sailaholic wrote::A after market turbo NBb would out perform a SE at a lower cost I would guess.
SE seem to be good and fine if your happy with stock power but get expensive if you start chasing more.
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If you want to keep everything legal without needing expensive engineering certification, an SE is a pretty good choice.
Out of the box the SE is pretty underwhelming for a turbocharged car - you get maybe 110rwkw and the car doesn't feel turbocharged at all.
Add a CAI and MBC, increase the boost to 10psi and you'll get around 135rwkw - you'll know that there is a small turbo working under the hood. This is a cheap DIY mod with no ill-effects and is how the car SHOULD have come from the factory in the first place. You'll be very happy with this mod but inevitably become infected by the "MOAR POWA" virus.
After this is where it gets expensive. Add a 2.5 or 3" exhaust and you'll be sitting around 140-145rwkw but the ECU can't really handle this (there's a "dead spot" between 4500 and 5000rpm where the ECU isn't supplying enough fuel - once it hits 500rpm, the ECU switches to Open Loop mode and everythings fine again). At these power levels you'll be running lean so will need larger injectors. On the stock ECU, 321cc injectors are largest ones it can handle but these are impossible to find and Toyota 305/315cc injectors are more commonly used.
You can try some band-aid solutions to overcome the ECU's limitations (such as the FM O2 mod and boost cut resistor mod) but they're a poor second to an aftermarket ECU as your car will never be "factory smooth" and will sound crook until it warms up.
Chiptorque's chip repacement is a cheap ECU solution and will work best if you do all the intake+exhaust mods first, take the car to them and allow them to upgrade your injectors and generate a chip soution for your car. Chiptorque produced the ECU for the SP (which you seem to have overlooked as an option).
You should be able to achieve ~150rwkw which is pretty sweet in an MX5 AND the car will still be suitable for trackwork+DD.
This was all with stock internals - 250hp is generally accepted as the ceiling for stock internals.
NBs (including SEs) have been traditionally difficult for aftermarket ECUs due to alternator control/input. The new Adaptronic Select ECUs now have an input for this and are easier to tune than in the past.
So:
* consider the SP as an option if you DON'T want to modify it any further (they're rare so keep them original - they pump out around 135rwkw).
* consider an SE, upgrade with CAI + 10psi boost for similar SP power levels and a better overall car (but do upgrade to 15" rims)
* buy an SE now and accept that you'll become infected with "MOAR POWA" and throw a lot of money at the car