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A lot of people that i know say that the best thing to do is to hollow out the catalytic converter or just not buy one and weld a 14" pipe in place off it . What I wanted To know is exactly how much power does the cat rob. Is it really worth the work. How much more horsepower would you have on the exact same system w/ just a welded 14" pipe instead of a cat. 2..3..4 more hp????
Help me out i just wanna know how power it takes away and if it's worth the ticket.

p.s.- buying a cat would be the same as getting the pipe welded on for me since i can't weld it myself.
 

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not really that much, and if your car was designed to use one it probably won't run right without one anyway so you won't gain didly chit by taking it off. Leave it be.

K
 

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back in the early days of cats there was some truth in the tail of cats power robbing how ever modern honey comb designs flow very well and you probably would't notice any difference after removing it how ever its very possible that you will cause problems drivability and codes in modern vehicals by removing it
 

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How much power does a cat really rob

Not that much really.Ya figure they only weigh about 12-14lbs evan fat one only weights 25lbs.Add another 8lbs for the litter box still not too bad though.
Now if they piss on the interior that could cause a problem.:D :D
 

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Re: How much power does a cat really rob

78 monte said:
Not that much really.Ya figure they only weigh about 12-14lbs evan fat one only weights 25lbs.Add another 8lbs for the litter box still not too bad though.
Now if they piss on the interior that could cause a problem.:D :D
ROFL!

I really needed a good laugh like that after the weekend I had. . . :mad:

At least I got my car up on stands to get a better assessment of body condition this morning, so all was not lost :thumbup:
 

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Re: How much power does a cat really rob

78 Monte said:
Not that much really.Ya figure they only weigh about 12-14lbs Even fat one only weights 25lbs.Add another 8lbs for the litter box still not too bad though.
Now if they piss on the interior that could cause a problem.:D :D
Doc here :pimp:

Hide yur women and Children...

HOW MUCH POWER DOES A CAT REALLY ROB...

Absolutely , positively, None at all...To my experience...They go for the Stocks, Negotiable Bonds, Jewelery, and cash in the wall safe....

And 78MONTE...Let's get real here...your way low on the weights you give...:D

You must have forgot to add the weight of his Beenie Hat, Scarf type mask, lock pick tools, second story equipment, and loaded firearm......must add at least 70 Lbs....

Gives a whole New rise To the Term "Cat Burglar" Dontja Think, eh what??:D :drunk:

WEBSTERS DEF: cats rob wealth...and are punished for it...
Politicians Rob Power....and are not....


Just Couldn't resist....

Doc :pimp:
 

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I had a 16 year old bad cat replaced and picked up substantial HP.

They do get clogged and that will rob your HP.
 

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I would have to disagree with everyone here and say that they do rob quite a bit of power.But also it depends on if it is clogged up or not.If it is not clogged leave it alone.But mine clogged on me and my car ran like garbage.Black smoke out the exhaust, stalling, not responding to throttle.Then I went and took it off and put a true dual exhaust all the way back with no converters and i would say I gained at least 10 horsepower.
 

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well there's a difference between saying a cat robs power in any situation and that a cat robs power when its clogged. I mean we could ask the question "does an air filter rob power?" and I could say "you're darn right they do, man I took mine out it was all full of grime and bugs! Picked up an easy 10 horse!"

Fact of the mater is most of the cats designed in the last 15 years work fine, and most cars that have them don't run properly if you take them off. If you're really that worried about it, spend 45 dollars and get a performance coverter out of summit (catco).

K
 

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I believe Lingenfelter and TPIS both did tests on a later year Z06 with and without cats. Their final results tallied around a 1hp lose with the cats on but they said that it was most likely not due to anything that they could control.

Bottom line is, unclogged, working properly for the car they were designed to work with, they shouldn't rob you of anything but your foul exhaust gasses.
 

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that article is a good one to read. A catalytic converter is just like anything else that's not a performance item. If you're trying to make serious horsepower, yes, its going to hold you back. But on a stock car that was designed around it a stock muffler, stock restrictive manifolds and small diameter stock exhaust (probably single) you really have nothing to gain by taking it off. And if you are going to build a motor that makes serious power, then you're goign to have to put an entire new exhaust system including headers, big, shallow bend pipe with performance mufflers on. I don't, however, believe that hacking a working converter out of a stock system is going to make that much of a difference. The example of taking one out that's plugged isn't really a valid example, because for all we know A: something malfunctioning in the engine caused the converter to be plugged, and B: how do we know that the truck wouldn't have run JUST AS WELL with a new, fully functioning converter put back on it?

The point here is what any hotrodder who is worth their salt will tell you, if you're going to make power you've got to treat your engine like a system. If you're going to upgrade the exhaust, do it correctly and upgrade everything from front to back. Hacking a converter out of a stock system is no less silly than putting a high rise manifold on a stock motor. Sure, you've got a manifold that flows great, and a set of heads, carb and cam that don't compliment it.

If taking a cat out makes more power in a stock condition car, then any means of lowering backpressure in the system should make more power. In fact, you should be able to simulate the condition of having no cat by making a nice big exhaust leak in front of it. Now I, for one, have never driven a car with a big exhaust leak that felt faster than it did when it wasn't leaking.

Just my .02-

K
 

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Cat

Doc here:pimp:

If were talking A Street Machine, within the smog window years, that YOU intend to keep Legally Street driving....

For what little amount it cancels in Overall Horsepower, Is well worth the headaches and cash you WILL go through in order to make a viable Stock WORKING smog system the next time you are REQUIRED to go through your Bi annual smog check....

Even if you strip the entire Smog system, and box it up in the garage for 2 years, and bolt the stuff back on, My experience has always been that it never plays right , at least not the first time out...and It's almost like the stuff just goes bad sitting in the box...

CATS are designed nowadays to play with Nice sounding , low flow Exhaust systems and is always a better investment...

If you really need to regain the Horsepower, Leave the spare tire and "Junk in the Trunk" at home...you'll make it up there ...

If yours is a Streeter, That requires annual Registration (in most states) Will most certainly require emission testing too, unless it happens to fall into a "Street Rod " Class (such as Nevada offers for hot rodders) or falls outside of the 30 year window for emissions.

I hear The Famous "I Can get around it next year" Statement, from many that actually think they can, until it's time to test...

Most end up upset because they can't get their tag, No one will "Bootleg" it for them because the fines and jail time is just too stiff and rising..and to get caught driving it without proper registration (at least in California) means losing the car for 30 days,
(Impound, 33 bucks a day for 31 days or $1023 for the month plus towing)

Or if more than 6 months out of REG, Seized (forever..) and either way (In California) even if you abandon the car to the impound yard, The CHP Sues you, and believe me, retrieves the impound fee's...

And just too get through Smog testing once every 2 years MAY not guarantee you a walk,

I'm not Sure if it's a federal Program or not, but here, (California) There is a 1~800 number ANY citizen can call to the Bureau of Automotive repairs, Who is following you down the highway, and doesn't like the Color or smell of your exhaust takes down your plate number and calls...The Result:

You get a notice to report (at any time even if you just passed) for smog testing TO PROVE you are within tolerance..Failure to do so results in revoking of your tag...(Back to the day it was issued) and getting pulled over will net you impound or loss of the car.

The only option is : If it's smogged, and you intend to drive it , work around the smog stuff..Leave the system alone, and working...Your far better ahead...

If you need horsepower and a street rod too get a 74 or under vehicle and go nutz...

OK, off the soap box...
Just a thought before
Ya' start unwrenching
yur smog system...

Doc :pimp:
 

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My cat on my '88 T-bird w/302 was a terrible restriction, & it got even worse when the brick inside it turned sideways, but then it was only a single-cat system. I beat it out with a tire tool, & freed up a boatload of power. If I had known the amount of power it was restricting, I'd have beat the thing out long before 150,000 miles went by. It does lend an odor to the exhaust, but hopefully a Mustang H-pipe with 2 cats will clean it up a bit.
 

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Hey Doc....that's why I'm glad I don't live in the Peoples republic of California. Too many politicians with too much time on there hands. Love the weather though....

I have a 90 Mazda RX7 (Rotary powered). Recently replaced my rusting exhaust with a parts car exhaust. During instalation I noticed the Cat was gutted. (some one must have need guitar strings) Because one of the 4 bolts on the old Cat was stripped I had to use the gutted Cat. I did notice a considerable difference in power. I had to bolt on the old exhaust for emmissions testing. Once again I noticed a drop in power. Also noticed about 2 miles/g drop. Naturaly I bolted on the gutted Cat. My guess is this Cat is partially clogged. It has 145K on it.
I do intend on replacing the entire exhaust eventually. It's gonna cost $1000. The rotary's pack more heat and require more durable Cats.
Right now all car cash is focused on the 59 Suburban.
 

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Discussion Starter #20
Not a stock exhaust

The reason i asked this question was because i was ordering a new system and wanted to know if i should get a cat w/ it or if i should just weld a pipe n there. I ordered hedman headers (shorty) and Y-pipe and a dynomax cat back exhaust. So i wasn't planning on just chopin the cat off my stock system. Any way i ordered a high-flow 2 1/2 cat from Catco. I don't think it will take off too much power. I am also planning on buying a 570cfm carb and dual plane intake manifold in the next month. After that I'm gunna get posi track.
 
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