I will be deleting my catalytic converter shortly, I was wondering if anyone could share the width and length of the pipe I would need to replace it? I was also wondering if there are any surprises I should be aware of?

V6? One surprise you're in store for is how absolutely crappy your car will sound without a converter.
Idle sounds pretty good, but revved up or when you back off, it'll sound like a UPS truck.

I deleted the converter on my Formula for a while and after the novelty wore off - about three days later - I couldn't stand it.

does the Fiero Store still sell the "down pipe"?

but 1-7/8" comes to mind for pipe size

It is an 87 GT. It's not so much for novelty as it is for price. Shouldn't the exhaust note also depend on the exhaust system though?

im sure if you installed a pretty decent muffler. it wont sound all that bad

It's 2" pipe. You can get a length for "patching" at an auto supply place that should be long enough.

I tend to agree that a cheap Cherry Bomb would probably sound better.

Arn

I deleted the cat with the FS pipe and with my SS Borla exhaust, I like the sound.

quote Originally posted by Fiero Incognito: I will be deleting my catalytic converter shortly, I was wondering if anyone could share the width and length of the pipe I would need to replace it? I was also wondering if there are any surprises I should be aware of?

Are you doing this to gain horsepower? You'll lose a little bit of "snap" off the line if you just go with a straight pipe.

The most IDEAL replacement would be a high-flow cat... (like the Ocelot cat from the Fiero Store). YOu get improved top-end, AND... you get to keep the low-end power too...

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Todd,
2008 Jeep Patriot Limited 4x2
2002 Ford Explorer Sport 2dr 4x2
2002 Ford Crown Victoria LX
1987 Pontiac Fiero SE / V6
1973 Volkswagen Type-2 Transporter

My Fiero recorded a 15.474 quarter mile without the CAT. Adding even a high flow CAT will not improve torque, power, or assist in high end hp. A CAT is simply a drag on performance. It is designed for emissions only. It is not a performance improver in any way. In fact an old CAT, that is clogged up with carbon is a pretty big power robber, even bigger than a new CAT.

Adding a CAT to improve torque comes from the same school that believes you restrict exhaust flow to increase low end torque.
Just for the record, you use long tube headers to increase low end torque. The reason is that the scavenging produced by long headers increases the evacuation rate from the cylinder at lower rpm more than what short tube headers can do. The performance issue at low rpm is how you get the exhaust gases out of the cylinder fast enough to get fresh gas mix into the cylinder.

Your low end torque goes up as the exhaust flow rate goes up. Slightly narrower primaries also help low end torque due to the cross sectional area of the pipe promoting higher gas speed at lower rpm. Unfortunately the narrower primaries run out of steam at higher rpm and limit the engine. This is the reason so much work has been done to determine the size for headers. (Generally the 1.5" pipe is used as a compromise). You will find a CAT is a much debated item, but, anyone who knows anything about engine performance will tell you that ideally you just don't want one.

I hope this helps.

Arn

quote Originally posted by Formula88: V6? One surprise you're in store for is how absolutely crappy your car will sound without a converter. Idle sounds pretty good, but revved up or when you back off, it'll sound like a UPS truck. I deleted the converter on my Formula for a while and after the novelty wore off - about three days later - I couldn't stand it.

that's wierd. Mine sounds fantastic without it. I get a awesome burbule and screaming rumble with it off. but I have a borla exhaust, not a cheapie, that may make a big difference.

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Best RV, Camper, and Trailer dealer in West Michigan. http://www.cliffstrailersales.com and he's a fiero owner too!

I'm deleting the Cat because it is clogged, I will also be replacing my stock muffler, which has holes in it, with the "performance" one from FS

25" long, 2"ID diameter pipe, Use a "glasspack" to replace it. If you use "straight pipe", whenever you let off the gas, you'll have "burbling" (alot of Backfiring) it'll sound more like an old truck. I already tried that, took me 1 day to take it off & put the glasspack in place of the "straightpipe."

Is there a decently priced glass pack? Don't glass packs eventually were out?

You can find cheap glass packs for less than $20. I dont know about now, but in the old days they were packed with course grade steelwool. We would install them, fill them up with water and let it set overnite. In a day or two they sounded great.

I have an Ocelot system on my 3.4 coupe, and no cat, presently.
I really like the way it sounds.
Of course, the big cam and the headers help, too.

------------------
Raydar
88 4.9 Formula IMSA Fasback..........................88 3.4 coupe -soon to be something other than red

Read Nealz Nuze! Praise the Lowered!

Incognito - You have a PM

I also have no cat with stainless steel exhaust system.
The sound is great for both idle and high revolution!

This topic interests me greatly as I have read about the problems with the 2.8 exhaust manifolds. If $$$ was no option what is the ideal set-up? I have a tendancy to run with the school of thought of no cat myself.

1.) Which are the superior headers
2.) What is the best solution in the spot the CAT lived in?
3.) What is the superior exhaust system?
4.) I would assume some companies headers, some sort or 2" pipe, and a Borla Exhaust. I would like to know what kind of horsepower and torque would be gained with a setup like that, assuming everything else on the engine is stock.

Thanks

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Seeking a 1988 Fiero, preferably a GT and automatic.

No input from anyone?

Arns85GT I have to disagree while most of your post is more or less correct, Catalytic converters in good condition are not always a power robber and in some cases can in fact increase power, by keeping the exhaust hot it can help keep exhaust velocity up and in turn flow. A clogged catalytic converter is another story but in all honestly other then just being a cheap skate theres no reason at all to delete your catalytic converters.

Catalytic converters being so awful for performance is a myth that needs to die about as much as the lotus suspension crock.

How can you determine if a catalytic converter is clogged (without taking it off of the car) ?

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Bob T.

quote Originally posted by Arns85GT: My Fiero recorded a 15.474 quarter mile without the CAT. Adding even a high flow CAT will not improve torque, power, or assist in high end hp. A CAT is simply a drag on performance. It is designed for emissions only. It is not a performance improver in any way. In fact an old CAT, that is clogged up with carbon is a pretty big power robber, even bigger than a new CAT. Adding a CAT to improve torque comes from the same school that believes you restrict exhaust flow to increase low end torque. Just for the record, you use long tube headers to increase low end torque. The reason is that the scavenging produced by long headers increases the evacuation rate from the cylinder at lower rpm more than what short tube headers can do. The performance issue at low rpm is how you get the exhaust gases out of the cylinder fast enough to get fresh gas mix into the cylinder. Your low end torque goes up as the exhaust flow rate goes up. Slightly narrower primaries also help low end torque due to the cross sectional area of the pipe promoting higher gas speed at lower rpm. Unfortunately the narrower primaries run out of steam at higher rpm and limit the engine. This is the reason so much work has been done to determine the size for headers. (Generally the 1.5" pipe is used as a compromise). You will find a CAT is a much debated item, but, anyone who knows anything about engine performance will tell you that ideally you just don't want one. I hope this helps. Arn

I think your looking at it from a weird "perspective". I'm not suggesting that he "ADD" a catalytic converter to "improve" low-end torque.

I am suggesting that he maintains a catalytic converter (a newer, larger CFM rated one) to "maintain" the low-end torque.

You WILL see a power gain by eliminating the stock catalytic converter on the Fiero, however, if you took two stock automatic Fieros (everything identical)... one with a larger CFM "high flow" (as they advertise it) catalytic converter, and one without a catalytic converter. I guarantee to you that the one with the "high flow" cat will win in the quarter mile.

Removing a cat on the Fiero will reduce restriction, but there's a lot to consider. The Fiero's V6 is a decent motor... the 60 degree angle gives it good balance, and if built and designed properly, it would do awesome. However, the Fiero's V6 is NOT a high performance motor... it's just a stock V6 engine with a few little nice features. It was NOT designed for high-rpm driving.

When they designed the exhaust system, they designed it taking everything into consideration. IE: the size of the exhuast piping was determined while looking at the total aspect of the exhaust including the catalytic converter and the muffler. Everythig is designed to match. Of course, they also design the car to meet several conditions, CARB for California, CAFE, noise and emissions regulations. But the size of the tubing was designed to match that of the cat. Remove the cat, and you'll see a decrease in velocity... especially if you go with 2" exhuast tubing. By eliminating the cat, you are reducing some backpressure which is beneficial for improving low-end torque.

While you will see more "snap" on the highway... your "off the line" performance will be reduced. Although, with the louder exhaust you might be inclined to think the car is performing better (but it's just your imagination).

Like I said though, if you're comparing a Fiero with no cat to one with a STOCK cat... yeah, the one without the cat will be quicker. But a high-flow cat will give you EVERY benefit that removing the stock cat will, but will still maintain the exhaust velocity and proper back-pressure.

What do you mean by primaries? Are you talking about the flanges on the exhuast manifold tubing?

For what it's worth... my Fiero currently has no catalytic converter on it.

When I had my new exhaust installed... the shop owner that did the welding for me actually cut the catalytic converter off before I could stop him! Totally illegal... but I guess he felt he was doing me a favor. I have a new cat and a new header pipe between the cat and the Y-pipe sitting in boxes to install once I finish the rest of the work on the car.

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Todd,
2008 Jeep Patriot Limited 4x2
2002 Ford Explorer Sport 2dr 4x2
2002 Ford Crown Victoria LX
1987 Pontiac Fiero SE / V6
1973 Volkswagen Type-2 Transporter

[This message has been edited by 82-T/A [At Work] (edited 02-19-2010).]

catalytic converter

catalytic convert

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catalytic con

catalytic c

catalytic

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it is now deleted. just use your backspace key

[This message has been edited by americasfuture2k (edited 02-19-2010).]

quote Originally posted by timgray: that's wierd. Mine sounds fantastic without it. I get a awesome burbule and screaming rumble with it off. but I have a borla exhaust, not a cheapie, that may make a big difference.

I had a stock Formula exhaust, so that will be different. Borla does have it's own sound, and with or without a cat, I think they sound great.

The easiest way to get rid of a clogged converter is to get the "Exhaust Head Pipe" from The Fiero Store. It's the pipe from the connection to the Y-pipe and is long enough to replace pipe cut out when you remove the converter. That's how I did mine.

On my car, my converter was clogged up. It was so bad the engine wouldn't rev past about 4000 rpm and the exhaust manifolds were glowing red, then the engine started over heating. When I put a new hi-flo converter back on, I didn't notice any real decrease in power. Maybe a little bit around 6000 rpm, but that's it.

quote Originally posted by fyrebird68: How can you determine if a catalytic converter is clogged (without taking it off of the car) ?

Typically shops will remove the o2 sensor between the engine and the converter, and install a pressure gauge. This is measuring exhaust system backpressure. You should see less than a couple psi when you rev out the engine. If you see more than a few psi cat's plugged. Other than that, a converter that is almost completly clogged will start killing your power once it heats up, to the point some I have seen the vehicle would not even accellerate past 20km/h and in very rare instances it wont even run.

my .02 on the question at hand, when my cat started plugging up and robbing me of power in my 87 gt years ago, i had it removed and replaced with a high flow resonator, and replaced the original muffler to a cheapo turbo muffler.. sounded real decent, not too obnoxious and offered a substancial improvement in seat of the pants power feel haha

- Jay

[This message has been edited by edmjay (edited 02-19-2010).]