what A/R T4 size for 66mm?

I bought a low mileage turbo off my mechanic, which has a supra himself and ran the turbo.

It's a Bullseye BW S366, and we put a T3 housing on it. I'm not sure what A/R couldn't find any stamping on it, but something like 0.63

This thing hits full spool at 3500rpm. Drives very nice I just feel like it's dying off really badly up top.

I want something that still gets quick spool (at or before 4000) but pulls like a train all the way.

I'll be keeping the turbo I just wanted to get a T4 housing.

I'm after 500whp and 550whp with a bit more boost. I won't got more than 550 on my setup.

In my case would something like .68 A/R be ideal? or 0.81?

I was also looking into the 50 series A/R sizes but I'm not sure if it would choke it up too much up top.

thanks in advance

For 500+ rwhp, a .68 or .81 is fine.

My BL366 (which is a billet version of the S366) is .91, and makes full boost on a race head with 280 cams around 4000 rpm.

Hmm yeah I was thinking .68 should be ideal.

One of my future mods will also include 264 cams.

I'm running a normal tubular mani nothing special.

I have been considering twin scroll not sure if it's worth it though

Twin scroll makes a difference for sure, our manifolds make a big difference in spool up over anything else we've tested over the last 13 years.

If you want the ultimate street turbo go with the 60mm Boostlab turbo with a 0.91 ex housing, these are amazing turbos, full boost around 3800rpm and over 700bhp depending on the spec you have.