When the fan comes on, the voltage drops from 14.2 to 13.5. at idle. Is there an internal voltage regulator in MSII, or will thisvoltage change effect things in an unwanted way? If there is no internal voltage regulator, is there a circuit that can be added to regulate the voltage supplied to the ECU?

Maybe this is a question for Matt on Monday.

Sam

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What is this voltage measured with what (car's voltmeter)? And where was this monitored on, at battery? Or at ECU? Etc.

Megasquirt and factory ECU designed in worst cases mindset on voltage noise and voltage drops as long as they are within specified ranges.
What gets people's in nads is direct and indirectly noise on signal (as data and control) wirings due to not addressing the proper practice of wiring & shielding, and where to route (avoiding noisy sources) to preserve the signal quality. Even the ground/power feed if the noise is powerful enough or poorly installed, megasquirt manual is very specific on that. Poor installation can cause this as well.

Cheers, Wizard

PS: data means pulses for timing either way and voltage levels (using linear sensors or control things) from either end that ECU monitors or send out to control things.

This voltage is measured inside ECU and displayed on the lap top gauge set in Tuner Studio.

Sam

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All the sensors and logic circuits on the MS2 run off a regulated 5 volt supply, as shown in the schematics, section 6.

http://www.msextra.com/doc/general/ms2v3schems.html

The MegaSquirt needs to know the real voltage so it can compensate for how the ignition and injectors behave at different voltages, but until the voltage dips below 8 volts or so, the MS itself is not affected by voltage changes. This doesn't mean that much voltage swing is a good thing (if your injector battery voltage compensation isn't spot on, it could lean the engine out and cause serious damage - seen that once before), only that the MS itself isn't hurt.

A 1 volt drop is not a big deal, particularly at idle. Lots of cars do this.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Thanks Matt.
Sam

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