Educate me Turbo men and women.
07-14-2005, 03:43 AM
#1
Rennlist Member
Thread Starter
Educate me Turbo men and women.
A wastegate is a spring operated "bleed valve" that usually resides on the exhaust side of the turbo, before the intake of the turbine correct? The wastegate has two or three holes in it, one for boost in, one for boost out to discharge pipe (in your case, back into the downpipe?) and one for vacuum reference?
Now - are these mechanical and electric? When you have a "Wastegate controller" what is controlling it?
Are you controlling it with other aparatuses? If some of you are TECIII or AEM or whatever, are you using a frequency controlled output to give a PWM to the unit itself?
Thanks
Now - are these mechanical and electric? When you have a "Wastegate controller" what is controlling it?
Are you controlling it with other aparatuses? If some of you are TECIII or AEM or whatever, are you using a frequency controlled output to give a PWM to the unit itself?
Thanks
07-14-2005, 04:25 AM
#2
Nordschleife Master
The stock 951 wastegate itself is totally mechanical, there is a pressure nozzle at the top which forces the wastegate valve to open. This pressure nozzle is connected to a short hose that goes directly to the stock "timing valve"... which takes a boost reading off the intercooler pipe, and controls the amount of boost going to the waste gate, to open or close it as needed. I think stock is something like 7-11psi.
If you want an easy way to increase boost, you fool the "timing valve" into thinking there is less air going into the intake manifold than there really is, by installing a boost controller which bleeds off a bit of air before it gets to the timing valve. My reliaboost bleeds off enough to make the timing valve think there is 11-12psi in the manifold when really there is 15psi. Of course I have guru chips as well to provide the increased fuel required.
On a car with a boost enhancer/boost controller installed, you can optionally bypass that "timing valve" completely because the boost enhancer can now control how much boost goes to open the wastegate. This is good because, in our cars, the "timing valve" is known to fail, which then limits your boost.
That is all the stock, single port mechanical wastegate stuff. A dual port wastegate basically has an extra hole in it to make boost adjustments far easier and more accurate.. as single port can be very touchy and sensative to adjust.
The stock wastegate can barely hold 15psi with shims installed to pre-load the spring. The 35 and 40mm TIAL dualport wastegates seem to be the popular upgrade in this crowd.
I don't know too much about electrical boost controllers (EBC's) but there are tons of other guys on here who do and can fill you in. And hopefully in the process, correct any wrongs that I may have written...
If you want an easy way to increase boost, you fool the "timing valve" into thinking there is less air going into the intake manifold than there really is, by installing a boost controller which bleeds off a bit of air before it gets to the timing valve. My reliaboost bleeds off enough to make the timing valve think there is 11-12psi in the manifold when really there is 15psi. Of course I have guru chips as well to provide the increased fuel required.
On a car with a boost enhancer/boost controller installed, you can optionally bypass that "timing valve" completely because the boost enhancer can now control how much boost goes to open the wastegate. This is good because, in our cars, the "timing valve" is known to fail, which then limits your boost.
That is all the stock, single port mechanical wastegate stuff. A dual port wastegate basically has an extra hole in it to make boost adjustments far easier and more accurate.. as single port can be very touchy and sensative to adjust.
The stock wastegate can barely hold 15psi with shims installed to pre-load the spring. The 35 and 40mm TIAL dualport wastegates seem to be the popular upgrade in this crowd.
I don't know too much about electrical boost controllers (EBC's) but there are tons of other guys on here who do and can fill you in. And hopefully in the process, correct any wrongs that I may have written...
07-14-2005, 04:34 AM
#3
Nordschleife Master
Here is the "classic" 944 turbo boost diagram (thanks OZ951)
and a few threads on the topic:
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/214541-looking-for-proper-plumbing-diagram-for-dp-wastgate.html
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/167069-i-need-help-with-boost.html
and a few threads on the topic:
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/214541-looking-for-proper-plumbing-diagram-for-dp-wastgate.html
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/167069-i-need-help-with-boost.html
07-14-2005, 04:37 AM
#4
Rennlist Member
Thread Starter
Thanks Rich. I'm trying to figure out of the wastegage is ever more then just a spring operated unit that is controlled by outside sources (EBC, timing valve or whatever).
Lets say the wastegage is on the intake side and the boost will be linear from 0-6500rpm 0-15psi. So the wastegate sits on the intake. It can limit the boost to 10psi from 3k to 6500. It may not even need a line referenced from these other things you mentioned? If the internal spring is set to release past 10, then it will do it mechanically with no outside help?
Can it be set to open under other circumstances, such as under vacuum?
Again, I am ignnoring it as an exhaust side unit. Imagin it on the intake side magically, there is a linear 0-15psi of boost created over the rev range.
Lets say the wastegage is on the intake side and the boost will be linear from 0-6500rpm 0-15psi. So the wastegate sits on the intake. It can limit the boost to 10psi from 3k to 6500. It may not even need a line referenced from these other things you mentioned? If the internal spring is set to release past 10, then it will do it mechanically with no outside help?
Can it be set to open under other circumstances, such as under vacuum?
Again, I am ignnoring it as an exhaust side unit. Imagin it on the intake side magically, there is a linear 0-15psi of boost created over the rev range.
07-14-2005, 04:56 AM
#6
Nordschleife Master
Brendan.. by DEFINITION a "wastegate" has to sit on the exhaust side of the engine. A "wastegate" dumps excess exhaust gases before they reach the turbine side of the turbocharger.
A wastegate can be a flapper door, or a valve, and it can be electrically or pneumatically controlled (or even with a cockpit pushrod, in some airplanes), but, it must control exhaust gases going directly to the turbo.
The reason you cannot have a wastegate on the intake side of the engine, is because then you will always have all the exhaust gases spinning the turbine. You need a WASTE gate in the exhaust plumbing to let out uneeded exhaust gases. You cannot dedicate the downpipe of the turbine for this because then the turbine will always be spooled up which will mean there will always be boost in the manifold.. even at idle! It's like putting the Cart in front of the Horse... Does that make sense?
A wastegate can be a flapper door, or a valve, and it can be electrically or pneumatically controlled (or even with a cockpit pushrod, in some airplanes), but, it must control exhaust gases going directly to the turbo.
The reason you cannot have a wastegate on the intake side of the engine, is because then you will always have all the exhaust gases spinning the turbine. You need a WASTE gate in the exhaust plumbing to let out uneeded exhaust gases. You cannot dedicate the downpipe of the turbine for this because then the turbine will always be spooled up which will mean there will always be boost in the manifold.. even at idle! It's like putting the Cart in front of the Horse... Does that make sense?
07-14-2005, 08:17 AM
#7
Drifting
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You can put the wastegate on the intake to control
boost but then you will be over spinning the turbo
at certain rev range which would cause failure.
Unless if you are able to keep the turbo spinning
within it's limit at redline it can be done but I would
imagine that it would be quite a laggy turbo.
boost but then you will be over spinning the turbo
at certain rev range which would cause failure.
Unless if you are able to keep the turbo spinning
within it's limit at redline it can be done but I would
imagine that it would be quite a laggy turbo.
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07-14-2005, 10:22 AM
#8
Three Wheelin'
Brendan,
In this book, the author describes a company that uses a BOV to control boost levels, rather than a wastegate. The standard practice is to use the wastegate; however, I would think that using the BOV rather than the wastegate would reduce lag, significantly, and would allow better control of boost levels. The concern would be spinning the turbo too hard. In that regard, close attention would need to be paid to turbo sizing and boost levels.
Wastegate = exhaust side valve between the exhaust ports on the head and the turbine of the turbo
BOV = a release valve located between the turbo compressor and the intake ports of the cylinder head.
The book is worth a read, IMHO.
-Jon
In this book, the author describes a company that uses a BOV to control boost levels, rather than a wastegate. The standard practice is to use the wastegate; however, I would think that using the BOV rather than the wastegate would reduce lag, significantly, and would allow better control of boost levels. The concern would be spinning the turbo too hard. In that regard, close attention would need to be paid to turbo sizing and boost levels.
Wastegate = exhaust side valve between the exhaust ports on the head and the turbine of the turbo
BOV = a release valve located between the turbo compressor and the intake ports of the cylinder head.
The book is worth a read, IMHO.
-Jon
07-14-2005, 11:31 AM
#10
Drifting
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Jon,
Is'nt it the same as what I mentioned ? Now keep in mind that
if a bov is used to control boost, is must be able to flow lots
of air so as not to cause boost spikes & it's go to be hook up
in the recirculating manner or there will be lots of noise. The
only bov that I know which can handle this is a HKS Type II
racing wastegate which I'm using but it cost much more than
a Tial 38 mm wastegate gate.
Is'nt it the same as what I mentioned ? Now keep in mind that
if a bov is used to control boost, is must be able to flow lots
of air so as not to cause boost spikes & it's go to be hook up
in the recirculating manner or there will be lots of noise. The
only bov that I know which can handle this is a HKS Type II
racing wastegate which I'm using but it cost much more than
a Tial 38 mm wastegate gate.
07-14-2005, 01:12 PM
#11
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Guys, why reinvent the wheel. There has been so much research that the wastegate is the most reliable way to go.
Quote: "I'm trying to figure out of the wastegage is ever more then just a spring operated unit that is controlled by outside sources (EBC, timing valve or whatever)."
Brendan, you would ideally want an external source either way. Thats one of the fun parts of EBCs, that you control when you want the valve to start opening. If not it would start to open early, little by little (since it's a spring), and you would slower your response.
Quote: "I'm trying to figure out of the wastegage is ever more then just a spring operated unit that is controlled by outside sources (EBC, timing valve or whatever)."
Brendan, you would ideally want an external source either way. Thats one of the fun parts of EBCs, that you control when you want the valve to start opening. If not it would start to open early, little by little (since it's a spring), and you would slower your response.
07-14-2005, 02:20 PM
#12
Three Wheelin'
Yeah, to clarify, I'm not recommending that you try to run a system without a wastegate, I'm just saying that it can and has been done. I believe that you're going a bit beyond the norm with a turbo 928, but I don't think you should try to reinvent the wheel when it comes to designing your FI system.
-J
-J
07-15-2005, 05:40 PM
#13
Rennlist Member
Thread Starter
I'm sorry. I guess I was too vague. There is no turbo in this system. Its a belt driven Centrifugal supercharger.
But I came to you guys because you all live this boost stuff day in day out.
I was asking about a wastegate because it seemed to be the good idea for bleeding intake tract boost "over a certain limit"
Sorry to confuse.
This is all very helpful. As I mentioned, the boost wil be created linearly via RPM. I believe it is RPM squared or something like that. 2psi at 2k rpm, 4psi at 3500rpm. So the idea would be to use a Wastgate, (or that dual use BOV that was mentioned to ramp off the boost once it gets to a set point - bleed it off the intake. 3krpm hits 8psi, 4krpm hits 10psi, and then the WG or BOV starts to bleed any volume over 10 psi until redline, as the Vortech will continue to provide more air up to say 16psi at 6500pm. But I want only enough VOLUME for 10psi after 4k. And ofcourse since the engine is breathing more it will require more volume, and the SC will give it more - but I want the total to provide a guage 10psi.
This make any sense?
I'm not good at math.
But I came to you guys because you all live this boost stuff day in day out.
I was asking about a wastegate because it seemed to be the good idea for bleeding intake tract boost "over a certain limit"
Sorry to confuse.
This is all very helpful. As I mentioned, the boost wil be created linearly via RPM. I believe it is RPM squared or something like that. 2psi at 2k rpm, 4psi at 3500rpm. So the idea would be to use a Wastgate, (or that dual use BOV that was mentioned to ramp off the boost once it gets to a set point - bleed it off the intake. 3krpm hits 8psi, 4krpm hits 10psi, and then the WG or BOV starts to bleed any volume over 10 psi until redline, as the Vortech will continue to provide more air up to say 16psi at 6500pm. But I want only enough VOLUME for 10psi after 4k. And ofcourse since the engine is breathing more it will require more volume, and the SC will give it more - but I want the total to provide a guage 10psi.
This make any sense?
I'm not good at math.
07-15-2005, 05:57 PM
#14
Three Wheelin'
Makes total sense, Brendan. I'd recommend a large blowoff valve (there has to be something designed for this application) and an installation point before an intercooler (if you're using one).
On the 944 forum, some guy made a centrifugal supercharger from a K26/6, and I believe he's using the same method to control boost.
Good luck,
Jon
On the 944 forum, some guy made a centrifugal supercharger from a K26/6, and I believe he's using the same method to control boost.
Good luck,
Jon
07-15-2005, 06:15 PM
#15
Rennlist Member
Thread Starter
Originally Posted by Jon Moeller
Brendan,
In this book, the author describes a company that uses a BOV to control boost levels, rather than a wastegate. The standard practice is to use the wastegate; however, I would think that using the BOV rather than the wastegate would reduce lag, significantly, and would allow better control of boost levels. The concern would be spinning the turbo too hard. In that regard, close attention would need to be paid to turbo sizing and boost levels.
Wastegate = exhaust side valve between the exhaust ports on the head and the turbine of the turbo
BOV = a release valve located between the turbo compressor and the intake ports of the cylinder head.
The book is worth a read, IMHO.
-Jon
In this book, the author describes a company that uses a BOV to control boost levels, rather than a wastegate. The standard practice is to use the wastegate; however, I would think that using the BOV rather than the wastegate would reduce lag, significantly, and would allow better control of boost levels. The concern would be spinning the turbo too hard. In that regard, close attention would need to be paid to turbo sizing and boost levels.
Wastegate = exhaust side valve between the exhaust ports on the head and the turbine of the turbo
BOV = a release valve located between the turbo compressor and the intake ports of the cylinder head.
The book is worth a read, IMHO.
-Jon
Thats a GREAT book. Great ideas. He's not hot on methanol boost coolers though.
