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jpreston's NC Miata GLTC Low Boost Turbo Build

jpreston · NC Miata

Mazda MX-5 Mk3 (NC)

NC GLTC low boost turbo build

Read the full write-up at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build

NC Miata converted to a Fab9 GT2860RS turbo GLTC racecar

jpreston documents swapping his caged NC Miata race car from a naturally aspirated 2.5 to a lower-stress turbocharged 2.0, chasing a flat power curve for GLTC classing. The thread covers turbo and wastegate selection, cooling and oil-drain headaches, a full Haltech rewire, and later a suspension overhaul with MCS triples and custom spherical suspension arms, ending with the car listed for sale after a minor track crash and repair.

Specs

As stated in the original write-up.

Engine
Unopened 75k mile 2011 NC2 2.0L (replaced earlier 2.5 Fusion motor)
Turbo kit
Fab9 GT turbo kit with Kraken top mount manifold and GT2860RS turbo
Gearbox
Stock NC2 5 speed
Rear axle
RX8 diff conversion with 2010+ 4.77 ratio, running stock LSD
ECU/PDM
Haltech Nexus PDM with full custom rewire
Fuel injectors
ID1050x injectors
Wastegate
Turbosmart dual port wastegate with custom bracket and clevis
Intercooler
Fab9 intercooler, shortened by about 6 rows/3 inches by a local friend
Radiator
Goodwin triple pass radiator (new)
Oil cooler
Derale 15865 25 row engine oil cooler with fan, mounted under the trunk
Alternator
Mazda3 alternator relocated to intake side
Suspension
MCS remote reservoir triple adjustable coilovers, 700/400 springs
Suspension arms
Keisler sphericals in stock front lower arms, P2M front uppers, SPL rear toe links, custom spherical conversions on other rear arms
Brakes
Custom front big brake kit with 13 inch Coleman floating rotor rings, Wilwood hats, and Afco calipers
Wheels
17x10 and 17x9 Konig wheels
Tyres
Continental ECS rain tyres on 17x9 Konigs
Fire system
Safecraft 10lb Novec fire suppression system
Seat
Sparco Evo or OMP HRC-R seat with custom floor-mounted mounts
Harness
Schroth Enduro belts
Body
2006 rust-free NC chassis, dark grey, 88k miles when bought

Parts used

Parts named as used in the original write-up, grouped the way the Parts page groups them. Where one of the shops we index lists the same thing for this car, it is shown underneath with a link to the shop.

Engine 1

  • 2011 NC2 2.0L engine

    Unopened low-mileage engine used to replace the 2.5 Fusion motor for the turbo build

Fuel & Ignition 3

Cooling 3

  • Derale 15865 25 row oil coolerDerale

    Mounted under the trunk with fan to manage engine oil temperatures

  • Fab9 intercooler (shortened)Fab9

    Cut down roughly 3 inches by a local fabricator to improve radiator airflow

  • Goodwin triple pass radiatorGoodwin

    New radiator ordered after the original was tweaked in a crash

    In the shops
    Single Pass Aluminum Race Radiator (ND) ↗Flyin' Miata· $549.00 USD

Gearbox & Drivetrain 2

  • RX8 diff conversion, 4.77 ratio

    Fitted with stock LSD as the rear axle for the turbo setup

  • Stock NC2 5-speed gearbox

    Used in place of the Walter Motorsports 6-speed for the turbo car

Suspension & Steering 5

Brakes 1

Wheels & Tyres 2

Interior 2

Electrical 2

Other 2

Photos

63 pictures collected from the write-up, in the order they were posted, shown from NC GLTC low boost turbo build. A picture opens larger here, with the way through to the page it is on.

jpreston · May 1, 2021 | 01:49 PM 9this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

jpreston · May 1, 2021 | 01:59 PM 3this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

jpreston · May 3, 2021 | 12:48 AM 1this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build

jpreston · Sep 6, 2021 | 11:48 PM 10this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

jpreston · Sep 7, 2021 | 12:08 AM 10this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

jpreston · Sep 7, 2021 | 12:32 AM 6this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

jpreston · Sep 7, 2021 | 12:53 AM 5this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

jpreston · Sep 7, 2021 | 07:08 PM 1this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build

jpreston · Sep 30, 2021 | 02:51 PM 2this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

jpreston · Apr 11, 2022 | 02:37 PM 12this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

jpreston · Apr 11, 2022 | 02:56 PM 4this post at NC GLTC low boost turbo build ↗

Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build
Photo: NC GLTC low boost turbo build

How it was done

Starting condition

The NC was bought as a track car already fitted with Ohlins coilovers, a Giken diff, rollbar and seat, making about 155whp stock. The owner liked it enough that when his other project stalled he committed to turning the NC into a caged GLTC racecar, taking it to a cage builder and beginning a 2.5 swap.

2.5 swap struggles and rewire

The 2.5 swap dragged through 2020 with bad junkyard motors and wiring problems, preventing any GLTC races. Over the following winter the factory harness was torn out and replaced with a Haltech-built loom and Nexus PDM, left unsheathed at first so it could be verified before adding braided loom.

Choosing the turbo conversion

After disappointing dyno results on the 2.5 (186whp against a 196 minimum) and seeing other NC GLTC cars breaking 2.5s and six-speeds, the owner switched to a stock 2.0L fitted with a Fab9 GT turbo kit and GT2860RS turbo, debating wastegate springs and actuator choice to hit a flat 195-210whp target.

Build and early turbo running

Work included drilling the block for an oil drain (an approach the owner regrets), relocating the alternator, fabricating a heat shield and downpipe brace, fitting a dual-port Turbosmart wastegate with a custom bracket, and swapping injectors to ID1050x after fuel issues on the dyno.

Cooling and intercooler fixes

Coolant and intake temperatures were an ongoing fight; the full-height Fab9 intercooler blocked radiator airflow, so a friend cut it down by about three inches to free up bumper openings, while ducting and grille mesh changes were used to try to keep coolant near 210F.

Suspension overhaul

In early 2022 the owner replaced the original Ohlins coilovers with MCS remote triple-adjustable units and converted the stock suspension arms to spherical joints himself, using Keisler-converted front lowers, P2M front uppers and SPL rear toe links, with custom bump stops and o-ring limiters to manage travel.

Racing and eventual sale

The turbo car raced at NCM, Gingerman, Autobahn and Mid-Ohio and proved reliable, though a broken 5-speed and handling tweaks followed. A minor low-speed crash at the end of 2022 led to frame straightening and bumper/paint repair, after which the owner decided to sell the car, listing its full specification and remaining to-do items.

A summary in our own words. The full account, with all its detail, is in the original write-up: read it at NC GLTC low boost turbo build ↗

Worth knowing

  • Drilling the block for a turbo oil drain made it hard to get a proper NPT seal, use the oil pan drain plug fitting method instead
  • Relocating the alternator to the intake side is a maintenance headache not worth it without good reason
  • A Turbosmart dual port wastegate has limited actuator travel that can bind before the flapper fully opens
  • A full-height intercooler blocks too much radiator airflow for NC bumper cooling, a shortened core works better
  • Heat wrap placed under a hose clamp near the turbine housing can burn, the clamp should go over the wrap
  • A stock junkyard 5-speed is a better choice than an expensive dog box for a naturally aspirated NC

NC GLTC low boost turbo build

forum thread: 3 of 3 pages and 42 of 42 posts inspected; 22 unquoted updates by jpreston used; 20 replies excluded on 7 November 2026. The original write-up and photographs remain with their creators. This page is a catalogue in our own words, and a signpost to the source.

Read the full write-up at NC GLTC low boost turbo build ↗

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