After my car's mapping i am trying to figure why i suffer lag. I am running a gt2560r and not getting full boost till 4250rpm. I have ruled out a few things and now my question is, Will the fact i am running a 3" system into a 2.5 catback cause flow problems? Obviously there is now a step in the system that could potentially affect flow. Any help would be greatly appreciated.
What A/R turbine housing do you have on the GT2560R? Is the catback an instant change from 3-2.5 inch? Ideally you want that transition as smooth as possible... As there will be for turbulence where the step in diameter is effectively reducing the diameter even further....
I cant remember the turbine size off the top of my head! When i had the 3" catback it used to reach full boost by 3.5k rpm. Yea it goes from 3-2.5 with a step.
If it used to boost that much sooner, and nothing else has changed, and there's no leaks, you've answered the question yourself.
