: Are CAT's really that restrictive???



Moparman4444
07-15-13, 10:03 AM
I was at a car show yesterday and spoke to a tuner who told me that the main CAT's just behind the manifolds, where not that restrictive as compared to a straight tube if you were under 620 hp. That seemed completely contrary to every thing I have heard for years. However he said that he had objective data to prove it from 2 cars he tested. I was told that there was less than 3 hp gained with open pipes but a definite sound increase inside the cabin. Those comments made me wonder. Has anyone else ever done a comparison between the stock CAT's vs an open pipe assuming the rest of the exhaust remains the same?

ptrd
07-15-13, 10:31 AM
Coming with no empirical data, I would probably say this is probably true. Maybe back in the day car manufacturers had more restrictive exhaust systems but nowadays with better technology they can push the limits more.

I know there is a lot of discussion on backpressure (is it good, bad, necessary, etc) and sometimes open headers just don't help as much. I've seen smaller NA motors lose power with bigger diameter exhausts installed.

Moparman4444
07-15-13, 01:06 PM
I know from experience that in a NA engine going to a larger exhaust header like 1 3/4" vs 2" can definitely lower hp because back pressure is an important part of the power formula, however in a boosted application, I didn't think that mattered as much.

rgp6373
07-15-13, 01:29 PM
I don't think being restrictive is the problem with cats, I have has two modded supercharged vehicles (2003 Silverado SS 700+hp and my 2009 Cts-V 640rwhp) and in both the cats disintegrated after a couple months even hi flow cats didnt last, maybe I just have bad luck with them or drive to fast lol

Moparman4444
07-15-13, 02:16 PM
Generate too much heat with the higher boost????? Nice rgp6373 !!!1 That means your doing something right.

CavemanB52
07-15-13, 04:38 PM
I had the same problem. Started melting the stock cats. So I went to Kooks headers no cats. No cats... No problems... :) little louder than I wanted. Stock muffler but its growing on me. Maybe ill go to Corsa's if it turns out to be too much.

rgp6373
07-15-13, 08:02 PM
Not to hi jack the thread but with no cats and headers corsa is way to loud, I had to put stock muffler back on. However I did ad QTP cutouts just in front of the mufflers for when I do want to be obnoxious lol
http://youtu.be/KqbsnTWXA98

Moparman4444
07-15-13, 09:42 PM
rpg6373, I love the electric cutouts. That is a modern twist on old school trick.

----------

What if the CATS were mounted further back like 3-4 feet so they would be in the middle of the car. Granted they would not heat up like if they were closer but would still be emission compliant and would quiet down the car. Just a thought.

rgp6373
07-16-13, 12:44 AM
That might work but where I live there is no emissions testing so not worth my time or money . Money better spent on gas and tires lol.
I installed the remote for the cutouts it's nice to have just a little key fob to control them

6speeder
07-16-13, 10:47 AM
rpg6373, I love the electric cutouts. That is a modern twist on old school trick.

----------

What if the CATS were mounted further back like 3-4 feet so they would be in the middle of the car. Granted they would not heat up like if they were closer but would still be emission compliant and would quiet down the car. Just a thought.Actually, that's not compliant. Compliant means factory cats in factory location. And you might get a CEL because the cats aren't getting hot enough, soon enough.

CavemanB52
07-16-13, 04:53 PM
I almost put cutouts on mine but someone scared me when he said they get stuck sometimes.

Naf
07-16-13, 06:31 PM
The stock cats are slightly restrictive. Switchin to the high flow will open up top end hp. But u would only do that if u upgrade the headers

Cutouts are mainly for stock catbacks that are very quiet and power robbin u put them before the mufflers.

CavemanB52
07-16-13, 07:30 PM
Again... no cats... no problems... :)

Naf
07-17-13, 03:33 AM
With a supercharger you need some restriction. If you run catless you will gain top end hp but lose on bottom and mid power, (power being hp and torque)

Put in high flow cats and let the power come to you.

We dynoed a supercharged car with and without out cats and the verdict was 5 hp gain at max rpm with a 15-20 power loss from 3500-5500rpm

was it worth it, AH NO!, cut the ac belt if you want more power, we have seen gains of 10hp by simply cuttin the ac belt...

Ppl will go to extremes to win races here, even if it costs them ac while drivin home after a victory race...

CavemanB52
07-17-13, 09:26 AM
The muffler is the only restriction you need to keep from losing HP due to back pressure. The low end HP loss your speeking of is from straight pipes. The test numbers are on this forum. Done with the same car and motor. You are right for the most part but there is no power loss with no cats. There is just not much of a power gain unless over 600 hp or there abouts. So you can't talk generalities. Most who have done more than just added an exhaust ie pulleys, meth, porting will see additional all around improvement with power and torque due to headers. Still need back pressure but a stock muffler to going to provide that. Cats or no cats doesn't make a difference except maybe sound increase. Cats for what they can and can't do is like talking a about purple dragons and wizards.

Moparman4444
07-17-13, 10:51 AM
Caveman and Naf bring up interesting points. I did a search on this forum and found countless comments and opinions about exhaust and CAT's but was more interested in objective evidence comparing an exhaust with Cats on a stock exhaust vs one without the cats. Granted everyone's other power components very and results will probably very accordingly.

But as a general rule of thumb for cars in the 580-640hp range I wonder what the difference would be in sound and power?

GMX322V S/C
07-17-13, 08:39 PM
I don't know about the close-coupled cats, but putting the main cats (the rear set) back in and re-tuning only cost me a little more than 1 RWHP.

It's been awhile (ca. 2009), but IIRC, Wait4Me built and tested a completely catless and muffler-less 3" mandrel-bent system connected to the stock exhaust manifolds (separate downpipes to replace the close-coupled cats were an option). With no other mods, again IIRC, the net change was only 6-8 RWHP or so. He reported his findings here, so they're probably in the forum archives somewhere.

CavemanB52
07-17-13, 10:03 PM
I've seen 10-25 hp increase for various header install before and afters but the one test I saw for the difference between cats or no cats was a 1 hp increase in the middle of the power band for a split second. So essentialy no change. Just some extra sound. I don't like dealing with the possibility of melting them. Besides they are useless after they go in the landfill they breakdown and release carbon into atmosphere anyway... so why even use them in the first place. Tree huggers do more damage to the environment than they anything else.

miamictsv
07-18-13, 09:38 AM
I removed mine using W4M cut delete pipe. My tuner warned me of melting them with my current power levels. 626WHP at this time. I really do not like the new louder sound compared to the stock one but had no options at the time.

Moparman4444
07-18-13, 10:40 AM
miamicts,

Did you ever ask if the replacements of the CATS with a glass pack type muffler would quiet things down? They are relatively cheap and could fit under the car with ease.

CavemanB52
07-18-13, 10:44 AM
I removed mine using W4M cut delete pipe. My tuner warned me of melting them with my current power levels. 626WHP at this time. I really do not like the new louder sound compared to the stock one but had no options at the time.

Same problem here. Decided to just through Kooks headers and Xpipe connected to factory muffler. If you do this ask for a modified connection pipe from Kooks to fit a coupe (If you have a coupe). Cause otherwise you will need to weld stainless steal and do your own modification to the exhaust. They cut and flanged mine to fit.

miamictsv
07-18-13, 01:00 PM
I have been thinking about it for a while but my car is not the most reliable one i have own and constantly something else goes wrong before i get to this. Now is time for a new evaporator and $1200 bill probably :(

miamicts,

Did you ever ask if the replacements of the CATS with a glass pack type muffler would quiet things down? They are relatively cheap and could fit under the car with ease.

GMX322V S/C
07-18-13, 03:02 PM
miamicts,

Did you ever ask if the replacements of the CATS with a glass pack type muffler would quiet things down? They are relatively cheap and could fit under the car with ease....or steel packs even, like the Porter Shorty: http://www.ravenworksllc.com/browse.cfm/4.0-body-3.0-inlet-outlet/4,110.html

I ran a bridge-ported 13B rotary engine in a Mazda RX-3 when I was a kid (~2,000 deg. F exhaust temps) and steel packs were the only things that would last more than about 6 months.

baabootoo
07-21-13, 09:43 PM
That "needs some restriction" is an old wives tale; the less the better. An engine is an air pump, the more air in the more power out. Now, if an engine is not tuned properly for the less back pressure, then it would lose some.

warmwater
07-22-13, 07:02 PM
Not to hi jack the thread but with no cats and headers corsa is way to loud, I had to put stock muffler back on. However I did ad QTP cutouts just in front of the mufflers for when I do want to be obnoxious lol
http://youtu.be/KqbsnTWXA98

What size did you use? And is that for the stock pipes? How much for the install?
It would be cool if you could control it with your iphone or andrioid via bluetooth.

rgp6373
07-22-13, 11:22 PM
I have the stock mufflers and there is only one size of the low profile oval cutouts

----------

And I gave a friend a case of beer for welding the mounting pipe on and I did the rest do nothing for instal

miamictsv
07-24-13, 09:59 AM
I just ordered 2 of the medium powersticks from http://www.classicchambered.com/classic/products.html to quite down the car a bit. I am using the 20" version in stock diameter. This will remove my secondary cats/resonators. I will update you as soon as i install these.

Moparman4444
07-24-13, 12:33 PM
Miamictsv

I would be real interested in your setup and results. Keep us posted.

-ATS-
07-25-13, 01:40 AM
If you're stock then the stock cats are fine, but if you're not stock then the stock cats aren't going to cut it.

miamictsv
08-10-13, 06:42 AM
134873

Here is the final look under my car with the new power sticks mufflers install. I already had the cat delete pipes and added these.The car idles like stock and WOT is just slightly louder then stock. Video to come soon.

Moparman4444
08-11-13, 12:14 AM
Very nice install!!!! I'm ordering my pipes tomorrow! Thanks for sharing.

lsxtuner
09-03-13, 10:53 PM
134873

Here is the final look under my car with the new power sticks mufflers install. I already had the cat delete pipes and added these.The car idles like stock and WOT is just slightly louder then stock. Video to come soon.

Any sound clips?

Do these have any fiberglass packing in them?

miamictsv
09-04-13, 06:54 AM
Any sound clips?

Do these have any fiberglass packing in them?

No fiberglass packing. I will try to record some sound clips soon, now i am dealing with the AC evaporator. :(

Moparman4444
09-04-13, 09:35 AM
Ok so I installed my Classic Chamber mufflers in the center of the car replacing the stock resonator. There is plenty of room for the 30" long mufflers. With the CAT delete, I was hoping for more noise reduction from the mufflers. At idle there is no difference, at cruse, there is no change under light throttle, but under acceleration the sound is definitely elevated.

I was hoping for something a little quieter. The stock CATS really do a great job killing the sound. I know some people like the roar and rumble but I prefer a quieter approach.

The addition of a cam shaft combined with the stock exhaust makes for a powerful sounding yet quiet cruising package.

I will say one thing, the removal of the CATS did make a difference in the power output. Im guessing 15-30hp from the butt dyno.

miamictsv
09-04-13, 05:23 PM
Ok so I installed my Classic Chamber mufflers in the center of the car replacing the stock resonator. There is plenty of room for the 30" long mufflers. With the CAT delete, I was hoping for more noise reduction from the mufflers. At idle there is no difference, at cruse, there is no change under light throttle, but under acceleration the sound is definitely elevated.

I was hoping for something a little quieter. The stock CATS really do a great job killing the sound. I know some people like the roar and rumble but I prefer a quieter approach.

The addition of a cam shaft combined with the stock exhaust makes for a powerful sounding yet quiet cruising package.

I will say one thing, the removal of the CATS did make a difference in the power output. Im guessing 15-30hp from the butt dyno.

Unless you use glass packed inline resonators the sound will be elevated under acceleration but glass packed tend to fail i think with our power levels. May be a high flow cats can do the trick for you?
I know they are 200 cel and even 100 cel cats. The stock are 400 cel if i am not mistaken. Not sure how long even the high flow cat's can survive if you are approaching the 600whp.
This is a sample pic of different type of cats i found online.

141977

Moparman4444
09-05-13, 12:41 PM
That's a big difference. But in looking at the stocks, I think they look more like the 200 cell design. I guess an experienced tech would know better.

Moparman4444
09-08-13, 05:20 AM
I miss my CATS. at cruise on the freeway under light load between 60-85, there is absolutely no sound difference in the car w/o the CATS and with my Classic Chambers in the middle than stock which surprised me. but with the windows open and at idle or under load, there is a 20% increase in sound level which is what a lot of people are looking for because it is a mellower deep tone w/o resonance and an ever so slight pinging exhaust sound from the straight pipes.

I guess Im getting old, but I like the complete quiet of stock.

Moparman4444
09-24-13, 02:22 PM
Now I have CAT delete pipes leading into 30" Classic Chamber mufflers then connected to the factory X pipe with all mandrel bent piping. At cruzing speeds and on the freeway the sound inside the car is exactly like stock. At idle I can still hear the pinging in the pipes w/o the CATS. Definitely sounds meaner and louder outside the car. However the Harley type rumble is great at times but also annoying at others when you want a quiet luxury ride like pulling up to a restaurant.

I'm wondering if 100cell CATS would melt if installed in the factory location with 640 hp at the wheels?

lsxtuner
09-25-13, 06:49 AM
Good wide open high flow cats aren't going to quiet the car much more than a straight pipe. More flow = more exhaust volume and possible drone. Want a quiet car keep the boost low :)

Moparman4444
09-25-13, 09:48 AM
"Good wide open high flow cats aren't going to quiet the car much more than a straight pipe"

I disagree.

I had my car tuned with all the performance upgrades and the stock exhaust. Got 608hp at the wheels and a quiet ride.

I replaced the factory CATS and center pipes to eliminate the crimps and bends and had the car retuned with a more aggressive tune then got 640hp at the wheels with the only change being the exhaust pipes. The sound increased significantly after changing the pipes. Since the pipes and CAT delete was the only change, its reasonable to conclude that the CATS do quiet down the exhaust significantly.

I think I will add some of Kook's "Green CATS" to the exhaust to quiet down the system. Kooks says the high platinum content can handle the heat from a 650hp engine and won't melt like the stock ones, yet still provide good flow with their 300cell CAT's, unless somebody can recommend any other CAt's?

lsxtuner
09-27-13, 01:17 AM
Been there done that more than once already

Really high flow cats do very little to muffle the sound, but if you get cats that do all that means is that you have added significant restriction

Having run AR headers with and without cats on the same V I can tell you sound-wise there was very little difference

GMX322V S/C
09-27-13, 01:49 AM
I tuned and dynoed with and without the main cats (not the close-coupled ones, the 2nd pair further back) and it cost me all of a little more than 1 RWHP that peaked at a slightly lower rpm. It made a significant difference in sound.

Moparman4444
09-27-13, 04:32 AM
I guess the hot ticket for a quieter exhaust is to install high flowing CAT's. According to KOOKs headers tech support, their CATS will not melt at the higher HP levels. This makes me question what the factory 400 cell CAT's can actually handle w/o melting. In other words, why not just keep the factory CAT's and replace the crimped pipe that comes off one.

I sure wish I had a dyno in my back yard and could test the difference with vs w/o CAT's.

CavemanB52
09-27-13, 05:13 AM
I guess the hot ticket for a quieter exhaust is to install high flowing CAT's. According to KOOKs headers tech support, their CATS will not melt at the higher HP levels. This makes me question what the factory 400 cell CAT's can actually handle w/o melting. In other words, why not just keep the factory CAT's and replace the crimped pipe that comes off one.

I sure wish I had a dyno in my back yard and could test the difference with vs w/o CAT's.

I melted my stock cats with just 600 at the wheels