I've been doing some investigations with the DoTaRs for my new car and it looks like thae changes to light car modifications may well allow rotary fans to legally fit a 13b Turbo to an MX5

Approval under Code LA1 allows for \"Fitting of replacement engine with not more than 20% greater weight and or power than engines offered by the first manufacturer as a standard or optional engine.\"
Then it must fit into teh following equation (for vehichles between 800 and 1100kilos)
Original weight in kgs x 2.5 = Max capacity in ccs.
\"The engine capacity used for rotary engines is twice the swept volume of all rotarts\"
What this means is a 13b has a \"capacity\" of 2616cc.
So working with the formula:
Weight(kg) x 2.75 MUST = 2616 (cc)
So weight MUST = 2616/2.75 (or more)
So weight must equal 952 or more....
Now an NA weighed from 940 to 990 dependant on year model and options, so SOME NAs would be eligable.
NBs weighed just over 1000kg, so they are definately in.
Then you need to meet emissions requirements, the engine must be newer than the car and comply with ADR emissions standards ADR 37:01.
A series 6 onwards RX7 will comply with these ADRs, as long as you get an engine/frontcut from an RX7 newer than your MX5.
There are a few other bits and pieces that'd need to be worked out but it looks positive for rotarians

Not sure how we'd go on teh powe not exceeding an additional 20% of the original, but definately go for NBs who had teh SP as an original mazda variant

Oh and NO, I'm not building a 13bt mx5.