Understanding Advance Correction?

General Topics for configuring, operating and tuning the Megajolt. Also see the <a href="http://www.autosportlabs.net/MJLJ_V4_Operation_Guide">Operation Guide</a>

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sunray
Posts: 61
Joined: Mon May 14, 2007 1:04 am
Location: Victoria, BC

Understanding Advance Correction?

Post by sunray »

I have noticed this new sub-menu in the V4 configurator. Can someone please explain in a little more detail how this function works? Is it a control for the interpolation between load or rpm bins? If so then, how does each value affect it?

brentp
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Post by brentp »

Think of it as a configurable over-ride for the current advance selected from the main Ignition Map. Note you can configure +/- advance correction.

For example, if you're current ignition advance is 35 degrees (based on where the engine is in the Map) and the currently selected Advance correction is -5 degrees (based on what the Aux input has measured) then the total ignition advance will be 30 degrees BTDC.

Operation Guide talks about this some more as well.

Hope that helps!
Brent Picasso
CEO and Founder, Autosport Labs
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sunray
Posts: 61
Joined: Mon May 14, 2007 1:04 am
Location: Victoria, BC

Post by sunray »

So this is simply a function based on a reference value of an aux input? So in most cases it would something like say a coolant temp sensor or intake air temp sensor that accomplishes the triggering of the advance correction table?

BRUCEROE
Posts: 96
Joined: Wed Mar 03, 2010 10:00 pm

Post by BRUCEROE »

It can also be used as a tuning aid. I connected a 2K variable resistor. With the internal 2.2K pullup, voltage varies from 0 to nearly 2.5V. That in turn is translated to -12 degrees at 0 ohms, 0 degrees at 1K ohms, and +12 degrees at 2K ohms. Voltage isn't linear, but the translation table fixes that. Logging will record performance with different settings, and a table can be optimized at each rpm for best acceleration everywhere. Unplugging the 2K variable resistor makes the input 5V. The translation table can be made to return the advance correction to 0 degrees here when unplugged. Bruce Roe

ian2000t
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Location: West Midlands

Post by ian2000t »

BRUCEROE wrote:It can also be used as a tuning aid. I connected a 2K variable resistor. With the internal 2.2K pullup, voltage varies from 0 to nearly 2.5V. That in turn is translated to -12 degrees at 0 ohms, 0 degrees at 1K ohms, and +12 degrees at 2K ohms. Voltage isn't linear, but the translation table fixes that. Logging will record performance with different settings, and a table can be optimized at each rpm for best acceleration everywhere. Unplugging the 2K variable resistor makes the input 5V. The translation table can be made to return the advance correction to 0 degrees here when unplugged. Bruce Roe
Sounds interesting but I'm afraid I don't quite get you! Any chance you can explain to a newb what you mean?

BRUCEROE
Posts: 96
Joined: Wed Mar 03, 2010 10:00 pm

Post by BRUCEROE »

You can program the AUX input (0 to 5 volts) to shift the entire timing map some number of degrees, can be plus, minus, or both. The amount of shift you program at some 10 different voltages, doesn't have to be linear. Your input circuit can be a temp sensor or a pot, with a circuit to generating the needed voltage. Bruce Roe

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