anyone GUT their cat?

[pr5owner]

if so how did you do it? stick a peice of wood in and start hammering or what?

istill have my 2nd cat, im contemplating replacing the mid pipe or just gutting it

 

[Captain KRM P5]

turbo matty P gutted his first cat, but for obvious reasons you can't ask him about the details

 

[Gen1GT]

Why don't you just go out and spend the extra $70 and buy a new hi-flow cat? Negligable loss in power, and still legal......

 

[SpicyMchaggis]

xelderx did i believe.

 

[Emode]

i did it to my cats on the stock msp exhaust
took a long pipe and pretty much just started ramming the s*** out, it takes a bit, and all the stuff is also surrounded by a screen which is a b**** to get out, you have to get out all the cat material first, then crush the screen until you can reach it with a pliers and pull it out.

mind you this was two full exhausts ago

 

[melicha8]

Please don't

 

[xelderx]

Gutting the pre-cat only works if you install the CEL eliminator too. There was a difference in response that I could tell just by driving it around. It also made the Mazdaspeed muffler sound really mean. basically, with the exception of the cost for the CEL eliminator it is free power. It has already been proven that the first cat is not needed and the second stock cat provides enough backpressure to keep good torque on a N/A FS

 

[pr5owner]

hmm since i don't have a precat.. i guess i'll just leave my remaining cat alone... poor pussy, i was going to gut him as soon as i could find out how..

 

[Emode]

cel fix is only about 15 shipped most places, not too bad

 

[WheelManATX]

hmm since i don't have a precat.. i guess i'll just leave my remaining cat alone... poor pussy, i was going to gut him as soon as i could find out how..

Just get rid of it and replace it with this,

Cherry Bomb Glasspack , about 20 bucks at almost any auto store.

It's the ANTI-RICE for the Protege......

 

[MP5onBOOST]

Keep the cat, just go ask for a test pipe. We just got crazy ass smog laws here in California, so when it comes time for me to smog my beast, ill just put my cat back on..

Pinky

 

[Gen1GT]

It has already been proven that the first cat is not needed and the second stock cat provides enough backpressure to keep good torque on a N/A FS

"Provides enough backpressure to keep good torque on a N/A FS?"

Dude, c'mon. That's an OLDSCHOOL theory that should have died with the muscle car era. You don't want any backpressure what-so-ever in your exhuast system. You want it to be zip, zero, nada.

It's VELOCITY that you want. And with backpressure, you hinder velocity. When people used to put in larger diameter exhaust which hugely lowered backpressure(older American exhaust sytems were poorly designed to begin with), they thought that was the reason they lost torque, but it has nothing to do with exhaust system pressure. Larger tubing lowers exhaust gas velocity(at low RPM), and hinders scavaging at lower rpm, which lowers torque. But larger tubing also allows for that velocity at higher RPM, which with any backpressure at all, would lower velocity. You can have a middle ground of course, with well designed exhaust having mandrel bends and only 2.25" tubing. Enough to lower back pressure and keep velocity up at low RPM, yet free flowing enough to not hinder high RPM power too much.

 

[xelderx]

"Provides enough backpressure to keep good torque on a N/A FS?"

Dude, c'mon. That's an OLDSCHOOL theory that should have died with the muscle car era. You don't want any backpressure what-so-ever in your exhuast system. You want it to be zip, zero, nada.

It's VELOCITY that you want. And with backpressure, you hinder velocity. When people used to put in larger diameter exhaust which hugely lowered backpressure(older American exhaust sytems were poorly designed to begin with), they thought that was the reason they lost torque, but it has nothing to do with exhaust system pressure. Larger tubing lowers exhaust gas velocity(at low RPM), and hinders scavaging at lower rpm, which lowers torque. But larger tubing also allows for that velocity at higher RPM, which with any backpressure at all, would lower velocity. You can have a middle ground of course, with well designed exhaust having mandrel bends and only 2.25" tubing. Enough to lower back pressure and keep velocity up at low RPM, yet free flowing enough to not hinder high RPM power too much.

Ok...lets take a good look at this from a logical standpoint. I have 92,000 miles on my car. 0% of those miles have been put on at a drag strip. My car is driven almost everyday and the majority of the time the engine is revving below the rpm's where it reaches peak torque. You put an identical car to mine beside me at a light, but it has a completely open exhaust and I'll beat it off the line everytime. Why??? Because even though they may have more torque when the engine is spinning at 6500 rpms, I make more torque down low. Don't look at peak torque and preach gains. If I gutted my exhuast completely, not only would my car sound like s*** but I would have to drive around like Ricky Racer wanna-be just to use the "extra" power I've found.

Now...lets look at this from a technical standpoint. The FS motor's cams have overlap in the cam cycle. That is that the intake cam starts opening before the exhaust cam is fully closed. Now pay attention, I don't want you to miss this. If both cams are open at the same time and you have no backpressure in the exhaust manifold part of your intake charge gets sucked out the exhaust manifold before the exhaust cam closes. Now your running lean...aka not stoich...and there isn't s*** your ECU can do to make up for it. Leave a proper amount of backpressure in the manifold so that the intake charge isn't partial scavenged with the exhaust gasses and you have a better running car.

Remember that your car came with bad exhaust from the factory. The 3rd Gens actually have pretty good exhaust flow for a N/A 2.0 motor. If you drive your car at 6000 rpms everywhere you go...bravo. My car really likes to pull around 4000 rpm...you know where it is driven 99% of the time. Don't start calling people oldschool when in all reality you are the one with a 93 Protege to base your findings on and you're arguing over a 2003 Protege. They are not the same motor. They don't have anything near the same exhaust system.

Bring on the flames...Ricky

 

[Captain KRM P5]

Just get rid of it and replace it with this,

Cherry Bomb Glasspack , about 20 bucks at almost any auto store.

It's the ANTI-RICE for the Protege......

that sucker looks awesome - gotta be loud as hell

 

[WheelManATX]

that sucker looks awesome - gotta be loud as hell

No it's really not loud at all, I had only a header - straight pipe no cats - muffler and talk about (rice)..... but after i installed the glasspack, it has a nice deep tone to it

 

[Gen1GT]

Ok...lets take a good look at this from a logical standpoint. I have 92,000 miles on my car. 0% of those miles have been put on at a drag strip. My car is driven almost everyday and the majority of the time the engine is revving below the rpm's where it reaches peak torque. You put an identical car to mine beside me at a light, but it has a completely open exhaust and I'll beat it off the line everytime. Why??? Because even though they may have more torque when the engine is spinning at 6500 rpms, I make more torque down low. Don't look at peak torque and preach gains. If I gutted my exhuast completely, not only would my car sound like s*** but I would have to drive around like Ricky Racer wanna-be just to use the "extra" power I've found.

Now...lets look at this from a technical standpoint. The FS motor's cams have overlap in the cam cycle. That is that the intake cam starts opening before the exhaust cam is fully closed. Now pay attention, I don't want you to miss this. If both cams are open at the same time and you have no backpressure in the exhaust manifold part of your intake charge gets sucked out the exhaust manifold before the exhaust cam closes. Now your running lean...aka not stoich...and there isn't s*** your ECU can do to make up for it. Leave a proper amount of backpressure in the manifold so that the intake charge isn't partial scavenged with the exhaust gasses and you have a better running car.

Remember that your car came with bad exhaust from the factory. The 3rd Gens actually have pretty good exhaust flow for a N/A 2.0 motor. If you drive your car at 6000 rpms everywhere you go...bravo. My car really likes to pull around 4000 rpm...you know where it is driven 99% of the time. Don't start calling people oldschool when in all reality you are the one with a 93 Protege to base your findings on and you're arguing over a 2003 Protege. They are not the same motor. They don't have anything near the same exhaust system.

Bring on the flames...Ricky

Ok, so you're preaching to me like you're a automobile shop teacher, yet you actually have NO CLUE what you're talking about. YOU NEVER, EVER, EVER, EVER want backpressure. Like I said, it's all about velocity. The whole point of having 'overlap' isn't for the intake charge to flow out the exhaust valve. I'm not sure what the FS overlap duration is, but on mine, it's 19 degrees. The point of overlap is take advantage of the negative pressure wave, and vacuum created by the exiting exhaust gases. That vacuum PULLS the intake charge into the cylinder, an effect called scavaging. NOW PAY ATTENTION, I DON'T WANT YOU TO MISS THIS. Free flowing exhaust, with LITTLE OR NO backpressure aids in this effect. Which mean that with a free-flowing exhaust, more intake charge is pulled into cylinder by the exiting exhaust gases, but neither of our cars has enough overlap to affect low RPM power or idle. If you're running huge cams, duration is high enough, that at low RPM you lose vacuum, and some of the intake charge DOES go out the exhaust valve. Yet at high RPM because you have less time to fill the combustion chamber, you get the desirable scavaging effect.

When intake charge is over-scavaged, you don't run lean. The intake charge will have the same A/F ratio no matter how much shoots out the exhaust port, you'll just have LESS of the charge in the cylinder. Which will just give you weak power. There is absolutely no disadvantage to a well designed, high-flowing exhaust, other than noise. When I installed my custom 2.5" exhaust, I didn't lose one bit of torque. But the large size will allow me to flow enough air to get my 170whp, 8000rpm goal.

Where in the powerband a car makes torque, has nothing to do with how fast it is off the line. If you make max torque at 3500rpm and I make mine at 5000, I just launch at 5000rpm(feathering the clutch of course). 60' times are based 95% on traction and launch technique, and 5% on how much torque you have. I've beaten plenty of Mustangs and Camaros off a light because I know how to launch. They spank me after 40 feet though, but it just proves that torque is not a factor in how quick your car is off the line. I don't neccesarily have to drive at 6000rpm either, since my car weighs much less, and needs less torque get accelerate it.

The exception is two cars driving at 10mph in first gear. The car with more torque will always win in that situation. Doesn't mean I can't put the clutch in, rev it up and drop it though.....

Any more 'OLDSCHOOL' myths you want me to shoot down for you?

 

[viVid]

The intake charge will have the same A/F ratio no matter how much shoots out the exhaust port, you'll just have LESS of the charge in the cylinder. Which will just give you weak power.

Which almost guarantees you won't pass emissions testing, dammit! Another reason for adjustable cam gears...

Where in the powerband a car makes torque, has nothing to do with how fast it is off the line. If you make max torque at 3500rpm and I make mine at 5000, I just launch at 5000rpm(feathering the clutch of course).

But even by feathering the clutch @ 5000, you are not putting down your max torque due to power loss through the slipping clutch... ?

The exception is two cars driving at 10mph in first gear. The car with more torque will always win in that situation. Doesn't mean I can't put the clutch in, rev it up and drop it though.....

Assuming the cars are of similar weight, and gearing...

 

[xelderx]

Ok, so you're preaching to me like you're a automobile shop teacher, yet you actually have NO CLUE what you're talking about. YOU NEVER, EVER, EVER, EVER want backpressure. Like I said, it's all about velocity. The whole point of having 'overlap' isn't for the intake charge to flow out the exhaust valve. I'm not sure what the FS overlap duration is, but on mine, it's 19 degrees. The point of overlap is take advantage of the negative pressure wave, and vacuum created by the exiting exhaust gases. That vacuum PULLS the intake charge into the cylinder, an effect called scavaging. NOW PAY ATTENTION, I DON'T WANT YOU TO MISS THIS. Free flowing exhaust, with LITTLE OR NO backpressure aids in this effect. Which mean that with a free-flowing exhaust, more intake charge is pulled into cylinder by the exiting exhaust gases, but neither of our cars has enough overlap to affect low RPM power or idle. If you're running huge cams, duration is high enough, that at low RPM you lose vacuum, and some of the intake charge DOES go out the exhaust valve. Yet at high RPM because you have less time to fill the combustion chamber, you get the desirable scavaging effect.

When intake charge is over-scavaged, you don't run lean. The intake charge will have the same A/F ratio no matter how much shoots out the exhaust port, you'll just have LESS of the charge in the cylinder. Which will just give you weak power. There is absolutely no disadvantage to a well designed, high-flowing exhaust, other than noise. When I installed my custom 2.5" exhaust, I didn't lose one bit of torque. But the large size will allow me to flow enough air to get my 170whp, 8000rpm goal.

Where in the powerband a car makes torque, has nothing to do with how fast it is off the line. If you make max torque at 3500rpm and I make mine at 5000, I just launch at 5000rpm(feathering the clutch of course). 60' times are based 95% on traction and launch technique, and 5% on how much torque you have. I've beaten plenty of Mustangs and Camaros off a light because I know how to launch. They spank me after 40 feet though, but it just proves that torque is not a factor in how quick your car is off the line. I don't neccesarily have to drive at 6000rpm either, since my car weighs much less, and needs less torque get accelerate it.

The exception is two cars driving at 10mph in first gear. The car with more torque will always win in that situation. Doesn't mean I can't put the clutch in, rev it up and drop it though.....

Any more 'OLDSCHOOL' myths you want me to shoot down for you?

Alrighty then. Your going to sit here and tell me that it is impossible to over-scavenge the exhaust gasses? You said it yourself that a "WELL TUNED" exhaust would show no disadvantage. Gutting your cats does not qualify as "WELL TUNED" no matter how lucky you get.

Your argument about beating Mustangs and the like "off the line" makes no sense what so ever. If they kick your ass after 40 feet you still lost "off the line" because the car with more torque earlier in it's powerband caught and passed you. 40 feet isn't even the width of a normal intersection. Plus...your comparing apples to oranges.

The whole basis of your arguement is still based on high RPM's. After reading over your arguement several times to make sure that I was clear on everything you said it came down to the second to last sentence that assured me that we will never be on the same page. If you clutch to get your revs up and then drop the clutch you've lost time. If the cars are that evenly matched where you think you can do that and actually make up for the lost time it took to get your revs up your crazy...and the car with more LOW END TORQUE DUE TO NOT HAVING A GUTTED EXHAUST will beat you because he still had more torque and could use it 100% of the time.

You're bench racing and you're good at it, but thats all it is...bench racing. Your talk doesn't hold water on the street.

 

[xelderx]

I'm also going to admit that I am using the word "backpressure" incorrectly. What we are really talking about here is scavenging or lack there of (backpressure as far as I'm concerned). I hope my mis-use of words is not what is causing us to butt heads.

 

[AlbinoMuntjac]

Alrighty then. Your going to sit here and tell me that it is impossible to over-scavenge the exhaust gasses? You said it yourself that a "WELL TUNED" exhaust would show no disadvantage. Gutting your cats does not qualify as "WELL TUNED" no matter how lucky you get.

Your argument about beating Mustangs and the like "off the line" makes no sense what so ever. If they kick your ass after 40 feet you still lost "off the line" because the car with more torque earlier in it's powerband caught and passed you. 40 feet isn't even the width of a normal intersection. Plus...your comparing apples to oranges.

The whole basis of your arguement is still based on high RPM's. After reading over your arguement several times to make sure that I was clear on everything you said it came down to the second to last sentence that assured me that we will never be on the same page. If you clutch to get your revs up and then drop the clutch you've lost time. If the cars are that evenly matched where you think you can do that and actually make up for the lost time it took to get your revs up your crazy...and the car with more LOW END TORQUE DUE TO NOT HAVING A GUTTED EXHAUST will beat you because he still had more torque and could use it 100% of the time.

You're bench racing and you're good at it, but thats all it is...bench racing. Your talk doesn't hold water on the street.

Dude, it's useless arguing with him. He trolls through the performance section looking for opportunities to spout off with his automotive "knowledge" as gospel. For proof, please see the current post about the NA cams. The way he tries to explain everything in a technical way to show he knows what he's talking about is merely smoke and mirrors. Most people here don't know all that much about the super-technical aspect of cars, and he capitalizes on that. Make it sound like it's the truth and believable and it is. I would suggest not wasting anymore breath on him.