So I rest my case, like my car did as a NA, it sounds like ass.

Of course that is your opinion. But note that I said it sounds almost like the one in that vid. In that vid you can still hear the raspiness from the car a little bit. With my car you barely hear that N/A raspiness. I'm trying to find someone with a video camera so that I can make a vid so you guys can hear it.

And of course, the sound of this tip is open for debate. I like it, but that doesn't mean everyone will.

http://www.youtube.com/watch?v=uPt4ku4t_PI

it sounded like michaels but alot quieter IMO.

I used to run a 2 1/4" with the stock cat, no muffler and a resonated tip, sounded ok, but mostly like my car now only quieter...

I know I need to pull my cat off because the exhuast is starting to smell funny, but I know if I pull the cat off, its gonna make the car sound like shit... I could always replace it with a new cat...

I have an n/a too but my exhaust works great! if i want to keep
the pressure for torque then upgrading seems useless....
would the best thing just be upgrading the cat only?

are you still digging up old threads?

back pressure = bad

flow = good

flow makes power, a good exhaust on a NA won't make you lose torque.

I replied with that before, but for some reason its not there...

Yeah, but I have read that too much flow is bad for torque in an NA. A good exhaust system is one that is properly sized for the engine size. A 4" exhaust on a Z31NA is not a good exhaust and should rob torque at low RPMs.

a 4" exhaust wont flow well. Its all about the exhaust velocity, the faster the exhaust can escape the more power it will make.

back pressure is not a bad thing. I went with a2.5 straight back no cat w/ a can on it. It was slower than stock untill I upgraded my Throttle body, Built an Intake system and Bored the plenum elbow. In my opinon it depends on how much air your intake side can move. Go from that to design your exhaust. You want bigger intake than exhaust for sure. And size doesnt matter on the exhaust side flow matters. If you have steps and areas that open up at the exhaust that are no chaphered you are limiting the size on the pipe by creating air turbulence there is less useable flow area. As well as bends. even mandrel bends cause turbulence just no as much. This turbulence helps add to the raspyness of the exhaust because the air is bouncing around in the pipes instead of flowing smoothly. i am no pro but my friend is a mechanical engineer and this is how it was explained to me.

Most of this is garbage. Some of it doesn't even make sense in a linguistic fashion.
Backpressure is bad, period.
Always want the intake bigger than the exhaust? This is also a load of crap.

In fact, like 99% of that post makes no sense whatsoever.

http://www.z31performance.com/forum/vie ... ckpressure

hate to link to outside threads but read up, and learn 1stcar86z



on a turbo car i agree for the most part, however, the intake before the turbo should be at least the size of the exhaust if not larger.

in an n/a engine, which is just basically an air pump, the above statement is somewhat true imo. pumps ALWAYS require a larger suction tube than output (or exhaust) tube to prevent cavitation and other unhappy things. however in the engine's case it's just trying to get rid of the spent charge as quickly and easily as possible. the intake should be at least as large as the exhaust, otherwise it will become the limiting factor.

Ok n00b. I had an '86 NA, stock exhaust had ok torque and no power up high. I replaced it with a 2.5" exhaust, no cat (2.5" pipe), and no muffler (also 2.5") with a 2.5" resonated tip. The low end power seemed slightly better than stock, and high end power kicked stocks ass.

http://videos.streetfire.net/video/Flyb ... 201460.htm
i have a turbo tho
but its a 3" no cat no muffler

http://www.howstuffworks.com/question172.htm

okay so like i said i am no pro but this is how stuff was expained to me i was appartently wronge and i have since read the post article. But my car was defiantly slower with the 2.5 no cat, stock intake side (except for a can filter).
And mike you forgot to ask questions. so i will, were did your 2.5 start and did some of your y piping have to be replaced when your cat was removed? Did you have vac lines remove or were you stock on the intake side?
And i am sorry but the high end only made alot of noise after replacing the exhaust. I couldnt even keep up with my friends civic any more. Although i do agree that it increased the low-end torque a little.

Exhaust started as 2.5" right off the 2.5" Y-pipe. Intake was a red-neck custom I guess you could say...

Heres an oooold pic of my engine bay:

yeah mine was cut off half way down the y pipe and was replaced with 1.5 to a new y to 2.5 so maybe the loss of back pressure/flow velocity was the difference in mine and yours and the reason mine. plus i had the full shitty intake w/ a pos can untill i built the new intake for it. ill post some pictures of the new intake. on the project area soon i have no pictures of my progress though.

You obviously haven't learned if you think back pressure makes horsepower.

And the stock Y-pipe is a 1.5" to 2.5" Y...