I am in a process of deciding for a bigger pair of turbos for my VR-4.
After some researching It came down to either pair of GT2530 (which are kind of pricey!) or a pair of “old style” Garrett T3 turbos for a more reasonable amount of money.
Playing with various formulas, turbo matching programs and compressor maps I came to a conclusion that a pair of Garrett T3 (60 or 50 trim and .63 or .48 exhaust A/R) will be quite a good match to our engine. They can provide almost 60~70 Lb/min (900~1000 cfm) of “rated air flow at 2PR” (or roughly at 1 bar boost pressure) and most of the points for our engine lie in the 70% of compressor efficiency for up to 1,5-1,8(!) bar of boost, with 5000-7400 range getting into max compressor efficiency at 1bar (74-75%). The best part of it is price! Remanufactured T3 go for 400-600$! New ones are from 700$ and up… Compare those prices to GT2530 that start from 1500$! *(prices for a single turbocharger)
GT2530
(+): They can provide good amount of airflow and generally believed of being capable of a wider “usable range”, can spool up fast (there are no exact figures… but everyone keeps saying so…). Utilize a new ball bearing design and use a ceramic compressor wheel…
(-):They are hard to repair, and the “new design” is more prone to failures… ceramic compressor wheels are less durable then the old style steel compressor wheels and ball bearing turbos require modifications to oil supply lines, since they are quite “sensitive” to oil pressure and are less tolerant to heavy loads (then old style turbos). Price is also a set off…
T3
(+): Good flow. Can be remanufactured. Cheap. Tolerant to abuses.
(-): Will probably lag more then GT2530 and are not of the “new design”.
PS: Either of those (pair of)turbos can safely produce 450-550 BHP on our engines with a maximum power closer to 700 BHP. That is, if everything else can cope with that kind of power!
PS2: I hope this information could be helpful to someone out there… and hope I didn’t make too many mistakes ! I am no “turbo expert”, so take this information at your own risk .
Looking forward to get input from Real Experts on this matter…