbling and I digress.
 

Threetirtyfive

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For what it's worth I've known more than one person to put the sensor on the return line back from the engine, yes a custom one. They did it because they thought it wouldn't impede fuel flow.

These were the things likely going through his head, there can be a return line with a sensor on it. I've seen it.

From there it turned into squabbling and I digress.

The only time you do this is from a PI rail (it's highly unusual) and on a PI rail fed of a separate pressure regulator from a separate tank. In such a case it would be 100% eth or meth, again completely irrelevant place to mount the eth sensor. Most (ALL)PI rails by default have one opening, the other side has a bolt on so return is optional.
A PI rail fed off the LPFP feed (where you would feasibly need to measure the eth mixture) will NEVER have a return line as you would be defeating the LPFP system in the car and reduce LPFP pressure.

Taking the arrogant attitude that everyone you speak to on the forum is a clueless idiot is why I'm making a point to Milan.
 

fmorelli

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For what it's worth I've known more than one person to put the sensor on the return line back from the engine, yes a custom one. They did it because they thought it wouldn't impede fuel flow.
Interesting. Does the sensor materially impede flows at the power levels the N54 produces?

On other platforms, when running the sensor on a return line (real ... big power builds), guys run software which locks the E content value under WOT, which prevents the sensor going to zero when the return line possibly goes dry. On a stock DME that would be a @jyamona kinda thing :-D.

Filippo
 

ifjd073

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Solved: Turned out to be the 12V reference line. I switched it to another 12v line and it cleared right up.

I'm assuming that the spikes were due to my PR coils. The reference wire would have more voltage running through it during WOT, so it would cause the output to spike.
Just to clarify, since I believe I'm having this same problem, you switched the orange "power" wire that the Reflex+ was drawing from, correct? If so, and one of the wires had fluctuating voltage, you'd think they'd recommend a specific wire to draw from in the install...
 

jakeg

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Just to clarify, since I believe I'm having this same problem, you switched the orange "power" wire that the Reflex+ was drawing from, correct? If so, and one of the wires had fluctuating voltage, you'd think they'd recommend a specific wire to draw from in the install...
So this was for the flex fuel module.

Yes, i just swapped the 12V line to another stable line and it worked fine.

I believe it started to happen again after a couple thousand miles but I cant remember exactly. I switched to the latest version of the reflex+ and have had no issues since.
 

mattjohnson650

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So this was for the flex fuel module.

Yes, i just swapped the 12V line to another stable line and it worked fine.

I believe it started to happen again after a couple thousand miles but I cant remember exactly. I switched to the latest version of the reflex+ and have had no issues since.
Could you specify which stable wire you switched it to for power? Having the same problem..
 

veiss335

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Solved: Turned out to be the 12V reference line. I switched it to another 12v line and it cleared right up.

I'm assuming that the spikes were due to my PR coils. The reference wire would have more voltage running through it during WOT, so it would cause the output to spike.
What power source did you end up using to eliminate the ethanol spike? I'm having the same issues and have tried different power sources with no luck.