Catless Headers and CEL

[bcoffin]

I am planning to install the Ebay catless headers on my 01 3.0i.

They don't appear to have an O2 bung, so what is the typical fix here for the Z3? Search bar isn't helping me much.

I don't mind the CEL as long as it does throw off the DME and performance.

[328 Power 04]

Custom flash to remove cats, or install cats somewhere downstream.

[MartyBtoo]

If you're living in Long Beach, I'm guessing that it isn't going to be registered for road use?

Marty

[bcoffin]

Custom flash to remove cats, or install cats somewhere downstream.

Can I drive without a custom flash after headers are installed and not suffer any engine issues due the the DME reading crazy O2 numbers?

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If you're living in Long Beach, I'm guessing that it isn't going to be registered for road use?

Marty

I am going to use the car 95% for the track, but I will still need to drive it to and from the track since I do not have a trailer.

So either I don't register for road use and take my chances driving to the track, or I do register for road use and take my chances driving to the track. Either way, there will be a legal risk in Commifornia with a race car.

[bmellott]

I had these on years ago. Options, 1. Custom tune to ignore post O2's 2.) get High Perf CAT's and weld in O2 bung's - custom exhaust work 3.) get an O2 simulator for Post O2's - I had done the customer exhaust with high perf cat thing - worked well till for a while - Oh and that silly O2 spacer bung idea that's out there doesn't work (at least on my 02' 3.0i) and I tried all kinds of stuff

In the end I put the stock manifolds back on - I didn't feel I gain that much Hp/Tq and I even had done a custom dual 2.25 mend bent ex with only a dual magadrone at the end - Stupid Loud, wife got pulled over in town just for driving

[328 Power 04]

For some reason I thought it didn't have the bungs for the post cat O2s only.

As I now understand, it doesn't have precat either? You really should have precat O2s.


You can drive without post cat ones, as they are only there to monitor the cat health. Nothing regarding engine running. The precats are the most important.

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I had these on years ago. Options, 1. Custom tune to ignore post O2's 2.) get High Perf CAT's and weld in O2 bung's - custom exhaust work 3.) get an O2 simulator for Post O2's - I had done the customer exhaust with high perf cat thing - worked well till for a while - Oh and that silly O2 spacer bung idea that's out there doesn't work (at least on my 02' 3.0i) and I tried all kinds of stuff

In the end I put the stock manifolds back on - I didn't feel I gain that much Hp/Tq and I even had done a custom dual 2.25 mend bent ex with only a dual magadrone at the end - Stupid Loud, wife got pulled over in town just for driving

The custom tune, if done correctly, completely ignores lack of rear o2s, and even sets readiness on MS43 DME. No CEL, nothing weird. Done it many times without issues.

[MartyBtoo]

(snip) So either I don't register for road use and take my chances driving to the track, or I do register for road use and take my chances driving to the track. Either way, there will be a legal risk in Commifornia with a race car.

Regardless of the legal risk of driving an unlicensed car on the street, if you do try to license it they will require a smog test, and every two years thereafter they will require it again. It's not worth the effort to remove the cats if you are licensing it.

Marty

[bcoffin]

I had these on years ago. Options, 1. Custom tune to ignore post O2's 2.) get High Perf CAT's and weld in O2 bung's - custom exhaust work 3.) get an O2 simulator for Post O2's - I had done the customer exhaust with high perf cat thing - worked well till for a while - Oh and that silly O2 spacer bung idea that's out there doesn't work (at least on my 02' 3.0i) and I tried all kinds of stuff

In the end I put the stock manifolds back on - I didn't feel I gain that much Hp/Tq and I even had done a custom dual 2.25 mend bent ex with only a dual magadrone at the end - Stupid Loud, wife got pulled over in town just for driving

Did you have a pre and post dyno with the headers?
I hear that the headers will give the biggest power gains. My goal is to get the car to ~260hp and 2600 to be competitive in NASA TT4.

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Regardless of the legal risk of driving an unlicensed car on the street, if you do try to license it they will require a smog test, and every two years thereafter they will require it again. It's not worth the effort to remove the cats if you are licensing it.

Marty

Not worried about smog. Where there is a will there is away.

I'm more concerned with dealing with the pain of catless exhaust and there be no real reward power wise.

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For some reason I thought it didn't have the bungs for the post cat O2s only.

As I now understand, it doesn't have precat either? You really should have precat O2s.


You can drive without post cat ones, as they are only there to monitor the cat health. Nothing regarding engine running. The precats are the most important.

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The custom tune, if done correctly, completely ignores lack of rear o2s, and even sets readiness on MS43 DME. No CEL, nothing weird. Done it many times without issues.

I will need to do more research to see if a pre-cat bung is in the headers for the O2. I would imagine there is. Good to know that post cat O2 will do nothing to performance.

[ZoO]

I have a set of headers I had on the car for a year before taking them off, they have o2 bungs, and I used o2 adapters to avoid CEL. I'm located in westminster if your interested.

Powerwise, it's the best mod per dollar. You will feel an instant increase in bottom end.

[bcoffin]

I have a set of headers I had on the car for a year before taking them off, they have o2 bungs, and I used o2 adapters to avoid CEL. I'm located in westminster if your interested.

Powerwise, it's the best mod per dollar. You will feel an instant increase in bottom end.

PM'd

[deni2s]

Can drive until you will get custom tune. Custom tune - nothing extraordinary, the same thing BMW offers for cars with catless option. I would stay away from o2 adapters, just do it properly with the tune.
I can't tell I felt instant increase in bottom end, but probably because I have 2.8 with other improvements. Still haven't measured on dyno, but car is much louder than faster after going catless

[328 Power 04]

Custom tune - nothing extraordinary, the same thing BMW offers for cars with catless option.

Except he will fail US inspections if flashed with catless EU flash.

[duckracer]

The Raceland Ebay header's are a good deal and have the required front O2 sensor bungs. Without the front O2 sensors you will be in "limp home mode", so you need the front sensors. As stated further back, the secondary O2 sensors are only there to monitor cat health. I am from San Jose Ca. so I had to have the cats to register the car. I used Vibrant high flow racing cats and built a custom 2.5 inch full system. I passed CA emissions with this set up. The 2.5 inch killed a little bottom end but gave it a really nice top end boost.

[bcoffin]

The Raceland Ebay header's are a good deal and have the required front O2 sensor bungs. Without the front O2 sensors you will be in "limp home mode", so you need the front sensors. As stated further back, the secondary O2 sensors are only there to monitor cat health. I am from San Jose Ca. so I had to have the cats to register the car. I used Vibrant high flow racing cats and built a custom 2.5 inch full system. I passed CA emissions with this set up. The 2.5 inch killed a little bottom end but gave it a really nice top end boost.

Awesome, that is what I was looking for.

Headers are near the tail end of my build (roll cage, wheels, suspension are the priority) but looks like Raceland off Ebay and a tune will be the path I take.

[Beemerman1967]

OK, so I need help in this area. I'm looking at the ebay headers and I understand that the OEM Cats are built in and will not work with the headers. Can I use ANY high-flow universal 2.5" Cat or are there certain specifications that I should be looking for?

[LannVouivre]

You need OBDII cats and to make sure you don't live somewhere that modifying the exhaust and catalytic converters is illegal.

You then lengthen the O2 sensor harnesses and put the post-cat O2s behind the cat's new location. Abel can also change your ECU tune to change your fuel management to match the new cat location.

[Beemerman1967]

I live in GA so to pass inspection I have to have the cats. Emissions are all they test for here. I'm assuming that as long as I'm not polluting, I'm good to go.
Thanks!!

[328 Power 04]

You can put them downstream, and it may work fine. If they're placed too far down they will have a harder time warming up (on stock ecu flash) so it may give you some trouble. On the 01+ inspections can be managed easily with flash.

[BimmerBreaker]

The Raceland Ebay header's are a good deal and have the required front O2 sensor bungs. Without the front O2 sensors you will be in "limp home mode", so you need the front sensors. As stated further back, the secondary O2 sensors are only there to monitor cat health. I am from San Jose Ca. so I had to have the cats to register the car. I used Vibrant high flow racing cats and built a custom 2.5 inch full system. I passed CA emissions with this set up. The 2.5 inch killed a little bottom end but gave it a really nice top end boost.

Racelands and ebay headers are not the same. Raceland only sells their headers on their raceland.com website, ebay headers are just that, only sold on ebay.

[LannVouivre]

Check your local laws and make sure you don't have to have the same number of cats as before. Although, most of the kids inspecting it won't know anything except to check for a catalytic converter at least being present.

If you don't have the primary O2 sensor bungs, they need to be basically in the airstream at the collectors. Might be supposed to be at a certain angle, too; I don't remember enough from whatever technical paper I was reading.

[Beemerman1967]

These are the headers that I bought:
https://www.ebay.com/itm/For-BMW-E46...torefresh=true

This is the Cat that I'm looking at. I'll need 2 of them. Not sure of the fitment.
http://vi.vipr.ebaydesc.com/ws/eBayI...1&secureDesc=0

[LannVouivre]

What my '06 Toyota had was a primary cat, which the sensor monitored, then a secondary cat with no sensor monitor. I previously had two cats on the Z3 in a similar manner to at least follow the letter of state law, which seemed to indicate that I needed to copy the number of components and have them functioning, but that they could be moved...or something. The Texas inspection guidebook is not worded clearly, and I was going by the licensed inspector version.

[danomite]

These are the headers that I bought:
https://www.ebay.com/itm/For-BMW-E46...torefresh=true

This is the Cat that I'm looking at. I'll need 2 of them. Not sure of the fitment.
http://vi.vipr.ebaydesc.com/ws/eBayI...1&secureDesc=0

Both of these will work, but you could save money on the cats, and get something cheaper...just make sure that it has a metallic substrate, and is at least a 200 cell count.

Also, be aware that since those headers are mass-produced for all of the M5X engined models, the O2 bungs may not be in the proper location/orientation for our Z's...that's typically the case, unless you buy Z3-specific headers. So, be ready to cut/drill/weld.

Good luck

[Beemerman1967]

will ceramic substrate work?

[danomite]

will ceramic substrate work?

Yes. The newer ceramic substrates will work also. Some say that they don't last as long as the metal ones, but I have yet to see/experience a failure personally. I'd imagine the muffler would die before the ceramic cat.

The metal ones are used for heavy loads. Some vehicles require these to pass ultra stringent emissions testing. The heavily loaded metallic substrates "clean" the exhaust gases more, producing "cleaner" emissions.

I'd also recommend a 400 cell count for longevity and performance.