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S30 RB25DET T4 Twin Scroll Turbo Manifold Design


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Couldn't resist. Here's the waste gate concept. True twin scroll, 1 waste gate. I'm posting these pics to see if there would be any interest for the actual parts involved in making the waste gate connection. Testing the waters. Also, what do you guys think of the concept?

 

Thanks for your input so far and it's been a fun ride!

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I really like it! Much more cost effective for sure, good priority, true twin scroll. 

 

My only concern would be the size of the ting if there is room for it to reach down like that. I'd be curious to see how well everything flows. 

 

A little bit of murder might be taking place, but not nearly as much as before lol.

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Yeah, I will have to see how the shaft comes into play. I really hope I'm onto something here! Anyway, here's some progress. Still have parts coming in. I went ahead and decided on a different flange (pictured separately) so the transition to pipe will be smooth. Plus, it's only $65.

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13 minutes ago, Neverdone said:

Usually you put the expansion joints just aft of the exhaust header to help mitigate vibration through the really long pipe that it's connected to.

 

Where would you put them?

Would you please give me a link to a typical arrangement?

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The euro L28et manifold has them.

 

im no expert by any means, but isolsating the left 3 cylinder and the right (splitting flange in 2), and then putting something like the burns stainless double slip joint in the lowest portion of the big “U” for each side of the manifold.

 

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I could understand using these in certain situations where the material isn't rated for such high temperature intermittent duty cycles (cast high carbon steels). Is the purpose to reduce fatigue on the welds due to thermal growth? If so, I lean towards the bellows being on the down pipe, some flex piece on the turbo air outlet flange, and reducing vibration on the engine itself through dampening. Thoughts?

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Take my opinion with a grain of salt. I’d take Tim’s advice seriously though. From my internet research most people including Tim who have used an aftermarket tubular header, experience cracking. This isn’t seen much in 4 cylinder applications, but the straight 6 is does.  I don’t know Tim, but he is one of the few who have gone down the unknown path of high horsepower L series engines and I’m sure has a wealth of experience from failure.

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Hmm I've heard of the stock cast manifold bowing so maybe there is some merit, although my current cast stainless one seems to be holding up fine.

 

I thought the concern was with thin wall manifolds? I guess it depends how thick OP went with his manifold if it would be a concern, then it may need bellows and support stays from the flange. The newer manifold styles seem to have similar dip down then come up design on the turbo honda's and they seem to get by without any bellows on thick wall tube.

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  • 2 weeks later...

FYI, I did a test fit because I was worried about the steering column. As it turns out, I'm clearing it just fine but I'm getting close to the engine mounts (Whitehead performance). I had a small set back (unexpected expenses) and will not be able to have these fabricated for another month. But I will keep everyone posted as progress is made. 

 

Jeff

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A recurring problem with exhaust manifolds for this head is that as they heat up they grow longitudinally.  Since they're held captive on the head, this eventually results in warpage and/or cracked primaries.  As HuD 91gt pointed out, this is why the Euro manifolds have them (expected extended high speeds on the Autobahn).  For the manifold in this thread, a slip/expansion joint on each of the two runners running longitudinally after the 3-1 collectors and before the wastegate/turbo would help alleviate that.  I post about this pretty much every time one of these designs comes up and nobody ever listens 😜

Edited by TimZ
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I have very little exposure to RB heads so ^ his advice would be more sound.

 

I've seen even nice mazworks manifolds crack which I imagine quality would not be the culprit which points towards an expansion issue being the culprit. Adding some supports off the head flange to the turbo flange and adding some bellows or those fancy 3 way slip joints would be snazzy and show quite a bit of intelligent design.

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  • 6 months later...

Hey everybody, a quick update. I went ahead and BOUGHT my turbo manifold. See picture attached...I hope I'm not violating policy. I purchased the mani from Sinco Customs. I thought the single waste gate design was something never done before. Well, they do it. I think they're the only ones who do it the way I had designed it. I sent the owner my design and told him about the priority I had given the waste gate. I gave him my clearance dimensions and pictures of my setup. 

 

Honestly, I was lucky to come across Sinco. It was between them, 6Boost, and Future Fabrication. I couldn't beat Sinco's price. I got it in Stainless but not the burn finish.

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  • 1 month later...

Sorry for the lack of different angles. This manifold is legit! Clean welds inside and out! It's rather heavy as it's thick wall pipe. As I'm typing this, I can't remember if the piping is schedule 10 or 40, but really feels and looks like 40...I'm a piper by trade. 

 

My only problem I have is that I purchased a titanium stud bolt kit from real street performance and will end up needing to go with hex-head bolts on 4 of the bottom flange bolts as I can't get a wrench around the nuts that came with the stud bolts due to their length and clearance between the ends and the pipe. I guess I could cut the stud bolts shorter, what do ya'll think?

 

ps I have a different hose end fitting coming to get rid of that high point in my oil line.

pss See the model specific 240/260/280z forum about my laser scanning post. 

 

Thanks,

Jeff

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