incubuseva

iTrader: (13)

So I was having some trouble with emissions... Long story short -- I was driving my 91 NA around with a cat that was too short.

While I was driving the car like this, I noticed a few things;

1. It sounds like ****. I mean really REALLY bad. Not really a big surprise to me.

2. I had NO power what-so-ever. This surprised me. I do have an SAFCII set from -10 to -20. This might be why. Or the 190k mi w no rebuild.

I thought that you could just chop off your exhaust (like a cutout) + get more power? Or do you need a long exhaust to get the engines full potential?


Discuss.

Roen

iTrader: (2)

lol....search, there are many exhaust threads.

Search under the user rotarygod. I think I may have created a couple of threads.

Eva001Ikari

iTrader: (7)

Ok instead of searching let me just say this.

The BEST possible exhaust set up is NO EXHAUST AT ALL. Plain and simple if you really want to set your engine bay on fire to get really good exhaust flow, go righth ahead and let us know how it turned out.

zbrown

I am gonna have to disaggree 100% in a NA application

a good header system scavanges between rotors aswell as other things........

zbrown

original poster, you confuse me with what you said..... so you are running a cat that is unhooked at the rear from the rest of the system? or what? If it isn't an original cat what is it?

demontwig

Not to make a huge debate out of this thread that could have been searched for, but at least with my old blazer oepn headers killed that thing. Granted, it was a 350, but I think the same principles apply since it was N/A. In higher rpm's it was okay, but accel sucked. Did sound SICK though!

Anyway, I believe a properly designed system is a must for anything not going straight for a 1/4 mile or full race prepped. Even then sometimes they benefit from an exhaust system depending on application.

zbrown

^^^ I think you burn the valve seats or guides up on a SBC super rapid with no exhaust, dont remember which

doesnt sound fun

Roen

iTrader: (2)

An exhaust system is not just a restriction, it's a power adder. You'll make more power with a properly designed exhaust than no exhaust.

demontwig

I think that's wrong...the drag racers do it all the time, right? I only did it for a mile to the exhaust shop. Now, had I been running NO headers, the story would be a little different.

And yes, I agree with the exhaust being a power adder.

TehMonkay

iTrader: (-1)

And na fc open header sounds like an angry weed eater on crack. No good.for driving around town.

Roen

iTrader: (2)

I think for turbo though, anything after the exhaust manifold is a restriction since there's no scavenging done there.

zbrown

Should of clarified i meant no headers or anything on the heads,......

Sideways7

iTrader: (7)

Not to mention it is louder than most people can imagine. Think dragsters at full throttle.... With just the exhaust manifold, turning it on would set off car alarms from several blocks away.

I love pop-up lights

^ I would do that just to be an ***

wackaloo13

iTrader: (3)

for a turbo, the less backpressure the better. for n/a a properly designed exhaust will add power

FirebirdSlayer666

iTrader: (3)

Yep, no exhaust equals **** for power, at least in the low end. My ears would not allow me to get into the higher RPM range to find out any difference.

eagleheart

just a funny thought but my dad has a 91 bronco with straight pipes after the cats and he started it up one day in the pep boys parking lot and both cars beside his alarms went off

Phantomkid

serious open header drag cars are designed for high rpm and the motors are rebuilt all the time. As for an na you want a properly designed exhaust. If you go to big you will lose scavaging and low end power. on a turbo car you want the least restriction....
But about passing emission what where you numbers what gas/s did you fail for. You will need to have cats to pass emission.

incubuseva

iTrader: (13)

So I had some aftermarket cat (maremont or something like that) But it was too short, so I had it unhooked after the cat/before the Y pipe.

Yeah, It totally sounded like an angry *** weed whacker on crack.

I failed emissions because of HC while driving. Required is 150ppm, I got 162. Fresh plugs, even tried the denaturalized alcohol or whatever it's called.

I have the new cat w an extension pipe welded on it so it should fit now.