Engine tuning status; the condition of the rotating components; operational condition of the control sensors and components; the presence of any air leaks in the turbocharger system; the control settings; and even the weather.
■ Boost Leak
When air (boost) is leaking within the turbo system or intake, it is referred to as “boost leak.” This may be caused by loose assembly of the components, a bad seal or a cracked component. Under such a condition, the turbocharger may not create enough boost pressure, or reach adequate levels.
■ Boost Spike
A boost spike is an erratic increase in boost pressure, mainly experienced when the vehicle is accelerating through the lower gears and the controller can’t adjust to the changes in engine speeds as quickly as would be ideal.
Several factors can influence boost pressure and affect turbocharger efficiency.
The key factors are:
Ambient Air Temperature and Pressure
As the air temperature rises, the ability of the turbocharger to compress the warmer air decreases. This phenomenon is directly due to the decrease in air density and the physical limitation of the turbocharger.
Even when the air temperature is low, the air density (barometric pressure or boost pressure) may be low. Under these conditions, lower than expected boost pressure may be experienced. The diameter of the exhaust system will vary the pressure differential across the turbine. A larger exhaust allows the turbocharger to rotate faster, which results in higher boost pressure.
Any increase in boost pressure would require “re-mapping” of the ECM programs to accommodate different air flow rates and resultant ignition change requirements. Over-revving of the turbine – trying to supply enough boost – can lead to turbocharger failure, particularly in conjunction with the increase in the pressure differential across the turbine.
Here are some service procedures, including steps to properly remove turbocharger components, and tests and inspections you can perform to check component operation.
You may need to remove the intercooler to work on other components beneath it. Removal of the intercooler must be performed carefully so that no damage occurs.
1.) Disconnect battery. Remove the two bolts that attach the bypass valve, then the valve.
2.) Remove the bolts from each end of the intercooler and disconnect the crankcase ventilation hoses from the intercooler.
3.) Loosen the clamps at the throttle body and outlet of the turbocharger.
4.) Gently move the intercooler side to side until the tension of the hoses at the turbocharger and throttle body loosen.
5.) Remove the intercooler from the engine compartment and cover the open areas with tape to prevent foreign material from entering, which could cause damage to the engine or turbocharger after re-installation.
Turbochargers are fairly simple in concept, but adapting the system to modern vehicles can be quite complex. This primer for those new to servicing turbos and review for veterans lays out the function and operation of turbocharging in Subaru vehicles.
The return of turbocharging in the 2002 Impreza WRX marked an absence of nearly a decade for Subaru vehicles. While the new generation has been around for half a decade, not everyone understands the function and operation of Subaru turbocharging systems.
Naturally, everyone knows these blowers are designed to get the maximum power out of engines by packing more air and fuel into the cylinders to get the biggest bang possible. Just how that is accomplished, however, may be a bit of a mystery to you. Here’s a primer on turbocharging and how it applies to Subaru vehicles.
Subaru Turbocharger Explained:
A Brief History of Turbochargers
Turbochargers were originally invented to increase the volume of air pushed into the cylinders of internal combustion engines, and, along with increased fuel, raise the level of energy produced by the combustion process
Historical references indicate that Swiss engineer Alfred J. Buchi adapted the turbines from steam engines to diesel engines as a method to improve air induction, and, therefore, smoother operation in internal combustion engines. In 1905, Buchi’s idea of powering the forced air induction by exhaust flow was granted a patent. Good idea or not, the fairly crude engines of the day could not sustain even or adequate boost pressures. Buchi worked another ten years before he could produce a working model of a turbocharged diesel engine. By that time, other companies had also produced turbocharging systems
The massive building boom of internal combustion engines to supply ships, trucks and airplanes for World War I saw technologies take a giant leap forward. The first turbocharged diesel engines for ships and locomotives appeared around 1920. Shortly thereafter, European car manufacturers began incorporating them into factory race cars and a few sporty luxury models.
The next milestone for turbocharging came with the military build-up for World War II, when turbo systems were fitted to fighter planes and bombers to allow them to fly at higher altitudes where the thinner air could be compacted into the engines to provide sufficient combustion. However, direct-driven superchargers quickly proved more reliable, efficient and more easily controlled, leaving turbochargers by the wayside.
It wasn’t until the mid-1950s when turbochargers started appearing on diesel trucks that modern turbos began to make a dent in the automotive market. Today, the vast majority of truck engines are turbodiesels.
When turbocharged vehicles began to dominate the international racing scene in the 1960s, car manufacturers began to use them in sporty models to appeal to performance-oriented drivers. By the 1980s, turbochargers for cars were a bona fide success, particularly in Subaru vehicles, due to improved metallurgy, intercooling and efficient boost controls.
The main components of a Subaru turbocharger system are a water-cooled turbocharger, an air-cooled intercooler, a wastegate control solenoid valve, sensors and a controller. Let’s review the individual components and the role they play in the system.
This is a step by step guide on how to install an aftermarket Pitch Stop Mount to your 02-07 Subaru WRX or STi.
1.) Locate and remove the three 10 mm Gold colored bolts that secure the black vacuum lines to the bottom of the intercooler. You will need a shallow socket as it gets tight around the BOV. Careful not to drop them into the engine bay, it will be a PITA to find and retrieve them.
2.) Locate and remove the two 12 mm bolts that secure the recirculating BOV to the bottom of the intercooler. Again be careful not to drop these into the engine bay as it’s a jungle down there and it will be a PITA to retrieve them.
3.) Locate and remove the two 12 mm bolts that secure the intercooler to the engine. These are located one on each side of the intercooler.
4.) Now the intercooler is only held in place by the rubber intake hoses with the clamps. The one that is on top, from the intercooler to the throttle body/intake manifold is easier so do them first. Using the Flat head screw driver or an 8 mm socket loosen the clamps holding the intake piping to the Intake manifold and intercooler. And leave it for now.
5.) This is a little tough to do, but its not impossible. You should be able to do it even if you have large hands. Using the flat head or 8 mm socket, loosen the clamp that holds the intake tube coming from the cold side of the turbo to the intercooler. This is located underneath the intercooler.
Deatschwerks injectors install on a Subaru STi w/ a FMIC:
We put together this DIY since there are some more specifics when working with the Deatschwerks injectors on a 2006 STI with a FMIC. YMMV and as with all DIY’s, you do this at your own risk. I will not be responsible for any damage you incur doing this yourself. (but seriously, it really wasn’t ‘that’ hard.)
1. Let the car sit overnight or relieve the fuel pressure by unplugging the fuel pump (green plug in upper right area of passenger footwell). (NOTE: I just let my car sit overnight)
2. Start on the driver’s side (it’s easier).
a) Remove negative battery terminal.
b) Remove the two 12mm bolts holding in the plastic bracket to the intake manifold and clip the two zip ties keeping the harness in the plastic bracket.
c) Now remove the plastic bracket (it will take a patient/creative rotation to get it out from the hoses/harnesses) and you’ll be able to clearly access the torx screws holding down the little bracket that holds down the injectors.
1.You may also want to unplug the blue connector and the Crankcase breather hose (regular clamp, not the crimped one) to provide maximum access to the injectors.
d) Unplug the injector, remove the torx screw (Proper size Torx Bit: T-25), swing the bracket up and out of the way, and pull the injector out. You will need a small screwdriver with a sharper tip to pop the injector up. Just be careful not to damage the injector seat or the injector housing / Rubber O-ring
3. Now, get one of your newly purchased Deatschwerks injectors. Open the tube of Super Grease (should be provided) and generously lube the lower O-Ring, and moderately-sparingly lube the upper O-Ring. ONLY LUBE the O-RINGs, try not to get lube on the injector screen or filters
4. Gently insert the Deatschwerks injector. You will want it to sit on the upper O-Ring, flush to the injector port. Then use the bottom of rubber mallet wooden handle to push the Deatschwerks injector in until it seats. There will be a noticeable but gentle “pop” not a sound but a “feel” once the Deatschwerks injector seats. If there is a fair amount of gas left in the injector port, it may even just slip in … no “pop” feeling.
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.
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.
The primary purpose of a top mount intercooler is to reduce post turbo air temperature prior to entering the combustion chamber via the throttle body.
HP gain is around 15HP. This figure can vary as many TMICs replace the restrictive OEM piping and 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.
How much HP can my stock TMIC hold? 300WHP on the WRX and 400WHP on the STi are attainable. That does not mean those power levels are 100% efficient, but that those power levels are attainable with their OEM TMICs. As discussed below though, TMICs are not meant to be HP rated, but rather CFM related, but this is an FAQ so the HP figures are given as a good “bad” answer.
Which manufacturer is best? This topic is highly debated. There have been no reported consistent “bad” TMICs on the market. Obviously, there may have been bad TMICs sold, but not enough to report as “bad” overall.
I have a 2008/2009 model, any differences? Yes. Your engine bay has an entirely new layout vs. the 2002-2007 models.