pistonsuk

i just wanted someone to explain what the trends are regaurding trailing ignition.
For example: generaly the more advanced your leading timing is the more power you will make but the trade off is the increased threat of detination.
what is the story with trailing? is a wide split good? or just the opposite? should the split vary with boost pressure? how does it affect torque and power? etc...
thanks,
justin

racermike

In the old days it was common to advance the leading by ~5 deg., and shorten the "split to 10 ~ 15 deg.
This would provide a little extra power at high rpm.
I will defer the boost question.

DavidDeco

There's a thread around here somewhere that talks about the results going from 12-10 degrees and then 10-8 degress split on the single turbo forum. Do a search by this topic or Dyno Sheets. I think that's when I read it.

In general I see that people report increases in HP with reduced split up to a point. A few say they lost HP going less than like 10 but that doesn't seem to make sense.

Some advocate 0 split if you have the guts. Just remember that the Trailing should never fire before the Leading....that could be very bad from what I understand.