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Discussion Starter #1 (Edited)
Turbo Mani: HMT-style 4-2-1 Top Mount
Wastegate: Tial V38/MVS 38mm
WG Merging into exhaust, before cat (no open dump)

Just wondering how/where to place the wastegate merge, back into the exhaust stream. I will be running a cat, so it'll have to dump back in before that. I realize a smooth merge (kind of like a 2-1 collector) is ideal, but how far from the turbo should the merge be? I've read some reports of moving it away from the turbine outlet will decrease turbulence and somewhat reduce spool time/increase power. But how far downstream of the turbo should it be placed? Can to merge be too far downstream?

What about the size of the wastegate merge? Should it be the same or slightly larger than the outlet port of the wastegate? Is this one of those things where you want to have it taper or slightly on the small side to keep gas velocity up, or?

Thanks.
 

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Optimally I'd not merge it back into the exhaust system. Run a separate pipe beside the DP and route it back past the firewall. Open to atmosphere. Whenever the WG will open will be at least when you are boosting and going at a decent speed. So I'd doubt there'd be an issue with fumes in the cabin. Perhaps a turn-down at the end of the pipe?
 

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Yah don't merge it. You'd be more likely to have boost control problems.
 

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As far as emissions are concerned the presence of the turbo doesn't have to matter if you were just pansy driving it like every day.

The argument of set ups with internal waste gates comes into play.
But Bob has experience to back up his statement.
For t25 style housings it's nice to have the option of running open dump.
 

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Discussion Starter #6
Optimally I'd not merge it back into the exhaust system. Run a separate pipe beside the DP and route it back past the firewall. Open to atmosphere. Whenever the WG will open will be at least when you are boosting and going at a decent speed. So I'd doubt there'd be an issue with fumes in the cabin. Perhaps a turn-down at the end of the pipe?
I'm keeping the wastegate merged for environmental and legal reasons.

Thus why I'm asking what the best way to do teh wastegate piping.
 

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I'm keeping the wastegate merged for environmental and legal reasons.

Thus why I'm asking what the best way to do teh wastegate piping.
The world doesn't mind that you're boosted, while you're at it you should get rid of that cat, its a turbo hater.
 

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Dont listen to these guys, yes it will have some small negatiove impact on power, but if you do it right it wont effect boost control at all.

The best thing to do is to merge it in on a bend in the DP/exhaust, basically route it in on the outside radius of the bend. This will be the best possible solution for flow.
If its impossible to do it that way youre second best option is to just have it enter at a very shallow angle
 

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I believe rule of thumb is min 15" downstream. Crappy old picture and ignore the oil leak but this is where I have mine. Cheap crush bent crap from autozone.

 

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I'm keeping the wastegate merged for environmental and legal reasons.

Thus why I'm asking what the best way to do teh wastegate piping.

not being an asshole but if your worried about the environment and legal system then i woould just buy a honda fit or toyota prius and drive like a grandma..... your turboing your car your gonna create the same pollution(imho) if you run an open dump tube or if you merge it.... but hey this is my .02
 

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I believe rule of thumb is min 15" downstream. Crappy old picture and ignore the oil leak but this is where I have mine. Cheap crush bent crap from autozone.

I think you have an oil leak. :smartass:
 

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not being an asshole but if your worried about the environment and legal system then i woould just buy a honda fit or toyota prius and drive like a grandma..... your turboing your car your gonna create the same pollution(imho) if you run an open dump tube or if you merge it.... but hey this is my .02
Who gives a shit? Maybe he doesnt want it to sound like an airplane when the wastegate opens?
 

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It doesn't sound like an airplane. At least it didn't on my car. I ran open dump for a week and when the wg kicked in it sounded more like a pissed off Snapper mower. Sounded like poopoo haha.
 

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Yah it wouldnt be so bad is a piston WG would actually not open until full boost, but it doesnt, they usually start cracking at about half spring pressure, and thats when loudness comes.
 

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It doesn't sound like an airplane. At least it didn't on my car. I ran open dump for a week and when the wg kicked in it sounded more like a pissed off Snapper mower. Sounded like poopoo haha.
Lol
 

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for a street car I'd route it back in for sure.

try to make a smooth merge when routing it back in, like everyone says

Here is what mine looked like
This is a little odd to say the least...
 
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