whats the symptoms of a turbo going bad?
 

ok, ive got a 10th Anniversary Turbo 2, its got about 6k on a new engine and racing beat cat-back.. when we got the car back they told us at mazda that they had checked the turbo and that it was fine. since then i have had no problems with the turbo boosting, but lately i have developed an exhaust leak... when we were having the car worked on they told us that there was small hole in the first cat.... but they said that it wouldnt yet be a problem... i think that possibly the cat has a bigger hole now and that is where my leak is.. but could it be the turbo? the turbo still boosts.. it just doesnt boost at the max like it used to.. i have a friend who works at ford on the big turbo diesels and he said that if there isnt sufficient backpressure, then the turbo wont boost like it normally does... any help here would be most appreciated... i would just rather spend 300 on a new cat than alot more on a new turbo... thanks alot.... oh... say i was to go the illegal route and just run a straight down pipe from the turbo... what would be the positive and the negative consequences? thanks again.
tim
p.s. one last question... has anybody ever had a problem with racing beat exhaust pipes hanging unevenly??? my driver side muffler hangs down about an inch and a half lower than the passenger side and its really annoying... :) thanks again

yeah mine hangs down on one side. just cut and reweld the hanger so it's straight.

first off, these are just my thoughts, and i would reccomend talking to someone who knows a bit more about this than myself.

It would seem that your exhaust being messed up would in fact lead to your turbo problems and that buying a new cat or running just a straight pipe would in fact correct it. However, running a straight pipe resulting in free flow exhaust, without an enlarged wastegate, could potentially cause boost spike that could be harmful to your engine and/ or turbo.

So unless you want to invest in some fuel system upgrades (AIC, larger injectors, etc.) I would just replace the cats for now. If I am wrong in any of this, please someone correct me, as I would hate to give out misinformation. just tryin to help a bit. :)

Backpressure will keep boost up?? Ohh. man....

The velocity in the manifold is important- that's why the s4 have a twin scroll system- to keep flow fast even at low rpm's. This is the flow that hits the turbine blades. BUT, once the flow is PAST the turbo, the less restriction the better. (To a certain extent- still need a bit of scavanging).

In theory- your friend is partially right- but if he actually works on turbos, he should know bascially how they work!!! The cat is definately after the turbo!

Fixing the hole in your cat may of may not increase power, because it would only be because of a smoother exhaust flow, but these things affect N/A's a LOT more... and it's doubtfull it would make a noticable difference on a turbo.

Oh- your other questions:
If you run a straight downpipe, and a catback, you will have to do at least 2 other things.

1-You WILL NEED a fuel cut defenser, they are not expensive, and will prevent your ECU from cutting fuel- since you will be boosting 8-9 psi or so minimum.

2- You should port your tiny damn wategate.... s4 turbos are bad for boost creep, and the boost spiking to 13-14 psi is not good for the stock turbo. Especially with the FCD, you will be running a little lean- that's OK up to 8-9 psi, but with 13 psi, you can kaboom your engine easily.

You will gain 30 hp easily by running a straight pipe+FCD, usually more.

My TII has the racing beat turbo back exhaust and I am boosting 13psi in 4th 11psi in third and it is running lean like wow in fourth. I have the fuel controller and bigger injectors to put in just don't have the time right now.

Just so you know the downpipe will be alot cheaper than a cat.