Time to go Stage II!

[turbojosh]

Time to O-ring the heads.
Helps to have the right tools.

View attachment 167248

Nice fixture!

 

[norbs]

You can put the WG at 90 degrees to the exhaust stream, ( as long as its not over 90 degrees) where the collector merges at the turbo flange ,it will work just fine, less angle would be better though if you have room to mount it.

 

[Alky V6]

You can put the WG at 90 degrees to the exhaust stream, ( as long as its not over 90 degrees) where the collector merges at the turbo flange ,it will work just fine, less angle would be better though if you have room to mount it.

You're right about that. I think the question was, what is the preferred orientation. 90 degrees will work. That's how my Stage I is setup.
The point of bringing up the question about the mounting of the wastegate and what works, and what does not work, was mainly to bring into question, if the wastegate is mounted past 90 degrees, why does that mounting orientation not work?

 

[norbs]

Well, all i know it will start to create a less pressure differential , like a venturi effect...

 

[turbobitt]

You're right about that. I think the question was, what is the preferred orientation. 90 degrees will work. That's how my Stage I is setup.
The point of bringing up the question about the mounting of the wastegate and what works, and what does not work, was mainly to bring into question, if the wastegate is mounted past 90 degrees, why does that mounting orientation not work?

You must first define "what doesn't work". If your boost targets are >30 than almost anything would probably work...
AG.

 

[turbobitt]

Btw regardless of WG orientation, the pipe intersection would most likely be 90 degrees to each other anyway.

AG.

 

[Alky V6]

Btw regardless of WG orientation, the pipe intersection would most likely be 90 degrees to each other anyway.

AG.

But isn't that the most important issue? The intersection of the WG piping to the main exhaust pipe?
As Norbs has correctly stated, anything past a 90 degree orientation would tend to create a low pressure zone in the WG piping leading to the WG.
Why wouldn't a similar low pressure zone exist in the other primary pipes of an exhaust collector?
There are some that feel that there are no pressure pulses in a turbocharged exhaust system. That all you have is a constant high back pressure between the exhaust valve and the turbine housing, and that this pressure is equal across all sections of the exhaust system, before the turbine wheel, at any given time. If that were true, then why would the WG piping orientation be important?

 

[turbobitt]

But isn't that the most important issue? The intersection of the WG piping to the main exhaust pipe?
As Norbs has correctly stated, anything past a 90 degree orientation would tend to create a low pressure zone in the WG piping leading to the WG.
Why wouldn't a similar low pressure zone exist in the other primary pipes of an exhaust collector?
There are some that feel that there are no pressure pulses in a turbocharged exhaust system. That all you have is a constant high back pressure between the exhaust valve and the turbine housing, and that this pressure is equal across all sections of the exhaust system, before the turbine wheel, at any given time. If that were true, then why would the WG piping orientation be important?

The statements are to general and are missleading to the unsuspecting reader. When you say low pressure zone, it is relative to manifold pressure and much higher than atmosphere. Even if the WG pipe was laid back over 90 with respect to the turbo inlet, the hole is still intersecting 90 degrees to the wall. Unless the actual WG pipe is intruding into the airflow, there should be much difference in performance.
Pressure pulses are still going to be higher than atmosphere so therefore pressure differential accross the gate would still favor flow in its normal operating condition and reduce some energy to the turbine.

AG.

 

[Alky V6]

The statements are to general and are missleading to the unsuspecting reader. When you say low pressure zone, it is relative to manifold pressure and much higher than atmosphere. Even if the WG pipe was laid back over 90 with respect to the turbo inlet, the hole is still intersecting 90 degrees to the wall. Unless the actual WG pipe is intruding into the airflow, there should be much difference in performance.
Pressure pulses are still going to be higher than atmosphere so therefore pressure differential accross the gate would still favor flow in its normal operating condition and reduce some energy to the turbine.

AG.

I think that's a bit harsh to use the term misleading. Too general? Maybe general. But too general? Most people reading this are simply not going to get what is being discussed. Others know enough about flow and pressure to understand. If you want to get picky and start better defining the exhaust pressures compared to this and that, be my guest. I can use the help. But to characterize this discussion as misleading? I don't think so. Hopefully, what it is doing is making people wonder a little bit and making them do their own research into this question.

Alan. If I mount a tube at a 45 degree angle to another tube and use a blow gun to blow through the straight tube in a fashion that the flow would have to reverse to escape from the tube mounted off of the straight tube, do you think that there would be flow OUT of the side tube?

 

[Alky V6]

An example of how the wastegate should be fed off of the exhaust pipe.

 

[Alky V6]

The O-ring grooves are ready to be cut.

 

[Mike E]

I think that's a bit harsh to use the term misleading. Too general? Maybe general. But too general? Most people reading this are simply not going to get what is being discussed. Others know enough about flow and pressure to understand. If you want to get picky and start better defining the exhaust pressures compared to this and that, be my guest. I can use the help. But to characterize this discussion as misleading? I don't think so. Hopefully, what it is doing is making people wonder a little bit and making them do their own research into this question.

Alan. If I mount a tube at a 45 degree angle to another tube and use a blow gun to blow through the straight tube in a fashion that the flow would have to reverse to escape from the tube mounted off of the straight tube, do you think that there would be flow OUT of the side tube?

That air or exhaust has mass, speed and direction. Force =1/2*mass*velocity^2 If the tube is small and the flow rate is high, it has more velocity. If the tube is large that velocity is low. For it to change direction and flow backwards, that velocity in the direction it was flowing must slow down. That takes energy to make that change and its a function of the square of the velocity and the mass.

So for your described the setup where it has to change diection to go out the wastegate, it depends on the flow rart, tube size and pressure. If the tube is large (low velocity) and the pressure is high, yes you would probably see some flow out the tube. If the flow is high, the tube small ( high velocity) and the pressure is low, you may not see anything. It's going to take less force and energy to make that exhaust flow out of a wastegate that is positioned so that the exhaust doesn't have to change direction or slow down to flow out of the gate.

The same goes for the primaries in the collector. It depends on pressure, tube size and flow rate. For most setups, pressure is high and flow rate is high and tube size is small, so it takes a lot of force and energy for reversion to happen in the tubes. For scavenging to happen you need a lot of pressure drop in the collector. Without having some real numbers I can't wrap my head around that happening "effectively" in a system that has 40, 50 or 60 psi of back pressure. What pressure spikes (high and low) do you think your exhaust pulses have? Are they the same as whatever the cylinder pressure is when you open the valve. What is that pressure? We've argued it before, yes there may be pressure pulses, but I think the gain from using them to scavenge is low for "most" tubo setups. Your setup with an overly large turbine and low backpressure is not like "most" setups.

 

[turbobitt]

I think that's a bit harsh to use the term misleading. Too general? Maybe general. But too general? Most people reading this are simply not going to get what is being discussed. Others know enough about flow and pressure to understand. If you want to get picky and start better defining the exhaust pressures compared to this and that, be my guest. I can use the help. But to characterize this discussion as misleading? I don't think so. Hopefully, what it is doing is making people wonder a little bit and making them do their own research into this question.

Alan. If I mount a tube at a 45 degree angle to another tube and use a blow gun to blow through the straight tube in a fashion that the flow would have to reverse to escape from the tube mounted off of the straight tube, do you think that there would be flow OUT of the side tube?

Don,
I don't dissagree that there is an optimum location such as you indicated through your pictures BUT in a system with high boost regulation, I doubt that there is much diference. With 30 PSI backpressure, even with pressure pulsing in the exhaust, the pressure differencial will still favor flow to atmosphere. At very low backpresures and boost, yes I would agree that WG placement would be critical.

To my comment about missleading, a good example is your blowgun experiment. It fails to take pressure differencials into the equation and only shows the effect of flow velocity. And I never implied you were intentionally missleading and that only you are being to general in your startements and not taking all the factors in consideration.

I'm not going to turn this into a full blown discussion about somthing I already know about. I would never mount a WG pipe away from the flow path. To say its totally ineffective is a little extream.

Allan G.

 

[Alky V6]

Don,
I don't dissagree that there is an optimum location such as you indicated through your pictures BUT in a system with high boost regulation, I doubt that there is much diference. With 30 PSI backpressure, even with pressure pulsing in the exhaust, the pressure differencial will still favor flow to atmosphere. At very low backpresures and boost, yes I would agree that WG placement would be critical.

To my comment about missleading, a good example is your blowgun experiment. It fails to take pressure differencials into the equation and only shows the effect of flow velocity. And I never implied you were intentionally missleading and that only you are being to general in your startements and not taking all the factors in consideration.

I'm not going to turn this into a full blown discussion about somthing I already know about. I would never mount a WG pipe away from the flow path. To say its totally ineffective is a little extream.

Allan G.

I agree with you, Allan. Incorrectly mounting a wastegate would not be completely ineffective, and I never stated it would be completely or totally ineffective. I am guessing it would just be less effective.

 

[Alky V6]

That air or exhaust has mass, speed and direction. Force =1/2*mass*velocity^2 If the tube is small and the flow rate is high, it has more velocity. If the tube is large that velocity is low. For it to change direction and flow backwards, that velocity in the direction it was flowing must slow down. That takes energy to make that change and its a function of the square of the velocity and the mass.

So for your described the setup where it has to change diection to go out the wastegate, it depends on the flow rart, tube size and pressure. If the tube is large (low velocity) and the pressure is high, yes you would probably see some flow out the tube. If the flow is high, the tube small ( high velocity) and the pressure is low, you may not see anything. It's going to take less force and energy to make that exhaust flow out of a wastegate that is positioned so that the exhaust doesn't have to change direction or slow down to flow out of the gate.

The same goes for the primaries in the collector. It depends on pressure, tube size and flow rate. For most setups, pressure is high and flow rate is high and tube size is small, so it takes a lot of force and energy for reversion to happen in the tubes. For scavenging to happen you need a lot of pressure drop in the collector. Without having some real numbers I can't wrap my head around that happening "effectively" in a system that has 40, 50 or 60 psi of back pressure. What pressure spikes (high and low) do you think your exhaust pulses have? Are they the same as whatever the cylinder pressure is when you open the valve. What is that pressure? We've argued it before, yes there may be pressure pulses, but I think the gain from using them to scavenge is low for "most" tubo setups. Your setup with an overly large turbine and low backpressure is not like "most" setups.

I'll post up some pressure traces for you to check out, when I get the chance. They're on the laptop at work.

 

[Alky V6]

I'm going to try an experiment with the exhaust pipe in the picture I posted a little earlier.
I'm going to blow air from an air gun into the turbo mounting end of the pipe, and hold a piece of paper close to the opening of the tube that will mount the wastegate.
Anyone want to guess what the piece of paper will do? Will it blow away from the opening? Will it suck to the opening? Will it do nothing but hang there and be uneffected?

 

[norbs]

It would probably just hang there and do nothing....

 

[Mike E]

What would it do if you restricted all the other outlets so that the pressure in the header was 60 psi.

 

[Alky V6]

What would it do if you restricted all the other outlets so that the pressure in the header was 60 psi.

One step at a time.
My guess is, the paper will suck to the opening of the pipe.
Any more guesses?

Alan. Since you already know, what will the paper do?

edit: To be clear, the WG piping does not extend into the main exhaust piping. It stops flush with the ID of the main pipe.

 

[Alky V6]

What do you think, Mike E? What will the piece of paper do?