Aldon "Amethyst" Mappable Ignition System
Downloads and resources


A specification sheet for Amethyst can be downloaded from here.

Frequently asked questions

Answers to some frequently asked questions are here.


A presentation about Amethyst given to the MGB Register can be downloaded from here.

Instructions and application software

The Amethyst quick installation guide can be downloaded from here.

Full instructions for Amethyst can be downloaded from here.

A troubleshooting guide can be downloaded from here.

Application software up to AM04 can be downloaded here.

Application software for AM05 can be downloaded here here.

Application software for Windows 10 and AMD64 here.

Revision history

Release 1.4 (17/5/13):  The application software has now been upgraded to allow you to select whether the Amethyst triggers from the rising edge (0v->12v) or the falling edge (12v->0v) of the signal from the distributor.  The default is the rising edge, i.e. when the points open.  If you are using an optical trigger such as Crane XR700 or Lumenition, you may need to trigger from the falling edge instead.

Release 1.5 (8/8/13):  Correction to manual dwell calibration.  Auto dwell reduced to 70% of duty cycle at maximum RPM.

Release 1.6 (21/1/14):  Ignition advance interpolated between 500RPM and 1,000RPM, as it is throughout the RPM range.

Release 1.80 (27/8/14):  V8 engines fully supported.  No vacuum advance applied below 1,000RPM, and vacuum advance tapered off between 1,500RPM and 1,000RPM.  This means that the vacuum sensor can be connected to the inlet manifold with no risk of maximum advance being applied at idle.

Release 1.85 (6/1/15):  Advance calculation corrected on 2-cylinder engines.  Switch from start mode to run mode now occurs at 300RPM, regardless of the number of cylinders.

Release 1.9.0 (23/4/15):  Improved noise immunity on USB link.

Release 1.10.0 (6/2/16):  Timing display accuracy improved at high RPM. Pressure measurement accuracy on boost version improved at pressures above 0.7 bar.

Release 1.11.0 (2/12/16):  Vacuum display now includes tapering off below 1,500RPM. Improved noise immunity on trigger input.

Release 1.11.4 (24/8/19):  Low-RPM code improved on multi-cylinder engines.

Library maps

Our database of ignition maps can be found here.  They are supplied without guarantee and are to be used entirely at your own risk.

We are always happy to publish new additions to our map library, and would be grateful if you would inform us of any errors in the published maps.  Please email us at