Jetting is a breeze with EGT gauges.

But, it's important that you have a base setting temperature to work to. This can be done on the dyno, or if you get a nice setting on the track that's fast and reliable then be sure to make a note of the temp.

For a given main jet, the engine will run lean as the ambient temperature decreases. Due primarily to the air density increasing, so more oxygen for a given volume of air. This will show as an increase in EGT.

If you're really looking for an edge, then consider that hot and cold conditions not only require different jetting, but you can also gain by altering other things.

For example, lets say you set everything in your engine for the average temperature. Setting #1.

As the ambient temperature rises and the air density decreases you would normally just lower the main jet. This will work up to a point where the engine geometry becomes inefficient and the torque loss is severe. Some of this can be claimed back with an increase in the secondary compression ratio (reduction in volume) and/or advancing the ignition timing.

The opposite should be considered when the ambient temperature decreases.

Cheers,

Matt.