Category Archives: Turbo

Ej20, ej20G, EJ257, JDM, TMIC, Tuning, Turbo, USDM, WRX

Turbo: STi/WRX VF Series Turbocharger breakdown:

Turbo: STi/WRX VF Series Turbocharger breakdown:

IHI VF Series
The numbering on both the VF turbos are for reference purposes and not necessarily indicative of its ‘performance’. On GC8/GF8 WRX STi, the VF turbos have gone ‘smaller’ from VF22 to 23, 24, 28, 29 while the release of the New Age STi GDB saw the introduction of a new breed of VF turbos with a bigger compressor wheel namely, VF30, VF34, VF35 for example. The previous VF turbos (VF22,23,24,28,29) have been ball bearing cored while the later ones (VF30, VF35) are Divided Thrust Bearing type core, with the VF34 being a Ball Bearing.

IHI VF22
(455cfm at 18.0psi, 250-325whp, Bolt-On)
The VF22 has the largest potential for peak horsepower. In other words, in the IHI model range, the VF 22 supports the highest boost levels. With its significantly increased turbine housing, the VF22 turbo is capable of producing upwards of 310 whp* on an EJ20. The downside of this turbo is the older center cartridge design and larger compressor housing, which makes for slower spool up but more top-end than the other VF series turbos.

This turbo is the best choice for those who are looking for loads of top end power. The top end power however, does not come without a cost. The VF22 spools significantly slower than the rest of the IHI models due to the larger P20 exhaust housing and is much less suited for daily driving than some of the other models. Although the largest VF series turbo, the VF22 is not quite optimal for stroked engines or those who wish to run more than 20PSI of boost.

The VF22’s compressor is rated at 35 lbs/minute. The VF22 was designed with the EJ20 in mind but because it has the biggest turbine in the IHI family it can be use on the EJ25 with a slight increase in performance. The VF22 is good for around a realistic 300 to 315 WHP on a 2.0L. The IHI VF-22 turbo is the largest of the VF-series turbos.

VF22: The IHI VF-22 turbo is the largest of the VF-series turbos.

IHI VF34
(440cfm at 18psi, 250-325whp, Bolt-On)
The VF34 is nearly identical to the VF30, with the same exhaust housing and compressor. However the VF34 goes back to the ball bearing design, and in doing so achieves full boost approximately 500RPM sooner than the comparable VF30. The VF34 is the most recent IHI design and as such costs slightly more than its counterpart.

Top end performance and maximum output are identical to the 30. The VF34’s compressor is rated at 35 lbs/minute but the turbo suffers from the same turbine restrictions found with the VF30. The VF34 was designed with the EJ20 in mind and will not have the same performance on an EJ25. The VF34 is good for around a realistic 290 to 305 WHP on a 2.0L.

VF34: The VF34 was designed with the EJ20 in mind and will not have the same performance on an EJ25. The VF34 is good for around a realistic 290 to 305 WHP on a 2.0L.
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Ej20, EJ257, STi, Subaru, Tuning, Turbo, WRX

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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AWD, Ej20, EJ25, EJ257, Intake, Intercooler, STi, Subaru, Turbo, USDM, WRX

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.

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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AWD, DCCD, EJ257, STi, Subaru, Tuning, Turbo, USDM, WRX

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

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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AWD, STi, Subaru, Turbo, USDM, WRX

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

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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Ej20, EJ257, STi, Subaru, Tuning, Turbo, USDM

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 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.) K&N Removal
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EJ257, STi, Subaru, Tuning, Turbo, USDM, WRX

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.

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.
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Ej20, EJ257, STi, Subaru, Tuning, Turbo, USDM, WRX

Spark Plug info for your Subaru WRX/STi:

Spark Plug info for your Subaru WRX/STi:

Refer to your owners manual for recommendations. Alternately, you can visit an auto parts store or online retailer for recommendations on suitable spark plugs designed for your vehicle. Major manufacturers are:
a. NGK
b. Bosch
c. Denso
d. Autolite
e. Champion

STi spark plug location

Who are the specialty spark plug manufacturers? These manufacturers make specialty plugs that have unique compositions or designs that claim increases over traditional plugs. They are listed for advanced users or those with interest.
a. Torquemaster
b. Beru (specifically the Silverstones found here)
c. SplitFire
d. PREP spark plugs
e. E3 spark plugs
f. Pulstar plugs

What types are there? There are really three main types:
a. conventional nickel alloy (commonly referred to as “copper”)
b. platinum
c. iridium

Which type should I use? That depends on how often you are interested in changing the spark plugs. Conventional spark plugs generally last one year. Platinum or iridium can last, depending on manufacturer specifications, up to seven years.

What’s some good background spark plug information?

Materials: The three main types of spark plug materials are nickel alloy, iridium, and platinum. Copper can be used in the core all plugs.

All ground electrodes are made of nickel. The use of Platinum and Iridium, which are stronger, allow for much finer CENTER electrodes (the ground electrode is still Nickel). These finer electrodes do not quench the flame core as much as a conventional style plug. This increases ignitability, therefore increasing HP. It’s not a huge gain, but cylinder pressures are measurably higher.

Platinum or iridium can be used as a thin pad which is laser welded on the ground electrode (the “J” strap), this serves to increase the life of the plug.

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