Timing Split

[dscholz]

I know this is something that I've read about all over the internet, but when I'm looking to reread I can't find answers to my questions.

What is the timing split for power vs economy?

I thought I remembered reading you use a 50/50 split for good balance of power and economy and a 60/40 for economy. Is this correct? I thought the more advanced the timing is the more power you make and the higher the cylinder pressures. Does the higher cylinder pressures mean more torque so less load and that's how you get more economy? Higher cylinder pressures would also spool the turbo quicker, correct?

Where should I do what split in the map? What will give me best economy when cruising, but make power and be reasonable for cylinder pressures when getting into the throttle?

Thanks!

Derrick

[Jim P]

Economy rail pressure 12.5-14.5k psi in the cruise region is what lots run. Main pulsewidth 550-1000uS in the cruise region. For myself I?ve found in the cruise region if you get above 1000uS it?ll start getting smokey. Play with timing, may find you need a little more or may need less, depends on your setup. Pilot can have a huge influence too. 50/50 split is a rule of thumb max timing split in upper load range on a street tune as beyond that you can easily and rapidly exceed timing limit where the pressures get into catastrophic areas, a dyno tune should be done to watch for when power starts dropping when timing is increased to know you?ve hit the limit. Within the spoolup region too much timing can hurt turbo spoolup

[Jim P]

For myself on my truck I only pay attention to the 50/50 split in the upper load region. Cruise region I shoot for what gives less throttle input, load and final quantity to maintain speed. My previous 05 I went from 15-16 mpg to 19 with main timing around 3 degrees BTDC, rail pressure floating between the 12.5-14.5k psi(increased as quantity and speed increased), commanded duration was typically around 550-600uS once up to speed and holding steady commanded quantity on a flat run with minimal winds.

[adamuise]

Ive heard that the higher compression engines like more timing as well.

[Jim P]

Higher ambient temperatures and higher altitudes need increased timing, not sure with higher compression ratio