Turbos: The Basic Break Down

[Fox Slaughter]

Since we don't have a sticky on basic turbo information I figured I would write something on the basics of Turbos. This is a work in progress.

Turbocharger:

A turbocharger works by compressing air to pressures greater than Atmospheric pressures (14.7 psi at sea level). The turbocharger basically takes exhaust gases, uses them to turn the compressor wheel, in turn this compresses air, which is then feed into the intake and forced into the cylinders. This follows the basic premise that more air/fuel = more power.

Parts of a Turbo system:

• Turbocharger
• Wastegate (internal or external)
• Blow off Valve
• Intercooler
• Boost Controller (Optional)
• Turbo Timer (Optional)
• Boost Gauge

Wastegate:
A wastegate is a device that protects your turbo from "over boosting". This means if you want to run 20psi and your turbo is producing 20.1psi you are "over boosting". The wastegate if external is installed after the exhaust manifold and before the turbo, on the hot side of the system. The way a wastegate works is it either has a spring with a ball in it or a leak system. When the psi builds the pressure works against the spring or leak system. Once it hits the desired psi the spring opens diverting the exhaust gases around the turbo, thus it doesn't build anymore pressure. The wastegate can be either external or internal (built into the turbocharger). You can either divert the gas back into the exhaust system or bleed it to the atmosphere.

Blow Off Valve:
Yes that little device that makes the PSTTT sound. A blow off valve is a device that prevents turbo surge. The blow off valve is installed after the turbo before the throttle body, on the cold side. Turbo surge is the pressure going backwards and spinning the turbo backwards. Once you are building boost if you take your foot off the accelerator, the throttle plate closes and the boost backs up, the place its going to go is back into the turbo, WHICH IS BAD! So the blow off valve takes the boost and blows it off.

Intercooler:
An intercooler is basically a radiator. When you compress air it becomes hot. Hot air is less dense (less oxygen molecules). This means you lose power, less oxygen = less power. So you route your hot pressurized air through the intercooler. Air passes over the intercooler cooling down your boosted air, making it more dense. There are two types of intercoolers. Air to Air intercooler, or water to air intercooler. The most common type is air to air.

Boost Controller:
A boost controller is a device that allows you to control the amount of boost your turbo produces. There is two types of boost controllers. Manual and Electric. A manual boost controller is much cheaper but isn't accurate and not every good protection for boost spikes. An electric boost controller is much more accurate and change be quickly changes, i.e. between a low boost setting to a high boost setting. A boost controller connects to the wastegate, to control it. The manual boost controller works by if you tighten the knob, you press down the a spring and ball that will take more boost pressure to open it and activate the wastegate. An electric boost controller has a solenoid which switches between the wastegate and atmosphere. When the controller doesn't see the desired boost it doesn't send pressure to the wastegate. Once the desired pressure is seen, if it goes over, it will send the pressure to the wastegate activating it to bypass the exhaust gas slowing the turbo down.

Turbo Timer:
A turbo timer is a device that runs the car a predetermined time after you shut the key off. A turbo is generally oil cooled (tap a feed line into your oil pan). So after beating on the car the turbo obviously gets hot from working. If you shut off the car, the oil will sit in the turbo and burn up. So the turbo timer allows the car to run for a time say a minute, so the oil circulates through the turbo and engine cooling the turbo down so you don't burn it up.

Boost Gauge:
Boost gauge is a gauge that measures boost. There is two types electric and analog. The analog uses a hose that runs into the back off the gauge and actuates the gauge by physically acting on it. An electric gauge uses a sending unit that tells the gauge what the pressure is. A boost gauge is a must so you know how much boost is built up in the system.

[Fox Slaughter]

Wastegate Breakdown:

As explained the wastegate is a valve that controls the exhaust flow for the turbocharger. Exhaust exits the engine through the exhaust manifold (commonly called turbo manifold when running a turbo) which then flows to the turbine side of the turbocharger. On this side of the turbo system between the head/s of the engine and turbo you mount the wastegate if external, if internal its built into the turbo charger. As the turbine spins the compressor side of the turbocharger pressurizes the air. Once desired boost is achieved you must bleed off the exhaust gases to the turbine won't spin fast anymore building more boost. That is the job of the wastegate, to divert the exhaust gases away from the turbocharger either to the atmosphere or back into the exhaust system.

Operation:
There is a plunger that sits where the wastegate is mounted to the exhaust if external. Above that is a diaphragm, above that is a spring. On the outside you have a booster controller nipple usually on the top and a boost reference nipple usually on the side, also a dump tube. The boost pressure flows in where the boost reference nipple is. As the pressure builds up to the spring rating it starts to force the spring to compress thus opening the plunger, diverting exhaust gas. The problem is the springs will start to open before the desired pressure is achieved. So you bleed off pressure not always giving you the desired boost nor spooling as fast. See boost controllers.

Internal vs External:
There are two types of wastegates, internal and external. Internal wastegates are build into the turbocharger. External wastegates are placed on the exhaust piping somewhere. Internal wastegates do what they need to do and thats it. You can't adjust them (can get more boost with a boost controller). External wastegate can change out the springs to increase or decrease the boost. They also can be placed anywhere you want on the exhaust side.

[Fox Slaughter]

Boost Controller Breakdown:
A boost controller is a valve that allows you to build up more psi then the wastegate would normally let you or to more accurately control your boost level. The boost controller allows boost to flow into the type of the wastegate adding pressure to help the spring stay closed, thus allowing you to build more pressure. There are two types of boost controllers, manual and electric.

Manual Vs Electric:
Manual is a valve that is manually manipulated to control the boost level. They are not as accurate as an electric but are rather cheap. They can be adjusted from inside the cabin. The manual boost controller uses a one way ball check valve. As you tighten the know you are putting more pressure on the spring meaning more boost will be needed to open it. These you put in line for the boost reference nipple. This "replaces" the spring on the wastegate. Until the desired boost is reached the wastegate will see no pressure allowing it to stay closed and build boost. These once again will tend to open before the desired boost is achieved. They also do not control boost spiking.

Electronic boost controller uses a head unit to control an solenoid. The controller will work like a manual boost controller on a single nipple wastegate such as an internal wastegate. Once the desired boost is reached it will open the solenoid to the wastegate instantly opening it. The best part about these is they won't open before the desired boost is achieved. They operated between 60-250hz roughly meaning they open and close crazy fast. Now with a dual port wastegate, the boost will be added to the boost reference point and the boost controller port which will equalize the pressure so the wastegate won't open but once the boost controller sees the desired amount of boost it will open the solenoid so the pressure to the top will cease and the wastegate will be instantly opened. These systems are better because you can change boost on the fly just by pushing a button, they are more accurate, they won't bleed off pressure until the desired boost is achieved, but they are more expensive.

Blow Off Valve Breakdown:
A blow off valve is a valve that blows off the pressure so your turbocharger doesn't spin backwards. When you have to boost and you let off the gas pedal say so to shift, the throttle plate closes and is no longer sucking in that boost. The boost has to go somewhere and if you don't blow it off, it goes back into the compressor. Thats a bad thing. Thats the job of the blow off valve to vent this pressure to prevent your turbo going boom. Once again there is two types of blow off valve. Vented and recirculating.

Vented vs Recirculating:
There is two types of blow off valves. Vented (most common) and recirculating. The way they both work is exactly the same. You connect the blow off valve to the piping between the intercooler and the throttle body. There is a boost reference nipple usually on the top of the valve. This is then connected to a vacuum port on the intake manifold. As you are boosting the pressure is positive inside the manifold. While you have pressure in the manifold the boost reference nipple will have the same pressure in the manifold. This will equalize the pressure in the blow off valve and the intake piping. Thus the blow off valve will be closed. Once the throttle plate closes the pressure in the intake manifold will drop. Cutting the pressure to the top of the blow off valve and then being overwhelmed by the pressure in the intake piping forcing the valve open till the pressure blows off then it will close again.

The vented valve is the most common blow off valve. This is a valve that produces that sexy PST! sound when ever it blows off. Some states loud ones are illegal. People say the problem with them is all that pressure you built up is wasted by just blowing it off to the atmosphere. If you ask me its worth it just for the sexy sound they make.

Recirculating valve has a line connected to is so when the valve blows off the pressure it is fed back into the system. Some say for MAF systems these are a must because the MAF has already accounted for the extra air in the system. Now you just blew that air off to the atmosphere, the MAF still thinks its in the intake system so now you run rich. To me I don't believe this because the MAF is located in front of the throttle body. So once you close that plate air is no longer moving through the MAF. So if you ask me these people are smoking some crack.

Intercooler Break down:
An intercooler is the same thing as a radiator, except for your intake charge. Physics dictate that when you compress something it gets hot. Air being compressed by a turbocharger is no different. When you compress the air in a turbocharger it will become hotter than the ambient air that was drawn into the charger. We all know that hot air makes less power, its less dense and contains less oxygen molecules. So how do we cool down this pressurized air? By using an intercooler. There are two types of intercoolers. They are Air to Air and Water to Air intercoolers.

Air to Air vs Water to Air:
The most common and easiest system to use is an Air to Air intercooler. As the hot compressed air flows into the intercooler through the intake pipe, it then flows through the passages within the intercooler. Just like a radiator, ambient air then moves across the intercooler cooling the fins that absorb the head from compressed air inside. Temperatures always move from hot to cold. So the colder surface absorbs the heat from the hotter surface. The reason these are the most common systems are because there is no extra parts required to set it up. They do not get heat soaked as there is always fresh air flowing across them. You don't have to worry about leaks because there is no liquid flowing through them. The only draw back is there has to be enough air always flowing across the intercooler. This is why generally they are front mounted.

Water to Air or Liquid cooled uses the same principal as the air to air but instead of using air it uses a liquid such as water. The compressed air enters through the intake pipe then there is a grid of passages filled with a liquid, the air passes over these once again transferring its heat to the liquid. The advantage to these systems are they are extremely efficient, therefore you can run a smaller unit. Unlike a air to air system they can drop temperatures past the ambient air temperature netting you more power. Also can be mounted in any location or orientation. The problem is they become heat soaked because the system can only contain to so much liquid once that liquid gets hot its not doing its job anymore. There has to be pipe plumbed for this system which means there could be leaks. Addition parts are required, plumbing, water pump to circulate the liquid, and a reservoir. These systems are what are used on dragsters because they just pack them full of ice and by time the 4 second run is over all the ice is melted, the runs are to short to worry about heat soak.

The best bet for your street/strip machine is just to run a air to air intercooler. How far an intercooler drops the temperatures depends on how big the intercooler is, how efficient it is, how many cores there are contained inside the intercooler and how much air is allowed to flow over the system.

[meissen]

thanks for posting

[Gregs_gsxr]

once I have to rebuild my 4200 vortec I-6 Ill be doing a turbo upgrade to it. Currently mileage is under 194k ish and I can feel a lil less pep on the lower end, still doesnt burn or leak oil.


Thanks TJ for all the great info !

[Fox Slaughter]

thanks for posting

Yupp no problem. As I said this is a work in progress. I'll be adding more every once in a while.

[DETROITMUSCLE]

Good info I'm sure everyone appreciates it.

[SS4Matt]

once I have to rebuild my 4200 vortec I-6 Ill be doing a turbo upgrade to it. Currently mileage is under 194k ish and I can feel a lil less pep on the lower end, still doesnt burn or leak oil.


Thanks TJ for all the great info !

Denny is putting a turbo vortex I6 in his 3rd gen last I heard. Very similar motor architect to a supra motor!

[1BADAIR]

how would an s475 do on a 4.8 ?

[DETROITMUSCLE]

how would an s475 do on a 4.8 ?

it would work great, if its laggy at all just add a little timing downstairs to help spool it up

[1BADAIR]

thats the plan for the nova. 4.8 4l60/80 s475.

[Gregs_gsxr]

nice, they actually make crazy hps

[DETROITMUSCLE]

thats the plan for the nova. 4.8 4l60/80 s475.

Nova? how many cars you got over there? That turbo should work great on that size motor, and they are very affordable. The only downside is the size/weight of it and I believe those units have a 5" downpipe but you can always run a reducer right off the turbine then again you probably have lots of room to work with under that hood.

[1BADAIR]

lol. junkyard laughed when i asked if they had a 4.8. said who would want one of those.
probably will even have a/c

[DETROITMUSCLE]

lol. junkyard laughed when i asked if they had a 4.8. said who would want one of those.
probably will even have a/c

CJmatt is selling a 5.3 with 3K miles on it for $400 thats real tempting to me, may not be enough motor for my turbo though.