I just replace my SMSP High Flow cat, 2.5" with a 2.5" Test pipe. I notice an improvement in TB response immediately. I'm just wonder what others have seen in power improvement with a similar type of change.
I will be doing just a simple street tune to clean up the A/F, no dyno trip at this time.
I will be going to the dyno when I change my Performer X manifold BACK to my GSR manifold later this year.

 

From past research it seems most people gain 3-5whp. I believe these cases are stock cats to a test pipe. I am trying to find more information about people who have changed from a high flow cat to atest pipe.

 

True. To me it 3-5hp wasn't worth the excessive noise. I could tune in 3-5hp

 

The test pipe is part of my noise reduction plan. I will have a 12" Resonator installed. Currently my exhaust has a muffler only.

 

I'm sure it depends on the setup. I haven't done it on a honda but on my 300whp 5.0 mustang, replacing the two test pipes with 2 2.5" high flow cats cost me 5whp. not worth it imo to run without cats. you're talking 1% maybe increase in power which is probably less than the impact of weather on any given day.

 

True, true. I did this as a step toward having a resonator welded in this location to reduce noise. Just trying to find out if any power would typically be gained with this type of set-up.

 

I think it's worth some horsepower but I would be surprised if a resonator quiets things down more than a cat? I'm a big fan of the stock muffler and DMH e cutout setup too. I actually enjoy commuting in my car again because I can hear the stereo on the freeway and when I want to rip on it, it sounds mean and is faster. the cutout with installation was <$250 and I was able to sell my old muffler and cat back setup for $100. If you're going for quiet but don't want to give up performance I think it is the best option.

 

The resonator will probably rob those 1-3 hp you gained from removing the high flow cat. I recall a dyno test on another forum where test pipe only gained 1-2 hp over high flow cat. Granted, not all high flow cats are created equal, but smsp 300 and 400 cell cats flow pretty damn good.

 

I run a 200 cell SMSP cat and I swear it's as close to a test pipe as you're going to get and still be called a cat.

 

i replaced my 3" high flow cat for a 3" in/out ultra quiet resonator by vibrant.

i cant tell you exactly how much power i gained because my setup is turbo...but it was quite a bit...

 

turbochargers make much better use of pipes like that over anything NA. the comparison isn't that valid compared to an NA setup

 

Good the hear it quieted your set-up. That will be all I'm looking for mine. I don't think the Vibrant Ultra quiet will fit so I'll be using there regular resonator.

 

So I replace the Ignition Coil Assy and Igniter Unit a while back, set the timing and lopey idle gets better. I guess replacing 11 year old ignition does that.
Then I replace my cat with a test pipe and the idle gets even better. Now I can no longer feel the lopeiness at idle, I can only hear it.
Very strange/odd I would say.
Is it possible the CAT had been creating a bit of pressure back up that is now gone.