So we think I have a bad cat on the drivers side after troubleshooting a slight rattling/fluttering sound coming from driver side exhaust. Car is running pretty good and does build boost but pretty slowly and feels held back by an exhaust restriction. Changed header gasket and tightened bolts and checked everything short of removing exhaust. Thinking the cat could be breaking up or clogged a little?

Does this make sense?

Anyone have those Fabspeed cat delete pipes I could swap in and see if that's the issue? Or 1 Fabspeed cat would tell us if that's it also.

thanks

 

I doubt thats it... I would look else where...

bottom line- did it do it before you put on recent upgrades? my guess no... thus your problem is not in the exhaust... just my opinion...

check your compressor wheel for damage...

mark

 

Nope it just started happening last week one day upon startup. had the EVOMS intake pipes put on and new clutch installed about 1200-1300 miles ago and it ran great for those miles. this is the exhaust that came on my car when I bought it 2+ years and 30k+ miles ago.... Fabspeed maxflo.

you think the compressor wheel coulda gone bad already? from what? Turbos have maybe 12-14k miles on them I think....

 

reading your explanation... you get boost but slower... etc...
that lead me to think it may be a turbo...
my point is you have to go over everything one by one... but I doubt its cat on a exhaust...

I would stop and just do a boost leak test form the turbos... that would tell you a lot...
you plug one turbo up and pressure test the other... many skeletons do show up... you just dont know about them yet... at the same time you inspect the turbo wheel, see if its rubbing... check for shaft play... look for oil....
spin each one with your hand and compare... etc... pressure test the Wgs.. are they both working properly...

Im just talking out loud ...

 

thanks for help Mark. that's a lot of stuff to check! We have looked all over for boost leaks and everything seems tight... last week (after the sound became present) I hit 1.5 bar a couple times (tuned to hit 1.3-1.4 max, usually see 1.3 on dash) and let off. But today we went for a test drive and I slowly added boost and it didn't see more than .7-.8 bar. No CELs either.... very weird. And the fluttering noise is still there but seems to go away above 2500 or so rpm. Man.......

 

Sounds to me like a messed up compressor wheel... but I may be wrong..
doesn't take a lot to check.. pull off the hoses its a quick one... check the wheels...
when you did the pressure test did you do it from the turbos? if not do it again...
You may have checkvalves that wen bad that are on top of the motor...
some pressure test the TB only.. thats not the right way... your skipping a major part of the test...
if you did not do a pressure test after you started getting the problem I would start there... also, do it on a warm motor... that way you get less blow by... and can identify, if any, leaks...
That's what I would do if you haven't since it all started going bad...

once more thing... how does the car run on lower boost... can you try that?
maybe your meth set up put the car into limp mode and your running only WG boost... that's the safety in case some thing is wrong...
mark

 

ok i'm showing this thread to my mechanic and we'll look at all possibilities.

i've had the aquamist failsafe kick in before and limit to WG boost, but it doesn't affect low end spool. this time something else is wrong and it's much laggier for lack of a better word.

i think we're gonna take the bumper off this week and really dive into it and check everything. gotta get it sorted out.....

thanks Mark.

 

Update: Swapped in a set of straight pipes that were at the shop and the car seems to run fine, boosting/spooling as it should, and the fluttering sound is good, although a slightly louder exhaust tone is now present with the cat/muffler bypass.

I need to figure out if I am going to get a new cat(s) or just go straight pipes.... I haven't heard the car yet (installer just called me) but I am guessing it's pretty obnoxious and my building neighbors would dislike me even more