Engine cold start parameters

[Alex B]

Hi fellow mates,

Mapping tuned engines (mostly Evos 4G63 and Subarus EJ20/25) in wide temperature range climate does require solid cold starting capabilities, sometimes up to -35C! So I would like to hear your thoughts and comments on getting reliable cold starting performance. The task could be split into 3 main sections: air, fuel and spark which could further be addressed by the questions.

Lets assume target engine to be 4G63 2.0
Ported head
272 cams
8.3 C/R
1000cc injectors @ 3 bar differential pressure
Forged pistons
#8 iridium plugs (non racing type)
stock ignition system (coils and leads)

1. Air
- what air flow / rpm to aim for in cold engine (say at -15C coolant) or in other words % addition to the idle valve's duty / position.
- tips for improving intake air speed with high duration / high lift cams, ported heads with oversized valves and reduced compression
- usage of VVT in aiding cold starts

2. Fuel
- calculating cold start cranking fuel requirements for the engine at -15C (if warmed up engine idles at 1.5-1.7ms fuel pulse at lambda 1.0)
- optimized fuel injection timing
- post start duration & enrichment fuel compensation
- coolant temp fuel compensation
- tips for improving fuel atomization

3. Ignition
- recommended spark advance at cranking
- coil dwell time vs voltage
- multispark option as an aid in cold starts

All comments from experience/theory/thoughts are welcomed.

Thank you in advance for your input

Regards
Alex