I'm getting a bunch of things installed this coming Wednesday, but I have a questions in regards to the downpipe.

I bought a new UR short downpipe and a Depo 200-cell HFC, both of which have the wideband bungs welded. I currently have a 2.75" Borla catback installed with the OEM DP and cat. I know I will definitely be replacing the cat, but I'm starting to wonder if using a bigger downpipe on the stock turbo is really worth it. I'm still unsure if I will go the X-turbo swap or the RAD turbo in the future. If I go with the X swap then the entire downpipe setup would need to be changed out anyway, and I'm thinking that going with the RAD would be best with a full long downpipe to get the most out of it.

I'd like some opinions on this, if it's not really worth it to install a new DP only for minimal gain, than I won't bother. I do plan on flashing the V2.7 TBE basemap and it said that a DP was ok but not necessary, just a HFC/test pipe with a catback would do.

 

Ideas and opinions were tossed around in my X swap thread. Some graphs are available showing the differences.

https://www.evolutionm.net/forums/09...rogress-9.html

 

Nice, but what about on the stock Ralliart TD04 turbo though? That's what I'm wondering.

 

the puny RA TD04 flows considerably less, so it'd be even less worth it

 

I have a UR short DP. I didn't get it for "power". I got it for an extra O2 bung. Since I didn't want to drill the stock DP, the extra O2 bung in the UR short DP made it "worth it" to me.

 

Safe answer would be use the UR short DP on either the TD04, RAD, or TD05 since it's interchangeable. It'll be a performance enhancement, albeit a minimal one. This is only because you said you've already ordered the short DP. You could use the short DP now and reuse it on the X or RAD.

If you want to go the route of selling the short DP and upgrading to the long DP, I don't think the long DP is interchangeable between the TD04 and TD05. Just remember the O2 housings looking different when I did the swap. It's more performance to go long but involves more work and funds so it depends on your budget.

My heart isn't broken using the short UR DP on my X swap, but that's my personal opinion.

The greater the airflow provided by the turbo, the more gains you'll see with a long DP.

 

That's how my thought process is going right now.

I didn't know the Depo HFC had one built-in as well, so in my case I can mount the wideband on either the Depo or UR, if I install it.

I have it sitting in my kitchen at the moment. The TD04 and TD05 do have different o2 housings, so I would indeed need a different housing if I went with an X swap.

I can see an aftermarket downpipe, short or long, working better even on the RAD setup, but not so much on the stock turbo. And since I have the ability to mount the wideband on the HFC next to the front o2 sensor, there is no real need for the DP. I may just see if I can return it for a refund then, no sense in spending $200 for minimal gain, if any at all. I'd rather use that towards something else more beneficial.

This is what I get for not doing as much research ahead of time...

 

Plus, since it's not completely necessary, it'll make things a lot easier when putting the stock cat back on for emissions, just tuck the wideband sensor away and I'll be fine. Only takes a few minutes to swap the OEM/aftermarket cats out anyway.

 

I'm getting stuff installed tomorrow, so any more advice or opinions on this would be great beforehand.