Fake converter

[zorrex]

Gutting cats gains NO horsepower over stock! All it does is return your car to the power it was when it came from the factory. If for some reason your cats are clogged, then yes you will see a "gain," but that "gain" is just bringing you back to stock power.

 

[SkullV]

Gutting cats gains NO horsepower over stock! All it does is return your car to the power it was when it came from the factory. If for some reason your cats are clogged, then yes you will see a "gain," but that "gain" is just bringing you back to stock power.

I'd like to see a dyno chart with a before and after, if you don't think your stock main cat is restrictive you are crazy. With the CTS-V's installing test pipes in place of cat's on stock manifolds gained an average of 15whp.

 

[Harrry]

Gutting cats gains NO horsepower over stock! All it does is return your car to the power it was when it came from the factory. If for some reason your cats are clogged, then yes you will see a "gain," but that "gain" is just bringing you back to stock power.

dude..please stop. I've let you go on soo many posts...but you just keep going. Plus your spreading false information that others like myself have to go back and correct!!!

Yes you do gain hp and tq from removing any cat material! End of story!

 

[zorrex]

I still disagree. I've never seen it proven. :shrug:

 

[BrApple]

if there is no difference to be made why install headers? granted that leaves out pipe sizing, etc. there is going to be some restriction in the exhaust due to the material in the cat. remove that and the exhaust can flow better. however having the increase in the exhaust manifold size after the cat material is removed isn't good for exhaust flow, and this is where headers make a difference.

 

[BrApple]

K&N gets those crazy HP claims by doing 3rd gear pulls instead of 4th gear pulls on the dyno (using gearing to their advantage) and they also do the pulls after completely clearing the long term fuel trims (LTFTs). This makes the stock afr slightly leaner which is how they get the power.

I had a back to back dyno pull done in third and fourth gear and it made little difference, just got to redline faster.

 

[zorrex]

if there is no difference to be made why install headers? granted that leaves out pipe sizing, etc. there is going to be some restriction in the exhaust due to the material in the cat. remove that and the exhaust can flow better. however having the increase in the exhaust manifold size after the cat material is removed isn't good for exhaust flow, and this is where headers make a difference.

The reason headers provide such good gains are because they flow MUCH better. This is also the reason an optimized or aftermarket Y-pipe nets large gains as well. Just gutting the cat will still leave you with a horribly turbulent chamber of exhaust gases, plus the length the gases are traveling through the manifold is short. A catalytic converter is designed to not restrict air flow, hence the reason of the larger cross-section. :shrug:

 

[SkullV]

I still disagree. I've never seen it proven. :shrug:

Then you must not have spent much time around performance cars on dynos...again, if you think the honeycomb inside a stock cat is completely non-restrictive you do not know what you are talking about. I HAVE seen it proven, time and time again. Just because you have never seen it doesn't mean it isn't true.

 

[zorrex]

In addition, the most restrictive part of the CSVT exhaust is the resonator. If you still have the resonator, I don't think having cats or having gutted cats will make any difference in the slightest.

 

[Harrry]

In addition, the most restrictive part of the CSVT exhaust is the resonator. If you still have the resonator, I don't think having cats or having gutted cats will make any difference in the slightest.

There is your problem...what you think doesn't matter in tis situation. Please go buy a svt or get a v6 engine contour then talk. Or even get an engineering degree which covers fluid dynamics.

Worst part of the contours exhaust...is tied between, it's y-pipe... which is a crush point that narrows each exhaust bend down to 1 inch.:blackeye:
So your half way right to one of the most asked simplest questions on ceg.:laugh:

But saying if you don't have the resonator removed you won't gain any power? So me putting on headers...won't give me any more power? Because the resonator is still the choke point? See what i mean? Just stop man...you thought you were right...but your really not..and i don't feel like going into detail to cover this. It's been beaten like i said.

 

[zorrex]

There is your problem...what you think doesn't matter in tis situation.

You missed the point of that statement. I don't think it'd make a difference because of other exhaust restrictions, even IF gutting your cats could net gains. Does that make sense? :shrug: haha

 

[Harrry]

You missed the point of that statement. I don't think it'd make a difference because of other exhaust restrictions, even IF gutting your cats could net gains. Does that make sense? :shrug: haha

What if i inrease tube size...while using all of the same components? Will i make gains because of these restrictions still ? :laugh:

 

[FIND]

Then you must not have spent much time around performance cars on dynos...again, if you think the honeycomb inside a stock cat is completely non-restrictive you do not know what you are talking about. I HAVE seen it proven, time and time again. Just because you have never seen it doesn't mean it isn't true.

Honeycomb style cats are generally fairly high flowing. It is the bat filled ones that are generally the problem

dude..please stop. I've let you go on soo many posts...but you just keep going. Plus your spreading false information that others like myself have to go back and correct!!!

Yes you do gain hp and tq from removing any cat material! End of story!

So.... I was looking into this. It is appearing to me that given the size and shape of our precats, they function pretty well as resonators with all the material removed. I tried to measure air flow through my old manifolds before and after removing the material, and I honestly didnt come up with much difference in flow, but then again my old cats were not clogged, so I didnt expect much difference in flow. My guess is that if people are seeing horsepower gains using gutted cats, the pulses and sound from the exhaust must create a resonance.

Granted I dont have a flow bench, I did my testing with a shop vac and some tubing and a ball to measure flow. Tried it with a squirrel cage blower too. The blower should move 450 cfm, so I figured that it was more than enough to test with.

Anyways, just figured I would throw that out there. Thats my theory at least, since otherwise in a lot of vehicles I have always seen loss of power through gutting cats.

 

[SkullV]

Honeycomb style cats are generally fairly high flowing. It is the bat filled ones that are generally the problem

But they still flow MUCH worse then test pipes. Plus the honeycombs have a tendency to collapse if there is a lot of heat in the exhaust from tubular headers/COT turned off.

 

[Harrry]

Honeycomb style cats are generally fairly high flowing. It is the bat filled ones that are generally the problem



So.... I was looking into this. It is appearing to me that given the size and shape of our precats, they function pretty well as resonators with all the material removed. I tried to measure air flow through my old manifolds before and after removing the material, and I honestly didnt come up with much difference in flow, but then again my old cats were not clogged, so I didnt expect much difference in flow. My guess is that if people are seeing horsepower gains using gutted cats, the pulses and sound from the exhaust must create a resonance.

Granted I dont have a flow bench, I did my testing with a shop vac and some tubing and a ball to measure flow. Tried it with a squirrel cage blower too. The blower should move 450 cfm, so I figured that it was more than enough to test with.

Anyways, just figured I would throw that out there. Thats my theory at least, since otherwise in a lot of vehicles I have always seen loss of power through gutting cats.

FIND...your logic is there..but you forgot 1 simple ingredient

You were pushing cold AIR...through a cold cat....
The engine pushes HOT gases...through either a cold cat...or at other times a HOT cat!

 

[SkullV]

Anyways, just figured I would throw that out there. Thats my theory at least, since otherwise in a lot of vehicles I have always seen loss of power through gutting cats.

I have never seen a loss of power in a stock application, however I have seen a loss of power over using test pipes. The gutted cats flow better then stock cats, but less then straight test pipes due to less turbulence.

 

[FIND]

FIND...your logic is there..but you forgot 1 simple ingredient

You were pushing cold AIR...through a cold cat....
The engine pushes HOT gases...through either a cold cat...or at other times a HOT cat!

yeah that was what I was trying to get at when I said the pulses from the exhaust. I figure the heat will change the flow characteristics of the gutted cat given the size and shape that it should function perfectly as a resonator. I had compared the cats on my old manifolds to the resonator on my escort and the size and shape are nearly identical. Flow is similar between the two.

But they still flow MUCH worse then test pipes. Plus the honeycombs have a tendency to collapse if there is a lot of heat in the exhaust from tubular headers/COT turned off.

Not really that much worse. Also, generally with good cats, I dont see a lot of breakdown in the honeycombs except what you would normally expect from age. My contour has had headers on it for quite some time. High flow honeycomb style cat. The cat doesnt look any worse on the inside than I would expect from a 2 year old cat. I always leave emissions equipment on vehicles, no matter how much I put on them, I leave the cars in a condition where they can pass any smog test, even though I live in states that have no smog testing.

I have never seen a loss of power in a stock application, however I have seen a loss of power over using test pipes. The gutted cats flow better then stock cats, but less then straight test pipes due to less turbulence.

Well I have. In dozens of vehicles.

 

[SkullV]

Well I have. In dozens of vehicles.

I guess it's kind of like adding headers without a tune, it richens up the mixture do to the fact that the uncalibrated MAF is reading more air flow. The fact is though, and I guess I'm changing my tone a bit here, but gutted/catless will ALWAYS make more power when the vehicle is properly calibrated for the modifications.

 

[zorrex]

I guess it's kind of like adding headers without a tune, it richens up the mixture do to the fact that the uncalibrated MAF is reading more air flow. The fact is though, and I guess I'm changing my tone a bit here, but gutted/catless will ALWAYS make more power when the vehicle is properly calibrated for the modifications.

...this post doesn't make a whole lot of sense to me.

 

[FIND]

...this post doesn't make a whole lot of sense to me.

You arent the only one who feels that way.