After the fitment of a 3 inch free flowing exhaust onto my vr4 engine the 16g turbo began showing symptoms of boost creep. After reading some threads on DSMtuners.com and watching a few videos on youtube. I decided to type up a little report on how I cured my boost creep. My aim is to help sufferers on team4g solve this problem. I found out the hard way and know it can be quite frustrating.
This is the thread which helped me out http://www.dsmtuners.com/forums/art...oler/186525-how-cure-boost-creep-porting.html.
Before I begin hear is a little info for the newbie's. IF YOU WANT TO ONLY READ MY METHOD USED PLEASE SKIP TO SECOND POST
-Turbochargers and How They Operate:
Turbochargers are simply a high volume air pump which can be incorporated with an engine. Their main purpose is to increase fuel economy and power output.
Now, let's take a look at how a turbo works. The exhaust gas coming out of the engine exits through the exhaust manifold and into the turbine housing (rear of turbo) allowing it to spin the turbine wheel. The turbine wheel is connected via a shaft to the compressor wheel (front of turbo) and in effect it spins at the same rate. This allows the compressor wheel to produce boost (Boost is the amount of pressure above atmospheric which is being built up in the piping connected from the turbo to the intake). The more exhaust that comes through the manifold, the faster the turbine wheel will spin, therefore the more boost the turbo will create. A wastegate is a component used with a turbo to control the rate at which the turbine may spin in effect controlling the level of boost.
-Wastegate Actuators:
Wastegate actuators are an important part of a turbocharger systems which are often overlooked. They have a big influence on the amount of power an engine can make. The purpose of the wastegate is to regulate the amount of exhaust getting from the turbine housing to the turbine wheel threw a bypass, this controls the amount of boost. If we did not have a wastegate on a turbocharger, the turbine wheel would keep spinning the compressor wheel faster and faster as the engine RPM increased until either the turbo was over speed or the engine was over boosted to the point where damage would most likely occur.
This is a Turbo boost versus Engine RPM graph
Internal Actuators:
Actuators come in two different forms, one of them being internal and the other external. An internal actuator is what is found on a factory turbocharger application. With this design, the actuator is integrated to the turbo unit itself. There is an opening at the rear of the turbine housing (wastegate) just before the turbine wheel, which is covered by a flap. This flap is connected via a rod to the actuator. When a specified boost has reached the actuator, the diaphragm within the actuator pushes down onto the rod which opens the flap up and reveals the wastegate in effect controlling the boost. On factory boost and power levels, internal wastegates work fine as they are usually matched to the size of the turbocharger. But once the power is increased with modifications such as a free flowing exhaust, internal wastegates begin to show their flaws. Internal wastegates are generally small in terms of diameter which makes them slow to respond with pressure change causing problems such as boost spike and boost oscillation.
This is an example of boost spike. The red line identifies 10PSI, (pounds per square inch of pressure) this is set boost and should not be exceeded.
But as can be seen by the blue line, the pressure spikes above this when the turbo first comes on to boost, but then holds steady for the rest of the engine's rev (RPM) range.
This is not desired and can become an even bigger problem (boost oscillation) when combined with boost controllers. Here is an example.
As can be seen, there are fluctuations in boost levels as the actuator struggles to reach the desired 10PSI.
The wastegate being too small can also cause over boosting at high RPM, this occurs when the wastegate literally cannot flow out enough exhaust to slow down the turbine wheel. This is known as boost creep.
Turbochargers can also suffer from wastegate creep, this is when the exhaust gas forces the flap open before the desired boost pressure and makes the turbo lag.
-External wastegates:
The benefits of the external wastegate actuator is that they are much larger in design. This means they also have a larger diaphragm which makes them much faster to respond to pressure change.
Other benefits are that they are separate to the turbocharger and are plumbed into the exhaust manifold. This design results in the exhaust gas exiting from the manifold rather than from the turbine housing. Since the exhaust exits from the manifold there are fewer limitations to how large a wastegate hole can be in terms of diameter. As a result, you will see a flatter and smoother curve on the �boost versus RPM graph�.
This gas exiting from the wastegate can be plumbed back into the exhaust downstream as is with the internal design or it can be vented out to the atmosphere. However, venting to the atmosphere is highly illegal due to exhaust emissions.
Due to the mentioned features, external wastegate actuators do not suffer from the problems which are apparent in the internal wastegate systems.
This is the thread which helped me out http://www.dsmtuners.com/forums/art...oler/186525-how-cure-boost-creep-porting.html.
Before I begin hear is a little info for the newbie's. IF YOU WANT TO ONLY READ MY METHOD USED PLEASE SKIP TO SECOND POST
-Turbochargers and How They Operate:
Turbochargers are simply a high volume air pump which can be incorporated with an engine. Their main purpose is to increase fuel economy and power output.
Now, let's take a look at how a turbo works. The exhaust gas coming out of the engine exits through the exhaust manifold and into the turbine housing (rear of turbo) allowing it to spin the turbine wheel. The turbine wheel is connected via a shaft to the compressor wheel (front of turbo) and in effect it spins at the same rate. This allows the compressor wheel to produce boost (Boost is the amount of pressure above atmospheric which is being built up in the piping connected from the turbo to the intake). The more exhaust that comes through the manifold, the faster the turbine wheel will spin, therefore the more boost the turbo will create. A wastegate is a component used with a turbo to control the rate at which the turbine may spin in effect controlling the level of boost.
-Wastegate Actuators:
Wastegate actuators are an important part of a turbocharger systems which are often overlooked. They have a big influence on the amount of power an engine can make. The purpose of the wastegate is to regulate the amount of exhaust getting from the turbine housing to the turbine wheel threw a bypass, this controls the amount of boost. If we did not have a wastegate on a turbocharger, the turbine wheel would keep spinning the compressor wheel faster and faster as the engine RPM increased until either the turbo was over speed or the engine was over boosted to the point where damage would most likely occur.
This is a Turbo boost versus Engine RPM graph
Internal Actuators:
Actuators come in two different forms, one of them being internal and the other external. An internal actuator is what is found on a factory turbocharger application. With this design, the actuator is integrated to the turbo unit itself. There is an opening at the rear of the turbine housing (wastegate) just before the turbine wheel, which is covered by a flap. This flap is connected via a rod to the actuator. When a specified boost has reached the actuator, the diaphragm within the actuator pushes down onto the rod which opens the flap up and reveals the wastegate in effect controlling the boost. On factory boost and power levels, internal wastegates work fine as they are usually matched to the size of the turbocharger. But once the power is increased with modifications such as a free flowing exhaust, internal wastegates begin to show their flaws. Internal wastegates are generally small in terms of diameter which makes them slow to respond with pressure change causing problems such as boost spike and boost oscillation.
This is an example of boost spike. The red line identifies 10PSI, (pounds per square inch of pressure) this is set boost and should not be exceeded.
But as can be seen by the blue line, the pressure spikes above this when the turbo first comes on to boost, but then holds steady for the rest of the engine's rev (RPM) range.
This is not desired and can become an even bigger problem (boost oscillation) when combined with boost controllers. Here is an example.
As can be seen, there are fluctuations in boost levels as the actuator struggles to reach the desired 10PSI.
The wastegate being too small can also cause over boosting at high RPM, this occurs when the wastegate literally cannot flow out enough exhaust to slow down the turbine wheel. This is known as boost creep.
Turbochargers can also suffer from wastegate creep, this is when the exhaust gas forces the flap open before the desired boost pressure and makes the turbo lag.
-External wastegates:
The benefits of the external wastegate actuator is that they are much larger in design. This means they also have a larger diaphragm which makes them much faster to respond to pressure change.
Other benefits are that they are separate to the turbocharger and are plumbed into the exhaust manifold. This design results in the exhaust gas exiting from the manifold rather than from the turbine housing. Since the exhaust exits from the manifold there are fewer limitations to how large a wastegate hole can be in terms of diameter. As a result, you will see a flatter and smoother curve on the �boost versus RPM graph�.
This gas exiting from the wastegate can be plumbed back into the exhaust downstream as is with the internal design or it can be vented out to the atmosphere. However, venting to the atmosphere is highly illegal due to exhaust emissions.
Due to the mentioned features, external wastegate actuators do not suffer from the problems which are apparent in the internal wastegate systems.
