Downpipe recommendation for autocross

[da johnny boy]

I'm pulling the turbo to fix the broken downpipe studs, so and it should be easy to do the downpipe while the turbo is removed. I'm trying to decide what to buy to either stay STX legal, or to switch to DSP, and therefore whether I need a cat or not. I mostly autocross my STR prepped Miata, so I'm not building the speed to be competitive. In my club, I run a PAX indexed class, so I can swap around cars and have that still count for the season standings. Or I can always just run the speed in a different club since it will not be competitive in STX or DSP.

Right now I have 17x9 wheels with 245 RE-71rs, a rear swaybar, deresonated midpipe, intake, HPFP, and e40 tune. If I ran STX, I'd just run 93 with stock boost tables. If I ran DSP, I could keep everything the same, and additionally, just run no cats. I don't want to spend much money. I'd probably go for one of the nicer high flow catted downpipes if I could find one used, but I my budget is around $200. If I did keep a cat, I'm not sure whether the better way to go is to eliminate the upstream or downstream cat.

What do you guys think about these options? I'm personally leaning towards option 4 or 5 with the ebay long downpipe.

1. STX - High flow catted downpipe with either the OEM catted test pipe or a catless test pipe
2. STX - Catless downpipe with OEM catted test pipe or High flow catted testpipe
3. STX - Long catted downpipe
4. STX - Long catless downpipe and add a high flow cat (I'd probably just use band clamps instead of welding)
5. DSP - Long catless downpipe

[Reedy]

I've had a CP-e DP for a few years now and the core of the CAT failed after only a couple of years worth of track days. We cut it out and welded in a new one and that's just recently failed on me as well, to the point where the core has fallen down into the pipe and destroyed my rear O2 sensor.

I am swapping that out to a Cobb DP once my new turbo arrives. I have no idea if it will last any better than the Cp-e one did but I guess my main point is, if you're gonna go cheap ebay shit, don't get a CAT.

[da johnny boy]

Originally Posted by Reedy I've had a CP-e DP for a few years now and the core of the CAT failed after only a couple of years worth of track days. We cut it out and welded in a new one and that's just recently failed on me as well, to the point where the core has fallen down into the pipe and destroyed my rear O2 sensor. I am swapping that out to a Cobb DP once my new turbo arrives. I have no idea if it will last any better than the Cp-e one did but I guess my main point is, if you're gonna go cheap ebay shit, don't get a CAT.

Haha, I wouldn't think of getting cheap cat from ebay. I don't know much about DIY exhaust parts, but I was looking at Vibrant, Magnaflow, or Flowmaster for high flow cats to add to the catless ebay downpipe.

Was the cat you replaced a metal core or a ceramic core? And do you know the brand? Looks like the stock CP-e DP has a metal core cat.

@Code Monkey, but wouldn't I still need an adapter from the stock K04 turbo discharge to attach a v-band flange?

[Reedy]

Originally Posted by da johnny boy Haha, I wouldn't think of getting cheap cat from ebay. I don't know much about DIY exhaust parts, but I was looking at Vibrant, Magnaflow, or Flowmaster for high flow cats to add to the catless ebay downpipe. Was the cat you replaced a metal core or a ceramic core? And do you know the brand? Looks like the stock CP-e DP has a metal core cat. @Code Monkey, but wouldn't I still need an adapter from the stock K04 turbo discharge to attach a v-band flange?

The original cat was a ceramic core, not sure what they use now but that DP was purchased back in 2010. The one we replaced it with was a metal core, which lasted longer but still failed eventually.

[Code Monkey]

Catted or catless, get a v-band DP and you will hopefully never have to deal again with broken DP to turbo studs.

[Code Monkey]

Yes, but the adapter is really short so it is super easy to install it on the turbo as you have easier access to all the five studs, Mazdaspeed6 example here. Then you simply connect the rest of the DP via v-band.

[Shottachris]

Nice

[monkey.bones.007]

Originally Posted by Shottachris Nice

Shit posting for a reason or just trying to build your post count to look like you contribute?

crapatalk it sucks for free

[Jonb82]

Originally Posted by monkey.bones.007 Shit posting for a reason or just trying to build your post count to look like you contribute? crapatalk it sucks for free

Nice


Sent while probably pooping

[Fstrnyou]

Originally Posted by Jonb82 Nice Sent while probably pooping

Ditto