MS6 Downpipe Difficulties

First off, short mod list. Stock engine, BnrS3, 3 inch intake, HPFP internals, magnaflow catback, tuned with Versatune, and now, a catless downpipe......

So today I installed an Ebay catless downpipe on my MS6. After the hell of getting the old one out, (seriously screw that thing), I got everything buttoned up, and it runs like crap.

A few things that I noticed:
1. The vband connection was leaking at first, so I tightened the crap out of the clamp. I think that fixed it, but I'm not positive.
2. The downpipe doesn't line up at the exhaust end because some previous owner had the magnaflow catback MODIFIED to fit their crappy test pipe and oem downpipe. So the flange is at the wrong angle. I wouldn't think this would be an issue as far as idling, but maybe I'm wrong.
3. I took a log, and the STFT's are pegged at -25% when idling, and the AFR is quite rich too. Granted this was a cold start, and I didn't let run too long because it's super loud now. But 11.4-10.3 seems excessive.

I also did make sure that the MAF sensor and 02 sensors were plugged in.
I've attached the idle log I took, although there are some spikes at the beginning and end where I revved it a bit. Does this look like an issue with a vacuum leak or exhaust leak? Or is it something else? I was thinking a downpipe wouldn't necessitate a MAF calibration, at least for idling, but maybe it does. I'm kind of at a loss.

 

My guess is exhaust leak. I've never been a fan of ebay downpipes to begin with.

A tune is highly recommended for this mod. Log looked ok but maybe i missed something.

 

That’s typical of a bad turbo/downpipe seal. Did you use a new upper downpipe gasket?


Sent from my iPhone using Tapatalk

 

I did, I used the supplied one, which I know aren't the greatest, but it's what I had. If that's the case though, it could also be the vband, since that's before the 02 sensor as well. I'll have to get a stick lighter tomorrow and check for exhaust leaks.

 

Just food for thought - the OEM upper downpipe gasket is like $70 for a reason. eBay you’re lucky to get a $7 gasket.


Sent from my iPhone using Tapatalk

 

I'll probably get one ordered and plan on replacing it no matter what. The new downpipe is so much easier to get out it shouldn't be too big of a job now.

 

I checked for exhaust leaks by the turbo today and found some, so I tightened the bolts I could get to (vband was in the way of some). The car now runs good enough that I could drive it. It's still a lot more negative in the STFT's than it has been in the past, but it was able to hit AFR targets. I did a wot pull to redline and the log looks good. (zero wgdc of course). Afr is in line and no knock at all, which is awesome. It boost creeps a bit but not so bad that it can't be tuned around.

I'll definitely get an OEM gasket ordered and pull it back apart and get everything tightened down good before putting it back together.

Thanks for all of the suggestions, I think I'll get this thing figured out. At least now I can get the stupid hacked up exhaust fixed. To the exhaust shop!

 

Hey there. I can't find any ms6 downpipe on eBay. Trying to get one asap, have you got a link you could share? Thanks!