I am new to the turbo scene and am looking to swap out the stock turbo. I swapped a J-Spec 87 TII motor into my 87 N/A. I am having the motor rebuilt and am keeping stock ports. Iam looking to put down 250 to 300 hp at around 10 psi. Some one told me that there are calculations to fiqure out what turbo you can use so that it is not too big or too small. I was looking at a Garrett GT28RS. Other mods that I have done to the car are a RB downpipe, high flow cat, Borla cat back, port matched intake manifolds, FCD, and front mount intercooler. Thanks for the help.



CHRIS

ya that turbo is way way way way too small for a rota. look at something like a 60-1 or gt35 or to4s to4r stuff like that.

What makes that particular turbo too small for a rotary? I am not looking to put down huge numbers, only around 300 wheel hp. Just looking for some clarification. Thanks.



CHRIS

one of the turbo guys in the forum can get into detail. but a gt28rs i believe is smaller then a s5 anyways, you will over rev that thing due to exhust pulses of the rotary and just plain wont produce the amount of air the rota needs. anyways a t4 foot print turbo works far better on a rotary anyways

What size A/R should I be looking for the compressor side and the turbine side? Are there ones for a rotary specifically that will work to the potential? Thanks.



CHRIS

A/R is dependent about turbine trim. Compressor a/r really doesn't make that big of a difference, and you usually don't have a selection. Thats all based on a compressor housings, To4E housings are .6, To4S housings are .7



As said stay away from the Gt28RS, that is a T2 turbine foot print, you can see the designation in the name GT(2)8rs. I would never use a T3 turbo either, just stick with a straight T4. Typical turbine housing a/rs for P trim turbos are .84 to 1.0.

250 to 300rwhp @ 10psi can be done on a To4E, or a To4S. There is a lot more to making the power than just the compressor though. We sell Garrett Turbos, shoot me a PM if can be of any assistance.

GT 35/40 .82 rear exhaust housing.



Will not have crazy top end but will reach your desired power figure with ease and have alot of boost early.

gt34/40 might be a little to big and have some lag issues im with 1revvin7 tO4E to TO4s should be right around there with a .84 a/r would be in its sweet spot.

gt34/40 might be a little to big and have some lag issues im with 1revvin7 tO4E to TO4s should be right around there with a .84 a/r would be in its sweet spot.

LAG?

Are you kidding?



Fullboost at 3200rpm is laggy? Man some people are either dumb, have no experience or kidding them selves.



The above figure is a non ported 13b.