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Stock Twins King
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Discussion Starter · #1 ·
In the effort to understand certain installations, I was wondering why HKS recommends hooking the control unit up this way. Usually, the facing down actuator nipple is capped off. In there installation, they recommend "T" ing the "input" to that bottom nipple. I can't figure out the reason, since our wastegate actuator is dual ported pressurized. (One nipple being sufficient)

Anyone hook theres up this way, and if so, how accurately does it boost according to the settings?

 

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Stu,

Mine is NOT hooked up this way, but you got me thinking. That is exactly how the boost is controlled in the stock form. The only difference is that in stock form VSV controlled by ECU is controlling boost. As pictured, you are simply replacing VSV with EVC. Also, MY theory is that the pictured way of controlling boost should be better, with the possibility of not needing the spring mod anymore. Let's think about it. If only the top actuator nipple is used, the boost in controlled by the amount of air passed by EVC to the actuator. So, let say our goal is 18PSI. EVC will keep the wastegate shot until 18PSI, then it will bleed boost. Since the load is still increasing, but boost is not the same, the exhaust gases will force the wastgate to open, causing boost lost. Because of this scenario the spring mod is a big help. The pictured way will allow full turbo boost help keeping the wastegate closed until 18PSI, and then it will still keep it in check when EVC forces the actuator to partially open the wastegate. The exhaust gasses would have the toughter time to force the wastegate to open more.
In MY opinion, the actuator is working more efficiently when used as designed rather than the modified way.
Keep in mind there could be a problem with my logic. If so, it would be nice to be nicely corrected by anybody who knows better.
On the other hand, is it possible to apply the boost pressure to the wastegate's second port? I believe in the stock form this comes from the intake not intake manifold.
If I can find an easier access to the turbo outlet nipple I will try to hook up my EVC, original, as recommended by HKS to see if it works better than the current way I have it hooked up.
 

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In stock form the pressure from the compressor side goes in through the top port of the wastegate and is bled off on the "vent" side (or downwards port) where the VSV regulates how much is bled off back into the vacuum side. Blocking off the downward port effectively transforms the unit into a single port wastegate where we can just T into the signal from the compressor to wastegate and bleed off air thereby raising boost pressure by reducing the pressure signal to the wastegate.

On the HKS diagram above, assuming that the (O)utput line will act as a vacuum regulator, then the functionality will duplicate the Supra’s stock VSV setup. I believe chris_k is correct in assuming that this should help keep the wastegate from opening at high RPMs. What I’m not sure of is, might this cause slower spoolup? because the actuator is seeing some small pressure signal initially and slightly opening?

Also, the stock setup has pressure coming in the top port and being vented on the down port, the HKS diagram has these two ports reversed. I don’t think this makes a difference.
 

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Stock Twins King
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Discussion Starter · #6 ·
crossways said:
In stock form the pressure from the compressor side goes in through the top port of the wastegate and is bled off on the "vent" side (or downwards port) where the VSV regulates how much is bled off back into the vacuum side. Blocking off the downward port effectively transforms the unit into a single port wastegate where we can just T into the signal from the compressor to wastegate and bleed off air thereby raising boost pressure by reducing the pressure signal to the wastegate.

On the HKS diagram above, assuming that the (O)utput line will act as a vacuum regulator, then the functionality will duplicate the Supra’s stock VSV setup. I believe chris_k is correct in assuming that this should help keep the wastegate from opening at high RPMs. What I’m not sure of is, might this cause slower spoolup? because the actuator is seeing some small pressure signal initially and slightly opening?

Also, the stock setup has pressure coming in the top port and being vented on the down port, the HKS diagram has these two ports reversed. I don’t think this makes a difference.
I agree, but what we dont know is how the internals of the HKS are designed. Your assumption is that the lower connection is for "sluff" otherwise why the connection. Maybe it keeps double pressure on the actuator to help "keep" the wastegate closed? Anways, and odd design and still not known its true purpose as yet.

I am still going to try moving the BC pressure sensor over to a "T" on the turbo compressor side. I am hoping that "pre-TB" pressure source will solve some other issues I have on surging.
 

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Stu Hagen said:
I agree, but what we dont know is how the internals of the HKS are designed. Your assumption is that the lower connection is for "sluff" otherwise why the connection. Maybe it keeps double pressure on the actuator to help "keep" the wastegate closed? Anways, and odd design and still not known its true purpose as yet.

I am still going to try moving the BC pressure sensor over to a "T" on the turbo compressor side. I am hoping that "pre-TB" pressure source will solve some other issues I have on surging.

Stu, the HKS EVC has a switch that allows for wastegate selection from (SW) swing valve type to (PO) poppet type. Assumedly if one was setting up boost control as pictured above with dual port functionality you would select (PO) whereby the poppet valve would bleed off the excess pressure that builds up and maintain a set boost signal. This would happen on the (O)utput line.

External wastegates function with this poppet valve, and if you notice in the EVC manual, HKS has the dual port and external wastegate installation setups as being identical.
 

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STU what happened to the SBC? Or do you just have too much time on your hands?
 

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crossways,

I guess I'm still confused on how does the external wastegate works. Question, does the stock supra actuator works in the same as would the external wastegate? If yes then I can see how we can use both actuator ports for better boost control. If not, I would imagine that converting the actuator to the single port, by blocking the second port, is the only way to control boost.
 

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That pic is for a dual port WG which does NOT apply to the supra.


The supra is not dual port..... although there are two ports..... they are both on the same side of the diaphragm so they count as one.


Hook up the EVC as a regular single port internal gate. Set the switch to SW on the back of the EVC and make sure you closely follow the instructions for setting that switch. IGN on, EVC off, then slide switch!
 

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Stock Twins King
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Discussion Starter · #11 ·
Sound Performance said:
That pic is for a dual port WG which does NOT apply to the supra.


The supra is not dual port..... although there are two ports..... they are both on the same side of the diaphragm so they count as one.


Hook up the EVC as a regular single port internal gate. Set the switch to SW on the back of the EVC and make sure you closely follow the instructions for setting that switch. IGN on, EVC off, then slide switch!
So that answers that~!

So the "bleed off" method above is incorrect for the Supra? I agree and disagree. If the HKS unit *has* the ability to bleed, then thier method makes sense. but if not then your correct. I do not have this HKS unit, nor am I thinking of getting one. I just was reading there hook up method and found it interesting. It makes sense if it controls bleed, but evidently it isnt designed that way, so for Supra owners, it needs to be installed as a "singal port" type actuator. I didnt honestly think or know that the 2 ports were on the same side of the diaphram, and yes that would make sense. The bottom port of the actuator is used to allow the realease of pressure built up on the turbo side by the stock VSV to sluff off boost.
 

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Sound Performance said:
That pic is for a dual port WG which does NOT apply to the supra.


The supra is not dual port..... although there are two ports..... they are both on the same side of the diaphragm so they count as one.


Hook up the EVC as a regular single port internal gate. Set the switch to SW on the back of the EVC and make sure you closely follow the instructions for setting that switch. IGN on, EVC off, then slide switch!


Thanks for clearing up everything!

This makes perfect sense since blowing in one port sends air right out of the other port.
 

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I hooked mine up according to the single port actuator diagram, if you guys are interested I'll post the results when I finally get a chance to make a few runs.
 

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So for those who have this unit...

Port O connected to top port on the WG, other port on the WG with the 90degree bend should be capped.

Port I connected to the turbo nipple.

Port B to the pressure source.
 

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Larry,

How would you hook the EVC Ez up on a Hks GT Wastegate on single turbo? I can't seem to control boost on my brand new evc ez. And what should I set the SW-PO switch to?

Thanks~!
 
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