VAG-Tools: MK4 1.8T Tuning Guide: Stage 4

+ Stage 4: Big Turbos

+ Ready to play with the big boys? Let's move on to big turbos to extract the most power out of the 1.8T. This section's style is going to be different when compared to the other sections, basically it will provide a list of parts you need, provide some background information on general BT setups, and then focus on turbo specifications. Many thanks to CZVDUB who helped complete this section.

• Turbo nomenclature:

Terms:	What does it mean?
1) Wheel trim	1a) Trim is a term used to express the relationship between the inducer and exducer of both turbine and compressor wheels. It is an area ratio of the turbo. The trim ratio is equal to: (inducer^2 / exducer^2) * 100 Illustration
2) A/R (area / radius)	2a) The A/R describes the relationship between the area of the intake (where fresh air enters) and the radius of the turbo compressor/turbine wheel. Illustration Larger A/R means more flow at the expense of more turbo lag. Basically, more top end at the expense of low end spool.
3) Log vs Tubular manifold	3a) Cast log manifolds are typical on OEM setups. They are usually dedicated to one type of turbo setup. Tubular manifolds are usually seen on serious race setups because they allow maximum flow with equal tube lengths. They are usually custom
4) Air / fuel ratio	4a) The A/F ratio defines the amount of air consumed by the engine compared to the amount of fuel. Proper A/F tuning is crucial to guarantee long engine life as well as promote better performance. Leaner setups result in higher combustion temperatures which means more power, but at the expense of higher EGT (exhaust gas temps) as well as a higher likelihood of knocking (bad!). Richer setups less prone to knock. Thus, tuning the A/F between too lean / too rich is very important to ensure RELIABLE power.
5) Compressor Map	5a) A compressor map graphs a turbo’s performance characteristics, including efficiency, mass flow range, boost pressure capability, and turbo speed. Example

• Big Turbo parts list:

Required parts:

Recommended parts:

- New turbo: ~$1100+
- Exhaust manifold: ~$500
- Uprated fuel pump (i.e Walbro): ~$150
- Downpipe (some come with manifold as a kit): ~$175- 400
- Turbo Inlet (may be included in a kit): ~$150
- New exhaust manifold gasket: < $100
- (4) M10x1.5mm bolts for mounting turbo to manifold (On the ATP T25 flange manifold for internal wastegate turbos the bolts are 8X1.25mm)
- Correct chip tuning (i.e Revo, Unitronic BT) or standalone (dyno tune recommended): ~$700
- Appropriate sized Fuel pressure regulator: ~$150+
- Correct Injectors (guide below): ~$275
+ 440cc: 330whp max
+ 580cc: 380whp max
+ 630cc: 430whp max
+ 750cc: 500whp max

+ More Big turbo cost guides

300-500 WHP: New Connecting rods:
+ Integrated Engineering
+ Pauter

Limited slip differential:
+ With much more power on tap, putting it down will be a problem. LSDs ensure that torque will be transmitted to both wheels, even if one is slipping. This will reduce the likelihood that only one wheel will spin while your vehicle remains stationary. Benefits: better acceleration, better track times, etc.
- Quaife LSDs
- Peloquin LSDs

• Purchase a complete kit or go custom?

Advantages of a kit such as APR's :	Advantages of piecing together a custom kit:
- You are getting a genuine product that has been engineered to work in your car and work at roughly the same OEM specs. - You will receive all parts needed for the install, as well as software and the backing of a company (including warranty). - APR video	- Usually cheaper than most kits. - More options (i.e turbo) - More enjoyable to some
Disadvantages of a kit such as APR's :	Disadvantages of piecing together a custom kit:
- Usually more expensive than custom kits - Limited options	- No company backing or support - May have to deal with unforseen problems - Limited software tuners

+ Basic boost guide for different turbos

+ Popular big turbos
+ Big Turbo Registry

List of popular turbochargers used in BT applications:

• GT28R: ~$1000+

Specs:	Info / Dynos / Kit
- Flow Capacity: Approx 310HP - Turbine + Wheel: 53mm w/ 62 trim + Housing: .64 ar - Compressor + Wheel: 60mm w/ 60 trim + -Housing: .60 ar	Garrett Basics Dyno APR Stage 3 Kit

• GT28RS: ~$1200+

Specs:	Info / Dynos / Kit
- Flow Capacity: Approx 350HP - Turbine + Wheel: 53.85mm w/ 76 trim + Housing: .64 or .86 ar - Compressor + Wheel: 60mm w/ 62 trim + Housing: .60 ar	Garrett Basics Dyno 1 Dyno 2 Dyno 3 APR Stage 3+ Kit Build-up

• GT2871R: ~$1200+

Specs:	Info / Dynos / Kit
- Flow Capacity: Approx 410HP - Turbine + Wheel: 53.85mm w/ 76 trim + Housing: .64 or .86 ar - Compressor + Wheel: 71mm w/ 56 trim + -Housing: .60 ar	Garrett Basics Dyno 1 Dyno 2 Dyno 3 Dyno 4 Dyno 5

• GT3071R (Internally Wastegated) : ~$1300+

Specs:	Info / Dynos / Kit
- Flow Capacity: Approx 500HP - Turbine + Wheel: 56.5mm w/ 84 trim + Housing: 0.64 a/r - Internally Wastegated (No Actuator) - Inlet: 2.75" - Compressor + Wheel: 71mm w/ 56 trim + -Housing: .50 ar	Garrett Basics Dyno Build-up thread

• GT3076R (Externally Wastegated) : ~$1400+

Specs:

Info / Dynos / Kit

- Flow Capacity: Approx 525HP

- Turbine
+ Wheel: 60mm w/ 84 trim
+ Housing: .63 ar, .82 ar, 1.06 ar

- Compressor
+ Wheel: 76.2mm w/ 56 trim
+ -Housing: .60 ar

Garrett Basics
Dyno 1
Dyno 2

• GT35R (Externally Wastegated) : ~$1400+

Specs:

Info / Dynos / Kit

- Flow Capacity: Approx 525HP

- Turbine
+ Wheel: 68mm w/ 84 trim
+ Housing: .63 ar, .82 ar, 1.06 ar

- Compressor
+ Wheel: 82mm w/ 56 trim
+ -Housing: .70 ar

Garrett Basics
Dyno
Map 1
Map 2

• T3/T4E : ~$700+

Specs:

Info / Dynos / Kit

- Flow Capacity: Approx 350-400+ HP

- Turbine
+ Housing: .63,.48, .82 ar

- Compressor
+ Wheel: 45, 50, 57, 60trim
+ -Housing: .58 ar

Garrett Basics
Build-up
50 trim dyno

• Continue on to Weight Reduction