What is the best cat setup that passes inspections anywhere?

[doublespaces]

I like that O2 arrangement, the harness looks much more comfortable. I'm curious if anyone has tried putting cats in the rear by the mufflers, I wonder how much efficiency is lost or if the catalyst would get hot enough to function. I'm mostly trying to tackle the smell.

 

[doublespaces]

Also there is just no way to make sure the car is warm, as it may be parked for an hour before they pick it up (they keep the keys while you wait).

Remote starter

 

[fmorelli]

I really want to find the best street-legal track-ready permanent setup. Also there is just no way to make sure the car is warm, as it may be parked for an hour before they pick it up (they keep the keys while you wait).

One other thought, at least from my experience in Virginia. From what you said it seems like you drop the car and wait at the shop. This seems to indicate that, while they may not do the test immediately, it is within some reasonable "sitting" time for you at the shop. In VA, we will run the balls off the car, get it really hot, then take it to the shop. They can test the car an hour later and those cats are far from cool - when they fire the car up, bring it in to the shop, the cats should be good to go.

Filippo

 

[RSL]

When I was running 200cell down-pipes only, the test that failed is called "double idle speed test", CO(%) and HC was too high. Lambda was also low, but only by 0.02. I dont know if measured with OBD or sniffer. I have seen both OBD and sniffing equipment used during annual inspections in China previously, but nowadays they don't let you observe their testing methods.

View attachment 26568

High HC is basically too much uncombusted fuel isn't it? Many things can impact it, but as far as basics go, plug change alone might be a noticeable help for high AFR area tests if you're one of the many running .018-.022" gaps.

Just saying, don't ignore what the cats have to clean rather than just trying to improve the cleaner, especially if it's in a particular RPM/AFR range. If it's close just on high flow primaries alone, redoing the exhaust system would be my last ditch effort.

 

[CAA]

You really need to consider to get by some way a few tens of liters of e85 to pass the emissions test.
I'm from spain. Here I have to pass the car inspection annually. The last time with half tank of e85 my CO was only 0,1% at idle. Max. permeted here for post 2002 cars is 0,3%, so considering I have a ST setup (obviously de-catted dp) with stock cat-back you can make an idea.
If you cant get e85 by anyway, you could consider mixing some decent amount of meth on your tank.

 

[Asbjorn]

Managed to snap a picture of the M4 stock downpipe thanks to @yuli8466 . I believe this is a 400 cell type cat.



I am told the mid pipe is even more high flowing, perhaps 2-300? All guess work from my side as I haven't seen it myself in person.

But definitely no N54-style 800 cell cats anywhere on the M4. The S55 probably also pollutes less without cats to begin with?

Anyway, this once again inspires me to try some good 400 cells with clamps for the mid-pipe, combined with my old 200 cell down-pipe (just to pass OBD test). Then I can move up (or down) in cell number/quality on the mid pipes until I find the right ones to pass the sniff test part in China.

 

[Asbjorn]

You really need to consider to get by some way a few tens of liters of e85 to pass the emissions test.
I'm from spain. Here I have to pass the car inspection annually. The last time with half tank of e85 my CO was only 0,1% at idle. Max. permeted here for post 2002 cars is 0,3%, so considering I have a ST setup (obviously de-catted dp) with stock cat-back you can make an idea.
If you cant get e85 by anyway, you could consider mixing some decent amount of meth on your tank.

Actually my car passes fine with just the stock down pipes and no mid pipes. The numbers you got are from a sniff test right? Not obd test?

 

[Hydra Performance]

@Asbjorn
You can also target 15.5-16 AFR in the tested area, this will significantly decrease CO and HC at the expense of increased NOx which, fortunately for you, is not tested.

 

[CAA]

Actually my car passes fine with just the stock down pipes and no mid pipes. The numbers you got are from a sniff test right? Not obd test?

Right, it was a sniff test. Obd test has been implemented here a few months ago and is only for euro V cars or later, so I have not to pass this kind of test. Anyway, I think that emissions test via obd shoudn't be a problem if you can trick the codes related to the o2 sensors with a proper tune that don't throw a it if you delete the first cats.

 

[Asbjorn]

Alright, here's the result of this thread on my car. Ended up with 400cell hi-flowers for the mid-pipes. Down-pipes are my old 200cells. I hope this combination is able to pass both OBD and sniff tests. Otherwise the V-bands make it fairly easy to swap things around to 800cell down-pipes in combination with de-catted mid-pipes, that I know can pass the test. If the car ends up exceeding the requirements by far, I can also consider swapping in 200 or 300cell mids.

I would say the exhaust sound right now is similar to running only 800cell down-pipes, perhaps with a deeper note. The loud burbles are gone and so is the "rasp".