Cold Weather Lope Tune

[Power Hungry]

Single shots always run a bit lower ICP at idle... usually about 3 MPa, vs 3.8 MPa for splits. I'd suspect that's what helped. The timing is usually negligible. At 700 RPM, the crank is rotating 4.2º per ms. On average, the difference between singles and splits is .3 ms (.8 for singles vs. 1.1 for splits) so the total timing difference at idle would be 1.26 degrees. Not really much in the grand scheme of things. There is also a modest change in the combustion point because of the raised ICP, but again, it's not anything significant at idle.

I suspect the rough idle was mostly from slight overfueling or an imbalance when trying to run relatively small pulsewidth values, which can often happen when ICP gets too high and the PCM is trying to cut back fuel to maintain idle speed.

Fuel pulsewidth and SOI are both DIRECTLY affect by changes in ICP. More to the point though, SOC (Start of Combustion) is affected in relation to ICP changes.

Too much pulsewidth causes an unstable idle. You can't really run a diesel lean or rich, it just makes power with the fuel you've got. More fuel and the RPMs climb. That's about it.