Right now the turbo i have is a T04E with 50 A/R cold with a 57 Trim and . 63 A/R hot and it start's to spool about 3300 RPM's and it's ok but i want to spool about 2500 RPM's so i was thinking changing the hot side either to a .48 or .36 so what do you guys think what would be better the .36 or .48 A/R to get me to my goal of 2500 RPM's Spool.

.36A/R



.48A/R

 

Start with the .48 and if you really need it to spool faster then go to a .36. That's tiny though equivalent to about 5cm like a TD04HL turbo. .48 is perfect for a quick spool.

 

I'd say stick with the .63. A .48 made my car fall off on the top side...it did spool earlier though

 

.36 is like k03s territory. full spool @ 2200, out of breath by 5000. fun for passing at highway speeds, not much else.

 

maybe autocross, I spend alot of time in mid 2nd gear

 

.36 is turbodiesel Rabbit junk, had a funky one-off flange pattern too.

 

Don't forget Peugeot diesel too!

 

Yes as well as some stage 1½ mercedes turbos that are also .36 a/r ! This is choking the exhaust stream big time!!

all the .36 setups i made, regardless of the engine, lacked top end. it just doesn't flow enough exhaust. I would also avoid it and stick with .48 a/r minimum.
Stage 1½ in .48 a/r is a good way to improve low end without impacting the top end as much as going .36 a/r.