Shortly after the Z32's release in 1989 (as a 1990 model year in the US), Nissan released the Twin Turbo version. There were several changes to this model that set it apart from the NA, which are detailed in this article.

Cosmetic/Visually Noticeable Changes

  • Twin Turbos came standard with a rear spoiler.
  • Twin Turbos had slots in the front bumper to allow air flow to the intercoolers.
  • In the US, Twin Turbos had wider (8.5") rear wheels.
  • Twin Turbos have a boost gauge in the gauge cluster under the speedometer.
  • When looking in the engine bay, Twin Turbos have four intake pipes visible, while NAs have two.
  • When looking in the engine bay, 90-93 Twin Turbos had HICAS solenoids mounted near the power steering reservoir.

Engine

  • TT had, well, turbos.
  • Differently angled oil squirters.
  • NAs had oil filter check valves installed directly in the block, TTs used a different oil tree which housed the check valves.
  • TT oil tree has a feed line for the oil cooler.
  • TT oil pan has returns for the oil cooler and turbochargers.
  • Pistons have different compression ratios (8.5:1 for TT, 10.5:1 for NA).
  • TT pistons have a hollow spot that fills with oil for better cooling.
  • TT oil pump has a tighter pressure relief spring (to compensate for oil flowing to the turbochargers and oil cooler)
  • TT exhaust valves are made from inconel to deal with higher exhaust temps.
  • TT heads have different (better) castings.
  • TT exhaust manifolds are completely different as they support the turbochargers.

Electrical

  • Coilpacks have different part numbers and slightly different high tension lead designs, but are considered interchangeable.
  • The TT ECU has provisions for a dual-speed auxiliary fan, three-speed fuel pump, and wastegate control solenoids. The TT's EPROM also has different programming due to the different fuel injector size and the nature of forced induction.
  • The TT EFI Harness contains connectors for the wastegate control solenoids.
  • The TT gauge cluster has a boost gauge under the speedometer.
  • The TT fuel pump is a higher output (supporting upwards of 700 HP), and has 3 control speeds (2 for the NA).
  • TT fuel pump controller is different and has an additional wire for the additional speed. Wiring from the ECU to the FPCU is also different for this reason.
  • TT Fuel Injectors are higher flowing (370CC vs 270CC)
  • The TT auxiliary fan has 3 speeds (versus the NA's 2 speeds).

Drivetrain

  • Different rear differentials (3.67 on the TT, 4.08 on the NA).
  • TT rear subframe is different to accommodate HICAS.
  • Driveshafts are different for practically every configuration (TT, NA, 5-speed, auto, 2+2, 2-seater).
  • Despite the transmission gearboxes being the same, the TT has a larger bellhousing to accommodate the larger flywheel, which also places the starter further outwards.
  • TT and NA speed sensors are different due to the difference in final drive ratios.
  • TT has a larger clutch and flywheel.

Other

  • Radiators (and fan shrouds) are totally different. NA has end-tanks on the top and bottom, TT has them on the sides. TT radiator is taller but narrower to make room for the intercooler piping.
  • A/C condensers are different shapes (similar to the radiators).
  • A/C piping is different.
  • 90-93 TT power steering pumps, lines, and rack are different due to the hydraulic HICAS. In 94, the TT switched to electrical SuperHICAS, and the power steering system (except for the rack) became identical to the NA's. 90-93 TTs also had hydraulic lines running to the HICAS rack at the rear of the car.
  • TT Steering Rack has a quicker steering ratio.
  • 90-93 TT has HICAS, 94+ TT uses electric SuperHICAS.
  • TT shocks had adjustable internal valves, which could be changed through a cabin-mounted "SPORT/TOURING" rocker switch. Sport mode made the shocks firmer for better handling, and Touring made them softer for better comfort.
  • TT alternator outputs 90 amps, versus the NA's 80 amp alternator.
  • TT intake system is totally different after the air box. The NA's piping goes straight from the MAF to the throttle bodies. The TT goes from the MAF to the turbo inlets, turbo outlets to intercoolers, and intercoolers to throttle bodies. The TT also has recirculation valves
  • USDM TT exhaust has pre-cats coming right off the turbo, mandrel bending in the mufflers, smaller resonators, and shorter catalytic converter pipes. JDM TTs don't have pre-cats, and instead using a simple downpipe, which bolt directly up to NA catalytic converter pipes.



Thanks to Z1Motorsport's handy guide for the bulk of this information.

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