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V3 MicroSquirt® - QuickStart Guide

You can get a base starting point for the VE table by using the 'Tables/VE Table/Tools/VE Specific/Generate Table' function of TunerStudioMS, using the peak horsepower and torque figures for your engine.

For timing, we don't have a generator written yet. The basic principles are to determine a maximum advance for your engine and work backwards from there with heuristics ('rules of thumb'):

• older engines (1960s up to 1990 or so) with two valves - max advance = 36°
• newer two-valve engines - max advance = 30°
• three or four valve engines - max advance = 26°

• under 3.5" (89mm) - subtract 3°
• between 3.5" and 4.000" (101.6mm) - no adjustment
• over 4.001" (+101.6mm) - add 3°

• regular - subtract 2°
• mid-grade - subtract 1°
• premium - no adjustment

We will use this to fill in the table at 100 kPa from 3000 rpm to the redline.

From idle to 3000 rpm, we want the advance (@100kPa) to increase fairly linearly from the idle advance to the maximum advance. Idle advance is really a matter of tuning, but assume 8° to 16° in most cases, with stock engines being on the lower end, and 'hotter' engines being on the upper end of that range.

So if we have a hot engine with 36° maximum advance and 16° idle advance (at 800rpm), the spark table might look like this for 100kPa:

Below 100 kPa, we add 0.3° per 1 kPa drop. So for example, if our total spark at 100kPa and 4000 rpm was 36°, the advance at 50 kPa would be:

and the advance at 45 kPa and 800 rpm would be:

However all of these would need to be tuned, and it often helps idle stability to limit the advance at idle to under 20°.

Finally, for boosted engines, you subtract 0.3° of advance for every kPa above 100 (it's not a coincidence that this is the same factor as for the 'vacuum' adjustments). Because 101.3kPa=~14.7psi, this works out to ~2° per pound of boost. It is often the case that you want to limit the retard under boost as well, typically so that it takes out no more than about ½ of the maximum advance at 100 kPa.

None of these will give you the 'right' values for your engine though, and like the VE table calculator, are just a relatively safe starting point. They should be somewhat closer than starting with an empty table, though!

For a spark advance table generator, see: Creating an Initial Spark Table for Tuning

Note: If you use 'calculated' for the cranking advance, you should use a low advance figure (5° or less) in the lowest rpm/highest kPa bins so that you do not have too much cranking advance (which can break starters, etc.).