[Alexander]

N52 section sucks, sorry.

I never went through with deleting my cats, until now. I just confirmed that in the state of NC, my state, they only use the OBDII port to check for codes thrown.

Q1: Does that mean that as long as I have O2 sims I'm good?

Q2: I'm pretty sure that I can just delete my secondary cats and no codes will be thrown right?

Q3: Primary cat delete, what do I use to prevent codes from being thrown?

[smallseafishie]

Don't pollute the world more than it already is...

[Alexander]

Thanks! Primary cat and 2 secondary cats is really necessary!

[galahad05]

1) Just get a full cat-back system and call it a day. This for a street setup. Race setup? Go for it.

Going for the cat delete only increases the smell and won't net you much power, unless you've integrated in a full exhaust system/engine calibration/high-flow intake that can properly time your ignition and valve events to efficiently flow fuel and air over a broad RPM.


2) Okay, for a more formal answer, could you list other engine-related mods that are in place? Bored/stroked motor? Changed valving, changed ignition timing or cam?


3) The whole point of the cat delete is to decrease backpressure...but the little-known truth is that, on many street cars, this can actually decrease usable low- and mid-range torque. Reason? It can over-scavenge your combustion chambers at lower RPMs, costing you power down low. That is, less torque. You will see a small increase in top-end power, however.

[Alexander]

Originally Posted by galahad05

1) Just get a full cat-back system and call it a day.

Going for the cat delete only increases the smell and won't net you much power, unless you've integrated in a full exhaust system that can properly scavenge your combustion chambers.


2) Okay, for a more formal answer, could you list other engine-related mods that are in place? Bored/stroked motor? Changed valving, changed ignition timing or cam?


3) The whole point of the cat delete is to decrease backpressure...but the little-known truth is that, on many street cars, this can actually decrease usable low- and mid-range torque. Reason? It can over-scavenge your combustion chambers at lower RPMs, costing you power down low. That is, less torque. You will see a small increase in top-end power, however.

Mods are in sig. Race pipes after secondary cats.

Well If I don't go with secondary cat deletes, are primary still viable? A member here gained 15whp on his 2.5L with primary deleted.

Or how about magnaflow high flow cats, any experience with these?

[galahad05]

Okay, I saw your setup and proposed changes. Not too bad. With the high-flow cats you have over 90% of the backpressure benefits of a cat delete but are still environmentally friendly (more or less). Also looks fairly stock to someone inspecting it. Overall Looks like you're doing a nice setup for power, without going overboard with a supercharger or such.

Any plans on the brakes or cornering? You put the same money and effort into those as the power-adders, you'll have a solid track machine.

[galahad05]

Oh, and O2 sensor simulators should keep your ECU (DME) happy....sorry, I've never played with them though.

I wonder if there won't be problems with your mixture leaning out too much with the simulators + cat delete? I'm sure your DME will richen the mixture when it detects detonation, but still....

[Nikolas]

Honestly the power gain you get from going catless is not worth the downsides of the smell of fuel in the car at every stop light. While it may pass the OBDII check, if the station has any sense they will question the smell of fuel - which by the way is federal offense up to a $10,000 fine. Go with a system with sport 100 cell cats and you will be much happier.

[Alexander]

Originally Posted by galahad05

Oh, and O2 sensor simulators should keep your ECU (DME) happy....sorry, I've never played with them though.

I wonder if there won't be problems with your mixture leaning out too much with the simulators + cat delete? I'm sure your DME will richen the mixture when it detects detonation, but still....

Well I am going with the Gintani tune and I will datalog and get them to adjust air/fuel levels accordingly!

I have a E30 M3 track car btw, this is just my daily driver, but I liked to ride in style, but the 328i stock is too slow, and I didn't want to own a 335i out of warranty, so I want a little more bang out of the N52 w/o dumping money.

I'm on stock ZSP suspension and after driving a E90 and E92 both with ZSP I can tell that my suspension at 50k is a little worn out.

[e90David335i]

Originally Posted by smallseafishie

Don't pollute the world more than it already is...

wow...

[Alexander]

Originally Posted by e90David335i

wow...

Thank you.