compound turbine housing sizing

This is a question I cannot seem to get a good answer on, so I figured I'd throw it out there and hopefully someone with a lot more knowledge than me can help me on this.

Trying to determine what size exhaust housing for my atmospheric turbo setup on my 4bt.

The hx30 up top is a 6cm

But the bottom turbo is an s256. .70 AR T3
I am concerned that it is too small. Before I build all the parts for it, I want to be on the right path.
I was thinking I need something bigger, but I don't have many options.
I can get a 1.0 or a 1.12 or 1.22 in a t4
I also believe there is a .82 in a t3 and t4

What is the difference? I mean is it just the flange size since the turbine wheel is the same regardless or is there more to it?

I had an he341 under it before, and it was choking pretty bad with the 9cm housing.
Was debating an 12 or 14 hx35, but decided to go with the BW turbo as it flows more.

Any info on this would be greatly appreciated.

Thanks!

I dont know enough about compounds to help, but I have a 1.0 T3 housing for a s256. So if that ends up being something you might need, shoot me a PM.

Im sure someone will be able to help you out.

nobody has this tech down?

I can't help you size your housings but that AR number is basically a volume measure. A .7 housing is small a 1.0 is bigger. A bigger housing will flow more on the top end but will spool slower on the bottom.

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camccardell said:

nobody has this tech down?

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I think the focus should be more on the compressor maps. Also wastegate sizing is critical. I have no experience with compounds however do know a couple guys that run them on large diesels.

:bang

It matters because I am trying to see understand at what point am I choking the engine and at what point am I wasting energy?