Are Catted Downpipes Worth it?

[PositvPresur]

I want to buy some down pipes but I am very concerned about the gas smell you get from catless pipes so my question is: Do you gain enough power from catted down pipes to justify the cost? I would be using these with a Berk exhaust and Dinan stage 2.

[rock1t]

Originally Posted by PositvPresur

I want to buy some down pipes but I am very concerned about the gas smell you get from catless pipes so my question is: Do you gain enough power from catted down pipes to justify the cost? I would be using these with a Berk exhaust and Dinan stage 2.

I have the exact same question.. Looking for answers.

[Jayock]

I don't have aftermarket *catted* downpipes, but I have read that they are not worth the price. Maybe someone can provide dynos. I have *seen* several catless installed, and there wasn't any discernible smell, especially inside the car.

[jibaholic101]

they are worth it because they are more free flowing and will give you some power gains, but nothing near catless.

[SV Concepts III]

Originally Posted by jibaholic101

they are worth it because they are more free flowing and will give you some power gains, but nothing near catless.

+1 IMO, if you are going to do it, go catless. If it's really a concern, they are still worth it but catless is the way to go.

[BMW86]

Going catless is illegal here so I'll be looking at catted downpipes also. What gains can we expect from catted downpipes on stock and tuned cars?

[ar design]

On a B5 S4 with K04s, we only saw a 7whp difference going from test pipes to cats - we use the exact same cats on our 335i downpipes.

[bradford]

Originally Posted by BMW86

Going catless is illegal here

Eliminating the cats is illegal pretty much everywhere.

[ar design]

Originally Posted by bradford

Eliminating the cats is legal pretty much anywhere in Mexico.

[BrokenVert]

It isnt so much the smell im worried about as much as this. Doesnt the computer use information sent to it by sensors in the cats to examine itself and make corrections in mixtures/timing?

[jibaholic101]

Originally Posted by BrokenVert

It isnt so much the smell im worried about as much as this. Doesnt the computer use information sent to it by sensors in the cats to examine itself and make corrections in mixtures/timing?

that is what o2 sims are for

but seriously OP, if you have the spare cash to throw and want them then go for it, but for me it would be catless or bust because of the gains. until you really start cranking up that boost with heavy modding, it doesnt become a necessity.

if i was in OPs shoes i would probably be looking at a catback exhaust, sure it is some more money, but you get like 20-30lbs+ weight reduction, sound, and like 10hp

[BrokenVert]

Originally Posted by jibaholic101

that is what o2 sims are for

I thought that those simply send the engine an all is well signal.

[ar design]

Originally Posted by jibaholic101

that is what o2 sims are for

but seriously OP, if you have the spare cash to throw and want them then go for it, but for me it would be catless or bust because of the gains. until you really start cranking up that boost with heavy modding, it doesnt become a necessity.

if i was in OPs shoes i would probably be looking at a catback exhaust, sure it is some more money, but you get like 20-30lbs+ weight reduction, sound, and like 10hp

The sims are for the rear O2 sensors.... the front O2 sensors tweak fueling etc....

[BrokenVert]

Originally Posted by ar design

The sims are for the rear O2 sensors.... the front O2 sensors tweak fueling etc....

Can you go into more detail?

[ar design]

Originally Posted by BrokenVert

Can you go into more detail?

The pre-cat (front) O2 sensors are what the ECU looks at to adjust fueling. The ECU looks at the difference between pre (front) and post cat (rear) O2 sensors to verify the catalysts are working correctly etc. When the catalyst is removed (which is ILLEGAL in any on-road application in the USA) the sensor readings go way out of range and the ECU goes HEY!!! wait a minute, something isn't right here. The DP fix brings the values for the rear sensor back inline to where they were with a catalyst, so the ECU thinks all is well. Make sense? When the ECU does detect the catalytic converter not functioning properly, it will go into a partial limp mode to protect the catalysts.

[SpacE82]

I have the CP-E full exhaust with Catless downpipes. I'm happy with it. It does smell, but I dont mind it. It actually reminds me of my dads 1968 Olds 442..

I have noticed some more throttle response, but I also did the DPs and the exhaust at the same time, so I dont know if thats from the DPs or because of the full exhaust.

The one thing that I love is the sound of the turbos..you can really hear them spooling up when you rev or get on/off the gas..

[BrokenVert]

Originally Posted by ar design

The pre-cat (front) O2 sensors are what the ECU looks at to adjust fueling. The ECU looks at the difference between pre (front) and post cat (rear) O2 sensors to verify the catalysts are working correctly etc. When the catalyst is removed (which is ILLEGAL in any on-road application in the USA) the sensor readings go way out of range and the ECU goes HEY!!! wait a minute, something isn't right here. The DP fix brings the values for the rear sensor back inline to where they were with a catalyst, so the ECU thinks all is well. Make sense? When the ECU does detect the catalytic converter not functioning properly, it will go into a partial limp mode to protect the catalysts.

So the only thing that is examined downstream of the turbos is whether or not the cats are functioning properly?

[Smac355]

i think it comes down to the issue that if you want to swap the DP's once a year for inspection, or know someone that will pass your car anyway then go w/ catless since you'll get more performance. I had DP's (catted) on my supercharged Grand PRix and the Cat busted after about 2 years and the manuf. said that is common w/ high flow cats. so might now really be worth it. i just put the stockers back on and bought a 1. lol.

[MadMan77]

There is also to consider his Dinan warranty. They will most likely have an issue with those down-pipes installed unless you can get them to make you a set for A LOT of money.

[MadMan77]

Originally Posted by Smac355

i think it comes down to the issue that if you want to swap the DP's once a year for inspection, or know someone that will pass your car anyway then go w/ catless since you'll get more performance. I had DP's (catted) on my supercharged Grand PRix and the Cat busted after about 2 years and the manuf. said that is common w/ high flow cats. so might now really be worth it. i just put the stockers back on and bought a 1. lol.

I didn't have an issue with my helix high-flow catted down-pipe on my STi. I had it on there for a brutal 3.5 years of tuned madness...

I guess it depends on how high of a quality cat that they use.

[jeremyc74]

Originally Posted by BrokenVert

So the only thing that is examined downstream of the turbos is whether or not the cats are functioning properly?

No, the first set of O2 sensors are between the turbo and the catalytic converter. They're the ones doing fuel trims. The second set is just there to verify that the converters are working properly.

[jeremyc74]

I haven't seen any before and after dyno runs that have proven a significant gain with catted DPs. That's not to say they're not out there, but the only ones I've seen posted here were showing 7Hp IIRC.