Q. How is boost measured? (Bar, mmHg, PSI) and How do you convert from one to another?
A. Boost is measured as the pressure that the turbo creates above atmospheric pressure. Normal Atmospheric Pressure (1 atm) = 14.7 psi = 760 mm Hg 1 Bar is not actually equal to 14.7 psi, but rather it is equal to 14.5 psi, = 0.9869 atm = 750.062 mm Hg
Q. What is the Exducer?
A. Looking at a compressor wheel, the exducer is the "major" diameter. For a turbine wheel, the exducer is the "minor" diameter. The exducer, in either case, is where flow exits the wheel.
Compressor wheel exducer diameter is incorporated into Garrett GT-series nomenclature: The "60" in the GT2860RS for example, has a 60mm compressor wheel exducer diameter.
Q. What is the Inducer?
A. Looking at a compressor wheel, the inducer is the "minor" diameter. For a turbine wheel, the inducer is the "major" diameter. The inducer, in either case, is where flow enters the wheel.
Q. How fast will my car go with xyz?
A. This question cannot be answered as how fast any given car will go depends on the unique individual setup, road/weather conditions, and of course, the driver's skill.
Q. Are oil deposits indicative of impending turbo failure? There is blue/black smoke, is my turbo going bad?
A. Blue/black smoke can be caused by numerous conditions, and one of them could be a turbocharger worn past its useful service life. The following are potential reasons that blue/black smoke could occur:
* Clogged air filter element or obstructed air intake duct. This condition creates a vacuum due to high differential pressure resulting in oil drawn into the compressor and subsequently burned during engine combustion.
* Engine component problems; i.e. worn piston rings or liners, valve seals, fuel pump, fuel injectors, etc.
* Obstructed oil drain on turbocharger resulting in pressure building inside the center housing and forcing oil past the turbocharger seals
* Damaged turbocharger or turbocharger worn past its useful service life
* Black smoke is also sometimes indicative of too rich an air/fuel mixture.
Q. What should I look out for when buying a turbo?
A. 1. Condition of the turbine housing - inspect for cracks on the exterior and inside the inlet of the housing. If the housing has cracks then the housing needs to be replaced.
2. Condition of the turbine and compressor wheels - inspect for cracks and damaged blades. If either of the wheels are damaged then the wheel (s) need to be replaced and the center section balanced.
3. Condition of the bearings - spin the turbocharger shaft and check for roughness. If roughness is detected then the turbocharger needs to be disassembled and the internal components inspected and replaced if necessary.
4. The most important factor is to make sure the turbo is the proper one for your application. A properly matched turbo will provide better performance and more reliable operation. A properly matched turbo includes matched turbine and compressor wheel sizes and appropriate housings.
Q. Should my turbo/exhaust manifold glow red after driving?
A. Yes, the turbo/exhaust manifold can glow red under certain driving conditions. The exhaust gas temperature can reach over 1600F under high load operating conditions; i.e. towing, extended uphill driving, or extended high rpm/boost conditions.
Q. How do I adjust my compression ratio?
A. The easiest and most effective way to accomplish this is through the use of either higher/lower compression pistons, and/or using a head gasket of a different thickness.
Q. What compression ratio should I run with my turbo engine?
A. Allowable compression ratio depends on many factors, and there is no one right answer for every application. Generally, compression ratio should be set as high as feasible without encountering detonation at the maximum load condition. Setting the compression ratio too low will result in an engine that is a bit sluggish in off-boost operation. Setting it too high however, can lead to serious engine problems due to knock.
Factors that influence the compression ratio can include: fuel anti-knock properties (octane rating), boost pressure, intake air temperature, combustion chamber design, ignition timing, and exhaust backpressure. Many modern engines have well designed combustion chambers that will allow modest boost levels with no change to compression ratio, assuming appropriate tuning. For higher power targets with more boost, compression ratios should be adjusted to compensate.
Q. What additional maintenance is required for the turbo?
A. Good, clean oil is extremely important to the turbocharger. It is best to change the oil and filter at least as often as the automobile manufacturer recommends. FRAM produces replacement oil filters for all levels of server use. Visit www.FRAM.com
to select the right filter for your application!
Turbo performance is sensitive to turbo inlet conditions. A clogged air filter can drastically affect the turbo inlet. Air filters should be inspected at every oil change and replaced at 12,000 to 15,000 mile intervals. FRAM produces replacement air filters including a new performance filter the FRAM AirHog.
NOTE: Never exceed the vehicle manufacturer's recommended filter change intervals.
Q. What is the purpose of an oil catch can?
A. An oil catch can's purpose is to catch oil blow-by gasses that can eventually create a carbon and oil sludge build-up in the intake and turbo.
Q. How can I remove and clean the oil condensation box/oil catch can?
A. The oil condensation box, or catch can, can be cleaned once it is removed with any cleaning solvent. Simply fill the box with a cleaner and slosh it around until oil deposits are gone. Removing the oil condensation box can be a challenge and varies by vehicle.
NOTE: some vehicles are not equipped with an oil condensation box.
Q. Do I really need the cool down procedure on my turbo?
A. The need for a cool down procedure depends on how hard the turbo and engine is used, and whether or not the turbo is water-cooled. All Garrett turbochargers must pass a heat soak test and the introduction of water-cooling has virtually eliminated the need for a cool down procedure. Garrett is one of the few turbocharger manufactures that subjects their turbos to several OE qualification tests
. When you buy a Garrett turbo you can be sure it's a reliable one!
Q. Should I run a Turbo Timer?
A. A turbo timer enables the engine to run at idle for a specified time after the ignition has been turned off. The purpose is to allow the turbo to cool down thus avoiding "coking" ("coking" is burned oil that deposits on surfaces and can lead to blocked passages).
The need for a turbo timer depends on how hard the turbo and engine is used. Running at full speed and full load then immediately shutting down (heat soak) can be extremely hard on a turbo. Water-cooling of the turbocharger's center housing has essentially eliminated the need for turbo timers or extended idling periods.
Q. What is Knock/Detonation?
A. Knock is a condition caused by abnormal combustion of the air/fuel mixture and can result in damage to an engine.
The three factors that result in engine knock are: 1) knock resistance characteristics (knock limit) of the engine, 2) ambient air conditions, and 3) octane rating of the fuel being used.
1. Since every engine is vastly different when it comes to knock resistance, there is no single answer to "how much." Design features such as combustion chamber shape, spark plug location, bore size and compression ratio affects the knock characteristics of an engine. In addition, engine calibration of fuel and spark plays an enormous role in dictating knock behavior.
2. For the turbocharger application, both ambient air conditions and engine inlet conditions affect maximum boost. Hot air and high cylinder pressure increases the tendency of an engine to knock. When an engine is boosted, the intake air temperature increases thus increasing the tendency to knock. Charge air cooling (e.g. an intercooler) addresses this concern by cooling the compressed air produced by the turbocharger.
3. The octane rating of fuel is a measure of a fuel's ability to resist knock. The octane rating for pump gas ranges from 85 to 94 while racing fuel would be well above 100. The higher the octane rating of the fuel, the more resistant it is to knock. Since knock can be damaging to an engine, it is important to use fuel of sufficient octane for your application. Generally speaking, the more boost you run, the higher the octane requirement.
Q. How much boost can I run on pump gas?
A. The primary limitation to maximum boost is engine knock. It is also not advisable to run the maximum amount of boost your car can handle on a daily driven basis as a precaution against if the boost spikes.
Q. Which boost controller should I get? (Manual or Electronic)
A. Boost controllers vary widely in performance, price, and functionality. For a comprehensive breakdown of some of the more popular options, see the July 2002 issue of Sport Compact Car Magazine.
Q. What is a boost controller?
A. A boost controller is a device that bleeds or blocks the boost pressure signal entering the Wastegates actuator. The idea is to keep the Wastegates closed to allow higher boost pressures than the actuator would otherwise allow. These can be simple mechanical or sophisticated electronic devices, with price tags to match.
Q. What other systems are affected by turbocharging? (Fuel, Oil, Cooling, Drivetrain, etc)
A. There are several factors that must be addressed when deciding to turbocharge a previously naturally aspirated engine, such as: Is the current fuel delivery system capable of providing increased, adequate amounts of fuel? Is the cooling/oiling system capable of handling the extra power and consequently, extra heat that is generated by the turbo? Is the clutch/transmission/drivetrain up to the task of handling the extra power? Etc
Q. The turbo gauges measures turbine speed, right?
A. The "turbo gauge", commonly called a boost gauge, does not measure turbine speed. It measures the intake manifold pressure. Under light loads the boost gauge will indicate a vacuum due to the turbocharger shaft not rotating fast enough to create positive pressure (boost). Once load (throttle position) increases, the boost gauge will indicate a positive pressure.