iin10ded

hey kids, noob here. first sti. just changed from stock catted dp / tune to invidia catless and cobb acn stg 2 for 91.

car was running perfect previously on stock catted dp and stock tune. now get loud popping from exhaust on 1-2-3 upshifts on moderate to hard throttle. wot / fast shifts not so much. moreso on mid throttle.

i drove the car before i bought it [reno - 5kft] with this trim and no issues. came down to sf with stock cat/tune to pass smog [flying colors] and just threw the speedy bits back on, and getting popping.

used new grimspeed gaskets, everything's tight [well as of install last night]..

any idears? all else is stock from airfilter to turbo save big ol perrin tmic.

thx in advance for the input
jim

WRXBOOST10

iTrader: (12)

Welcome to the catless world.

HammsBear

iTrader: (3)

Yeah, get a high flow catted dp to cut down on the popping

Edit: the computer may need some time to relearn too

Superusdm

iTrader: (6)

My guesses are either the stage 2 Cobb tune has you running super rich, or you have a boost leak.

Superusdm

iTrader: (6)

Just wanted to add that even though you're catless, popping is NOT normal.

ddavis

iTrader: (4)

My catted popped more then my catless on deceleration... just saying. Is your tune made for a catless downpipe also? Im scheduled for a retune for my car because now im seeing higher boost numbers after going catless.

iin10ded

thanks for the comments. yea catted would have been my first pick but it came w the car so...

should add that the car ran fine on stock dp/tune. put on the catless dp and get popping. then loaded the tune and still popping.

tune is the off the shelf cobb acn stage 2 91 file that's supposed to be for an otherwise stock car w/ only TBE.

what *should* i be seeing for vacuum? via accessport if that's accurate..?

boost was steady 17.8 max at wot.

afr's looked normalish -a gain via accessport. 11.1 at wot.

any solution paths out there other than catless vs catted boxers/briefs discussion?

thx!
jim

Superusdm

iTrader: (6)

~18-21 mm/hg (anything less could indicate a vaccum leak). I believe AP reads vaccum in psi- so around -14 psi.

The AP uses a narrow band reading for AFR so I dont think its very accurate. Also you said that at WOT you dont get the popping, Id be curious what your ARF is at half throttle.

iin10ded

ahh ok that's helpful. i was seeing around -10 psi at idle iirc, which seemed low. any tips on common leak points on these.. ?

yea it's narrowband. pretty useless but better than nothing.

iin10ded

on second thought if i had a leak it likely wouldn't make full boost, which it seems to. would usually also idle weird.. which it doesn't. runs like buttah.

ahh the joys of a new car brand learning curve.. =)

Superusdm

iTrader: (6)

Your car will still make full boost with a small leak, the turbo will just be working harder. Additionally, the MAF will be reading more air and your ecu will be injecting more fuel, but if youre losing some of the air between the turbo and the heads you will end up with unburned fuel and ... pop pop.

Check all the charge pipe connections you messed with when installing the downpipe. Turbo-->Intercooler Y-Pipe, Intercooler-->Throttle body, Intercooler-->BPV. If you remove the intercooler, check all the y-pipe connections as well.

If you want to do some actual troubleshooting you can build a boost leak tester and pressurize your intake track. A quick google search with 'wrx' thrown in as a keyword will bring up some good threads on the DIY.

ddavis

iTrader: (4)

Both my subys have always idled around 9psi at idle without leaking

ddavis

iTrader: (4)

Just thinking about this... both my engines was built engines... so vac is prob different.

Superusdm

iTrader: (6)

Mine idled around 10-11psi when I had my AP. but Im pretty sure I had some leaks I didn't know about at the time. During that time my gauge would read around 15mm/hg and after fixing the leaks (and I'm sure they are fixed now) my gauge sits around 18mm. My car has always had low vacuum though. My cylinder compression is low too, about 120 across the board, so maybe that has something to do with it... I used a converter I found on google to cross over to psi for AP purposes or the OP. I did think 14psi sounded high, but that's what the conversion came out too...