Retune for adding hi flow cats?

JWExperience

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Hi all, I just got a 03 terminator vert with 50k on it. The setup for the last 10-15k miles is a 2.8 pulley, intake, stock manifolds, o/r x, and Borla stingers. This exhaust setup is too loud for me. I don’t like drone, just a deep rumble and something that gets a little louder when I step on it. I’m debating on getting a couple magnaflow hi flow cats welded into the mid pipe and maybe getting magnaflow mufflers instead of the stingers if the cats don’t tone it down enough. Would I need a retune for adding hi flow cats and would they even quiet it down enough in your experiences? I’m also considering looking for someone local that is looking for something louder to trade.
 

TK1299

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I have stingers on my terminator and had hi flow cats welded into the x-pipe, but it did almost nothing to quiet things down. It’s too loud for me as well, so if you do go with the magnaflow let me know if that helps. You do not need a retune for cats.
 

CobraBob

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Yeah, your key factor with the loudness is the Stinger. It's designed to be LOUD. I would replace the Stingers first, with Magnaflow, Bassani or Steeda/Borla. See how it sounds, and then if necessary weld in the high-flow cats.

Here is some good catback/midpipe info from my Terminator FAQs.
Catback/Midpipe Information
 

JWExperience

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Awesome, thx for the info fellas and I’ll start there. I also read that people had put bullet mufflers into an x pipe to lower the volume as well. I’m curious if this would further lower volume? I’m prob just a stock h pipe kinda guy!
 

JWExperience

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Just found a catted magnaflow x pipe and catback system here locally, hopefully my tune agrees with it! Are there any settings on a tune that may cause issues with cats or am I good to just bolt this up? Sorry, I’m trying to research and I’m finding info that is creating more questions. I don’t know a lot about my tune other than it was done at a performance shop in Houston. All I have for documentation is a dyno sheet.
 
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Quick Strike

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You might be a little richer, but that will not hurt your engine. It might hurt power a little. The danger is removing cats or putting on a less restrictive exhaust system can cause a lean condition.
 

01vert

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Your rear O2s are turned off. You have an air fuel ratio that is not adjusted from the interaction of the upstream and downstream O2s. Get a retune and you won't have the unburned hydrocarbon smell at idle and could get better mpg at part throttle and cruise.
 

JWExperience

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Your rear O2s are turned off. You have an air fuel ratio that is not adjusted from the interaction of the upstream and downstream O2s. Get a retune and you won't have the unburned hydrocarbon smell at idle and could get better mpg at part throttle and cruise.

Thank you


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JWExperience

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I have stingers on my terminator and had hi flow cats welded into the x-pipe, but it did almost nothing to quiet things down. It’s too loud for me as well, so if you do go with the magnaflow let me know if that helps. You do not need a retune for cats.

Installed the magnaflow cat back so far and left my off road x which made a big difference in the volume. It still has a nice rumble but less rasp and volume in general is noticeably less. There’s very little if any drone up to 60 cruising and that was flat roads. It definitely gets loud when you step on it. I’m interested to take it on the highway now to see if there’s any drone.

Can anyone ID these mufflers that are welded into this hacked up magnaflow cat back?

6ffafe63423cc639188556e8c19a0a4d.jpg




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TK1299

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Installed the magnaflow cat back so far and left my off road x which made a big difference in the volume. It still has a nice rumble but less rasp and volume in general is noticeably less. There’s very little if any drone up to 60 cruising and that was flat roads. It definitely gets loud when you step on it. I’m interested to take it on the highway now to see if there’s any drone.

Can anyone ID these mufflers that are welded into this hacked up magnaflow cat back?

View attachment 1710110



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Mine is so loud, at the last cars and coffee i revved it a little before pulling out and a girl behind the car screamed and jumped. I may have to try the Magnaflows. Thanks for the update
 

44shelby

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Installed the magnaflow cat back so far and left my off road x which made a big difference in the volume. It still has a nice rumble but less rasp and volume in general is noticeably less. There’s very little if any drone up to 60 cruising and that was flat roads. It definitely gets loud when you step on it. I’m interested to take it on the highway now to see if there’s any drone.

Can anyone ID these mufflers that are welded into this hacked up magnaflow cat back?

View attachment 1710110



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those muffler are similar design to the stainless work retro chamber mufflers. There used to be a company out there than made mufflers identical to them and they were called sweet thunders. its just a chambered round muffler long story short.
 

01yellercobra

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Your rear O2s are turned off. You have an air fuel ratio that is not adjusted from the interaction of the upstream and downstream O2s. Get a retune and you won't have the unburned hydrocarbon smell at idle and could get better mpg at part throttle and cruise.

The rear O2's have nothing to do with the A/F. Their only job is to make sure the cats are functioning correctly. They check to make sure there is a difference in the A/F between the inlet and outlet of the cats. Only the upstream O2 sensor affect the A/F. Unless it's pig rich currently there won't be any smell after installing a catted mid pipe. And if it's currently that rich I think he'd notice the fumes with the current O/R pipe.

Honestly I prefer a catted mid pipe anymore. A couple friends have O/R pipes and I hate getting stuck behind them in traffic. Man I'm old.
 

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