512 kB main loop reference

[NSFW]

I agree that fuel cut is not lean. Each combustion cycle has either the tuned AFR, or it has pure air.

Well maybe on the first cycle after fuel cut there's a negligible amount of residual fuel hanging around from the previous cycle, if you really want to be pedantic about it.

[Gampy]

IMO Fuel cut is better for traction control, max rpm and it's less abusive on expensive parts, however I also see the advantage of spark cut on the two step for turbo cars ...

So, Have a 'Turbo' flag that Spark cuts the two step if enabled else fuel cuts, and fuel cuts for traction and max rpm.

[Highlander]

I agree that fuel cut is not lean. Each combustion cycle has either the tuned AFR, or it has pure air.

Well maybe on the first cycle after fuel cut there's a negligible amount of residual fuel hanging around from the previous cycle, if you really want to be pedantic about it.

it is just not enough to combust, just a miss if it even combusts... I've never had issues with hitting the rev limiter on any ecm when its via fuel . Even with nitrous (which we run dry). This is the reason I haven't made the mod for spark cut. Even for a 2-step, LPE has a very nice box and very configurable.

[Highlander]

IMO Fuel cut is better for traction control, max rpm and it's less abusive on expensive parts, however I also see the advantage of spark cut on the two step for turbo cars ...

So, Have a 'Turbo' flag that Spark cuts the two step if enabled else fuel cuts, and fuel cuts for traction and max rpm.

Again, turbo cars all they need is a bit of cut to make the line and retarded timing and plenty of fuel. If all you want to do is have big pops on the back, then yes spark cut is the way to go.

[Gampy]

Again, turbo cars all they need is a bit of cut to make the line and retarded timing and plenty of fuel. If all you want to do is have big pops on the back, then yes spark cut is the way to go.

So, How do you get a "bit of cut" and "plenty of fuel" without using spark cut for the "bit of cut" ??

[Highlander]

Again, turbo cars all they need is a bit of cut to make the line and retarded timing and plenty of fuel. If all you want to do is have big pops on the back, then yes spark cut is the way to go.

So, How do you get a "bit of cut" and "plenty of fuel" without using spark cut for the "bit of cut" ??

Fuel Cut. Always a fuel Cut. that keeps rpms where you want them and then added fuel when its actually firing and retarded timing.

[turbo_bu]

I thought the function was already there or is that on the E38s? BUt even then.. why would you want a spark cut? I think the only time you would need spark cut is for anti-lag function? and that what it actually needs is timing retard.

Yes, the Gen IV ECM's have spark cut. The older LS1 PCM's are setup with just fuel cut.

Reason for spark cut is mainly for boosted / N2O applications. Fuel cut leads to a lean condition, spark cut does not. Additional reason would be for 2 step. That would require an input channel, but could be very useful.

how do you figure you get a lean condition?

The lean would occur as you hit the rev limiter during WOT. It would be very brief, but very damaging on a forced induction setup. Or as was pointed out on a wet nitrous setup.
The assumption is that somebody wanting to use this most likely doesn't have catalytic converters.

[NSFW]

I don't think it's lean though. Fuel cut just alternates between ordinary combustion and no combustion at all.

It's pretty much the default way of doing it in the Subaru world.