Rough — engine program only.
Stand-in numbers to frame the scope — the builder's quote replaces these.
| Phase | Range |
|---|---|
| Engineering, design, mock-up (CAD, brackets, fixtures) | $8–15k |
| Teardown, inspection, machine work | $18–28k |
| Rotating assembly | $14–20k |
| Valvetrain and cams | $4–7k |
| Supercharger (twin-screw blower, drive, brackets, inlet, throttle, bypass valve) | $12–20k |
| Custom lower manifold (design + fab or cast) | $8–15k |
| Intercooler system (bricks, heat exchanger, pump, plumbing) | $5–10k |
| Engine management + calibration (ECU, harness, sensors, 40–60 dyno hr) | $16–28k |
| Fuel system (E85 pumps, injectors, lines, rails, regulator) | $5–9k |
| Oil and cooling | $10–15k |
| Exhaust | $6–10k |
| Integration and assembly | $8–14k |
| Shakedown and refinement | $5–10k |
| Total (incl. ~20% contingency) | $145–240k |
Excludes suspension, brakes, the UN1 upgrade (already done), clutch (~$3–6k; see the main page), driveshafts, tires, bodywork, consumables. The gearbox matters more here than on 918NA — this build is gearbox-limited, and if the UN1 can't be made to hold the torque, a replacement transaxle is a separate, substantial project. One-off programs at specialist shops routinely overrun — plan against the top of the range, not the middle.