How Much Power Does a Borgwarner Efr 8374 Turbo Upgrade Add to Your R35 Gt-r?

Why the BorgWarner EFR 8374 Turbo is a Game-Changer for the R35 GT-R

The Nissan R35 GT-R has rightfully earned its reputation as a supercar slayer from the moment it launched. Its twin-turbocharged V6 and sophisticated all-wheel-drive system set a new benchmark for performance at a relatively accessible price point. Yet for many owners, the stock power is just the beginning. The real potential of the VR38DETT engine is unlocked when you look beyond factory components. Among the most respected turbocharger upgrades available today is the BorgWarner EFR 8374. This unit has become a staple for enthusiasts chasing a reliable 700+ horsepower daily driver or an all-out track monster. But how much power does it actually add? And what does it take to wring every pony out of this machine?

This article breaks down the horsepower gains you can expect from the BorgWarner EFR 8374 on an R35 GT-R, examines the supporting modifications that make those gains happen, and offers real-world perspectives from tuners and owners who have pushed this platform to its limits.

BorgWarner EFR 8374: A Technical Overview

Before diving into power numbers, it’s essential to understand what makes the EFR 8374 so effective. BorgWarner’s EFR (Engineered for Racing) series is built around aerospace-grade materials and advanced aerodynamics. The 8374 model refers to the compressor wheel dimensions — 83mm inducer, 74mm exducer — giving it a massive airflow capacity while remaining responsive. Key features include:

• Twin-scroll turbine housing: This design separates exhaust pulses to reduce reversion, dramatically improving spool time and low‑end torque.
• Forged-machined compressor wheel: Lighter and stronger than cast counterparts, boosting durability at high boost pressures.
• Integrated wastegate: A high-flow, compact wastegate system eliminates boost creep and improves boost control accuracy.
• Ceramic ball bearings: Reduce internal friction for faster spool and better transient response than traditional journal bearings.
• Speed sensor and compressor map: The EFR series includes a speed sensor port, allowing precise turbo speed monitoring to stay within safe limits during extreme tuning.

For the VR38DETT, the EFR 8374 is typically used in a twin-turbo configuration (one per bank) rather than as a single conversion. This retains the engine’s original layout and packaging, simplifying installation while delivering headroom for over 800 whp with the right fuel and tuning.

Power Gains: Stock vs. BorgWarner EFR 8374

The factory R35 GT-R outputs approximately 480–500 horsepower at the crank (roughly 440–460 whp on most chassis dynos). Swapping the stock turbos for BorgWarner EFR 8374s can transform that baseline dramatically. Potential power levels fall into three common tiers:

Tier 1: EFR 8374 with Minimal Supporting Mods

If you install the EFR 8374 turbos on an otherwise stock engine with only a quality tune, you can expect a gain of roughly 100–150 wheel horsepower. Typical dyno results land between 580 and 630 whp on pump gas (93 octane). The factory fuel system can handle this level with careful tuning, though injector duty cycles become borderline. Most owners stop here for a street-friendly setup that still feels immensely more responsive than stock.

Tier 2: EFR 8374 with Integrated Supporting Upgrades

Adding a high-flow downpipe and exhaust, a larger intercooler or charge air cooler, and a fuel system upgrade (injectors, pump, or return system) allows the turbos to breathe and fuel sufficiently. On pump gas or a high-octane blend, these builds commonly produce 650–720 whp. That’s a gain of 180–250 wheel horsepower over stock. This is the sweet spot for most daily-driven GT-Rs because it retains OEM drivability and does not require internal engine modifications.

Tier 3: Full Build – EFR 8374 with Engine and Fuel System

When combined with ported heads, upgraded valvetrain, a built short block, and a larger fuel system (e.g., return-style with 1300cc+ injectors and a surge tank) plus E85 ethanol or race fuel, the EFR 8374 can support 800–900 whp. Some tuners have even pushed past 950 whp with these turbochargers at high boost levels (28–32 psi) and precise timing control. However, at these power levels, the rest of the drivetrain — transmission, transfer case, axles — requires strengthening to survive repeated abuse.

Configuration	Estimated Wheel Horsepower	Fuel Requirements
Stock R35 GT-R	440–460 whp	93 octane
EFR 8374 + Tune	580–630 whp	93 octane
EFR 8374 + Bolt-ons + Fuel System	650–720 whp	93/E85 blend
EFR 8374 + Full Built Engine	800–950 whp	E85 / race fuel

Factors That Influence Real-World Power Output

Horsepower numbers from a brochure or a forum post are just starting points. Your actual results hinge on several variables:

Supporting Modifications (The Critical Path)

Without proper intake, exhaust, intercooler, and fuel delivery, the EFR 8374 will be choked. A common mistake is bolting on big turbos while keeping the stock intercooler, which heat-soaks quickly and forces the ECU to pull timing. You also need a boost controller capable of precise duty-cycling for the integrated wastegates. Expect to budget for at least a cold air intake, 3‑inch downpipes, a free-flowing midpipe, and a cat‑back exhaust that doesn't create backpressure.

Tuning Expertise and Fuel Quality

The VR38DETT is knock-sensitive, and the EFR turbos move a lot of air. A poor tune can destroy an engine in seconds. Choose a certified tuner with extensive R35 experience (e.g., Cobb ProTuners or top shops like AMS Performance, T1 Race Development, or Specialty Z). Using ethanol blends (E50–E85) dramatically increases knock resistance, allowing higher boost and earlier timing without detonation. On pump gas, you’ll be limited to around 12–14 psi of safe boost; on E85, you can run 20+ psi safely.

Engine Health and Mileage

High-mileage VR38s may have carbon buildup, worn piston rings, or weakened valve springs. A leakdown test and compression test are mandatory before upgrading. Many shops recommend refreshing the top end with new timing chains, guides, and head studs at the time of turbo installation to ensure reliability at elevated power levels.

Installation: What’s Involved?

Swapping the stock turbochargers for BorgWarner EFR 8374 units is a 24–30 hour job for a professional shop. The labor cost is significant, but the procedure is well-documented for the R35. Key steps include:

1. Removal of engine covers, intakes, intercooler piping, and exhaust manifolds.
2. Unbolting and extracting stock turbos. (The stock units are heavy and prone to oil drain restriction.)
3. Prepping oil and coolant lines. The EFR uses different fittings; a proper adapter kit is essential.
4. Installing the EFR 8374s with new gaskets and hardware. Verify turbo clocking and wastegate actuator clearance.
5. Reassembling all intake and exhaust components, then filling with fresh oil and coolant.
6. Base mapping and final tune on the dyno.

Many tuners also recommend upgrading the wastegate springs for better boost control, and rerouting the oil drain to a scavenge pump if you plan to track the car.

Real-World Owner Feedback

Reading about horsepower is one thing; hearing from actual GT-R owners who have made the swap brings the picture into focus.

• throttle response: “The twin-scroll design on the EFR 8374 spools noticeably faster than my old Garrett GT2860s. Power comes on hard by 3500 rpm and pulls to redline like a freight train.” — R35 owner on GT-R forums.
• daily drivability: “I drive mine to work every day with the 8374s on 93 octane. It’s totally docile in traffic but when I get on it, it’s a monster. No surging, no heat soak issues so far.” — Owner of a 660 whp street car.
• reliability at 750+ whp: “18 months of hard driving — multiple track days and pulls — with zero turbo failures. BorgWarner builds a solid product. Get a quality oil cooler and keep temps in check.” — Track-focused build owner.

Cost Considerations and Payoff

There is no getting around it: a quality turbo upgrade on an R35 is expensive. Expect to spend:

• EFR 8374 twin turbo kit (including lines, gaskets, and flanges): $4,000–$5,500
• Labor (shop time): $2,500–$4,000
• Supporting mods (intercooler, fuel system, intake, exhaust): $3,000–$6,000
• Professional tuning: $1,500–$2,500
• Total typical investment: $11,000–$18,000

While steep, this investment yields a car that can outrun many exotics costing three times as much. Resale value of a well-built GT-R also holds better than a stock car with similar miles, as enthusiasts are willing to pay a premium for proven reliability and power.

Alternative Options and Direct Comparisons

Competitors to the EFR 8374 in the GT-R market include the Garrett GT3076R (slower spool, less top-end), Precision Turbo 6266 (strong midrange but heavier), and the stock frame upgrade options like the GT-R turbos from AMS Performance. The BorgWarner EFR 8374 sits in a sweet spot: it offers faster spool than most ball-bearing Garretts of similar size, better top-end flow than the smaller Precision units, and a proven track record in endurance racing.

For those who want to keep the car responsive on the street while still having 700+ whp capacity, the EFR 8374 is hard to beat. If you are targeting over 950 whp, you might consider the larger EFR 9180, but that sacrifices spool time and drivability significantly.

Bottom Line: Is the BorgWarner EFR 8374 Worth It for Your R35?

The BorgWarner EFR 8374 turbocharger can add anywhere from 100 to over 400 wheel horsepower to your R35 GT-R, depending on the extent of supporting modifications and fuel. The most common builds adding 180–250 whp are streetable, reliable, and exhilarating. The upgrade transforms the car from a quick supercar into a serious track weapon capable of humbling modern hypercars.

For any GT-R owner looking to take their car to the next level without daily driving compromises, the EFR 8374 is an excellent choice. Just be sure to budget for proper supporting modifications and a professional tune — skimping on either will leave power on the table and risk engine reliability. When done right, this turbo upgrade delivers what every R35 enthusiast craves: more power that you can actually use.

Additional Resources

For further reading, check out BorgWarner’s official EFR technical guide for detailed flow maps and specifications. You can also browse owner experiences and dyno charts on GTR Heritage for real-world builds. For a comparison of different turbo options, the NA GT-R Owners Club forums have extensive discussions.