Here's my dyno of stock cat vs test pipe. The blue line is no cat (test pipe) and the red line is my stock cat.

Looking at that, if you were me, would you use the test pipe or stock cat? The benefits of the test pipe might not really justify all the other crap that comes with it.

 

Maybe the difference between a new stock cat and the test pipe wouldn't be that much different. You could have had a clogged cat seeing that your Max is a 95'. I say you should go with a random tech hi-flo cat.

 

Uhm...what? The blue line is no cat? The red line is test pipe?

That's more of a gain than I would have expected to see going from cat/no cat.

 

I think that was a mistake... I'd keep the test pipe in, but I'm a lazy *******

 

I will be dyno testing a hi-flow cat this weekend, but I can't really justify spending a couple hundred bucks for something that cannot give more than a couple of HP gain. There's no way that a hi-flow cat will out-perform a test pipe so in my opinion - go all or nothing.

 

do what i do, whenever i go through emissions, i put stock cat back on, after that day, once a year, i put the test pipe back on...Stay with test pipe

 

Yeah I had the test pipe on for about 6 months. That is what I had planned to do. However each time emissions comes around, I have to find the time and then take the trouble to crawl under the car and bust open 4 bolts that could be rusted to hell from 2 Winters, and spend the money on gaskets ($14 for 2)... and then swap back... all for what - 3-5HP?

Another thing is that my motor seems to be burning oil... a test pipe makes that even more apparent! I did a compression test and all my cylinders are running great, but this oil issue is a little bothersome especially with a test pipe.

Another reason is that my stock 95 muffler rattles like mad when I have the test pipe on. However there is NO rattle at all with the stock cat. Now why would that be? Could it be the increased flow of the test pipe is causing the baffles to slap?

 

The cat interrupts the flow with all those tiny square chambers, probably 2000 or so and this breaks up all those exhaust pulses. With a tp, that flow is straight and the muffler does a poor job of breaking down these pulses and this is why a exhaust resonator would be used. I have a test pipe from being supercharged in the past and I just left it on. I will just put the carsound cat on for emissions when the time comes.

 

I do have a resonator on my b-pipe... but the muffler still rattled with the test pipe on. That is why I don't know if I got an aftermarket muffler, if that would solve the rattling problem with the test pipe or not.

Did you have the same problem at all?

 

i agree all or nothing ! i have been wondering if my test pipe was free-ing up HP or taking away. I understand we are not talking about much. From driving the car I felt like I was gaining power, it was hard to tell. This dyno helps me put these fears to rest, but im not sure which TP you are using. But for little HP, how do we justify a 200 dollar hi-flow cat ?

 

When I 1st put on my ypipe and had a 2.5" mandrel cat back installed with a 2k2 variable muffler. Also I had a carsound cat from wspd installed at the same time so the cat didn't solve my noise issue. I didn't have a resonator and I had a raspy note at around 3k and when coming off a redline shift. I couldn't stand it so I bought one of those spiral style resonators with a 1.5" center straight through design that has the outer portion like a screw that breaks these pulses. I know jegs/summit carries these and it made all the difference with my setup. I currently have y,tp,2.5catback with spiral resonator, 2k2 muffler, and no annoying noises. When I leave my neighborhood in the morning and everything is quiet I can just hear a nice growl with slight acceleration.

 

Maybe the problem is with my 95 muffler being worn out then. I don't get a 'noise'... the rattle that I'm talking about is more evident when the car is cold and it happens only at low-mid RPMs when I nail the throttle. Outside of that, the exhaust sounds awesome.

I wonder if even a new 95 muffler would do the trick... or even a 2K muffler.

Edit: To further elaborate on this 'rattle' - it sounds like metal pans clanging against each other... hope that helps explain the issue with the test pipe and stock muffler.

 

That pan clanging sounds a little more extreme than my raspy sound.
I would assume that since this is happening when the exhaust is still heating up that when it is hot this sound is not heard? If thats the case maybe the age of the muffler is an issue. I have had a good number of aftermarket mufflers i.e. greddy, flowmaster, super turbo, dynomax, and I was never very impressed. I like an exhaust as quiet as possible without sacrificing to many ponies. I think my 2k2 muffler maybe hurting me 2tq/2hp to the wheels, not enough to justify a louder muffler imho. I would suggest maybe finding a later model rear section from a junk yard for like $20 and bolting it up your self. See if that helps before spending $125 on some aftermarket loud pos muffler.

 

is that dyno with a MEVI? because that car is pulling all the way to redline

 

There is absolutely NOTHING wrong with your muffler. What your are hearing is the ugly sounds of the VQ without cat. My Maxima made the same exact noise when I had the Stillen non-resonated B-pipe. It sounds like metal clanking (assumed baffles). I went as far as replacing my 96 stock 4th gen muffler with a 99 4th gen muffler. The same exact sound came through. I then put the stock B-pipe back on and everthing was peachy again.


Dave

 

AllGo I like the sound of the stock muffler too... that is why I haven't gone out and bought something else already.

DaveB I know we had this conversation before. But one thing about what you just said, did you try to put an aftermarket muffler in with your test pipe and see if the clanging (baffle?) sounds still persist?

All I had to do was put my stock cat back on and voila... no more clanging (baffle?) noise... but that is also due to the pulsing that the mesh in the stock cat provides, as outlined earlier in this thread.

I will try a 2K muffler this weekend and see what results that yields. I don't mind putting the test pipe back on, as long as there is no clanging noise. But for a loss of a few HP, I'd rather do that than have that annoying rattle.

The other issue is my oil burning - with the test pipe it is easy to see blue smoke out the tail pipe when I floor it, but with the stock cat, there is no blue smoke at all.

The motor itself is healthy - compression tested at 170 - 180 across all cylinders.

 

especially considering that many states are adopting random drive by emissions tests (i drove by one last week), and that you dont lose much power, i would keep the stock cat. also, isnt there something morally wrong with daily driving without a cat? (dont get me started on 2 stroke scooters...) for racing, take out the cat, for day to day driving, leave it in.