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Old 06-13-2011, 01:34 PM
  #31  
Black51
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Originally Posted by Oddjob
If the WG reacts to manifold pressure, it will see vacuum and the WG will close pushing all exhaust energy thru the turbine. Which might even increase the turbo output momemtarily, causing a pressure spike in the plumbing between the turbo and closed throttle plate. Maybe not significant. At most might only cause a little quirky behavior/response from the engine during full load throttle liftoff situations.
Au contrare, Onspeed mentioned that the WG would open under vacuum. So which theory is correct? If it does, then this wouldn't be the case on lift off since the engine turns back into a vacuum.
Old 06-13-2011, 03:38 PM
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Care to explain how putting the WG under vacuum would open the valve?

Simple diaphragm opens under pressure, vacuum has the opposite effect. What are the directions of fluid flow when you suck, and then blow thru a straw?
Old 06-13-2011, 03:59 PM
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I have seen more problems with people running DP mode than not. And no one yet has proven any gains in running DP mode. At least none posted with data on better spool up, etc.

Boost gauge should T off the KLR line which is off the manifold.

Also, I read about and tried my WG line into the IC into the manifold pipe also and noticed no differences.
Old 06-13-2011, 07:47 PM
  #34  
Black51
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Originally Posted by Oddjob
Care to explain how putting the WG under vacuum would open the valve?

Simple diaphragm opens under pressure, vacuum has the opposite effect. What are the directions of fluid flow when you suck, and then blow thru a straw?
I never said the WG opens under vacuum. Onspeed mentioned he thought that's what happens. I was asking which theory is correct. I am still having a hard time trying to figure out how that could at all be possible, but then again, maybe it was someone with a lot of credibility who told him.
Old 06-13-2011, 08:02 PM
  #35  
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Originally Posted by toddk911
I have seen more problems with people running DP mode than not. And no one yet has proven any gains in running DP mode. At least none posted with data on better spool up, etc.

Boost gauge should T off the KLR line which is off the manifold.

Also, I read about and tried my WG line into the IC into the manifold pipe also and noticed no differences.
My boost gauge is of course hooked up to the manifold. That's never been an issue for this car.

The problem I am having is that the boost spikes and holds in higher gears, and therefore I need to turn it down. That then makes the boost much lower in the lower gears in order to account for the spiking in higher gears.

It appears thus far that it shouldn't make a difference if the WG line is hooked up to the manifold. My reasoning is that when the engine is under vacuum, I can't see how the WG would possibly open. So someone explain in detail, if you think/know it would open, 'how' that is possible.

And TurboTommy, explain 'how' this loss of power and fuel inefficiency would occur just by having the WG hooked up to the manifold. As long as it is shut when off boost, and opens at the right moment under boost, where is the power being lost? There must have been a reason why Porsche originally didn't hook the WG to the boost pipe.
Old 06-13-2011, 08:41 PM
  #36  
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My thinking was that in dual port mode, you'd get a vacuum on top of the diaphragm which would work with the spring to open the wastegate.

Porsche did hook the wastegate to the boost pipe, just fyi.
Old 06-13-2011, 09:16 PM
  #37  
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Originally Posted by onspeed

Porsche did hook the wastegate to the boost pipe, just fyi.
every turbo car i've worked on the wastegate is connected to a bango to the turbo compressor housing (usually internal WG) or boost pipe
Old 06-14-2011, 09:08 AM
  #38  
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Originally Posted by Black51
My boost gauge is of course hooked up to the manifold. That's never been an issue for this car.

The problem I am having is that the boost spikes and holds in higher gears, and therefore I need to turn it down. That then makes the boost much lower in the lower gears in order to account for the spiking in higher gears.

It appears thus far that it shouldn't make a difference if the WG line is hooked up to the manifold. My reasoning is that when the engine is under vacuum, I can't see how the WG would possibly open. So someone explain in detail, if you think/know it would open, 'how' that is possible.

And TurboTommy, explain 'how' this loss of power and fuel inefficiency would occur just by having the WG hooked up to the manifold. As long as it is shut when off boost, and opens at the right moment under boost, where is the power being lost? There must have been a reason why Porsche originally didn't hook the WG to the boost pipe.
Understood. And that boost spike, lower in lower gears etc. is also a symptom I have heard from people running in DP mode.

Those problems can also be attributed to boost controller issues.

DP mood has nothing to do with a vac signal. It simply allows airflow in two directions at the same time (think parallel vs. series) to allow the WG to open and close quicker, thus resulting in quicker spool and recovery of spool up in gear shifts. However, I have yet to see or hear from anyone that this befefit is achieved.

Did you have this problem before running in DP mode or your current MBC?
Old 06-14-2011, 11:06 AM
  #39  
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Dual port is usually used for holding the wastegate shut longer on a high back pressure Turbo for quicker spool. On a single port the set boost will open the valve but the backpressure will also push the valve open. With a dual port there's pressure applied at the top where the spring is to hold it shut for longer thus quicker spool.
Old 06-14-2011, 02:22 PM
  #40  
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Originally Posted by Paulyy
Dual port is usually used for holding the wastegate shut longer on a high back pressure Turbo for quicker spool. On a single port the set boost will open the valve but the backpressure will also push the valve open. With a dual port there's pressure applied at the top where the spring is to hold it shut for longer thus quicker spool.
And if this is not done the same all the time he will get boost spikes sometimes and less boost other times, etc. If that valve does not open and shut the same all the time. In single port mode it is open or shut. In DP mode it is always fighting with itself to open or close.

Get rid of the DP and go back to single port. lol

Also, on any Tial and most other aftermarket WG, the backpressure already keeps it closed, as converse to the stock WG alignment in which the valve does open with backpressure.
Old 06-14-2011, 06:27 PM
  #41  
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Since owning the car, it's always been in DP mode. The PO did that.

Now from what I can remember, the car is running the same as it did before since switching the lines to the WG. Those were clearly backwards.

But as far as boost levels go, I don't recall the boost spiking like it does in higher gears. I could be wrong though. It makes sense that it is different now, since I've noticed it. It seems like no matter how far I turn the MBC one way or another, it has little to no effect on the 1st and 2nd gear boost levels. That seems to really stick out to me unlike before.
Old 06-14-2011, 07:17 PM
  #42  
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Originally Posted by Black51
And TurboTommy, explain 'how' this loss of power and fuel inefficiency would occur just by having the WG hooked up to the manifold. As long as it is shut when off boost, and opens at the right moment under boost, where is the power being lost? There must have been a reason why Porsche originally didn't hook the WG to the boost pipe.

Just so we are clear; the loss of power and fuel efficiency is at part throttle.

For example, at fairly high speed cruise or moderate acceleration there is by far enough exhaust gases to power the turbo and create boost. This boost is sort of trapped between the turbo discharge and the throttle plate. In this section is where the boost line to your wastegate should come from. Therefore, when this boost (which could easily be 10 psi higher than what the intake manifold sees, at part throttle) reaches the spring strength of the wastegate, the wastegate will open slightly to vent exhaust gases. If it didn't, the exhaust back pressure acting on the exhaust valve would go through the roof compared to the absolute pressure the intake valve would see. This takes power from the crankshaft just to pump the air in and out of the engine, nevermind driving the wheels.
Now, this power loss is not huge; not like having to drive a super charger, but it's significant enough. And it also diminishes as the throttle is opened more. Some might say that "premature opening" of the wastegate causes loss of response. Maybe just a bit. But remember, once the turbo is spinning and the boost is sitting if front of the throttle, you have it instantly as soon as you move your right toe.
Old 06-14-2011, 07:24 PM
  #43  
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Originally Posted by toddk911
Also, on any Tial and most other aftermarket WG, the backpressure already keeps it closed, as converse to the stock WG alignment in which the valve does open with backpressure.

Actually, this is not true.
With a Tial, the valve does face the exhaust which is opposite of the stock configuration. But the valve moves inside the body of the wastegate in the direction of the exhaust.
Well, this is with the 46mm unit; I can only assume the 38mm Tial would be the same.
Old 06-14-2011, 10:58 PM
  #44  
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So then it's fair to say that the IC pipe is under 'boost' when the engine isn't under boost? That makes sense to me. Thanks for shedding light on this TurboTommy.

I ask again though to you guys who have responded in this thread, where would one get a banjo bolt to go in the IC pipe? All it's got in there right now is a bolt that simply plugs the hole.



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