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K04 Internal Parts and Operation

23K views 55 replies 15 participants last post by  Robotech 
#1 · (Edited by Moderator)
This discussion is nothing new, but something I think is missing from this forum. Many who come on here understand what a turbo is and what a turbo does but not everyone may know how it works, the different parts, and what these parts look like. While turbo models vary and where their parts are located are different, they all have these same parts to do the same jobs. So realize that the way these parts look on different setups may not be the same, but they will operate the same way and have the same job.

On that note however, keep in mind when we discuss valves in the turbo, there are two different types, recirculating and atmospheric. Recirculating valves will take whatever airflow they are controlling and recirculate it back into the system. Atmospheric will take the airflow and vent it out to the atmosphere. As a matter of fact, a Blow Off Valve and a Bypass Valve are the same thing with the only difference being a Blow Off Valve vents to atmosphere while a Bypass Valve recirculates. In the K04, all the valves are recirculating systems and all OEM turbos (at least all the ones I've seen in cars since 1992) are this way for smog reasons.

Let's start with a picture of the K04 assembled and the different components of it.

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Thanks to Jgasser, I was able to document a disassembled K04 and take these pictures. This turbo wore out and needs to be rebuilt but if you just looked at these pictures you may not realize it. This first picture shows the center section of the turbo. This is the heart of the turbo. This includes the compressor fan, turbine fan, turbo shaft, and the oil and water passages used to lubricate and cool the turbo shaft and it's bearings. Hence on this part you will find all the oil and water line ports.

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In this picture the turbine fan is on the right and the compressor fan on the left. The turbo shaft connects these two through the center of this part.

The turbine fan's blades are curved to meet the incoming flow of exhaust and use it's energy to spin up the fan. Here is a picture of the turbine fan and the housing that it goes into on the turbo body. (note the housing is in the distance, hence why it looks like the fan is too big to fit in the housing)

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This spins the turbo shaft and, with the compressor fan attached to the same shaft, turns the compressor fan. This fan also has curved blades to catch the incoming air, compress it, and force it out the turbo's outlet. Below is a picture of the compressor fan and housing.

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The concept behind these components is pretty easy to understand and is the part most people know about when it comes to turbos. The more exhaust gases move into the turbine housing, the faster the fan spins the shaft. The faster the shaft spins, the faster the compressor fan spins. The faster the compressor fan spins, the more boost is produced in the compressor housing and delivered to the engine.

What is less understood is the amount of boost a turbo can make, the amount it should make, and controlling the amount you want it to make. To understand how this works and why it needs to work you have to understand a couple of general ideas about compressing air.

When you compress air, you also are heating the air. As air compresses it gets hotter and while the pressure of the air will go up, it's density will go down. This presents means the two are a bit counter productive. We're compressing air to get more air in the engine per revolution but hot air is less dense and thus the hotter air charge has less air in it at a given pressure than a colder air charge at the same pressure. This is what we have intercoolers for. Because of this fact, a turbo has a certain range of boost it can generate effectively without the heat that boost range generates overcoming the amount of air the boost level it is generating delivers.

For instance, say a turbo flows 30,000 cfm of air at 23 psi of boost, the upper limit of it's boost map. If you push that turbo to 24 psi, the cfm generated drops to 29,000. 25 psi and it drops to 27,000...and so on. That's called running a turbo off it's map.

The K04 turbo can generate more than 25 psi of boost but on the LNF, running more boost than that is running it off it's map. If left uncontrolled, the turbo would regularly exceed 24 psi of boost generating unnecessary heat and cause detonation in the engine. To prevent this from happening, turbos are equipped with a wastegate. Many times people confuse the wastegate with the blow-off or bypass valve...the valve that makes that signature PSSST sound on a turbo car when you let off the gas after accelerating really hard. The wastegate controls the amount of exhaust that is allowed to move through the turbine and drive the turbo.

When the boost level of the turbo reaches where the system designer wants it, the wastegate begins to open (which is done mechanically with the wastegate actuator) allowing some of the exhaust gases to bypass the turbine and go directly to the exhaust outlet. This limits how much energy is driving the turbine to a level where the turbo will only produce a certain level of boost. Here is the integrated recirculating wastegate valve in the K04 in the closed position. The studs you see in this picture are the studs that connect the catalytic converter to the turbo housing.

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#2 · (Edited by Moderator)
Continued ....

And here it is in the open position. As you can see, when the wastegate opens the output is directly into the exhaust stream heading into the cat.

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Below is a picture of the turbine housing to give you a better idea of how the wastegate is oriented. To the right is the part of the housing that connects to the exhaust manifold. The hole next to the wastegate to the right of the picture is where the exhaust gas exits the turbine after driving the turbine fan. Exhaust gases flow from the manifold, through the housing, to the fan, and then out that hole. The wastegate is open to this exhaust flow just before the turbine housing so that when it opens, part of this flow goes right out the exhaust bypassing the turbine fan.

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In an atmospheric wastegate system the air diverted from the turbine just goes to atmosphere. These systems can be very loud and obviously this exhaust gas will bypass any catalytic converter. Thus for noise and smog reasons, manufacturers use a recirculating system. With the LNF, the wastegate is controlled by the ECM. The ECM dictates when the wastegate opens via the Wastegate Control Solenoid.

The bypass (or blow off) valve system is on the compressor side of the turbo. When you are accelerating hard, the throttle plate is mostly open and allowing large amounts of air to pass into the intake manifold. The intake track is pressurized by the boosted air charge from the turbo, through the charge pipes, through the intercooler, the throttle body, the intake manifold, into the heads and into the engine.

When the driver lets off the gas the throttle plate goes mostly closed causing the intake manifold, heads, and engine see vacuum again rather than boost but the rest of the intake system from the throttle body back to the turbo is still pressurized and the turbo is still trying to push boost. If this pressure isn't relieved, it can flow back into the turbo (which will stop producing boost since the engine is now seeing vacuum and thus the pressure in the compressor side of the turbo is lower than that in the charge pipes and intercooler) causing what is called compressor stall. This condition can cause damage to the turbo.

To prevent this from happening, the bypass valve vents this excess pressure and recirculates it back into the intake track (or a blow off valve vents it to atmosphere). Below is a picture of the port in the compressor housing that will see the pressure left in the intake track when the throttle plate is closed.

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The two holes you see in that fitting we're looking through is where the output elbow bolts to the turbo housing on the K04. This is the elbow the first charge pipe going to the intercooler connects too. In the following picture, we see another port that is entering the area where fresh air enters the turbo to be compressed (I think it is the square port...the round port feeds a tube that gets connected to the wastegate control solenoid on the LNF):

Automotive tire Tin can Rim Tin Wheel


Between these two ports is the bypass valve itself. You can see it here in the photo below. The fitting we were looking through in the first picture can be seen just above this valve. The red cap below the beige valve is the intake to the turbo and it is in this intake track where we saw the other port.

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The nipple on the valve you see here is connected to the intake manifold. When the intake manifold is under pressure, this valve stays closed and the two ports we've seen are not connected. When the manifold sees vacuum, the boost pressure in the intake port pushes the valve open and allows the pressure to be vented through the port going into the intake of the turbo thus preventing compressor stall.

This is how our turbos work and the parts we talk about when we deal with boost and controlling boost. Hope this helps out those that may be unfamiliar with how turbos work and if any of our experienced members find problems in my post, please feel free to point them out so I can make corrections to this.
 
#3 ·
Troy, nicely written. Thank you for doing this.
A couple of questions:

1). Often when one describes the size of a turbo, it is referenced by millimetres. How big is the K04?

2). So the system from the factory vents back internally. I see some on here venting to atmosphere via blow off valves. How does this affect the operation/ecm/life/dependability of the car. Is it an easy conversion. Does it throw off the computer?

Thanks.
 
#5 · (Edited)
Thanks guys.

Troy, nicely written. Thank you for doing this.
A couple of questions:

1). Often when one describes the size of a turbo, it is referenced by millimetres. How big is the K04?
I know someone mentioned once the size of the K04...but I cannot remember for the life of me what that size is...that said...

When they talk in mms, it usually is talking about the diameter of the compressor wheel though it can be in reference to the turbine wheel as well. I'm still relatively new to the world of turbos (writing stuff like this helps me organize my thoughts and get the information down in my head better) but from what I can understand so far, the bigger the wheel the greater the volume of air you can compress and thus your airflow rises even when boost pressure stays the same.

There are also TWO wheels on one fan...an Inducer and an Exducer. So usually mms refers to one of these wheels.

Think of it this way (and mind you, these numbers I'm just pulling out of thin air...). Lets say you have a 45mm compressor wheel and it moves 30,000 cfm of air at 25psi. Now you upgrade to a 50mm compressor wheel and now you move 35,000 cfm of air at 25 psi. While your boost pressure hasn't changed, you're moving 5,000 cfm more of air and thus can inject a bit more fuel to make a bit more power off that larger compressor wheel. This is overly simplified but the general premise. Keep in mind though that moving that extra air usually comes at a price of a slightly longer "lag" time when spooling up. There are doctorates written on lag, compressor wheel size, turbine wheel size, housing design, and how all these things affect boost levels and spool time.

2). So the system from the factory vents back internally. I see some on here venting to atmosphere via blow off valves. How does this affect the operation/ecm/life/dependability of the car. Is it an easy conversion. Does it throw off the computer?

Thanks.
Good question and it all depends on where the blow off valve is in relation to the Mass Air Flow (MAF) sensor. In the stock LNF, the MAF is in the air intake before the turbo. Thus by using a recirculating system, the air entering the engine has already been measured and feeding it back into the system before the turbo (but after the MAF) keeps the measurements accurate.

In my setup, the MAF is in the cold side charge pipe between the intercooler and throttle body. If I changed my bypass valve to a blow off valve it would have no affect on the ECM settings since the measurement of air entering the engine is being done well after the turbo and where the bypass or blow off valve is doing it's thing. So long as I keep the blow off valve before the MAF, I'm golden.

Now this is in a MAF based Electronic Fuel Injection (EFI) system. Some cars don't use a MAF like my girlfriend's Veloster Turbo. It is on a Manifold Air Pressure (MAP) system. In her car, the stock bypass valve is on the Intercooler just before the charge pipe that connects the IC to the throttle body. The stock bypass valve has a hose connecting it to the intake tube before the turbo. Veloster owners can make their bypass valve a blow off valve just by removing this connection tube and capping off the attachment point on the intake tube. Since their ECM uses a MAP based fueling system, this modification doesn't affect the ECM programming at all.

In either case, if properly set up converting a Bypass Valve system to a Blow Off Valve system isn't going to hurt anything or affect engine longevity since all we're doing is changing where this excess air goes. Even if we have a MAF based system and don't change the ECM programming the worst that will happen is, for a split second, the Air/Fuel mixture is going to be rich because less air is coming into the engine than the ECM believes it should. I don't think the amount or the longevity of the incident is enough to cause any reliability issues.

Good question. In any case, small as the engine size doesn't warrant a larger turbo.

The big wheel Werks mod only takes it up to around 46 mm compressor.

Robo - excellent write up - you should pin it somewhere as a reference!
It is pinned in Sky Technical Discussion...or it should be. :D

The size of the engine doesn't necessarily dictate the size of the turbo. Remember, the turbo's job is to cram more air into the engine than the engine could normally draw in NA in an effort to add more fuel to get more power. The limiting factor is how much extra air/fuel can the engine take before one of two things happen:


  • You push too much air into the cylinder and the head/head bolts can't keep the head on the engine to maintain the seal between the head and the block causing you to pop something.

  • You start to see detonation or your other bottom end parts can't handle the extra combustion pressure and you pop something.

For the record, popping something is bad.

But you can build the engine to take the extra air.

Setting a lift or duration of your intake and exhaust valve timing and/or increasing valve size can allow the engine to draw in a bigger gulp of air without raising boost pressure and with it, air charge temperature.

Bigger intercoolers can reduce the intake charge temp to near ambient levels to reduce the chances of knock.

Higher octane levels can let you run more boost. This can be achieved by fuel octane level or meth injection.

Harder head studs and forged internals can all strengthen the block to allow it to withstand higher pressures.

All these modifications would allow you to run a larger turbo on the 2.0 LNF.
 
#4 ·
Good question. In any case, small as the engine size doesn't warrant a larger turbo.

The big wheel Werks mod only takes it up to around 46 mm compressor.

Robo - excellent write up - you should pin it somewhere as a reference!
 
#10 · (Edited)
Now that I have the time, I want to expand on these two images a bit for those unfamiliar with why our turbo is called a Twin-Scroll and why that is important.

First off, there is the issue of exhaust gas pulses. These pulses are what drive the turbo. The problem in a normal turbo is these gases are funneled together before entering the turbo. What can happen is the exhaust pulse from one cylinder may strike the exhaust pulse from another cylinder and this collision takes energy away from the exhaust stream. This can slow down turbo spool up and decrease efficiency. By separating the cylinders into two separate paths, these exhaust pulse collisions can be avoided and the maximum energy from the exhaust flow can be utilized to drive the turbo.

The second part to this is how the two exhaust paths in a twin-scroll system work to achieve less lag without compromising top end power output as well. The following image I found does a good job of explaining this.

 
#11 · (Edited)


I also wanted to make another comment on this picture (and post it like this so it's easier to see in the thread). This picture, while showing exactly how the intercooling system on the LNF works, also shows the reference point for the Boost Bypass Valve we talked about in my first post. If you follow the blue air path out of the intercooler it goes into the throttle body then into the intake manifold before heading into the engine. If you look at the cut-away section just before the blue air charge enters the engine, right above that section you'll see a sideways "L" shaped part that is facing towards the intercooler.

This is the first part of the reference line that runs back across the front of the engine to the nipple on the K04's stock bypass valve we looked at earlier (and which you can see here just above where air enters the turbo). This line is what allows the bypass valve to "see" what the pressure is in the intake manifold and causes it to open when the manifold is seeing a lower pressure than the charge pipe/intercooler intake track.
 
#14 ·
Sorry, Robo. I was quite misleading there, by accident. BW puts the literature for many turbos all in one .pdf and I don't know how to isolate the 2 or 3 pages for the K04 and copy and paste them here. My bad

Yogi
 
#15 · (Edited)
Oh...if you post the link I can pull the couple pages out we need after I get home tonight and post the new PDFs/JPEGs.

You can also link to the pdf and use the #page=X to link to a specific page like so:

http://www.example.com/myfile.pdf#page=4
(This link is just as an example...it does not link to anything. Clicking on it will give you an error.)
 
#16 ·
Oh...if you post the link I can pull the couple pages out we need after I get home tonight and post the new PDFs/JPEGs.

You can also link to the pdf and use the #page=X to link to a specific page like so:

http://www.example.com/myfile.pdf#page=4
This is a great thread. I was not aware that we had a dual scroll turbo. Now I think I understand it much better. But the link is not working for me, Error "500 internal server error"
 
#21 · (Edited)
It uses a K04 but that info sheet lists three different "Versions" of it and they all are a little different than the one on the LNF.

Also, this is the turbo map being thrown around the Cobalt SS forum (Which is also an LNF powered car in 2009) and it looks very different from the turbo maps in that link.



Which is why I ask the question. I don't know enough about turbo maps to make the call and hope someone else who knows more may offer some insight. Like I said in my first post, I'm still pretty new to this whole turbo thing too. I have some stuff down, but some stuff I'm still learning. Turbo maps are the latter.

What I DO know about turbo maps is you want to keep your boost output within the Turbo's efficiency range. That range is represented on the map by the complete "circles" in the mid area of the map.

I look at that map and think of it like a topography map where each line represents an elevation on a topographical map (and may be why they call it a map...who knows). You see how some lines are not complete and tend to run off the scale while there are two in the center which you can see are complete and make a continuous circle. These "elevations" are your Turbo's operating range.

I also know there is what is called a surge line and you want to stay on the "circle side" of that surge line. (If I remember correctly, the surge line is the very first line on the left of the plot area of the turbo's operating range and is darker in color than the rest of the lines...but it was a while ago I read this stuff so I'm not certain of this.)

Now there is a formula for figuring out...based on engine displacement and boost levels with possibly a few other variables...where in that map your current boost level falls. As a matter of fact, I'm going to need to figure out where my boost level falls within this map based on my engine displacement.

That said though, which map is right and are the maps different because the Audi uses smaller displacement engines (1.6 and 1.8L) than the LNF (2.0) or is there another reason? I thought a turbo map was for that turbo and the engine displacement only came into play when figuring out where on the map your current setup falls.

But like I said, I'm still new to this and am trying to figure this out as we go along in this thread too.
 
#23 ·
#25 · (Edited)
Playing catch up on our forum after a couple of weeks (where does the time go). What a great writeup Robo. I am glad that the demise of my turbo has helped to augment such a great article, that and I know you will breathe life into my old K04 some day. I wish I had cleaned up some of the dirt on the old parts now before you documented them so well! My new K04 is working great :)

This week my turn signal has stopped cancelling after completing a maneuver, and I have to manually terminate it. Once I get that annoying problem solved I might be giving you some more parts for another writeup!

(UPDATE: Already found articles via our forum on replacing or repairing the turn signal switch. Looks pretty easy :) )

Cheers
 
#27 ·
New turn signal installed this morning Robo, Found several good articles on our site and ended up using one one written by Marvic which helped me out. Tedious steps are pulling apart the dash trim but got it installed in a couple of hours, now as good as new :)

See ya soon
 
#29 · (Edited)
Other than the top cover over the steering wheel, everything was below the wheel. Top cover is disconnected but never removed.

  • Removed 3 screws in the knee bolster under the steering wheel
  • Separated top and bottom trim covers around steering wheel (clipped together)
  • Lowered steering height adjustment lever
  • Dropped three "big" plastic pins down by the OBDII (mounted either side) port
  • Took two more screws out left and right of OBDII (but not the ones holding the OBDII in place), took the driver side plastic cover off, which is revealed when the door is open
  • Removed two more screws inside that cover so I could pull the ventilation portion of the dash down
  • Loosened, but did not remove, the two bolts holding the steering shaft to the upper dash (this gives a couple more millimeters and was needed!)
  • Released clips (top and bottom) holding turn signal unit in place
  • Pulled turn signal/lights control out (its still tight but can be done without damage), disconnecting the two electrical connectors in the back

This is Marvic's original post that I followed -->click here

TC's article on removing the dash to get to the stereo covers (excellently!) most of what I had stripped out to get to the turn signal -->click here

I can come down and assist when you wanna do this, making myself useful for a change in your garage :)
 
#32 ·
This is exactly the reason you bump an old thread.
@Administrator, the images are on the server if you copy and past the image links from the first post in this thread in a browser, you'll find them. I don't know why they're not displaying. I just copied and pasted the links to the images again and they're still coming up blank.
 
#36 · (Edited)
Whoop, got it to generate the error and then explain it on the same page, captured it and saved it.

It's a certificate issue. Probably why the images are not displaying in the 1st message of this thread.


[url]http://www.b17queenofthesky.com[/url] works
[url]https://www.b17queenofthesky.com[/url] generates the error.


Sometimes I amaze myself.

:thumbs:

.
 

Attachments

#37 ·
Whoop, got it to generate the error and then explain it on the same page, captured it and saved it.

It's a certificate issue. Probably why the images are not displaying in the 1st message of this thread.

B-17 Queen of the Sky Homepage works
https://www.b17queenofthesky.com generates the error.

Sometimes I amaze myself.

:thumbs:

.
Interesting. @skl8260, is this the same kind of message you get?

#DaveOC , that would make sense since I don't have a SSL cert for that server...never needed one since it was all public content. The URL to the images is an open (HTTP) connection so I don't know why the forum software would be trying to connect to them with an encrypted secure connection. That's odd. @Administrator, any input on this?

EDIT...god I really need to get in there and do some updating...LOL
 
#40 ·
asking for k04 turbo and stock one

thanks for your writting

but i couldn't understand whole thing you wrote cuz my English isn't that good.

so.. i have a question.

i need to change my turbo since the previous owner installed aftermarket turbo and it's broken.

k04 turbo on ebay is okay to install? cuz it's way cheaper than stock oem turbo..

i was going to buy k04 turbo but i saw the part number is different.

please answer if you guys know about this.. thanks!
 
#41 ·
This discussion is nothing new, but something I think is missing from this forum. Many who come on here understand what a turbo is and what a turbo does but not everyone may know how it works, the different parts, and what these parts look like. While turbo models vary and where their parts are located are different, they all have these same parts to do the same jobs. <snip>
Hi RT,
Is it possible to have the photos reposted in this message? I love the text but, as usual, photos make a huge difference.

Cheers!
 
#43 ·
I have looked at this and the problem is either the forum not playing well with the database, or there being too many pictures in one post. I am still looking into it.
 
#45 · (Edited)
Great thread, this was very helpful. Does anyone happen to know if the boost bypass valve is sold separately? Being brittle 15-year-old plastic, the hose connector on mine has snapped off. I will be the second person to repair it so it's probably time for a new part.

e: I ended up picking one at the junkyard. Worked fine but I didn't have it on there long until I had to replace the whole turbo anyway
 
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