lowering boost threshold with wastegate antics - Page 3 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 04-02-2009, 10:47 AM   #41
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That's pretty much the idea, you are using pressure differentials on the wastegate diaphragm to control it. It's supposed to be the best way to control an IWG with high boost.

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Old 04-02-2009, 10:54 AM   #42
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Yes- generally you split the signal from the same source and run both to the actuator. Difference being the back/spring/close side has a regulator in line that keeps the boost level lower than that on the opposite side. That way the opening force is always stronger than the closing force when it comes time to open the gate.

16psi is my target, 18psi threshold.

As Jason said, ideally you want direct total control over signals on both sides. That way the opening signal doesn't have to over come the closing signal when it's time to open the gate. But using the regulator will work - similar to the helper spring.
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Old 04-02-2009, 11:05 AM   #43
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Nice, pics once you have it all in please.
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Old 04-02-2009, 11:24 AM   #44
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Brainy- that graphic lacks the regulator. It's not the only one I've seen that way and there's no explanation as to how the opening signal line will overcome that. Add to that the spring pressure on the close side.
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Old 04-02-2009, 11:33 AM   #45
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the boost solenoid would act as a regulator. same idea.


but you you need the same diagram with a regulator in place....

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Old 04-02-2009, 12:16 PM   #46
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Which port opens the gate? I thought it was the top port...

Here's my diagram laid out complete:

This way the actuator close port has boost applied to it from onset up - unlike the other side (open port) that is shut off from the boost signal by the boost controller. The only force to open the valve will be from the turbine exhaust back pressure. This allows the boost controller to be tuned without impact to the regulator signal - and the regulator can be tuned separately too.
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Old 04-02-2009, 12:32 PM   #47
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the top port pushes against the diaphragm opening the wastegate.

so in theory, if both had the full boost signal to the top and bottom, the wastegate would stay closed.

with the regulator, since you are limiting the amount pushing the diaphragm back, then your wastegate will open.


.......aw crap you're right I was looking at EWG diagrams which are in reverse.
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Old 04-02-2009, 01:31 PM   #48
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dammit - that HF regulator isn't going to work. It leaks 7psi shut. Maybe that's the HF quality? I know Mac Tools sells a unit that looks the same. My sears regulator leaks 4psi shut - but that would be usable in this application IMO. I just couldn't get the HF regulator to make any kind of pressure drop in line at 16psi. It's more like a flow regulator than a pressure regulator.

Though messing around with this stuff gave me an idea. A bleeder hole could be installed in the single line to the close port. It would be simple matter of trying different size holes at the target boost level to see what each yielded for boost drop. That hole could either be placed in the line (hard spot) or in the can (if you dare). The down side- it's going to bleed a percentage of pressure at all points, meaning that the full impact of existing boost pressure to keep the valve shut is lost. Here's the new plan:


Is my hesitation to T the signal line with a bleeder justified? I'm thinking it might impact the signal to the boost controller...
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Old 04-02-2009, 02:06 PM   #49
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Default ignore that ^ bleeder post

I think I found the ticket to precise regulation to the second (close) port in my plumbing box.

Needle Valve


Mine has the 1/4" compression fittings. I'll just use some copper tubing on both ends and flare it to fit the vacuum hose. Don't know if you can get them with pipe threads for barbs or not.

I put 16psi through the valve with the boost gauge on the other side and was able to dial down the pressure level to anything - from just under 16psi to nothing. And the valve is tight- so no worry on it moving.

edit:
Here's another option- more proper and reliable. This is the stuff that synapse engineering is swearing by for high boost systems, industrial grade pneumatic parts. But it requires special high temp hose.

Needle valve air, flow control, tube to tube, 1/4"

Last edited by m2cupcar; 04-02-2009 at 02:33 PM.
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Old 04-02-2009, 06:13 PM   #50
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Hooked everything up using compressed air to my actuator mounted on the turbo for a test drive. There's no way to T off the actuator signal line and run a regulator to the second port from that T without impacting both signals. Since the regulator is nothing but a valve that bleeds pressure to atmos, it drops the pressure of the entire signal line. So the two lines need to be source separately.

With the close signal pulled from elsewhere you could run a regulator, needle valve set up as a bleeder or just a bleeder hole in a hardline to regulate pressure. Examples of what would work based on my mock up:
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Old 04-02-2009, 11:16 PM   #51
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Quote:
Originally Posted by m2cupcar View Post
Hooked everything up using compressed air to my actuator mounted on the turbo for a test drive. There's no way to T off the actuator signal line and run a regulator to the second port from that T without impacting both signals. Since the regulator is nothing but a valve that bleeds pressure to atmos, it drops the pressure of the entire signal line. So the two lines need to be source separately.

With the close signal pulled from elsewhere you could run a regulator, needle valve set up as a bleeder or just a bleeder hole in a hardline to regulate pressure. Examples of what would work based on my mock up:
Shouldn't you change pressure sources? You will have unpredictable WG openings with that configuration. I believe you want them both to be post-intercooler or you will be dealing with a sometimes unpredictable pressure drop between sources. Just my . Edit: Or at least from the same source wherever that is...
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Old 04-03-2009, 10:33 AM   #52
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I could. I might. As it stands now I've always run off the compressor and never had an issue. That might be because I've run electronic boost control. The ecu gets it's signal from the manifold and makes the changes on the signal line running from the compressor to the actuator. But yes - based on the comments here the lines would work better swapped. I just haven't had the same experience with EBC or MBC that others have with a compressor signal.

You'd want the two sources separated just make sure they don't impact each other. Reason for removing the T in the line because the bleed was dropping the signal to the actuator. The regulator will need to be tuned much like an MBC. It needs to be adjusted so that the pressure combined with the return/close spring rate is still less than that of the boost target, yet keeps the gate closed during boost rise and can be overcome at (or just before) boost target. This is exactly the same thing that has to be done with the helper spring and tension adjustment. Speaking of which- there are internal WG actuators that are rebuildable- which provides the opportunity to swap out return springs just like an EWG. The problem (for me) is they cost as much or even more than going to the EWG.

Diagram updated per the mt.net boost signal principle.

Oh- I tested a 1/64" bleed hole at 15psi on a 1/4" copper tube and it showed a 9psi drop.
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Old 04-03-2009, 06:16 PM   #53
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I'm thinking that because the pressure drop across the intercooler increases as you increase boost pressure/flow that your differential between the two sides of your actuator will be changing so that it either won't open when you need it to or it will open much sooner than you would like, depending on which way you had it plumbed. I wasn't suggesting that they needed a common port, but to both be located on the same side of the intercooler. Ideally, between the intercooler and the throttle body, of course.
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Old 04-03-2009, 06:39 PM   #54
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Autospeed republished an article this week about keeping the wastegate closed longer. Their approach isn't as potentially effective, but is much simpler. Basically, add volume on the IWG boost signal...essentially adding wastegate "lag"

Article
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Old 04-03-2009, 07:57 PM   #55
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The main issue we are trying to address here is that the pressure inside the turbo itself is pushing open or at least helping push open the flapper door so longer boost signal line to the actuator ain't helping.
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Old 04-03-2009, 09:45 PM   #56
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^ Guess I should have read the thread before posting
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Old 04-04-2009, 02:23 AM   #57
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Quote:
Originally Posted by Atlanta93LE View Post
Autospeed republished an article this week about keeping the wastegate closed longer. .. Basically, add volume on the IWG boost signal...essentially adding wastegate "lag"

Article
That will cause overshoot.
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Old 04-04-2009, 02:29 AM   #58
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None of the above dual port schemes will help hold the flapper door shut because none of them allow pneumatic pressure to assist the internal spring while the other port (which opens the 'gate when boosted), sees atmo.

The only way to achieve that is to either have 2 solenoids, or a solenoid that does "steering" of the boost pressure (forgot the official name for that).
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Old 04-04-2009, 02:29 PM   #59
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I disagree. My EBC shows absolutely no signal to the open side port on the actuator until it's near target (16psi). Therefore the close side port is seeing all the boost the car is making minus a few psi with the regulator/bleed. That would work exactly the same as the helper spring I had installed. My actuator starts to move just over 4.5psi. I'm not trying to control the signal to the open side, I'm trying to hold the gate shut from the internal turbine pressure. Here's the above diagram showing the setup on spool to target:


Tell me what I'm missing here if this won't work. It's based on several solutions I've seen cited, with an adjustment to signal source. Should work the same with an MBC too - just not as precise.

I understand that two solenoids is ideal, but a lot more work. Ideally you'd want electronic boost control that could manage a dual port setup- something I don't have.

Last edited by m2cupcar; 04-04-2009 at 02:40 PM.
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Old 04-04-2009, 02:41 PM   #60
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Ah yes you are correct; adding pressure to the side that normally sees atmo will make it act like you installed a stiffer spring inside. (BTW your setup above needs a restrictor between the compressor and the tee)

I was thinking about also being able to make it run at mechanical boost. To do that, your bleed control valve also needs to be a solenoid.
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