atmdc

I know this is retarded, but with no money I cant afford a test pipe atm. I was wondering if I could take off my universal cat and drill a 2 1/4" inch hole right through the center to match the piping, would it be like having a resonated test pipe? its an oval cat, I dont want to completely gut it because ive done it on an oval one before and hurts the exhaust flow horribly having to circulate in the empty cat. Just wondering about this...

ILLEGAL

you can gut the cat, just dont forget to the the seconday o2 extender trick to avaid codes and pass emissions. (sparkplug defowler)

It will sound like shit though.

atmdc

its an obd0 b16, both o2 sensors in the primaries

::edit:: just thought about it some more. the catalyst will probably all break to hell anyways when drilling, so nvm haha

ILLEGAL

what year is the car?

atmdc

89 civic b16 swap, but its an aftermarket cat i put on just to pass inspection in va. car ran better with the test pipe, but it was a home made test pipe and i had to cut the ends off to weld to the universal cat.

edit:: when i say ran better i mean ran better to my likings, not any statistical information here hah

BentValve

Not sure if you explained why you wanted to do this. I hope you aren't expecting a lot of gains from it.

ILLEGAL

oh it will def be faster with a test pipe. The problem you have with the age of the car, is you still have to do the sniffer test to pass emissions. Are you just gonna swap it back everytime?

BentValve

A test pipe on a B16 might get you 5hp, emphasis on might. After frictional loses, you will be lucky to see 1hp. Then you have to deal with emissions and smelling fumes at a stop. If you are willing to sacrifice all that for next to nothing, good luck.

Fabrik8

Frictional losses from an exhaust? What?

So putting on a test pipe gains 5HP, but then something else takes away 4HP? So if you gain 1HP, you didn't gain 5HP because you wouldn't be able to measure the 5HP if you only gained 1HP.. So you gain 1HP. Not 5.

And why would you lose 80% as friction anyway? That would mean a B16 makes 800HP but only puts out 160 because of friction (do the math, it's the same ratio). Something about the tiny size of the OEM radiator doesn't make sense all of a sudden if 640HP is lost as friction (heat).

shonanspeed

Okay- I got you on the super cheap test pipe. Get the cheap exhaust flexpipe from autozone, remove cat, band flexpipe on. Insta-test pipe. I had to do it once as a quick fix on my old rx7- mine broke and I needed to get home 2 hours away.