nissan 1.8 with edis and mega squirt.

i have the fuel constants set to 7.5 is that to high or low, when i rev it theres black smoke and a slight back fire also a very smart flame.

what do we think, to advanced / retarded

to much juice ? if i lean it out will it run and rev up smoother ?

backfire points toward timing, black smoke suggest too rich.

I'm also currently faffing around with a MS on a V8

What does the O2 gauge in megatune say?It may well be to rich, as i found mine ran very rich with the default VE table.Have you tried running autotune whilst driving or data logging and adjusting to suit ? I am still adjusting mine and trying different set ups but it runs fairly well just by using the methods mentioned.
Paul.

If its back fireing out of the exhaust then i'd guess the timeing is retarded too far and was fireing when the exhaust valves have opened? presuming the Cam timeing etc are correct.

If it was too far advanced it'd pink and backfire up the inlet I wolud have thought.

And maybe as suggested running a little rich.

When I fired up with megasquirt using the initial calculation is ran extremely rich, it was throwing in more than twice the amount of fuel required ( I have noticed this on other posts, maybe a safty factor that they built to stop people buring valves etc).

If you are getting lots of black smoke and flames out of the exhaust it sounds to me like unburnt fuel is passing through the engine then getting ignited on the overun.

Regards Mark