SAS
Obviously you need to get a quote from an avionics shop but in 2002 I paid about 3.5k+VAT for an EDM700 installation,
factory fitted. Engine was an IO540 (as you may guess
) The actual instrument costs a disgustingly small fraction of this amount; you could buy it mail order with an 8130-3 form but then you need someone willing to put it in just on the labour charge.
I can see, one day when I get old, dumping all this "IFR capability" nonsense and flying a permit plane, and doing all the work myself. I envy those people who fly some carbon fibre/kevlar plane at 140kt IAS on half the fuel I use and can put in their own non-TSO avionics...
MMF
I don't think car engine management is directly applicable to the old Lycos because car engines are water cooled so you can always get the heat out of everywhere. Whereas these old designs are very economical with where the metal is (for low weight) which is why we have to watch it. Car engines also vary the ignition timing, which is a huge advantage in controlling detonation etc. FADEC would do a lot in the old engines (not in terms of
cruise efficiency but in terms of easier management) but until it is certified... even then I would be wary, having seen the absolutely cr*p design and build quality prevalent in GA avionics. Even Thielert have not been able to make it reliable. I suppose two completely redundant ECUs, magneto-powered, would be OK.