Thread: SR20 Turbo 02 Housing R&D

i was hoping some this this week because i'm slapping it on next week. i'll just wait till i save up and get the evo manifold for a different car

What is the size of the initial turbine outlet pipe? 2.5"? Do you plan to make a version that goes strait to 3" for those of us using an external wastegate? or perhaps a full single piece downpipe version?

For these scenarios, people should keep in mind that most aftermarket downpipes (such as VRS) are 2.5" or 2.25" at the 3 bolt flange and quickly flare to 3" after the flange, so modifying the existing downpipe or making a single piece dp would be ideal.

Flange shipment is scheduled to arrive on Tuesday. I could have one built by the end of Wednesday at the earliest.



The initial dia. is 2.25 in. This was the only way to bend to the stock location flange while keeping a decent radius. It then transitions to 2.5 in. at the 3 bolt flange...which is the thick version of the standard 2.5 in. 3 bolt flange. The dump tube dia. is 1.5 in.

I do plan on a 3.0 in. right off the turbine, but it will be a "bellmouth" design instead of the divorce waste gate style. This also will require our down pipe which is also in the works. I do not think a 3.0 in. down pipe that terminates at the stock location will be offered...its possible but would be $.

I have to respectfully disagree with you there. Getting the wastegate flow separate from the main exhaust flow is possibly even more important when you're recirculating. Unless you're not doing a divorced setup.In which case, carry on.


Best of luck to you in this endeavor. You've picked a hard component to make, but the reward should be worth it.

I've read the rest of the thread now and I see you're getting there quite well. The turbo outlet is 2.25" and that is obviously where you have to start. Going any bigger right away is impossible for a few reasons, mainly because the hardware gets in the way. Then you want to get up to 2.5" at some point which I see you've done.

The cheater bend is what's really killing me. Obviously this thing is leaps and bounds above the stock piece, and if that's how it has to stay then that's fine. I'll still recommend it. It looks great.
However, what radius do you have for the 2.25" pipe piece and for the 2.5" pipe piece? I would almost guarantee that a tighter radius that limits that "cheater bend" (if you're following me) would flow better than a shallow radius with that abrupt bottleneck.
They make doughnut shaped metal bends for this exact purpose that have smooth internal shape but much sharper radius than what can be done with a mandrel bender.
Have you looked into those? Are you using that already?

As someone who's made a few of these divorced downpipes now and considered production I'm quite intrigued with your product. I'm sure you've found out by now the myriad of (often opposing) design criteria you have to take into account when designing this thing. Probably more than you expected when you started.

I'm rooting for you!

I'm not seeing how you'd have any issues with leaks? Yah, there could be leaks with both the recirc and dump designs, but who cares? So what if a bit of the main exhaust leaves out of the dump pipe while the wastegate is closed? You know?

javier you have a pm.

CLR (center line radius) on the 90 bends used are 1D, which means it is 1 X tube diameter...the 2.25 bend has a 2.25 CLR. CLR on the donuts is 1D as well...you would end up with the same exact angles/bends if you used a donut. Tighter radii require "pie" or "miter" cuts on tubing. If you know someone with a die set that is sub 1D, let me know

On a daily driven street car, an exhaust leak at idle or at cruise would drive me nuts lol!

I wish the SR turbine housings were made like the EVOs...screamer pipes would be so much easier to fab Here's an EVO VIII housing for example. The divider is built right in. Weld on a couple of tubes, surface the flange, and bam your screamer pipe is done. Using a tube as a divider works just as well, it's just more time consuming and the potential for exhaust leaks is greater.



***EDIT***
Screamer pipes on the SR20 Evolved Manifold will be a very affordable option

thanks for the clarification