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Old 01-21-2004, 06:11 AM   #1
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catalytic converters do I need them?

I live in Michigan and we do not have to have our cars smog tested. Would the sound and breathing improve if i pull off the catalytic converters? or would my service engine light come on?
Has anyone tried this ?
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Old 01-21-2004, 08:37 AM   #2
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Well, to get any real noticable performance gains you need to be able to increase HP and/or Torque by about 10%. If you remove them the car should see a moderate HP increase maybe 1-2%.

I would guess maybe 3-5 hp.

The car will be:

lighter, slightly louder and have better gas mileage.

Since I've never seen a no cat boxster setup it may also cause some of the electronics to be readjusted. The computer reading the fuel system and exhaust may be confused if the temperature changes in the piping system. The back flow of the exhaust system will change. This might actually have a negative effect on HP gain.

That's what I'd say if we were drinking beers in the bar.

Anyone with 1st hand knowledge?
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Old 01-21-2004, 08:48 AM   #3
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Old 01-21-2004, 11:21 AM   #4
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are those resonators that I see? Is that the Gembala system?
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Old 03-28-2008, 08:49 AM   #5
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Toolpants, thats a nice exhaust setup. Can you tell me a little bit about it?
Thanks
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Old 03-28-2008, 09:17 AM   #6
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are those four smaller mufflers or cats (first set post headers underneath cross bars and post large mufflers before end of exhaust)?
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Old 03-28-2008, 11:10 AM   #7
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Unless you reprogram the DME the car will trip a CEL. The OBDII program looks at the before and after cat readings to determine catalytic efficiency.
The ROW program or a custom program could be used to ignore the secondary O2 sensors and just use the primary sensors for mixture adjustment.


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Quote:
Originally Posted by Automon
I live in Michigan and we do not have to have our cars smog tested. Would the sound and breathing improve if i pull off the catalytic converters? or would my service engine light come on?
Has anyone tried this ?
Regards,
Automon
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Old 03-28-2008, 12:01 PM   #8
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When I first put headers on my car I also had the secondary bypasses so no cats. The throttle response was noticeably improved but the sound was horrible. I have the PSE on my car and it had always produced a great growl at RPM's. Without the cats, the sound was higher pitched and raspy. I slunk down in my seat it sounded so bad though others really liked it. I tripped a cel about every 300-500 miles. I put the secondary cats back on. I little less HP but much better sound.
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Old 03-28-2008, 01:30 PM   #9
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Well, since nobody's brought it up, I'm going to state the obvious.

It's illegal in most states to remove, or otherwise tamper with, emissions equipment.

And, without the cats, you are certainly producing more harmful emissions.

If you don't have any moral conflict over this, then go ahead.

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Old 03-28-2008, 03:37 PM   #10
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And, without the cats, you are certainly producing more harmful emissions.

If you don't have any moral conflict over this, then go ahead.

I guess the way I look at this is we all make choices everyday. If you drive your car versus riding a bike or walking you are producing more harmful emissions. Should I feel bad about taking my car to the track and creating the resulting emissions for a day of driving for pleasure? I'm not aiming this back at you Lil bastard, you are just stating facts but I get irritated over some of the hypersensitivity in our society that in many instances is just personal feel-goodism. There are people in my area that are letting their yards go to rat infested jungles because they want to spout out how noble they are because they are no longer polluting the environment with emissions from their lawnmowers as they drive off in old volvos belching blue smoke. Ok I'm done. Whew!!!
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Old 03-28-2008, 03:44 PM   #11
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@Steve00s,

It's all good, I take no offense.

As you point out, I was only stating the facts. I did not endorse or condemn such a move.

But, there can be some issues if the car is sold, inspected, etc.

I'm nobody's priest, and I ain't preaching.

But, there are lots of newbys here and it's helpful to know all the potential consequences of your actions.
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Old 03-28-2008, 04:06 PM   #12
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You are right. Its all good. Other than it is snowing here when it should be sunny.
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Old 03-28-2008, 05:43 PM   #13
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Quote:
Originally Posted by Lil bastard
Well, since nobody's brought it up, I'm going to state the obvious.

It's illegal in most states to remove, or otherwise tamper with, emissions equipment.

And, without the cats, you are certainly producing more harmful emissions.

If you don't have any moral conflict over this, then go ahead.

Just replace all you household light bulbs with energy efficient ones and hook up a generator to your stationary bike to power your PC while using it and you will even everything out.
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Old 03-28-2008, 09:31 PM   #14
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Hey Toolpants,

Very cool setup!

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Old 03-29-2008, 11:38 AM   #15
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Well alot of guys on the viper forums remove cats and can gain 20 or so hp 4-5% on a 500 hp car. The guys with twin turbos or superchargers almost always have all cats removed and performance exhaust or no exhaust for max horsepower. It will trip a CEL if you have no cats, you can buy O 2 simulators but they may or may not worked based on what I've read on other cars.
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Old 03-29-2008, 05:07 PM   #16
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Toolpants- Which exhaust is that?

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Old 03-30-2008, 07:57 PM   #17
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Does it take 300-500 to have the CEL trip if the all of the cats are removed? I always assumed it was quicker than that.
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Old 03-30-2008, 09:12 PM   #18
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Quote:
Originally Posted by steve00s
You are right. Its all good. Other than it is snowing here when it should be sunny.

Steve do you still have the cat by-pass pipes if so. I can hook up with you this week if you want to sell them.
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Old 03-31-2008, 08:48 AM   #19
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I sold them a while ago.
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Old 04-11-2008, 03:19 PM   #20
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Here is another set up with no cats. www.myspace.com/tcechelon I'm still tinkering with getting the bugs out but should have it this month then for the chip. I used to race my friends 03' M3 and he would pull away from me on the highway bad. He installed a race exhaust... type slips my memory. I installed Evo intake, che's headers, exhaust, and fabspeeds test/ bypass pipes now he only moderately pulls on me. The sound is loud when on it but doesn't quite get you pulled when behaving. This car deserves to sound that way. I think people expect it when they see a modified Porsche... maybe a little different if that was the only thing's done. The resonance is not bad because of the motor firewall.

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