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Old 01-04-2014, 04:26 PM   #1 (permalink)
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MPGuino + FlexFuel device?

Hello!

I installed an FlexFuel device on my car, and then the MPGuino did'nt work anymore.

I understand that the order should go like this:

ECU -- FFV device --MPGuino -- injector.

But it does'nt work. If i keep it like this:

ECU -- MPGuino -- FFV device -- injector.

It appears to work, but as i understand, it shows false reading because it takes what ECU gives, not what actually happens at injector, as the device extends the pulse.

It should work as i installed it, but it just does'nt. The MPGuino is hooked on the minus wire of the injector.

Any suggestions?

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Old 01-04-2014, 05:15 PM   #2 (permalink)
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It would help if we were to know what this FlexFuel device was.

It would also help if we knew if your engine used a common supply voltage for your fuel injectors, or if it used a common ground.
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Old 01-04-2014, 05:34 PM   #3 (permalink)
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PT-E85: E85 BIOETHANOL
It is basically what pretty much all of the flexfuel boxes do:
Two wires from ECU goes into the box.
There is a circuit that sniffs the pulses. It does'nt matter if the two wires are reversed or not. Basically a logic IC makes it understandable to the core (atmega).
Atmega sends identical but extended pulse to the N-FET, and that controls the injector.
The injector gets positive straight from the battery, and negative from the device.
And it does'nt matter if the wires are reversed or not, because injector does'nt care about polarity.

My engine uses common ground.


EDIT: Oh, i just searched from internet, and someone claims that some injectors might have a flyback diode. And if the wires are reversed, it might do that the MPGuino can't get signal.
Just a wild guess. Reading more...
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Last edited by Quezacotl; 01-04-2014 at 05:40 PM..
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Old 01-04-2014, 05:41 PM   #4 (permalink)
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The injector may not care about polarity, but the MPGuino certainly does.

Does your MPGuino react at all when it is between this gizmo and your fuel injector?
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Old 01-04-2014, 05:44 PM   #5 (permalink)
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It does'nt react at all.

But to be sure about the polarity, i'll try reversing it tomorrow if it has any effect.
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Old 01-05-2014, 06:15 AM   #6 (permalink)
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I tried reversing the polarity, but no effect.
And actually it was the right way the first time. I checked that the injector says + and -.
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Old 01-05-2014, 06:34 AM   #7 (permalink)
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Not related to the topic I'm afraid, but did you have to change any of the other components of your fuel system to suit the E85? I have an E85 station near me (Mäntsälä) and was thinking about converting the Golf to run on it. I heard that the rubber o-rings in the fuel system could degrade in contact with methanol, and that the fuel pump would need to be changed.

On the original topic, and I don't know the mpguino at all, but could you change the injector flow rate stored in the mpguino until it matches the actual fuel consumed? Just fooling it into thinking the engine has bigger injectors/worse FE - it doesn't need to know what fuel you're using, or does it?
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Old 01-05-2014, 06:53 AM   #8 (permalink)
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Quote:
Originally Posted by syncro_user View Post
Not related to the topic I'm afraid, but did you have to change any of the other components of your fuel system to suit the E85? I have an E85 station near me (Mäntsälä) and was thinking about converting the Golf to run on it. I heard that the rubber o-rings in the fuel system could degrade in contact with methanol, and that the fuel pump would need to be changed.

On the original topic, and I don't know the mpguino at all, but could you change the injector flow rate stored in the mpguino until it matches the actual fuel consumed? Just fooling it into thinking the engine has bigger injectors/worse FE - it doesn't need to know what fuel you're using, or does it?
I did'nt have to change any parts.
Only things that you possibly need to do is adjust the timing, or else it affects the acceleration.
And after some time of using only E85, you need to change your oil filter and oil because the ethanol cleans the motor. But that is every year routine anyway.
My car can handle E85 without any boxes on summer, but on winter, either a box or five times of cranking until it starts.
About the O-rings and such, as i have read and heard, those are issues of old cars and stories when people were making moonshine to run their cars. New (around 90's) are already ethanol resistant.


MPGuino does'nt know what fuel you are using. It only counts the duration of injector pulses. Regardless what values you have stored, it should display anything else than 0.00 consumption.
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Old 01-07-2014, 06:33 AM   #9 (permalink)
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I found the problem.
The flexfuel box was not giving enough current to the injector(mono point), so i modified it by paralleling the inputs and outputs.
And when that was solved, the MPGuino got a proper signal.

I always thought that the injector is the most common type, but it's not.
It's low impedance, but still normal, not peak-and-hold.

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