Turbochargers – Pump It Up

By Jim Marotta

At 100 horsepower per liter, GM’s newer turbocharged 1.4L has the power of a larger engine but retains the efficiency of a small-displacement four-cylinder in most driving conditions. Courtesy GM

A naturally aspirated automobile engine uses the downward stroke of a piston to create an area of low pressure in order to draw air into the cylinder through the intake valves. Because the pressure in the atmosphere is no more than 14.7 psi, there is a limit to the amount of airflow entering the combustion chamber.

A turbocharged engine uses a radial fan pump driven by the engine’s exhaust that consists of a turbine and a compressor on a shared shaft. The turbine converts exhaust gases exiting the engine into rotational force, which is used to drive a compressor which draws in ambient air and pumps it at high pressure into the intake manifold to improve the engine’s volumetric efficiency. This results in a greater mass of air entering the cylinders on each intake stroke.

There are four main components to a turbocharger: the housing, the impeller/turbine wheels, the center hub and the bypass.

The size and shape of the housings fitted around the impeller and turbine affect performance,  response, and efficiency. Courtesy Borg-Warner

The size and shape of the housings fitted around the impeller and turbine dictate the performance characteristics of the overall turbocharger. This allows the designer of the engine system to tailor the compromises between performance, response, and efficiency to application or preference.

The impeller and turbine wheel sizes also dictate the amount of air or exhaust that can be flowed through the system. Generally, the larger the turbine and compressor wheels, the larger the flow capacity. The shape, curvature and number of blades on the wheels allow infinite variability in design to tailor a turbocharger to a given engine.

Water-cooled bearings, such as the one shown, allow engine coolant to keep the lubricating oil cooler, avoiding possible oil coking from the extreme heat found in the turbine. Courtesy Borg-Warner

The center hub connects the compressor impeller and turbine and uses a bearing lubricated by a constant supply of pressurized engine oil. While the engine oil cools some systems, the preferred method is to use engine coolant to keep the lubricating oil cooler, avoiding possible oil coking from the extreme heat found in the turbine.

Turbos use a bypass or wastegate to prevent over-pressurizing the system. At a specific boost pressure, a bypass feeds part of the exhaust gas flow around the turbine. The wastegate which opens or closes the bypass is usually operated by a spring-loaded diaphragm in response to the boost pressure.

There are several tips to maintaining and servicing turbochargers:

• Engineers design turbochargers to last the lifetime of the engine. They normally do not require any special maintenance; however observe strict adherence to the engine manufacturer’s service instructions. Ninety percent of all turbocharger failures are due to either foreign bodies entering into the turbine or the compressor, dirt in the oil, inadequate oil supply, or high exhaust gas temperatures.

• The most important maintenance factor is clean oil. Since turbochargers can be easily damaged by dirty or ineffective oil, most manufacturers recommend more frequent oil changes for turbocharged engines. The use of synthetic oils, which tend to flow more readily when cold and do not break down as quickly as conventional oils, is also a common practice.

• Since the turbocharger generates heat when running, many automakers recommend letting the engine idle before shutting off the engine if the turbocharger was used shortly before stopping. Most manufacturers specify a 10-second period of idling before switching off, for a couple of reasons: (1) to ensure the turbocharger is running at its idle speed, and (2) to prevent damage to the bearings when the oil supply is cut off. Idling lets the turbo rotating assembly cool from the lower exhaust gas temperatures, and ensures that oil is supplied to the turbocharger while the turbine housing and exhaust manifold are still very hot; otherwise coking of the lubricating oil trapped in the unit may occur when the heat soaks into the bearings, causing rapid bearing wear and failure when the car is restarted. Even small particles of burnt oil will accumulate, lead to choking the oil supply, and failure.

• The easiest way to diagnose a weak turbocharger is to observe the turbo boost. If the turbocharger does not show normal boost at full throttle (typically 9 to 14 psi), the system needs further diagnosis. One common but overlooked condition is excessive exhaust backpressure (often due to a clogged catalytic converter) which can prevent the turbo from developing its normal boost pressure.

Planning to service or repair your vehicle? Chilton can help! Access procedures, specifications, tips, and more at http://www.ChiltonDIY.com/.

A muscle car enthusiast and drag racer, Jim Marotta is a freelance automotive writer with more than 20 years experience in the automotive industry.

How to Refill the Coolant without a Bleed Tool

Draining and refilling the coolant is one of the easier maintenance tasks you can do on most vehicles. In addition to saving money, doing your own maintenance is a way to monitor the health of your vehicle.

Why Perform a Regular Coolant Flush and Refill?

Coolant loses effectiveness over time, so it’s important to periodically drain and refill the cooling system. In addition, as coolant becomes dirty, and rust and particles can eventually degrade cooling system components, such as the engine and water pump.

Bleeding Air from the Cooling System

If you drain the system and then pour coolant in, there is still air trapped within the hoses and components that hold coolant. That air must be removed. You’ll need to bleed out the air and then top off the coolant to the proper level.
Some car manufacturer refill procedures use a special tool that automatically fills the cooling system and bleeds any excess air. In most cases, if you don’t have the special tool, you can still fill the cooling system and bleed it manually. In rare cases, vehicles need to be serviced with specialized cooling system equipment, due to the complexity of the cooling system. Air will become trapped in the cooling system, and cause the engine to overheat! Check the service information before you attempt the procedure.

Research the vehicle’s cooling system.

How to Refill the Coolant System Manually

Caution
Do not work on the coolant system when the system is hot and under pressure: Coolant can cause serious burns. Do not remove the radiator cap, cylinder block drain plugs, or loosen the radiator draincock, when the engine is hot.

1. Tighten the radiator draincock.

Tighten the radiator draincock. 2010 Chevrolet HHR shown. Image: General Motors

2. Tighten the cylinder block drain plug(s).

Tighten the engine block drain plug. 2010 Chevrolet HRR shown. Image: General Motors.

3. Fill the cooling system with the manufacturer-specified antifreeze. You can find the correct specification in your Chilton DIY subscription or in your owner’s manual. Because specifications change occasionally, such as with new technology, it’s a good idea to check the technical service bulletins in your ChiltonDIY subscription too.
4. Fill the radiator to the top and install the radiator cap. Add sufficient coolant to the overflow tank to raise the level to the FULL mark. Check your Chilton DIY specifications or the owner’s manual for the coolant amount including the overflow tank.

Fill the radiator to the top and install the radiator cap. 2010 Chevrolet HHR shown. Image: General Motors.

5. Run the engine with both the radiator cap and reservoir/overflow tank cap in place. Turn on the heat with the blower on high. When the engine reaches normal operating temperature, shut the engine off and allow it to cool.
6. Top off the coolant level to the reserve/overflow tank as necessary to bring it to the FULL mark. Only add coolant when the engine is cold. The coolant level in a warm engine will be higher due to thermal expansion – that is, hot coolant expands and so the coolant level will appear to be higher.
7. Repeat the procedure and recheck the cooling system level.

How To Tell If Your Fuel Filter Is Clogged

The fuel filter may be part of the in-tank fuel pump.

Fuel: your automobile runs on it, obviously, but it’s not the only thing that gets into your car. Contaminants, dirt, and the odd thing make their way into your fuel, which goes all throughout the car.

If there’s no fuel getting to your engine, the vehicle won’t go. So how do you prevent this problem? Read on.

The fuel filter will collect all manner of contaminants. Remember how you get your gas from the gas station? Well that gas is also stored in giant tanks underground. These tanks corrode and get dirty‚ just like your gas tank can. Dirt, rust, and other contaminants go from the gas station;s tank to your vehicle’s, and it’s the fuel filter’s job to prevent that stuff from reaching your fuel injection system and engine.

You can tell that you may need a new fuel filter by looking for a few basic signs. When you hit the gas, your vehicle does one of the following:

• Shudders
• Sputters
• Hesitates
• Lacks Power
• Stalls

When your fuel filter gets clogged, not enough gas gets to your engine, which causes a loss of power, or could even result in a vehicle stall.

In addition, your vehicle may be underperforming because the fuel filter is getting dirty or clogged without showing obvious signs of distress. For older vehicles, manufacturers may recommend changing your fuel filter every 12,000 miles, but that number may varies widely. Depending on your environment and driving habits, you may have to change your filter sooner than the recommended interval. Some are designed for extended service and there is no maintenance interval for fuel filter replacement. Check your Chilton subscription for maintenance intervals as well as tests, troubleshooting, diagnostics, and technical service bulletins.

Some fuel filters are inline, rather than integrated with the fuel pump.

You can also remove your fuel filter to see how it looks. You’ll need a few tools like wrenches, sockets, screwdrivers, and pliers‚ although, again, your specific needs will vary based on your vehicle. Fuel filters are attached to the fuel line in various ways. Check your Chilton subscription for instructions for your vehicle.

Filters are fairly inexpensive, starting at around $15, and some cost much more than that. Consult your owner’s manual for information about the specific fuel filter you need.

When you remove the fuel filter, you’ll see what sort of fuel spills out. Gasoline should be relatively clear, with a bluish hue. If the fuel in the filter is brown or more opaque, that’s a sure sign you should change it.

If you’re handy, changing your fuel filter is an easy, inexpensive project to do at home. It usually requires few tools and only a little time. Consult your Chilton subscription for the fuel filter maintenance interval and fuel filter replacement procedure.