The Mazdaspeed Miata in the North America, Roadster Turbo in Japan or MX-5 SE in Australia were the only turbocharged versions of the MX-5 produced in the Mazda factory in Japan. However, the Australian market gets a special mention here as they had an altogether different turbo model previous to their production.
The MX-5 SP (Special Performance) was a limited production model (just 100 units) created exclusively for the Australian market by Mazda in 2002 to test the plausibility of a turbo model MX-5.
Australia had a good reputation for motorsports at the time, so companies were commissioning low volume cars to test out market options for upcoming models. The whole reason the SP came to Australia was because Mazda knew there was a very strong aftermarket for turbocharging, but they didn't know if that would translate into actually being able to sell an expensive Mazda MX-5 turbo. The test market would determine if it succeeded in Australia, it would succeed elsewhere.
Mazda Australia’s Motorsport Division, with support from Headquarters in Japan, commissioned a turbo conversion developed by Melbourne based Prodrive Racing Australia. At the time Ford owned a large share in Mazda and already had motorsport links with Prodrive. The development of the car was led by Mazda Motorsport's guru Allan Horsley, whom at the time managed Mazda's racing team in Australia - SP Motorsport, hence the SP name. Horsley had previously prepared the race-winning RX-7 SP (in 1995) and the Mazda 800 SP (in 1998).
The SP project had two objectives:
To develop and produce the SP for retail sale
To compete at 2001 Targa Tasmania in road going trim (It did and won showroom class finishing 20th overall)
So what makes a MX-5 a SP?
Mazda Motorsport's conversion consisted of the installation of a Garrett GT2560R ball bearing turbo, bespoke cast manifold, intercooler, higher capacity radiator, an ECU remap, carbon fibre air box, and an upgraded stainless exhaust system. Rerouting of the air-conditioning, power steering and wipers were required leading to hundreds of unique parts for the SP. The turbo install was low boost at 8 psi to maintain reliability of the otherwise standard BP-VE engine and six-speed transmission which were backed by a factory warranty.
These modifications gave the SP a significant power boost to 157kW (211Bhp) @ 6800rpm and maximum torque of 289Nm (213 ft-lbs) @ 4600rpm while only increasing weight by 29kg (63 lbs). This improved the power to weight ratio (W/kg) from 103.7 to 140.3.
But no other mechanical changes were made. The brakes, gearbox, engine internals, suspension and wheel/tire combo. were all stock MX-5 affair. It didn't even come with a limited slip differential or body kit, the only visible changes to the vehicles' appearance are the 'SP' decal at the rear of the car, and the visible intercooler at the front.
The turbo conversion wasn't particularly neat, but gave the MX-5 a 0-60 mph time of just over 6 seconds, as of 2021 this is still the most powerful factory released MX-5. The SP ate clutches but it outperformed an unmodified RX-7 around a technical track, so the conversion worked.
The commercial success of the SP paved the way for the development of the Mazdaspeed Miata/Roadster Turbo/MX-5 SE (MSM/RT/SE) released in 2004, which was detuned in order to accommodate a larger market appeal.
When the MSM/RT/SE was released, it needed to have three things changed:
Cost: This was controlled by moving to the non-VVT engine, running a smaller and cheaper turbo and by scaling up production (obviously something impossible on an SP). That is the main reason the non-VVT engine was used, it was just cheaper.
Performance: They needed to slow the car down so it would maintain a market gap between it and the RX-8 (Mazda's flagship model at the time), that was pretty much a marketing decision
Reliability: Less power makes the clutch more sustainable, lower temps, less blow by etc., Mazda asked for an even more conservative program to make the car as "idiot-proof" as possible in order to reduce potential warranty issues.
The main complaint Mazda got though - the trim level was unchanged, that's why the MSM/RT/SE received a multitude of cosmetic changes and optional leather seats to distinguish the model in order to justify the increase in cost.
Although produced and sold in such a small quantity the SPs were really more of a way to convince Mazda HQ that it was worth the effort and cost to develop a proper factory turbo model which would become the MSM/RT/SE.
SP Unique Features
Apart from a turbocharger (Garrett T25) and 2" stainless steel exhaust, other addition/changes were:
SP front mounted intercooler
SP custom made carbon-kevlar air filter box
Mazda front suspension strut brace
Mazda chromed interior trims (air vents, gear shift lever and surround)
Mazda chrome fuel cover
SP specific chrome scuff plates
SP badge decal (located at the rear)