Emissions/Cat Help

[Brown9348]

Searched a bit and didn't find much info on the subject so I figured I'd ask.
I have a obd2 e36 m3, now with a technica turbo kit intsalled with the tuning mostly worked out! (Thanks to Brett for working hard to sort it all out)
Im running low boost for now until I can get the car registered again. My problem is that im failing emissions for hydrocarbons.. my limit is 1.2, last time I tried I was at 1.6. I have to get the sniffer test (im240).

Can anyone suggest a particular cat I could use to get past emissions?
Im using a really cheap 400cel high flow cat right now, don't mind getting a new one, but not sure which will get me past emissions. I will probably run a cat after emissions regardless, but am open to suggestions.

An even better alternative would be if I could get away with using e85 in a given % to get past but I don't know if it's safe to do.

any advice on how you guys have passed or what you use?
thanks!

[vwmikel]

The factory cats would probably be far better than most of the aftermarket stuff. I had a problem HC (I think it was) before and it was actually the NGK plugs. They caused an intermittent miss. Bosch plugs fixed it.

[Brown9348]

What Bosch plugs did you use?
My exhaust is single 3" now. It was recommended to me to use a cat from an n55, which have a two pipe outlet, I supposed it could be chopped up for a single 3" vband on the one side, but the exhaust shop in using is killing me with prices so I'm trying not to have to ask them to heavily modify an oem n55 cat and chop up my existing downpipe, plus that cat has such an odd shape already, it may be a tough fit.

[vwmikel]

They were just the OE M3 dual electrode plugs. They looked pretty much identical to the NGK plugs, but apparently there was something quite different about them. If you don't have the intermittent miss then that's probably not your problem though. It's been discussed a bit here on the forums and seems not to be all that uncommon.

I was more suggesting you use the OEM E36 cats.

[Def]

I've heard the Vibrant GESi cats are good, and anything sold as CARB legal. The usual CARB legal cats are pretty restrictive.

Or you could try 2-3 cheaper cats in series for the emissions test, and just run 1 after the fact? I've seen that work. Running even a cheap cat gets rid of like 90% of the nasty stuff, and the good for emissions aftermarket cats typically don't hold up to high HP turbo usage very well in my experience. Kinda a compromise to get a workable setup.

[tofunin]

I've seen Random Technology high flow cats pass sniffer test here in strict California before they implemented STAR testing were visual is really enforced against non CARB approved aftermarket parts. The closer to the header/ turbo the better the cat will be at burning up the excess HCs.

[Brown9348]

Thanks guys.
retested today, limit is 1.2, and right now I'm at 1.31 for HC! Soooo close! I heat wrapped the cat to help keep it warmer and got much better results...

??Now, can I safely run a bit of e85 to get that last .1 down? I just don't know if it's safe to do!??

the new cat will be delivered and installed next week if I can't use e85, I want to avoid getting more exhaust work done. It's cost me so much money already.

[Def]

You could try 15-20% total ethanol I imagine without issue. You are running right at stoich on the measuring points? It sounds like you're running a bit rich at the points, which will cause your HC to shoot up. A little ethanol will tend to lean things out until the ECU can dial things back via trims, so it's worth a go.

[Kevin325i]

Where is the catalyst located, as in how far downstream from the turbo? Getting any brick lit post turbo is very very difficult and moving it closer always helps but packaging usually makes it difficult.

How much margin do you have on the other constituents?

[Def]

Is it that hard with header wrap on the DP to keep a cat lit "far" from the turbo outlet? I was going to put a cat ~5-6' from the turbo outlet on my MR2, but if it's not going to stay lit, I could try to move it about 3-4' away from the turbo, but things will be super tight there as it's between the engine and rear crossmember.

[Kevin325i]

Honestly it can be. Do you have emissions testing? Most of your output is going to be on initial start up/ drive away which is before the catalyst lights off/ is up to temp.

If you don't have testing then your plan will most likely be fine. Plus if you can pull a few degrees of spark out at start up for ten seconds you'll be fine for cat life.

[Brown9348]

I tried 20% ethanol and it made no difference.. my cat is too far away from the turbo to really get hot enough, sitting in the spot where the oem cats were I think, it's just in front of where the oem hangers are.
I have the cat from a 335i n55 but it looks like it's going to cost me a fortune to get fabbed up to fit temporarily for emissions testing. This particular cat is gigantic so I personally don't think it's even going to fit.

Maybe i can get an additional cat and put it about one foot upstream of the current cat? Maybe I just need to run 2 of them? Somehow I still think it'll be borderline as far as the HC during the sniffer.
Also, my fuel trims suggest that I'm still running a bit rich, but I finally got rid of my fuel trim CEL.

[Kevin325i]

So two cats in series without temp considerations will equal bad times. Closer will be better.

Getting any heat into the face will help. Can you take the wastegate spring out? Having exhaust bypass the turbine down into the exhaust will get that cat to temp fast enough to get your pass.

[Brown9348]

My wastegate is vented to ATM, otherwise I like that idea a lot!
my shop is going to try to get this new cat installed with vbands way up near the turbo. If it fits, I shouldn't have any issues but I have a feeling it'll be too tight.

[Def]

Honestly it can be. Do you have emissions testing? Most of your output is going to be on initial start up/ drive away which is before the catalyst lights off/ is up to temp.

If you don't have testing then your plan will most likely be fine. Plus if you can pull a few degrees of spark out at start up for ten seconds you'll be fine for cat life.

No emissions testing, just trying to take the stink out with a high flow metallic core spun cat. It's a "universal" one, so it probably wouldn't do all that much up close to the turbo anyway. It'll be installed in roughly the stock location, and stock it had a turbo, but I don't think emissions requirements were all that tough to pass back in '93!


Interesting stuff here, don't see emissions talked about too much on older modified cars that still have to pass the sniffer.

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My wastegate is vented to ATM, otherwise I like that idea a lot!
my shop is going to try to get this new cat installed with vbands way up near the turbo. If it fits, I shouldn't have any issues but I have a feeling it'll be too tight.

What kind of cats are you using? The "universal" 49 state ones are cheap, and don't have much catalyzing metal inside, so I've heard of people failing on NA cars with them install up close to the header ports (stock location on most cars).

Just throwing that out there, since the universal cats are cheap and readily available now.

[vwmikel]

No emissions testing, just trying to take the stink out with a high flow metallic core spun cat. It's a "universal" one, so it probably wouldn't do all that much up close to the turbo anyway. It'll be installed in roughly the stock location, and stock it had a turbo, but I don't think emissions requirements were all that tough to pass back in '93!


Interesting stuff here, don't see emissions talked about too much on older modified cars that still have to pass the sniffer.

It's kind of surprising to me that you have issues with the aftermarket cat. I ran one of the spun metallic ones on a VW Golf with a GT3076 (no turbo when stock) and it passed the sniffer without issue. I don't remember it smelling particularly bad either.

[Kevin325i]

There is literally an endless amount of catalyst combinations. Things that look very similar can be very very different with just a simple change to the substrate and wash coat.

Even across product lines for aftermarket ones as well. Engine out needs to match the precious metal composition, needs to match a cell density and wash coat thickness, needs to match a substrate thickness and pattern. The real world sniffer tests are nothing like what an OEM deals with for certification though.



Another thing I forgot to mention for the OP. Did you paint the exhaust? Catalysts are very prone to poisoning from things like paint and rtv. I've had my fair share of test cats rendered useless because of paint.

[Brown9348]

so the cat is a high flow 40$ cat from eBay( yes I know, I'm sure it's terrible, but a friend recommended it because he got it to pass on his obd1)
no, it's not painted.. the next thing is going to be trying to fit this n55 cat near the turbo if there's enough room, but it's going to cost me a fortune.
I'm really curious what high flow(or not hi flow) cat you all think would be a good fit?? People keep saying kooks green cats as a recommendation. I wouldn't mind trying one, but for 350-500$, I would like to know it's going to actually work. A shop suggested two of these particular in line, that one may not be enough.
i was going to try to get this n55 cat put it in at the original cat location but the shop says it still may be too far away to really get hot.
Tuner says the cat I have now is too far away and too small, I think they are right.

[Def]

It's kind of surprising to me that you have issues with the aftermarket cat. I ran one of the spun metallic ones on a VW Golf with a GT3076 (no turbo when stock) and it passed the sniffer without issue. I don't remember it smelling particularly bad either.

I didn't say I have issues with it, but in my experience, the cheap aftermarket cats don't run anywhere near as clean as OEM level ones, especially from more luxury marques that boast a low emissions category for a relatively high output engine.


I got a $60 high flow metallic 3" cat to put on my MR2. I think it'll do fine to take the stink out of the exhaust, which is all I'm really looking for. I'm going to run it a bit further away from the turbo so maybe it'll survive track usage better.


OP, is everything heat wrapped before the cat? Trying to fit a giant N55 cat would probably work, but sounds difficult.

I'm still wondering why 2 cheaper cats in series wouldn't do a better job? I've seen some guys do this to pass emissions on SR20DETs. Basically stock downpipe with 2-3 cheap cats welded in.

[Kevin325i]

So, depending on what the other constituents are at, for a catalyst to work properly (specifically to scrub NOx) you need CO to make it further downstream. Catalysts in series take a long long time to get the second one hot (not speaking about two bricks in one 12" housing) because the HC scrubbing happens mostly across the face and they're not close enough together for the first to light the face of the second. That spacing is usually about 10-20mm to light the second.

Now you've got all the active sites in the brick full of HC and a really hot first catalyst without additional substrate to act as a heat sink. This will cause much more rapid deterioration of the washcoat and substrate, is prone to cracking or pitting, and be unlikely to pass an emissions test in a couple months. You also create an area that can generate more NOx because you've filled the entire length of the catalyst with a slow lighting HC scrubber only that's really hot.


BUT limits on this test are gonna be waay more than I have to deal with, and don't need to survive through warranty. Two cats in series will most likely be the cheapest solution. Another option is a larger cell face. Rule of thumb is usually HC and CO with width, NOx with length but there's a lot more to it like everything.

[Def]

What about on cars that have a really close pre-cat and then another cat further downstream? I admit I don't see this very often now compared to ~10-15 years ago, but does an OEM just take the hit on potential durability of the secondary cat in this configuration?

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Also OP - what about doing some streetracing-nasty 2 step action outside the emissions test station right before you go in to really light stuff up?


Only half kidding...

[Kevin325i]

I was assuming that the OP got it hot before the test...


That's a good question honestly. I think the thought was to get it lit early because we didn't really care about NOx or CO or CO2 back then. I'll ask around cause I'm curious too. Those were usually platinum and palladium (1,1,0) cats meaning 1:1 ratio in the wash coat. There's a big shift for using more rhodium (1,0,1 is common) which handles higher temps a little better or so the manufacturers that control the precious metals claim.

[Brown9348]

I've been trying to get the cat as hot as possible before the test. Best results I've had so far have been driving for about 20 minutes and getting into some boost during that, and that day only had to wait about 5 minutes.
The time I tried 20% ethanol I didn't get into boost at all on the drive there because I was worried about running lean during boost. It's hard to keep the cat warm if I have to wait in line at all... but If I can't get the shop to look at the car tomorrow I may try to wrap the small section between the flex portion and cat and just try to drive it hard for 30 minutes before.
ive had a friend suggest that my lower temp thermostat could be preventing the motor from getting hot enough, he suggested, without switching the thermostat, I could try blocking off the radiator or remove the mechanical fan to get the car nice and hot. Don't know if that'd really work though. I could try an extra cat about a foot or so closer to the turbo. That may be the easiest and cheapest next step. Should I be looking for higher than 400 Cell count?

[Kevin325i]

400 cpsi, cells per square inch is plenty high. 200 or 300 is pretty common too.

I would just put that n55 cat instead of the one you have already. If it looks bigger or about the same I can almost guarantee it has more metal in the washcoat and will handle everything better. Insulate and shield it as best you can and give it a shot.

[Def]

I wouldn't worry about going lean with a tiny bit of ethanol in the fuel. It's like going from a 11.5:1 AFR to like 11.9:1 AFR adding 10% more ethanol, but the fuel itself will be more detonation resistant as you up the ethanol content. E30-E35 with 87 AKI octane "base gas" is about the same or better on detonation resistance than 93 octane E10 in my experience.


If you have to turn the car off, I'd recommend getting in it and revving it up to a fast idle for a bit to warm the cat back up as much as possible before the test. At least 30-45 sec of a fast idle to try to heat things up. EGTs at idle are very low. so a prolonged low warm idle isn't going to put much heat into the cat if it's had a chance to cool down.