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External wastegate on housing options

Tfrasca

Active member
Joined
Apr 20, 2015
Location
Ben Lomond, CA
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:

A4TcDAS.jpg


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:

ZjSaY4d.jpg


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?
 
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.
 
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?
 
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.
 
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.

images
 
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.
 
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.
 
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?
 
Further thought... Have you considered just running the NA manifold and going J-Pipe style?
 
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:

80-img_1713_1644af37fe64add7d1e914ca776bc948f973f590.png


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.

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.
 
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.

127794935.jpg


Just food for thought at least.
 
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.
 
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.
 
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):

suby_pedistal_2.jpeg


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.
 
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.
 
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.
 
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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