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Old 08-14-2018, 10:08 PM   #1
Tfrasca
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Default External wastegate on housing options

So, I know that putting an external wastegate directly on the turbine works, but I am trying to figure out exactly where to put it. This would be my first choice, for packaging and downpipe making:



My gut tells me this is less than ideal, since it leaves 180 degrees of the turbine with a full exhaust flow. Also, the hole would have to be smaller in that location, because the area for the exhaust in the housing has tapered so much by then. This seems like it would be a better option, but I like it less for packaging reasons:



Anyone have any educated guesses on whether it even makes a difference? Or if I'm even correctly thinking about the way exhaust travels through a turbine?
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Old 08-14-2018, 10:14 PM   #2
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Either one of those is sub-ideal...you will be seriously disrupting flow from the housing into the wheel. You are correct that the WG in the top position will still allow about half of the turbine to get full flow, making your wastegate effectively much smaller than it physically is.

Most internally wastegated housings place the port as close as possible to the inlet flange, in the "entrance section" between the inlet and the start of the volute (scroll) which is demarcated by the tongue (at 6:00 in your setup).

It looks like you could get away with a short adapter piece between the manifold and turbine housing, with the wastegate down below and maybe angled back a bit. If you're married to using the stock Volvo manifold then I'd suggest something like that, without cutting into the turbine housing.
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Old 08-14-2018, 10:26 PM   #3
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I just had a thread about those adapters that go between turbo and manifold. Since you don't seem to have a 240, that would be an option... though you didn't mention if there was some reason you were intending to go on the turbine housing vs the exhaust system or whatever...

Is there some logic to your logic?
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Old 08-14-2018, 10:35 PM   #4
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Either one of those is sub-ideal...you will be seriously disrupting flow from the housing into the wheel. You are correct that the WG in the top position will still allow about half of the turbine to get full flow, making your wastegate effectively much smaller than it physically is.

Most internally wastegated housings place the port as close as possible to the inlet flange, in the "entrance section" between the inlet and the start of the volute (scroll) which is demarcated by the tongue (at 6:00 in your setup).

It looks like you could get away with a short adapter piece between the manifold and turbine housing, with the wastegate down below and maybe angled back a bit. If you're married to using the stock Volvo manifold then I'd suggest something like that, without cutting into the turbine housing.
Yeah, I wanted to put it below, where the scroll starts, but there's no room. I was under the impression that those manifold to housing adapters were bad for wastegate priority because they're at 90 degrees to the exhaust.
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Old 08-14-2018, 10:41 PM   #5
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Originally Posted by EivlEvo View Post
I just had a thread about those adapters that go between turbo and manifold. Since you don't seem to have a 240, that would be an option... though you didn't mention if there was some reason you were intending to go on the turbine housing vs the exhaust system or whatever...

Is there some logic to your logic?
I've been looking at those adapters, but I have heard mostly bad things about boost creep with the wastegate at 90 degrees to exhaust flow like that. My logic for putting it in the housing is because it's compact, and people seem to have success with that. Lots of companies offer housings with external provisions cast into them already.

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Old 08-15-2018, 01:41 AM   #6
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Yeah, I wanted to put it below, where the scroll starts, but there's no room. I was under the impression that those manifold to housing adapters were bad for wastegate priority because they're at 90 degrees to the exhaust.
You could make a y pipe that mounts to the volvo manifold and splits between the turbo and wastegate. It could angle the turbo up a bit for more room.
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Old 08-15-2018, 02:29 AM   #7
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You could make a y pipe that mounts to the volvo manifold and splits between the turbo and wastegate. It could angle the turbo up a bit for more room.
Maybe. It'll still be super tight unless I put the wastegate on the housing. But angling it up might give me more room to put it on the better part of the housing.

But seeing how many aftermarket housings are available with cast in wastegate ports exactly where I want to put mine makes me think it'll be good enough.
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Old 08-15-2018, 09:48 AM   #8
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Yeah, I wanted to put it below, where the scroll starts, but there's no room. I was under the impression that those manifold to housing adapters were bad for wastegate priority because they're at 90 degrees to the exhaust.
Wouldn't it going on the housing also be 90* to the exhaust flow?

I see what you're getting at though and I'm not sure I have much to offer in the way of advice. I for the life of me can't wrap my head around how using that adapter would be any different than just putting it on the manifold or on the turbine housing or...

We could have a case of everyone trying to just cheap out on welding stuff and thus cheaping out on WG or more likely... not actually understanding how a wastegate is actually supposed to be sized?
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Old 08-15-2018, 09:50 AM   #9
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Further thought... Have you considered just running the NA manifold and going J-Pipe style?
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Old 08-15-2018, 10:41 AM   #10
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Originally Posted by EivlEvo View Post
Wouldn't it going on the housing also be 90* to the exhaust flow?

I see what you're getting at though and I'm not sure I have much to offer in the way of advice. I for the life of me can't wrap my head around how using that adapter would be any different than just putting it on the manifold or on the turbine housing or...

We could have a case of everyone trying to just cheap out on welding stuff and thus cheaping out on WG or more likely... not actually understanding how a wastegate is actually supposed to be sized?
Well, if I put it on the housing, I'd try to angle it to "catch" the exhaust flow a bit. Something similar to this:



That said, even if it's just sitting on the housing at 90 degrees, it seems like it'd work better because of the higher pressure in the turbine housing compared to the manifold. I honestly have no idea if that's even the case, but it makes sense to me. Really, I have no way of testing all of this, so I'm going off of what has worked for others. I've seen several other forum guys saying that they had boost control issues until they put the wastegate on the housing.

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Further thought... Have you considered just running the NA manifold and going J-Pipe style?
I don't know exactly what the NA manifold looks like, but I seem to remember a j-pipe placing the turbo too high and too far forward for my setup.
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Old 08-15-2018, 11:49 AM   #11
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Interesting. I had just never considered this whole concept before.

This is probably the best picture... I suspect you could easily get the turbo in a reasonable position though.



Just food for thought at least.
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Old 08-15-2018, 11:51 AM   #12
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Addendum. I'm betting that particular photo comes UP and FORWARD to that extent because it's 240 and the lateral space is quite limited.
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Old 08-15-2018, 12:40 PM   #13
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If I have to go through that much work, I think I'll try to build a whole manifold exactly how I want it. The reason I wanted to keep the Volvo one is so the turbo stays nice and tight to the block, and because that would mean less changing all the other stuff (downpipe, intake tubing, etc.).

I'm doing another old car rally on September 14th, and I was going to try to bust this out before then. Now I'm realizing that it's going to be too complicated, so I'll wait until after the rally. That will allow me to change my mind 20 or 30 more times.
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Old 08-15-2018, 01:00 PM   #14
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This is the best pic I could find of what I think would work best in your situation (but imagine the correct flange on both sides):



All of the other T3-T3 wastegate adapters I could find had the WG inlet at 90 degrees to exhaust flow. The gentler the angle the less restrictive your wastegate inlet will be. With a 90 deg tube it makes the wastegate effectively smaller than the physical valve diameter. So a 44mm might only flow as much as a 38mm, as an example. It's pretty much the same situation as an intake port leading up to the intake valve.

Placing the wastegate on the turbine housing scroll past the tongue is going to do all kinds of nasty things to the turbine wheel inflow and will affect performance. Kind of like cutting off one leg of a cyclist and asking him to pedal just as fast as before. It may work in some situations, sure... might make a wastegate that was sized too large behave more like it should, but at the expense of causing higher exhaust backpressure (pre-turbine) which reduces engine VE, and increasing lag.
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Old 08-15-2018, 01:12 PM   #15
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Tyler, piggybacking on our conversation from earlier, I think a modified version of the solution I showed you may be a good option; putting the gate inlet on the turbine housing, right next to the T3 flange at the bottom side. You could simply add a 180 degree section of tube that hugs the turbine housing and puts the gate assembly close to position 1. It would be less bulky than the adapter that Chris showed while putting the gate inlet in a more optimal position.
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Old 08-15-2018, 01:32 PM   #16
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I wanted to avoid any tubing longer than an inch or two before the wastegate, but looking at some other common setups, it seems like maybe that concern is unwarranted.

If the extra tubing isn't a big deal, I think I'd want to do exactly what you're saying. Keep the hole in the housing close to the flange, before the scroll part of the housing, and run a pipe to mount the wastegate next to the turbo. Then we could also add a little bracket over to one of the housing bolts to help it not crack.

Chris, if Harald's idea doesn't work, something like what you linked might. A t3 to t3 90 degree (or a bit less) could work, with a Y off the 90 degree part. I would have to take some more measurements, though, because that puts things pretty close to the hood, since my engine is upright.
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Old 08-15-2018, 01:40 PM   #17
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I actually wish I had done that. getting under the car and squeezing myself in between the manifold and downpipe is less than ideal.
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Old 08-15-2018, 01:47 PM   #18
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I think the real solution here is to raise the boost, max out the turbo and not use a wastegate.
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Old 08-15-2018, 01:55 PM   #19
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The realest solution is to use a variable geometry housing
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Old 08-15-2018, 02:04 PM   #20
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Crush it.
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Old 08-15-2018, 02:05 PM   #21
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Whatever happens in here though... someone should follow up because I'm interested.

I need to get my angled 19T downpipe in 240 pics up but I'm so embarrassed about the welds it might not be worth the flaming lol.
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Old 08-15-2018, 04:16 PM   #22
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Originally Posted by Harlard View Post
Tyler, piggybacking on our conversation from earlier, I think a modified version of the solution I showed you may be a good option; putting the gate inlet on the turbine housing, right next to the T3 flange at the bottom side. You could simply add a 180 degree section of tube that hugs the turbine housing and puts the gate assembly close to position 1. It would be less bulky than the adapter that Chris showed while putting the gate inlet in a more optimal position.
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If the extra tubing isn't a big deal, I think I'd want to do exactly what you're saying. Keep the hole in the housing close to the flange, before the scroll part of the housing, and run a pipe to mount the wastegate next to the turbo. Then we could also add a little bracket over to one of the housing bolts to help it not crack.
Yesss. This sounds like a good compromise. The power of TBcrowdsourcing exhaust design.

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Chris, if Harald's idea doesn't work, something like what you linked might. A t3 to t3 90 degree (or a bit less) could work, with a Y off the 90 degree part. I would have to take some more measurements, though, because that puts things pretty close to the hood, since my engine is upright.
That should work pretty well too. Would get close to approximating a full-on header with a Y after the collector with turbine and wastegate on either side of the Y. That shouldn't bias one or the other too much and provide good wastegate flow without sacrificing turbine inlet flow. If you're going to run super low boost on a big engine, it even makes sense to bias the wastegate with the collector going straight into it, and put the turbine on a 90 deg tube to the side. EDIT: with a gentle bend into the turbine, not a sharp 90 tee, of course.

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I think the real solution here is to raise the boost, max out the turbo and not use a wastegate.
YESSS. Free float all the redblocks.
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Old 08-15-2018, 11:06 PM   #23
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Yeah, I just looked at the housing and I think Harald's idea is going to work out well. I just ordered a mild steel 1.75" 180 degree bend with a 6" radius which should make the bend nicely.

Since the housing isn't stainless and is getting ceramic coated, I didn't think this pipe needed to be stainless. Does that seem like it'll weld ok? Should I be looking for some schedule 40-type pipe instead?
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Old 08-15-2018, 11:30 PM   #24
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I need to see a pic of this to comprehend it (unless I missed it here) it sounds like you guys had an "off forum" convo...

The type of welding and the filler will probably make or break this... I think going to SCH40 might make it easier for someone (like myself) that is out of practice, but if you can properly manage the fusion of the two different masses of metal should be fine...

There are others much more qualified to answer though. At this point I'm just talking for the sake of talking on the web.
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Old 08-16-2018, 01:18 AM   #25
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Use schedule pipe for sure, and even then hanging a gate off a long stretch of pipe is asking for failure. Pretty sure those small gate flanges accept 1 1/2 schedule pipe nicely. I've done a few turbine mounted gates and they all worked okay. I have done one similar to your first pic on a turbo v8 with a 50mm gate. Previous combos with normal gate mounting I can normally control boost to sub 5 psi, but that turbine mounted one wouldn't make any less than 12 pounds even with a 3 pound spring in the gate. Ones with the gate right after the flange worked great as expected.
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