Hi All -

Just a couple quick questions. Have any of you ever seen a voltage fluctuation under boost when you are logging? If so, what was the problem or what did you do to fix it?

Here is my scenario: we were logging some EMS parameters while doing dyno runs. On almost every run once the engine got to about 5000 or 6000 RPMs the smooth voltage line would start to fluctuate rapidly beween about 12-13 volts (might have been 12.5-13.5 volts). It looked like it went from a fairly flat line to what looked almost like a sine wave, up and down, up and down.

You could also see a bit of a flicker in all of the dash and accessory lights - they would dim and brighten repeatedly.

Battery? Alternator? ECU? Ignition? Loose ground? Any ideas where to start?

Thanks!

EVOlutionary

 

Forgot to mention - this happened with both a COP ignition (AEM box) and with the stock coils running off the new Sun Auto ignition box.

 

Anyone? What can I test?

 

Maybe the belt is slipping? Is it old?

 

I am assuming you are talking about the belt to the alternator? The car has 50K miles on it. Could the belt slip in a rhythmic pulsing manner to cause the described fluctuation?

 

bump for ideas. . .

 

did you ever find out the problem to this? Having the same problem now, voltage is jumping from like 12.8-13.6 or so under WOT which is causing afr oscillation.

 

No I don’t t think so. I switched tuners and then sold the car and built a new “06 the following spring. Post up if you track down the issue.