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I'm wondering if a backward-curved compressor impeller like on a T3 is available as a replacement for different turbos? The increased boost at higher RPM's sounds intriguing.

Can you post a pic of the differences you are talking about?

This is a stock T3 impeller. It looks like this style is available for a TD5.

The short answer is yes, but all compressor wheels have the backward curve.

I got the information here. Maybe the T3 has subtle differences?

http://people.physics.anu.edu.au/~amh110/turbo_page.htm

If you want to do something really worthwhile, and not tried around here as far as I know, how bout going with a twin scroll design?!

I really want a T3 but there is not a lot of them around used. I'll probably end up with a 28 or a TD4 because they are common.I'm wondering how many more problems a twin scroll would create? I have to watch some videos on how to clock a turbo.

I think just finding a twin scroll and then building an equal length header would be the only issue.
I still have my T3 if you can't find anything.

I'm going to go with the worst case scenario and get a beat turbo that needs a rebuild .I tried to source a used type IV case for a couple of years and learn a lesson from that.

I guess If I could find a small twin scroll I would buy it if it was in good shape at a reasonable price. My car is torn down and I plan on making a custom subframe for the front. It's a 72 super.It's going to be over 2 years before I get to the engine so it's not a pressing need.

Only things I know of with twin scroll are newer mini coopers and I think I saw once 2014+ Subaru Forrester.

It's a good idea but I think the coopers are a 1.5 liter. Diesels are sometimes twin scroll.

They may be I don't know. Even if they are, being made for a small engine and being twin scroll it would probably be awesome. Twin scroll makes boost sooner and with less back pressure can usually make more and hold it better on the top end. If I remember right the mini makes over 200 hp so you know the turbo is good for at least that. VE goes up too with twin scroll. Dang. Now I'm interested in it!

Do a search on this forum. I’m pretty sure Wally did s twin scroll build a couple of years back.

I will have to take a look. I'm interested