Low Boost, Catback questions

[Boostmaniac]

Originally Posted by J-Rat

Did you re-adjust the boost controller to compensate for the difference in pressure differential? As with anything else on this and other forums, its all up to personal experience. I can hold 25 PSI all day long to the redline on my 2.5 inch catback. Is it optimal? HELL NO! At my HP level I should be more on a 4 inch exhaust.


The thing that bothers me is that the car is STOCK. Even a stock turbo with a pre-cat, main cat, and crappy stock exhaust system should spool faster then that. All things being considered, I am not entirely convinced its the exhaust. It sounds like how my car ran years ago when I thought I would be smart and wire the Twin Scroll open.

That made me laugh.

Ok, during my general overhaul of my braking system yesterday, we got to the turbo to start removing it and swapping it out with the S5 unit and I made a few notable discoveries.

There seems to be no oil coming out of the turbo, shaft play is minimal to none that I can tell. I'll be able to make a better assessment once it is removed from the car. I did notice something on the compressor wheel, but I need to get a pic to show you, I can't quite explain it on here adequately.

I did see the twin scroll rod and it does seem normal. Maybe it is malfunctioning, maybe it is wired open and I just can't see it. Again, upon further removal, I'll be able to give you all the down low.

If it isn't the exhaust (which should help me out a little bit) then it is either the turbo or my engine. I am praying it is the turbo, I don't want to rebuild just yet. I just want ONE GOOD PULL the way my car is supposed to pull.

The pics should be high quality also, my buddy that is helping me has been bringing over his incredibly awesome camera.

Edit:

Don't laugh at this. I believe in doing baseline pulls on a dead stock car to see where any improvements I make can be found and to also give accurate reports back. This is my baseline pull, dead stock, crappy catback exhaust.



The car was at WOT at 2500, the target window started at 3000. Boost on this pull didn't really hit positive (maybe 1 psi max) till about 3500 - 3800. Yes I know the AFR is pig rich, that is getting fixed very soon. Yes I also know my power peak is 1k higher than it is supposed to be and I can't explain that at all. Also worth noting, this car has NO acceleration until it gets into boost and it still makes power to 8k or higher and it will hold boost the entire way.

Next time, I'll see if I can datalog boost if I am still having the same problem. There ya go, tell me what you think.

-Maniac