TD 998 big turbo upgrade recommendations
TD 998 Big Turbo Upgrade Recommendations
Version 1.0 — Check back for updates and additions
This guide outlines the required and recommended components for the TD GAP big turbo and TD MOD stock hardware upgrades, covering power levels from 250HP to 550HP.
Table of Contents
- Required Upgrades
- Power Level Requirements Summary
- Recommended Upgrades
- TD Stage 6 Camshaft Compatibility Guide
Required Upgrades for TD GAP Big Turbo / TD MOD Stock Hardware
250–550HP Applications
ECU & Tuning
| # | Component | Purpose |
|---|---|---|
| 1 | TD Multimap ECU reflash | Required base tune for big turbo operation |
| 2 | TD Flasher or Copitrail | Allows flashing of ECU tuning and datalogging (if equipped with option) |
| 3 | Closed Loop | Maintains optimal air/fuel ratio for better economy, consistent power, and improved response |
| 4 | 4 Bar MAP sensor upgrade | Allows ECU reading above 17 psi of boost |
Fuel System
| # | Component | Purpose |
|---|---|---|
| 5 | 1050cc Injector Dynamics kit | Provides adequate fuel flow for high power levels |
| 6 | TD Wideband O2 Kit | Required for Closed Loop operation; reads air/fuel ratio |
| 8 | Fuel pump upgrade | Supports increased fuel demand |
| 9 | Adjustable fuel regulator upgrade | Allows precise fuel pressure tuning |
Intake & Boost Control
| # | Component | Purpose |
|---|---|---|
| 7 | TurboSmart Blow off valve | Proper boost pressure management |
| 10 | TD Cold Air OR GAP Ram Air | TD Cold Air for trail use; GAP Ram Air provides more power for race sleds |
Clutching
| # | Component | Application |
|---|---|---|
| 11 | Primary Clutch Upgrade | Under 350HP: Dalton Clutch weights (STM clutch weights also work) Over 350HP: Tapp Clutch |
| 12 | Secondary Clutch Upgrade | Over 350HP: Torsion conversion kit or STM secondary clutch |
Engine Components
| # | Component | Purpose |
|---|---|---|
| 13 | Retainer and spring upgrade for cylinder head | High RPM reliability—the big turbo makes power at 9200–9600 RPM, making this upgrade essential |
Chassis & Safety
| # | Component | Purpose |
|---|---|---|
| 14 | Big 4-wheel kit | ⚠️ SAFETY REQUIREMENT: The extra power will not work reliably with only the factory two plastic wheels in the rear |
⚠️ Power Level Requirements Summary
| Power Level | Required Upgrades |
|---|---|
| Above 350HP | • Tapp Clutch (primary) • Torsion conversion kit or STM secondary clutch |
| Above 360HP | • TD HD head gasket with HD head studs (strongly recommended) |
| Above 400HP | • Carrillo rods (MANDATORY) Lightweight or regular set available |
| Above 430HP | • Forged pistons (recommended) • Maximum compression ratio: 9.0:1 |
Compression Ratio Guidelines
| Application | Recommended Compression | Notes |
|---|---|---|
| Race Sleds | 9.0:1 | Optimal for race fuel applications |
| Trail / Pump Gas (91 Octane) | 8.5:1 or lower | Allows more boost and power on pump fuel; lower compression piston sets available in stock |
Recommended Upgrades
1. TD Stage 6 Camshafts
See the TD Stage 6 Camshaft Compatibility Guide below for detailed information on when to use these camshafts.
2. TD Super Cooler Kit
| Benefits |
|---|
| • Significant HP improvement • More consistent performance • Sustained pull that never stops • Cooler intake temps • Reduced knock |
3. TD Header
| Benefits |
|---|
| • Significantly more power than stock manifold • More power on pump gas at the same boost level |
4. Datalogging Option
Available for TD Flasher or Copitrail. Allows monitoring and recording of engine parameters for tuning and diagnostics.
? TD Stage 6 Camshaft Compatibility Guide
⚠️ IMPORTANT: TD Stage 6 camshafts require a minimum of 26 psi boost when used with the TD GAP big turbo kit.
| Turbo Kit | Fuel Type | Recommended Camshaft | Notes |
|---|---|---|---|
| TD GAP Big Turbo | Pure 91 Octane (Trail Use) | Stock Cams ONLY | Do NOT use TD Stage 6—minimum 26 psi boost requirement exceeds safe pump gas limits |
| TD GAP Big Turbo | 91 Octane + C16 Mix | TD Stage 6 OK ✓ | Race fuel blend supports the higher boost requirement |
| TD GAP Big Turbo | Race Fuel | TD Stage 6 OK ✓ | Optimal configuration for maximum power |
| TD MOD Stock | Any (including 91 Octane) | TD Stage 6 or Stock ✓ | Works fine at any boost level with either camshaft option |
Summary
| TD GAP Big Turbo + Trail Riding on Pure 91 Octane | Use Stock Cams |
| TD GAP Big Turbo + Race Fuel or Fuel Mix | TD Stage 6 Recommended |
| TD MOD Stock | Either Camshaft Works (Any Boost, Any Fuel) |
Quick Reference Card
| Big Turbo At-a-Glance Requirements | |
|---|---|
| Power Range | 250–550HP |
| MAP Sensor | 4 Bar (required) |
| Injectors | 1050cc Injector Dynamics |
| Operating RPM | 9200–9600 RPM |
| Clutch Upgrade Threshold | 350HP |
| Head Gasket/Studs | 360HP+ |
| Carrillo Rods (MANDATORY) | 400HP+ |
| Forged Pistons | 430HP+ |
| Race Compression | 9.0:1 |
| Pump Gas Compression | 8.5:1 or lower |
| TD Stage 6 Min Boost (GAP) | 26 psi |