Nameless Downpipe: Official 5th Gen GT Install Thread

Couldn't the external arm (not the rod) on the wastegate flapper be modified (I think shortened) so that the same actuator throw produced more movement in the flapper, opening it farther. All it would need to be shortened is 1mm or 2 or 3. Kinda like the mechanical wizardry used on short shifters. By that video it seems it could open about 10-15, maybe 20% more before it even breaks the plane of the turbo flange. Edited February 22, 2017 by GTEASER

Couldn't the external arm (not the rod) on the wastegate flapper be modified (I think shortened) so that the same actuator throw produced more movement in the flapper, opening it farther. All it would need to be shortened is 1mm or 2 or 3. Kinda like the mechanical wizardry used on short shifters. By that video it seems it could open about 10-15, maybe 20% more before it even breaks the plane of the turbo flange.

 

Yes, if you shorten that pivot arm you will get more rotation for the given movement of the rod(this angle shows the pivot arm nicely http://www.turbosmartdirect.com/Product-Categories/Subaru-Actuators/IWG75-Subaru-Impreza-WRX-STI-09-Current-7-PSI-Black.html), just like how drifters move the steering pivot closer the the hub to get more steering angle out of a stock rack. the only question is how much can it open before it starts hitting things?

Yes, if you shorten that pivot arm you will get more rotation for the given movement of the rod(this angle shows the pivot arm nicely http://www.turbosmartdirect.com/Product-Categories/Subaru-Actuators/IWG75-Subaru-Impreza-WRX-STI-09-Current-7-PSI-Black.html), just like how drifters move the steering pivot closer the the hub to get more steering angle out of a stock rack. the only question is how much can it open before it starts hitting things?

 

Would this depend on the actuator as well? It'd need enough force to rotate (or prevent rotating) the rod the wastegate sits on with less leverage. Or is that not really a concern?

Would this depend on the actuator as well? It'd need enough force to rotate (or prevent rotating) the rod the wastegate sits on with less leverage. Or is that not really a concern?

 

I believe boost pressure holds it open once the resistance of the internal spring is overcome, so the EBCS is controlling the position of the flapper. Unless you dramatically increased the leverage by making it really short, there shouldn't be an issue doing that. You would need to be tuned for a mod like that I believe, you couldn't just do the mod and run on an existing tune.

Edited February 22, 2017 by GTEASER

Would this depend on the actuator as well? It'd need enough force to rotate (or prevent rotating) the rod the wastegate sits on with less leverage. Or is that not really a concern?

 

that's true, if it takes a considerable amount of force to open the flapper, that force will increase by what ever factor the length of the pivot arm was decreased. I was under the impression that there is no spring on the actual flapper and that if you disconnected the actuator arm it would just flap around. can someone confirm this? but if that is true and all closing force comes from the actuator I'd be willing to bet that the force it has will be enough to hold a few more psi even with the slight mechanical disadvantage you are giving it, and worse comes to worst you won't be able to hold high levels of boost but you will be able to prevent over boost better.... in theory... if the flow past the flapper is actually the restriction and not the flow out of the poorly ported hole.

can someone confirm this?

 

Confirmed.

Why not weld another actuator arm mount point to the top of the pivot arm?

 

Use a cotter pin to secure.

 

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Think simpler, just drill another hole and reuse the c clip. Personally I would port it and mod the arm for more throw just in case. The waste gate just flaps around on its own no pressure to speak of, so moving the arm should be fine as long as it doesn't affect the angle of the actuator arm too much. If anything a port and arm mod will mean you underboost.

 

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I would guess once the wastegate puck gets to certain point that there are diminishing returns of opening it further in terms of air flow through the port. You're not going to be able to get the wastegate puck completely out of the way. I would focus my effort on porting 1st.

I would guess once the wastegate puck gets to certain point that there are diminishing returns of opening it further in terms of air flow through the port. You're not going to be able to get the wastegate puck completely out of the way. I would focus my effort on porting 1st.

I would agree, here are some closeups of how far it opens before interference from the housing and how far I think would be about the beginning of diminishing returns. And you can see there is room to drill another hole and then you can probably bend the bracket on the actuator to accomodate the angle change.

 

 

 

 

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In either of those positions, does any part of the wastegate poke out past the plane of the DP mounting face? If so, a little clearance grinding around the wastegate port on the DP may not be a bad idea- all the external modifications in the world won't matter if the flapper hits the DP flange and can't open.

I would be concerned with binding with another hole that close to the pivot point.

I would be concerned with binding with another hole that close to the pivot point.

 

This. A second hole would be too close. As I suggested originally, I would recommend taking a millimeter or two out of the middle of the arm and welding it back together. In fact, the thickness of a cutoff wheel would be perfect.

You could also heat it up cherry red with a torch and put an offset bend in it to clear the flange. More clearance, and it'll effectively shorten the arm, too.

Wouldn't we need an actuator that has a little bit longer range of motion? To open the flapper more, wouldn't the arm need to move further? Longer doesn't do you any good with the same location, because then it may not shut all the way. The VF-46 on my bench needs to extend the arm to open the flapper, I'm not seeing how shorter would be better.

 

(Maybe it's been a long day and I'm not firing on all cylinders...)

Edited February 23, 2017 by Infosecdad

Lengthening the actuator arm travel or shortening the flapper arm will both do the same thing with the other variable held constant, it's just easier to tweak the flapper arm in this situation unless you were to completely replace the actuator.

Ah, I was a bit out of it. You are talking about shortening the flapper arm, I was thinking you were talking about shortening the actuator arm and it didn't make any sense to me. Now I see why :-D

In either of those positions, does any part of the wastegate poke out past the plane of the DP mounting face? If so, a little clearance grinding around the wastegate port on the DP may not be a bad idea- all the external modifications in the world won't matter if the flapper hits the DP flange and can't open.

The roughly 40 degree open position is where the flapper starts protruding, but the divorced pipe will allow this. Idk about the stocker, but I would guess not. I can dig it out of the shed tomorrow and look for sure.

 

I am certain you could make it work with a second hole, the actuator is already at an angle...I should have taken pics with the actuator still attached, lol. Also the second hole could overlap with the first kind of like a peanut so it's not too far forward and shouldn't bind.

 

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Edited February 23, 2017 by FLlegacy

I will mock it up in the AM before shipping out the housing so you can all see what kind of clearances we are looking at on the actuator arm and housing.

I would agree, here are some closeups of how far it opens before interference from the housing and how far I think would be about the beginning of diminishing returns. And you can see there is room to drill another hole and then you can probably bend the bracket on the actuator to accomodate the angle

 

Would it be possible for you to reassemble the actuator and rod, then put a bar of pressure on it to see what the opening angle actually is?

 

It's been mentioned that there are diminishing returns on opening the flapper further. Beyond a given angle it won't flow any more. Would be nice to know however if the angle is very small and thus restrictive.

 

Kamak / Kinugawa billet actuators are junk. Unreliable, sticky, short-lived junk.

Edited February 23, 2017 by fahr_side

So, English now thinks that there's no additional room available for the flapper to open more before it hits the downpipe. It sounds like they have the turbo off and are fiddling with it, and going to port the wastegate area tomorrow. Here's hoping I have a car back by the end of the day.

Judging by the earlier pics, it does not look like there is much extra room in there. I know the invidia I have just has a flat plate of metal where the door is. No way for it to open more there. Please keep us informed. I would like to know your thoughts on the vf54. Edited February 23, 2017 by BBPeik

Would it be possible for you to reassemble the actuator and rod, then put a bar of pressure on it to see what the opening angle actually is?

 

It's been mentioned that there are diminishing returns on opening the flapper further. Beyond a given angle it won't flow any more. Would be nice to know however if the angle is very small and thus restrictive.

 

Kamak / Kinugawa billet actuators are junk. Unreliable, sticky, short-lived junk.

Wastegate opening video.

 

 

My idea is to drill another hole or two to overlap the first and add more throw, although it may be insignificant. And the heat the actuator rod and bend it slightly toward the new hole.

 

How I would drill the holes and where I can see will need clearancing, and don't forget somehow you have to adjust the mounting of the actuator to line up with the new hole on the arm.

 

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Edited February 23, 2017 by FLlegacy

Wastegate opening video.

 

 

 

My idea is to drill another hole or two to overlap the first and add more throw, although it may be insignificant. And the heat the actuator rod and bend it slightly toward the new hole.

 

How I would drill the holes and where I can see will need clearancing, and don't forget somehow you have to adjust the mounting of the actuator to line up with the new hole on the arm.

 

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Good work!

 

Note however that shortening that lever reduces it's, er, leverage. Lower mechanical advantage means the spring becomes effectively weaker, so you will need to retune and you may have slightly slower spool. Shouldn't worry the stock turbo too much but the guys tuned to 20psi+ peak might find they don't hit that anymore as the pre-turbo gas pressure will find it easier to push the flapper open.

 

And good on you for organizing the group port-a-thon.

Good work!

 

Note however that shortening that lever reduces it's, er, leverage. Lower mechanical advantage means the spring becomes effectively weaker, so you will need to retune and you may have slightly slower spool. Shouldn't worry the stock turbo too much but the guys tuned to 20psi+ peak might find they don't hit that anymore as the pre-turbo gas pressure will find it easier to push the flapper open.

 

And good on you for organizing the group port-a-thon.

I am assuming that is a matter of adjusting the duty cycle?

 

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