I will soon be changing from a JDM OE downpipe to a Autoexe twin tube DP, and changing from a stock main cat to the Feed twin metal cat setup. My catback is an Apexi Noir, which is probably one of the more restrictive systems as it is not a straight through design.

I have no issue with boost creep now, but I am wondering if these changes will case creep to occur. I should also say that I have a set of 99 spec twins that I will be installing along with these other parts.

Should I be concerned with boost creep with this setup? I can port the wastegate on the 99 spec twins but I really do not want to do this unless absolutely necessary. I like the exhaust noise level and sound with the Noir so I don't see changing this to a more free flowing system in the future. Will the cats and catback setup be enough restriction to keep boost creep away?

Thoughts / advice are appreciated!

 

The Noir will help a bit with the creep but the high flow cat may allow it to creep still. It definitely won't be as bad as if you were running a can style muffler like the HKS high power or Apexi N1 that are essentially no restriction. I don't have any personal experience with the Feed twin cat but heard the flow well. Are the turbos out of the car? Realistically, porting the wastegate is going to be the best and safest long term solution to combat the creep, especially which higher flowing exhaust components. I wouldn't expect it to creep really bad with that catback but I still don't think it will be ideal. I'm guessing you already have an ECU to handle the added fuel for the mods?

 

Thanks for the feedback. Yes, I have a Power FC with FC Tweak, I'll be remapping after all the changes.

The turbos are out of the car, I just didn't want to have to disassemble and modify them unless it was really necessary.

 

I almost have the exact same exhaust set up, I have the Knightsports twin DP, FEED twin cat (expensive af), and the FEED cat back, Sonic AS-V. Sorry buddy, but you'll have to port your waste gate. The twin cat flows as if it were a midpipe, you can try it but I wouldn't recommend it.

 

How well does that cat work? The price of those are insane but if they cut the smell and allow the flow and last a while they may be worth it for a bolt on option. I'll be looking into these once I decide which EMS to go with. I've got a knightsports downpipe waiting to be put on after my next dyno session.

 

Thanks for all the feedback.

Okay, I guess I will port the wastegate on the 99's before I install.

Next question - is there a good thread on the best way to do this? I found one from about 20 years ago but it was a little lacking in detail.

 

This guy does a good job explaining it and preforming it.

 

Thanks for the link!

 

The twin cats perform above my expectations. I didn't have my air pump hooked up for logging, and it still got rid of most of the smell without the air pump. That is actually the main reason why I got the cats. Also, here is my dyno sheet if you were curious: 99 specs, Greedy V-mount, Knight Sports DP, FEED cat, FEED cat, stock crate engine, stock injectors, FC tweak. I'm actually hitting 91% duty cycle with this setup, so I need to upgrade my injectors and not drive the car like I stole it.

 

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Great to know. That's essentially what I'm planning on doing, safely maxing out the factory injectors then drive it. I'll have to upgrade my turbos eventually as I don't expect them to last forever even at stock boost. Either going to go with 99 spec or BnRs