No It’s Not an STI: GST Motorsports Mighty Subaru Impreza

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No It's Not an STI: GST Motorsports Mighty Subaru Impreza
The Forced Performance HTA 3586 turbo is basically a Garrett GT35 hotside with the ported shroud compressor housing contoured for an extended tip inducer Borg Warner compressor wheel.  The extended tip is claimed to make the turbo spool faster.

A Forced Performance HTA3586 turbo with a 1.06 A/R twin scroll turbine housing is fed by a Full Race twin scroll header and up pipe.  A twin scroll turbo means that cylinders firing 180 degrees apart are sequentially fed into opposite sides of the turbine housing.  This results in much faster spool and better boost response with absolutely no drawbacks.  Keeping the pulses separated also means that tighter cam lobe centers can be run which also helps spool and boosts midrange power.

 No It's Not an STI: GST Motorsports Mighty Subaru Impreza
 The Cosworth intake manifold actually has a plenum.  Large volume Cosworth fuel rails feed 1000cc RC Engineering injectors.  A 70mm billet throttle body feeds more air into the engine.  An Aeromotive fuel pressure regulator on the return line controls fuel pressure.

A Hydra Nemesis ECU which is linked to an AIM MXL electronic dash handles engine management.  A World Electronics TBC-1 boost controller is tasked with boost control.  The car runs 3 different engine control maps.  Map one uses a native wastegate 22.5 psi and is used for testing and chassis setup.  The engine puts out 575 whp on a conservative Mustang dyno at this level.  Map 2 is used after the second lap of all timed sessions. Map 2 runs at 27 psi and makes 650 whp.  If even more power is needed, Map 3 has 32 psi and 713 whp on tap.  The team has only used Map 3 once for 44 seconds during this year’s Super Lap Battle when the high boost pressures caused a welded seam on the intercooler to split.

 No It's Not an STI: GST Motorsports Mighty Subaru Impreza
 GST fabricated the up pipe, down pipe and charge piping.

A GST custom fabricated stainless downpipe and dump tube handle exhaust gas post turbo.  A Turbosmart CompGate 40 wastegate and 50 series blow off valve are used to control boost pressure and lift throttle surge.  GST intake piping strains air through a large K&N filter.  A Ron Davis radiator handles cooling and is paired with a GST Motorsports fabricated V-Mount intercooler blowing into a Cosworth intake manifold armed with RC engineering 1000cc injectors.  The fuel system uses several Walbro 255 LPH pumps lifting fuel to a surge tank where Bosch 044 motorsports pumps feed the engine.  An Aeromotive fuel pressure regulator is used.  Oil cooling uses Setrab heat exchangers.

 No It's Not an STI: GST Motorsports Mighty Subaru Impreza
 A Setrab oil cooler with a Mocal adapter handles oil temperature issues.  Ductwork feeds air to the cooler.

 

No It's Not an STI: GST Motorsports Mighty Subaru Impreza
Ron Davis radiator with twin Flex-A-Light fans keep things cool.
No It's Not an STI: GST Motorsports Mighty Subaru Impreza
A Ron Davis radiator is V Mounted with a GST fabricated intercooler.  V Mounting allows both heat exchangers to have their own air flow unimpeded by another heat exchanger.  Hot air is ducted up out of vents in the hood.

 

No It's Not an STI: GST Motorsports Mighty Subaru Impreza
A close up of the intercooler, charge pipe and Tial blow off valve.  The Tial part has since been replaced with a Turbosmart piece.

 

No It's Not an STI: GST Motorsports Mighty Subaru Impreza
Rota 18×9.5″ wheels are shod with Hankook Ventus Z214 C91 super sticky tires.

 

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