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Old 14-07-2014, 03:46 PM   #1
Alex1380
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Join Date: Jul 2012
Location: Nottinghamshire
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Subframe: Allspeed
Make: Suzuki
ECU: Megasquirts
Default Voltage drops

Hi Guys,

I'm loosing voltage from the alternator to the battery and then back to the ecu which i think is messing my tuning up.
Measured at the alternator i get 14.2-14.5v, at the battery this has dropped to 13.5-13.7v then at the ECU the laptop is telling me i'm getting 12.5-13v
Now I've got it wired from the alternator to the starter then from the starter to the battery. The ECU, injectors, coil pack, fuel pump (all the injection related stuff) runs off a good side wire from the battery though a relay which is switched by the ignition.
I was advised to do this so the battery would even out the voltage from the alternator and act as a capacitor.

should state its a megasquirts ECU.


Any ideas?
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Old 15-07-2014, 10:55 AM   #2
bobjonah
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Subframe: Home Made
CC: 1298
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ECU: standard
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where does the voltage sensor wire come from ?

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Old 15-07-2014, 12:19 PM   #3
Alex1380
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The ecu records the voltage it is receiving which it also logs.
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Old 15-07-2014, 12:54 PM   #4
Richspec
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Default

not familiar with megasquirt but on other ecu's the ecu acts as the earth signal and the power is supplied from elsewhere, which sounds exactly like you have it?
So I'm failing to see how that is affecting your tuning? what symptoms is it displaying?
You of course could have a bad earth which is why your ecu is showing 12.5 -13?
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Last edited by Richspec; 15-07-2014 at 12:55 PM. Reason: spelling
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Old 16-07-2014, 10:14 PM   #5
evolotion
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most likely an earthing issue as stated. if you measure the voltage between the body of the alternator and the earth input to the megasquirt and get a reading thats your problem
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