Nameless Downpipe: Official 5th Gen GT Install Thread

[GTEASER]

Its almost like the wastegate pipe needs to be lower in the flange.

[Starks]

That's exactly it! I know what to do. The Australian member who posted about his install has the right idea. That covered all bases!

 

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[FLlegacy]

The problem with that theory is the flow of the exhaust gases is fast and hard the opening of the waste gate only matters as much as it is actually restricting the flow through it.

 

As fahr-side has pointed out before, the exhaust flow has to make a turn to go out the waste gate.

 

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[Infosecdad]

There is a "vacuum" from the main exhaust, right? That should help pull the gases through at the sharp angle. Not as good as a physical barrier, but there should definitely be a good draw.

[jertfunk]

From Nameless

 

 

 

Install was a breeze and took them about an hour and a half. There were no install issues and no flapper issue.

 

 

 

 

 

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Edited March 4, 2017 by jertfunk

[dgoodhue]

There is a "vacuum" from the main exhaust, right? That should help pull the gases through at the sharp angle. Not as good as a physical barrier, but there should definitely be a good draw.

 

Their could be a vacuum created from the exhaust flow of the air through the exhaust housing.

 

The exhaust pressure going into the turbo from the exhaust manifolds is probably around 35-45psi at full boost, so the wastegate port isn't going to be much different than that. Wastegate pressure should significantly higher than the pressure that exists in the down pipe, even if isn't in a vacuum.

[dgoodhue]

Its almost like the wastegate pipe needs to be lower in the flange.

 

If the wastegate puck is centered on the tube it might restrict the air flow going through it more than the way it currently is. The restriction might actual help the boost control issue though.....

[FLlegacy]

If you attach your actuator you will see how little the wastegate actually opens, so I'm not surprised there wasn't an issue with installation.

 

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[Starks]

If the wastegate puck is centered on the tube it might restrict the air flow going through it more than the way it currently is. The restriction might actual help the boost control issue though.....

Wait, I'm not following this. In its current capacity if the flapper was able to open 100%, it can't with this dp. Impossible. The restriction is creating back pressure at the moment. Though minimal, I think we can agree that the angle isn't desirable. It'd be best to be open completely with no resistance for waste gate gasses.

 

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[fahr_side]

There will be a point where opening the flapper further will not increase flow at all. That point will be much less than full 90* open. I'm sure that Nameless realized the flange would be in the way if the flapper could open further but since it can't without changing the actuator, didn't think it worthwhile to make more room for that.

 

If the wastegate dump pipe were exactly concentric with the port that would actually make for the most convoluted pathway for the gas to escape through when you consider the flapper is shrouding the port. Offsetting the dump from the port actually makes for less turns after bending around the flapper.

[BBPeik]

I imagine that Subaru limited the flapper to the angle they did for a couple reasons. One even with the factory DP if it opens much further the flapper will begin to hit things. Second, by having the door open at the angle it does it directs the wg flow towards the exhaust. More than likely the flow of the exhaust helps to pull the wg gasses out of the wg passage. Kinda like how Nascar runs exhaust in front of the back wheel. The pressure differential from the tire causes a vacuum and helps pull the exhaust out. Granted ours is not a perfect design, but I am sure Subaru did quite a bit of engineering when they adapted the vf54 to our manifold, one mind you that was a totally new design for them. Crazy I know, equal length headers, lol. We know for a fact that porting seems to work. It is not optimal or easy, but it works without fault when done properly.

Slightly ranty post over, sorry:soap_box:

[Starks]

I see now. So just to confirm we're grinding down the red marked areas right?

 

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[dgoodhue]

I imagine that Subaru limited the flapper to the angle they did for a couple reasons. One even with the factory DP if it opens much further the flapper will begin to hit things.

 

I have never seen a wastegate flapper open that much in the few turbo application I have looked at in some detail.

 

If you thinking of putting you thumb over a water hose. If crack it open slightly you are limiting the water flow, but the difference between lifting your thumb 1/2" and 3/4", the water flow limitation is likely minimal, I think that is what is happens with a wastegate flapper as well.

[dgoodhue]

Wait, I'm not following this.

 

My logic is using the stock wastegate's range of motion.

[dgoodhue]

I would be porting it here and bell mouthing the upper edge of the entry to the watergate port. You could port a little bit of where you marked, but to make more of a ramp to direct the air into the watergate port. You don't want to remove too much material where you marked because it will likely just increase air flow past the waste gate port.

 

Obviously I don't have a turbo Legacy, but my truck has the same issue of removing back pressure causes the stock turbo to overboost, because the wastegate port can not flow enough air to bypass the turbine (exhaust blades of the turbo). Porting the turbo exhaust housing to scoop air into the wastegate port was a way to help the overboost issue. I ported my exhaust housing in this manner.

Edited March 4, 2017 by dgoodhue

[FLlegacy]

I see now. So just to confirm we're grinding down the red marked areas right?

 

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Best way to figure out where to port by my reckoning is to hold the wastegate as open as it goes and look through it to see what can be removed to make the escape bigger, smoother, straighter. If you aren't sure look through this thread at the pics from those who have ported it. That is a better reference.

 

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[fahr_side]

 

 

 

Could you tell us how close the wastegate flapper comes to the dump pipe flange at full open? Just wondering if there's room inside the housing to open the flapper any further with a different actuator. I have a turbo here but it doesn't have an actuator. If you hold the actuator in that position and hold a ruler across the flange we can see how much further it could possibly open. TIA.

 

Lets look at the upside of it all. We have a DP that can provide non stop boost for high power levels. Just need to complement everything around it since it cant be controlled easily.

Or you can install and support an 18G turbo which loves running 18psi all the way to redline.

There is a "vacuum" from the main exhaust, right? That should help pull the gases through at the sharp angle. Not as good as a physical barrier, but there should definitely be a good draw.

I doubt it. The gas that came out the cat has been slowed by both the turbine and the cat, so it has less velocity than the gas coming out the wastegate. Therefore it isn't going to create that sort of carburetor effect and pull gas out of the wastegate. The wastegated gas is having to push it's way into the main exhaust stream at an angle.

Their could be a vacuum created from the exhaust flow of the air through the exhaust housing.

 

The exhaust pressure going into the turbo from the exhaust manifolds is probably around 35-45psi at full boost, so the wastegate port isn't going to be much different than that. Wastegate pressure should significantly higher than the pressure that exists in the down pipe, even if isn't in a vacuum.

Peak EGBP should be in the range of 1.5 to 2x MRP, but yes the pressure pre-turbine is much higher than post, which is closer to atomospheric.

I imagine that Subaru limited the flapper to the angle they did for a couple reasons. One even with the factory DP if it opens much further the flapper will begin to hit things.

I'm thinking much further and it will hit the stock dump pipe flange which is just a big flat plate with one hole in it. Would be nice to have this data though, and I'm sure FLlegacy will be forthcoming

Second, by having the door open at the angle it does it directs the wg flow towards the exhaust. More than likely the flow of the exhaust helps to pull the wg gasses out of the wg passage.

Yes the flapper will direct gas toward the flow coming out the turbine but gases at different temperatures and pressures are then fighting to get out through that one round hole in line with the turbine.

I am sure Subaru did quite a bit of engineering when they adapted the vf54 to our manifold, one mind you that was a totally new design for them. Crazy I know, equal length headers, lol.

Well, as I know it there was a twin-scroll turbo available on the 2.0L models for Japan, hence the divided header. The flange shape is unique to this car so it's not like the header was adapted to the turbo, they were developed together. IHI did not just have this laying around for Subaru to pick up. OTOH, notice stock cars do not have boost creep. Subaru build these cars to be driven and disposed of, not to be modified.

We know for a fact that porting seems to work. It is not optimal or easy, but it works without fault when done properly.

Depends. I have one customer here with our 18G turbo, ported by myself. He has an active exhaust that's 3" and straight-thru to the tips with the butterfly valves open. He wanted to have independent boost targets for different Si-Drive modes. With the valves open we can hold him at 18psi at redline but only just, maybe down to 5% WGDC at that point. With the valves closed it comes right down to 14psi on command. So he has to drive the car with the valves closed in S mode to hold him to the 14psi target. With them open he's straight up to 18psi again and boost targets be damned. Too bad there's no easy way to tie the valve operation to the Si-Drive setting.

 

I would be porting it here and bell mouthing the upper edge of the entry to the watergate port. You could port a little bit of where you marked, but to make more of a ramp to direct the air into the watergate port. You don't want to remove too much material where you marked because it will likely just increase air flow past the waste gate port.

 

Obviously I don't have a turbo Legacy, but my truck has the same issue of removing back pressure causes the stock turbo to overboost, because the wastegate port can not flow enough air to bypass the turbine (exhaust blades of the turbo). Porting the turbo exhaust housing to scoop air into the wastegate port was a way to help the overboost issue. I ported my exhaust housing in this manner.

 

Please have a look at the earlier post I made with tips on porting the VF-54. http://legacygt.com/forums/showpost.php?p=5471980&postcount=915

I should be doing another in a few weeks so I'll try to make some video for you guys then. I am sure that adding a bellmouth to Nameless' downpipe as Ellesdil did will be of benefit. That will let the gas flow more evenly around the flapper and more easily into the dump tube. Of course no-one should have to modify a properly developed part like this in order to make it function as-advertised.

http://legacygt.com/forums/attachment.php?attachmentid=245291&stc=1&thumb=1&d=1487714017

 

This Tial part below in my mind is how you do a dump from an internal wastegate. The flapper opens with no restriction into a larger chamber, the only sharp turn the gas makes is from the turbine throat into the port, and then it can flow cleanly past the flapper at almost all angles. The large chamber formed around the wastegate port reduces turbulence, again by not letting the wastegate and turbine flows interfere with each other. Wastegate flow is smoothly directed in the same axis as the flow out the turbine and only then allowed to mix concentrically and into a larger dump pipe, meaning there's no increase in pressure from mixing the two flows. There's no fighting for space in the dump tube and associated turbulence or restriction. Yes, it would be possible to design all these features into a dump pipe and not touch the turbo itself.

 

http://cdn3.volusion.com/quvpr.powmx/v/vspfiles/photos/TURGT996TT-5.jpg

 

http://ep.yimg.com/ca/I/titanmotorsports_2269_720177867

 

While the performance of these turbos didn't match the hype, being a bit small for the application, boost control was buttery smooth.

Edited March 4, 2017 by fahr_side

[BBPeik]

As always,

Thanks a ton fahr_side

[Ellesedil]

I am sure that adding a bellmouth to Nameless' downpipe as Ellesdil did will be of benefit. That will let the gas flow more evenly around the flapper and more easily into the dump tube. Of course no-one should have to modify a properly developed part like this in order to make it function as-advertised.

http://legacygt.com/forums/attachment.php?attachmentid=245291&stc=1&thumb=1&d=1487714017

 

The only thing I want to mention right now is that there was no apparent difference in boost after the downpipe was modified. So, if this modification of the downpipe does help, it must be, in my mind, in conjuction with some other modification or entails a slightly different approach for determining where to remove this material.

[fahr_side]

The only thing I want to mention right now is that there was no apparent difference in boost after the downpipe was modified. So, if this modification of the downpipe does help, it must be, in my mind, in conjuction with some other modification or entails a slightly different approach for determining where to remove this material.

I think you've done the best you could with what you have to work with. Perhaps if that mod allows the flapper to open further, with a longer-stroke actuator, or perhaps in conjunction with porting the housing, maybe that will do it.

 

I am checking with my guys here if it's possible to fit a larger flapper to the stock arm, which would allow the port to be bored larger. My fear with that approach is that increasing the area of the flapper also increases the force applied to it via exhaust pressure in the header, which may then require a stiffer actuator.

[FLlegacy]

Unfortunately, Fahr-side my turbo housing is now in the hands of Starks. I am sure he will keep us updated on his progress.

 

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[Ellesedil]

Ok, now that I have my car, I'm going to quickly recap my experience.

 

English Racing installs the Nameless TBE with 5" mufflers and the Nameless BPV. My car, exactly like Ryan's, boosts to 20 PSI. Thus begins the attempt to try to get that under control.

 

1. Idea of the flapper not opening enough is floated almost immediately, but no action is taken
   
2. First attempt is to modify the downpipe to have more of a bellmouth entrance into the wastegate dump pipe - fahr_side has covered that well enough. This resulted in no change on the dyno.
   
3. Port the turbo - this was the only thing that I was actually unhappy about. As we've covered here, English decided to enlarge the wastegate port a bit while rounding off the edge all around the port, and also remove some material in the passage way which would appear to not do anything at best. While I sent them the porting information we have here, they either didn't read it or ignored it. Porting resulted in a 1 PSI increase of boost - the opposite of what we wanted
   
4. It's noted here that the flapper doesn't have much room to open anyway without contacting the downpipe, so how far it opens is moot in terms of a "what to do about it now" context
   
5. The next idea is that since the flapper can only open so far and that the wastegate dump pipe is only so large, the flapper is blocking the path of air to the wastegate dump pipe and there's not much room for air to flow around the flapper. The suggestion, on a Friday, is to remove the seperation between the wastegate dump and the main exhaust to allow more space for air to flow around the flapper.
   
6. Everyone thinks about it over the weekend and we end up pulling the ripcord on this experiment. Besides, instead of hacking up a part like this, there are others available that are already designed this way that we could simply go with. So, what we end up doing is re-install the OEM BPV. Boost is lower, but now it is inconsistent.
   
7. Suggestion is to install a Grimspeed EBCS. The EBCS is installed and boost control is effective again. My final peak numbers are 275 WHP at about 6000 RPM, 325.22 WTQ around 4000 RPM, and a max boost of 16.41 PSI at around 4200 RPM.
   

 

I unfortunately don't have a pre-install dyno plot for comparison. Some of these final numbers seem a tad low to me. For instance, I was expecting peak boost to be closer to 18 PSI than 16 given the exhaust + BPV consistently lived in the 20+ PSI range. The car definitely accelerates differently now than it did when on the stage 1 OTS tune, and not just in a "it's faster" sense. It behaves a bit differently, with the power seeming to come on later compared to stage 1.

 

I've attached the dyno plot. The tune more or less levels-off power from 4000 RPM (where we peak on torque) to redline with only gradual changes.

 

I do have some unmodified logs and a dyno plot comparison when my car was experiencing boost control issues with the OEM BPV reinstalled. While I can attach them, I'm not sure how useful they are for situations outside of the one I found myself in. I did ask for the log of my final dyno run, but I've yet to receive it.

Edited March 8, 2017 by Ellesedil

[Starks]

Man, that sounds like a headache but I bet you're glad it's over and resolved.

 

Are you planning on doing anymore HP mods in the future or is this the end of it?

 

If you could get your hands on another hotside to correct the port would you go that far?

 

Any ideas as to why the English tune feels less torque in the lower rpms than the ots?

 

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[FLlegacy]

The ots tune hits boost pretty abruptly compared to custom I would guess that is the reason for the discrepancy. The custom tune does bring power on smoother and more linearly.

 

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[GTEASER]

I like the jolt of full boost power at 3000-3500 rpms. Maybe this Stage2 thing is not for me. That's another dyno graph with peak torque after 4000.