What is an Exocet?

"Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere." - Colin Chapman

The car pictured above is not ours, but is an example of an Exocet. What you're looking at is a 1990-2005 Mazda MX-5 Miata, or more precisely, the powertrain from a 1990-2005 Miata swapped into a tube frame chassis fabricated by Exomotive LLC in Atlanta, Georgia. An Exocet is essentially a body swap for a Miata that deletes anything unnecessary for driving such as air conditioning and other creature comforts. Below is a picture from a local owner showing a 2004-2005 Mazdaspeed Miata Exocet next to a 1999-2000 Miata.

What You Need

To build one of these cars, you need a donor to pull the powertrain and necessary supporting components from. This kit car is designed to accept the powertrain from any 1990-2005 Miata. 2006-present years of the Miata are not compatible.The entire conversion kit including frame, body panels, and supporting pieces is ordered from Exomotive LLC.

The original Miata was produced from calendar years 1989 to 2005. While the overall design remained unchanged for almost 16 years, small updates were made over time and the car was refreshed once. The Miata is built on the "N" platform and each generation is denoted by the chassis code and following letter in the VIN. There are four generations: NA, NB, NC, and ND. The NA is distinct for having pop-ups headlights, the NB is a visual refresh of the NA but it otherwise mechanically the same. These two generations were produced from 1989 to 2005. In 2006, the NC was introduced as a complete update and did not share any components with the prior generations. The ND was introduced in 2016 and is another complete update that returns to the dimensions and weight of the original NA Miata despite modern safety equipment.

• 1990-1993 - NA Miata - 1.6L I4 Engine (B6ZE), 5-Speed Manual, Viscous LSD

  • "The one with pop up headlights."

  • These cars are referred to as NA6 due to their 1.6L engine.

• 1994-1997 - NA Miata - 1.8L I4 Engine (BP05), 5-Speed Manual, Torsen LSD

  • These cars are referred to as NA8 due to their 1.8L engine.

• 1999-2000 - NB Miata - 1.8L I4 Engine (BP-4W), 5 or 6-Speed Manual, Torsen LSD

  • These cars are referred to as the NB1 generation, the pop-up headlights were replaced with fixed headlights

  • Updates to the 1.8L engine used in the 94-97 cars

  • There was never a 1998 model year, 1997 cars were produced until the 1999 model was introduced

• 2001-2003 - NB Miata - 1.8L I4 Engine (BP-Z3), 5 or 6-Speed Manual, Torsen LSD

  • These are cars are referred to as the NB2 generation

  • Variable Valve Timing (VVT) was added to the 1.8L engine

• 2004-2005 - NB Miata - 1.8L I4 Engine (BP-Z3), 5 or 6-Speed Manual, Tochigi-Fuji LSD

  • Still referred to as the NB2 generation

  • For 2004-2005, Mazda offered a Mazdaspeed trim which added a turbocharger and 34 hp - these cars are relatively rare and carry a premium

• 2006-2015 - NC Miata

• 2016-Present - ND Miata

The End Result

The end result of this conversion is a car with 116-178 crank horsepower (depends on the model year and options) that weighs about 1500 lbs. While that doesn't sound like a lot of power, the stock Miata weighs approximately 2116-2529 lbs (depending on the model year and options on the car) so the Exocet is a >600 pound drop in weight. Power to weight ratio is what matters:

• 1997 NA Miata - 129 hp / 2293 lbs = 0.056 horsepower per pound

• 2005 4.6L Mustang GT - 300 hp / 3450 lbs = 0.087 horsepower per pound

• Exocet (1997 Miata Donor) - 129 hp / 1500 lbs = 0.086 horsepower per pound

Depending on the donor car chosen, the power to weight ratio of an Exocet can be similar to that of much more powerful cars. Because it weighs so little, the wear and tear on the vehicle is significantly less when taking the car to a race track or autocross event and the handling is significantly sharper.

Why A 1990-2005 Miata?

There are a few reasons why this is a popular kit car conversion (many of these reasons are why the Miata is popular in general as a project car, weekend track toy, and for racing in its own series - Spec Miata):

• Between calendar years 1989-2005, almost 322,000 Miata were produced for the US. It is the best selling roadster in history, donor cars are plentiful and relatively cheap as a result.

• The Miata was (overall) unchanged from its introduction in 1989 to model year 2005 with the majority of parts being either direct swaps or requiring little modification to use. Spare parts including engines, transmissions, differentials, and other major components are plentiful, relatively cheap, and easy to source.

• The overall design of the Miata is robust, major components such as engines, transmissions, and differentials are easy to work on and reliable.

• Because the Miata is such a popular and common enthusiast vehicle, there is huge aftermarket support for it with shops specializing in maintenance/modification/tuning of them - Flyin' Miata and Moss Miata are just two examples.

• The cost of consumable parts - brakes, tires, gasoline - is cheap to begin with for these lightweight cars and only becomes cheaper with an Exocet conversion that puts less stress on components designed for a heavier car.

• The Miata uses a Power Plant Frame (PPF) that ties the front and rear subframes together through the transmission - this makes the conversion as "simple" as removing the body and dropping on the Exocet frame (see picture below for an example).

2023 Exocet Kit

The kit received from Exomotive features a full race cage powder coated in Grabber Blue with gloss black, fiberglass body panels. Included are small bits and pieces necessary to complete the conversion, fabrication of mounts for many components will still be necessary.

The total time to complete the conversion is stated as 100+ hours by Exomotive. Results from other owners online indicate a conversion takes about 1-2 years to complete and can be done by inexperienced, shade-tree mechanics. We will see how long it takes us.

High Level Plan

The high level plan for this conversion consists of work to disassemble, part out, and prep the donor car before prepping the Exocet chassis to be mated with the PPF and have necessary systems reassembled.

• Document condition and functionality of all components to be sold after removal

  • Functional status of all electronic systems such as lights, windows, etc. documented for sale

• Have the A/C system professionally discharged

• Remove Major Body Panels:

  • Front/Rear Fascia

  • Hood

  • Trunk

  • Fenders

  • Doors (including all internal components)

  • Headlight assemblies

At this point, the car will not move again under its own power until the conversion is completed.

• Remove Non-Functional Interior Components

• Disassemble Engine Bay:

  • Drain Coolant System, Remove Radiator

  • Label and Disconnect Wiring Harness

  • Remove HVAC system including A/C, Heating System

• Remove Dashboard

• Disconnect and Remove Steering Column

• Remove Remaining Engine Bay Components:

  • Remove Emissions Systems (for later reinstallation)

  • Remove Exhaust System (for later reinstallation)

  • Remove Brake System

• Remove Remaining Wiring Harnesses

• Discharge and Remove Fuel System

• Support the Front & Rear Subframes

• Disconnect the Body Shell from Subframes

• Lift Body Shell from PPF

At this point, the body shell from the donor car will be either sold as-is or cut up for scrap metal if it is too rusty for sale.

• Fabricate and Mount Brake and Fuel Lines to Exocet Chassis

• Align PPF, Drop Exocet Chassis onto Subframes

• Reinstall Brake System

• Reinstall Fuel System

• Reinstall Wiring Harnesses

• Reinstall Emission and Exhaust Systems

• Reinstall Steering Column and Gage Pod from Dash

• Reinstall Cooling System w/ Modification to Delete HVAC

• Install Racing Seats, Harnesses