Tach signal and EFI, Megasquirters and Subaru converters please read... |
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Tach signal and EFI, Megasquirters and Subaru converters please read... |
falcor75 |
Jul 25 2016, 01:39 AM
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#1
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Senior Member Group: Members Posts: 1,579 Joined: 22-November 12 From: Sweden Member No.: 15,176 Region Association: Scandinavia |
I'm running my 2.0 four cylinder with an aftermarket ECU.
In the settings for the tach signal I've selected 12v, 50% duty and this worked fine for a few months of testing. The day before my dyno session the tach started behaving wierdly. It would start up fine but after a little bit of running it would settle between 3k-4k rpm. Revving the engine would momentarily get it back to normal but after a few seconds at constant rpm it would return to its new favorite position. Any ideas what could be causing this? |
stugray |
Jul 25 2016, 12:54 PM
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#2
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Advanced Member Group: Members Posts: 3,824 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
Where are you grabbing the tach signal?
If it is from the coil (points) then it is not just 12Volts, but more like +/-200. I have a homebuilt datalogger (ECU) and I pull the signal from the optical sensor in my Mallory Unilite. It IS a nice clean 0-12VDC signal, but unlikely it is 50% Duty Cycle. Can you put an oscope on the signal and look at it? If you dont have access to an oscope, you could use one of these for $26 US: http://www.banggood.com/DSO138-DIY-Digital...-p-1051616.html But if you are not sure of the signal amplitude you would use an attenuator (variable resistor) to first check the signal to avoid blowing up your scope. |
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