Category Archives: Subaru

TGV Deletes for Subaru WRX/STi

TGV Delete on WRX/STi’s:

The primary purpose of a TGV delete is to remove the divider bar and butterfly valve inside the TGV assembly to improve airflow to your engine.

TGV Delete: Top is a deleted TGV and bottom is the stock TGV.
TGV Delete: Top is a deleted TGV and bottom is the stock TGV.

HP gain is 12 HP. This figure is highly debated as different manufacturers use different dynos with different cars with different levels of mods.

What is the purpose of TGV Deletes? The are meant to reduce cold idle emissions. Nothing more, nothing less. Once your vehicle is warm, the butterfly valves open fully and remain that way.

Which manufacturer is best? This topic is highly debated with no real winner in terms of performance. There are several companies that offer the TGV delete service as well as purpose built units or Japanese models which are, in essence, hollow units.

Japanese model, what is that? TGV internal assemblies are only used for cold start emissions on US cars. Hence, the Japanese TGVs do not have the divider plate or butterfly valves. Some models are one piece intake manifolds with longer runners that make up the TGV portion and other models are just like their US cousins with no internal plates or butterfly assemblies. Neither units have the associated TGV external motor controllers as well.

Which TGV Delete has the best gains? There is no irrefutable evidence that any TGV Delete option has better gains than another. The consensus, if there is one, is they are all within 5HP or less, gain wise, of each other.

Do TGV Deletes cause a CEL? Yes. By removing the TGV motors, it will throw quite a few CELs. The bad news with this, is the TGV CELs will throw your car into limp mode, meaning unlike some other CELs that you can still drive around with and have no fear, the TGV codes limit boost/RPM operation meaning they must be taken care of in order to drive your car for any reasonable distance.

How do I fix the TGV CEL? You have three methods:
1. Normally, you remove the TGV motors and the rod that holds the butterfly valves in place. You could leave the rod in place (sans butterfly valves) and reinstall the TGV motors. This would allow them to actuate normally making the system think everything is working correctly.
2. APS makes a block that you attach the TGV motors to, this allows them to actuate normally making the system think everything is working correctly. These are not sold separately though, but can occasionally be purchased in the Private For Sale Forum or on eBay.
3. Various engine management systems can remove the associated CELs.

Do I need to perform the CEL fix? Yes. The TGV CEL codes will throw your car into limp mode. This will limit boost/RPM seen by your vehicle. It will still drive, but it should only be driven a short distance with the TGV CEL. Meaning you can drive it across town or a few short trips, but by no means should you drive it as a daily driven car for weeks on end until you get the proper fix.

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Legacy: 1989-1994 Subaru Legacy (BC/BF) GT/RS

Prior to the Legacy RS turbo, Subaru had never enjoyed the experience of distributing a genuine performance car. Of course, there had been the 4WD turbo RX and Vortex, but neither could crack 10 seconds for the 0-100km/h sprint – although they were very reliable. The RS was the gun version of the first Legacy series released in 1988 and discontinued in 1994. The RS (Rally Sport) model was aimed squarely at world rallying, with many of its components and concepts carried over to the dominating Impreza WRX.

Legacy: The BC/BF is unique in having an Air - Water intercooler with a front mounted radiator for optimal cooling. The bonnet scoop only provides cooling to the turbo. While later model legacy's have all used air to air intercoolers.
Legacy: The BC/BF is unique in having an Air – Water intercooler with a front mounted radiator for optimal cooling. The bonnet scoop only provides cooling to the turbo. While later model legacy’s have all used air to air intercoolers.

The center Viscous LSD on the MT models initially starts out with a 50/50 torque split, front and rear, and will up the ratio towards the end with more traction. The manufacturer doesn’t give a final figure, so the max split is either 65/35, or could even venture as high as 95/5, since the A/T model has a different system that is marketed at a 65/35 maximum split. A higher ratio would explain some of the handling characteristics at the limit. The rear differential is also a Viscous LSD model.

The BC/BF is unique in having an Air – Water intercooler with a front mounted radiator for optimal cooling. The bonnet scoop only provides cooling to the turbo. While later model legacy’s have all used air to air intercoolers.

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Timing Belt and Water Pump Replacement Subaru WRX/STi

Timing Belt and Water Pump Replacement Subaru WRX/STi:

Timing Belt and Water Pump Replacement is critical in keeping your Subaru WRX/STi in good condition and to prevent the valves from hitting your engine’s pistons.

Tools used:

3/8 Ratchet
1/2 Ratchet
10, 12, 14, 22mm sockets
short extension
Impact wrench or strap wrench (I used both on separate occasions.)
Torque Wrench
Small metal ruler to measure belt deflection.
Drain pan and funnel for the coolant.
Brake Kleen
Lots of paper towels/shop rags.
3/8 socket driver (very handy.)
Feeler gauges
2mm allen wrench
allen socket for the right camshaft (6mm maybe?)
C-Clamp

Timing belt kit and misc:


Gates TCK328RB Timing Belt Component Kit

Gates 42030 Water Pump

Gates 34012 Thermostat


NYPPD Billet Timing Belt Guide Subaru Impreza WRX EJ20 STi EJ25 2002-2013 Turbo

Genuine Subaru SOA868V9270 Super Coolant

Subaru SOA635071 OEM Coolant System Conditioner

Helpful tools:

Subaru Camlock Tool for Subaru 2.0L and 2.5L DOHC turbo engines C23-506

Subaru Crank Pulley Tool C23-503

Subaru STD Int/Exh Cam Sprocket Tool – similar to 499207400-A

Subaru Cam Sprocket Tool – AVCS Int C23-501

Go to the next page to get started.

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FMIC (Front Mount Intercooler) STi/WRX FAQ

FMIC: The primary purpose of a FMIC (front mount intercooler) is to reduce post turbo air temperature prior to entering the combustion chamber via the throttle body.

FMIC install in a Subaru WRX STi.
FMIC install in a Subaru WRX STi.

HP gain is around 15HP. This figure can vary as results can be further enhanced with post installation tuning. This is one modification that is extremely difficult to put a traditional HP figure on as results truly vary from car to car based on tuning and turbo output in terms of CFM.

Which manufacturer is best? This topic is highly debated. There have been no reported consistent “bad” FMICs on the market. Obviously, there may have been bad FMICs sold, but not enough to report as “bad” overall.

Which FMIC construction method is best? FMICs have two main construction methods:
1. tube and fin
2. bar and plate
There is much debate as to which construction method is best. There are many pros and cons with each design type, but no real hard data. Bar and plate designs are consistently reported as more damage resistant which gives them the edge with regard to appearance longevity. In the end, you are best advised to chose a FMIC based on other qualities rather than concentrate on construction design.

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Transmission: STi 6-Speed basic swap info into a WRX

Front Differentials:
02-07 WRX: open
04 STi: “SureTrac” LSD
05-07 STi: “Helical” LSD

Transmission: Sti 6-Speed vs. WRX 5-speed
Transmission: Sti 6-Speed vs. WRX 5-speed

Rear Differentials: R160, R180
These were originally used in the Datsun 510, 610 and other IRS Datsuns. The “R” stands for Fuji Heavy Industries. The R180 was used in the front axle of Datsun 4×4 trucks (720, etc). The number represents the ring gear size in millimeters.

R160 – 52lbs. WRX rear differential. It has a viscous LSD which is no better than an open differential since the unit is so tiny in this differential.
02-05 have a 3.54 gear ratio
06-07 have a 3.70 gear ratio
R160’s on 2.2L Legacy/Impreza’s have a 3.9 gear ratio

R180 – 64lbs. STi rear differential. It has a mechanical clutch type LSD.
04-05 R180’s have a 3.90 gear ratio
06-07 R180’s have a 3.54 gear ratio

Center Differentials:
02-07 WRX: Viscous coupling type
02-05 has a 1.1:1 gear ratio
06-07 has a 1:1 gear ratio
04-07 STi: DCCD (Driver Controlled Center Differential)
04-05 has a 1:1 gear ratio
06-07 has a 1.1:1 gear ratio

Do I need different front axles?
02-early 04 WRXs have female axles and need to use stubs that go inside the transmission . Late 04-07 WRXs use male ended axles that slide inside the front differential so there is no need for stubs. For the female axles, you need axle stubs, circlips, and seals to reuse the WRX axles (check out the seal differences link for part numbers). You can use the stubs from your 5MT. For the male ended axles, they just slide right into place with the correct seals and circlips. 04 STi front axles will work too.

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How to shift with AWD or a Manual Transmission.

How to shift with AWD or a Manual Transmission:

Where can I find good background information of transmissions? A good general reference for new people as well as a refresher for more advanced users is How Stuff Works’ Transmission Tutorial.

Where can I find good background information on differentials? A good general reference for new people as well as a refresher for more advanced users is How Stuff Works’ Differential Tutorial.

Shift: STi Shifter
Shift: STi Shifter

Is shifting different with an AWD car vs. a FWD or RWD car? One has to visualize the power transfer in a car to get a better understanding. In a FWD or RWD car, if you shift or launch the car too aggressively, the excess power is transmitted to the tire(s), which will spin. Put another way, excess power is “burned off” through tire smoke. In an AWD car, if you shift or launch the car too aggressively, the excess usually isn’t enough to overpower thetires’ grip. In this situation, the excess power must be absorbed somewhere else in the drive train. Though some drive train shock is normal, in an overload situation, excess power is transmitted to the various driveline components, which can accelerate wear and tear.

Where are the shifting differences most apparent? Starting off in first gear and the 1-2 shift are the most common causes of driveline shock. Obviously, there is reason to shift responsibly in every gear but these are the most commonly seen problematic shifting issues.

Is resting my hand on the shifter bad? From the WRX Owners Manual: “Do not drive with your hand resting on the shift lever. This may cause wear on the transmission components”. This advice should apply to every Subaru MT model. That being said, the safest course of action is to keep both hands on the wheel unless actually shifting.

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Spark Plug replacement on a Subaru Impreza STi/WRX

The following procedure explains removing and replacing spark plugs on a Subaru Impreza STi. The original instructions below specifically refer to fitting Denso Iridium spark plugs that are one step colder however these procedures are generic for OEM plugs also. Please click the thumbnail pictures below for a full size version.

The author indicates this took around 1 hour to complete the first time, perhaps half that next time. Right, off you go you are being timed!

Procedure

Remove the battery and windshield washer fluid reservoir (Step 1)

This is simple, just four bolts holding the battery and two bolts (<< seen in step one), a hose and a clip (<< seen in step 1.1) holding the washer reservoir in.

Spark plug step 1.) Battery Removal.
Spark plug step 1.) Battery Removal.
Spark Plug removal step 1.) Windshield washer reservoir.
Spark Plug removal step 1.) Windshield washer reservoir.

Removing intake and assembly (Step 2)

Note: the author can break this down further as he doesn’t have the stock intake, instead the K&N typhoon is shown. The stock intake is very easy just a couple of bolts, clamps etc. (<< steps 2 and 2.1)

Spark plug step 2.) Remove intake duct.
Spark plug step 2.) Remove intake duct.
Spark plug step 2.) K&N Removal
Spark plug step 2.) K&N Removal
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Coolant use and Cooling System for Subaru WRX/STi

What type of coolant should I run in my car? You can never go wrong by using Genuine Subaru Coolant available through your local dealer.

Subaru Genuine Coolant. To the left Super Coolant and to the right long life coolant.
Subaru Genuine Coolant. To the left Super Coolant and to the right long life coolant.

Is the Subaru coolant pre-mixed or not? They have both kinds, but BE SURE to read the labels carefully as they are nearly identical in appearance except the wording on the package!

Is there a required coolant additive? Yes. Subaru Cooling System Conditioner has recently been required to be added with every coolant replacement to prevent coolant system leaks. This recommendation applies to every Subaru model for every model year.

Subaru Cooling System Conditioner has recently been required to be added with every coolant replacement to prevent coolant system leaks. This recommendation applies to every Subaru model for every model year.
Subaru Cooling System Conditioner has recently been required to be added with every coolant replacement to prevent coolant system leaks. This recommendation applies to every Subaru model for every model year.
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