AFR transition from vac to boost, like an N/A on WOT?

[Herman Toothrot]

Just thinking about this, as the turbo spools and goes from vacuum to boost hitting atmospheric pressue, should the AFR be 12 at this cross over point? I was just thinking this as 12's supposed to give the most power on n/a engines WOT in the power band so is a turbo at the transition wanting similar fueling before its providing positive pressure?

[dnb]

It's a slightly different game to NA engines when trying to spool the turbo - you're less interested in running the engine perfectly to make power. Instead, you are trying to make lots of hot exhaust gasses to spin the turbo.

[Herman Toothrot]

so run it a bit leaner then, at present i appear to be 13:1 AFR on the transition.

[ringram]

As an aside you will probably find NA power max leaner than 12:1, more like 12.8 or 13:1

[dnb]

Herman Toothrot said:

so run it a bit leaner then, at present i appear to be 13:1 AFR on the transition.

No! Richer and less ignition advance. (13:1 is probably OK.) It'll make the engine run less efficiently and produce more exhaust gasses. After the turbo is spooled, ramp the timing back up.

[Herman Toothrot]

dnb said:

Herman Toothrot said:

so run it a bit leaner then, at present i appear to be 13:1 AFR on the transition.

No! Richer and less ignition advance. (13:1 is probably OK.) It'll make the engine run less efficiently and produce more exhaust gasses. After the turbo is spooled, ramp the timing back up.

Sorry I meant leaner than 12:1, at present I have it at 13:1 so thats as lean as you'd want to go, my starting of the thread was to determine if I should richen it up a bit. Timing is quite pulled as its an n/a engine thats been turbo'd to avoid det, piston design is far from ideal as other similar CR'd turbo cars seem to be able to manage more advance than I can put in without on-set of det, theres no det how it is at the mo.