[1] http://www.msextra.com/product-range/traditional-megasquirt/
I had heard of them but I thought they were a Miata specific ECU replacement not a general purpose one.
The use scope for replacement ECUs is pretty limited. Limited to a handful of 80s and 80s cars with extremely primitive ECUs (by today's standards), old cars that are being retrofitted to run fuel injection, and specialty one-off builds (where even most of these people buy something like a Motec, AEM, Holley, etc, etc ECU that plugs in and goes).
The possibility of damage is the same whether or not the ECU is DIY or not. It's all in the tune whether you will blow up your engine or not.
I think you're right. In fact the only reason I'm digging into this is because I have one of very few 90s Nissan ECUs that hasn't been piggy backed (R33 S2 RB25DET). Because all others have a piggy back board available and aftermarket standalones are so common here, no one does flashing for that ECU either. You can use an R32 RB25DET ECU and piggy back that, but they are scarce here now and too expensive.
> The possibility of damage is the same whether or not the ECU is DIY or not. It's all in the tune whether you will blow up your engine or not.
I more meant from failure of the board or the code. You can be relatively confident with a modern commercial board, but I am worried about board failure on the street with DIY boards. If this were a track only car I wouldn't be as bothered, but it will be a street/track day car.