What size HJS Catalytic Converter is needed to get rid of exhaust smell

[maupineda]

Would they really fit.............with Euro Headers on an E46 M3?

They need to be modified. If you can source a second hand one, you would have OE high flow cats to harvest.

actually, it would be rather simple as you may just need to shorten the header connections, and clock the flanges to the resonated section.

https://z4-forum.com/forum/viewtopic.php?t=137175

[0-60motorsports]

They need to be modified. If you can source a second hand one, you would have OE high flow cats to harvest.

actually, it would be rather simple as you may just need to shorten the header connections, and clock the flanges to the resonated section.

https://z4-forum.com/forum/viewtopic.php?t=137175

Interesting and good to know! Thanks. I'll keep a look out and maybe even installing those cats on the SS V1 Catless pipes might be a good idea.

[Altaran]

Interesting. Might be worth ceramic coating them to try and keep the heat in.

I don't have my cats coated, but I coated my headers and added thermal insulation on top. Heats up the cats faster than before and it keeps the engine bay cooler.
I only have smell upon cold start, same as my 986 S which is on stock cats.

So coating or insulating cats may do the trick for you.

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[MC346]

At what operation point do you want to get rid of smell? Is it right at/during/after cold start while your car is idling, or any other condition? If we are talking about idle, or day-to-day part load driving / cruising cat size won‘t be the deciding variable. What matters is getting the catalytic material on the washcoat hot enough for it to start performing the desired reactions. As soon as the cats are warm and lambda control is active, there should not be much of a smell. Since the cats are located rather far away from the exhaust ports, it might take some time to reach operating temps especially if the car is just left idling. Size will decide how big of a mass flow can be dealt with and usually contribute to higher oxygen storage capacity that will serve as a buffer for any temporary deviations from stoichiometric AFR. As for higher loads: as soon as you leave the operation window for active lambda control, you will anyway run rich and emit some smelly hydrocarbons.

[MC346]

I have the SSV1 catted Sec 1, and you still smell it.
GESI gen 2 cats are 300 cell, yet move the same exhaust flow as 200 cell. I would look at them.

I was driving behind my car last month... dude floored it and it smelled like it was catless, lol.

That‘s simply because of the DME‘s component protection strategy and/or full losd enrichment . Under high loads lambda control is inactive and the system is running at a precontrolled rich AFR. That means some of the excess fuel is not taking part in the combustion. As you are dealing with excess hydrocarbons and very low O2 concentrations, your cat will effectively let the hydrocarbons pass through without any reaction
, therefore smell.

Only since recently are concepts with stoichiometric AFR over the whole operation map being realized for the upcoming Euro 7 emission standard. Those cars you might be able to follow while accelerating hard without any smell.

[bmw m3 s50]

Is all about metal content load. A certified Euro 4/5 car will do a good job a removing the smell, smell is directly related to gas catalyst / reduction.

so you need as much as possible surface area coated with active metals (platinum, radium, etc.) so the more dense, the more effective but will reduce flow. From those photos is obvious that the factory mesh is more dense.

the problem I see with the size needed to fit our chassis is that it limits the active surface, that is why the factory euro cats are long to compensate for the limited cross section area.

You think any Euro 4 cats would do a good job of removing the smell regardless of the size?

[bmw m3 s50]

At what operation point do you want to get rid of smell? Is it right at/during/after cold start while your car is idling, or any other condition? If we are talking about idle, or day-to-day part load driving / cruising cat size won‘t be the deciding variable. What matters is getting the catalytic material on the washcoat hot enough for it to start performing the desired reactions. As soon as the cats are warm and lambda control is active, there should not be much of a smell. Since the cats are located rather far away from the exhaust ports, it might take some time to reach operating temps especially if the car is just left idling. Size will decide how big of a mass flow can be dealt with and usually contribute to higher oxygen storage capacity that will serve as a buffer for any temporary deviations from stoichiometric AFR. As for higher loads: as soon as you leave the operation window for active lambda control, you will anyway run rich and emit some smelly hydrocarbons.

I don not mind it temporary during cold start but get rid of the smell while driving and stopped when the car is up to temperature is what I am looking for.

Also the cats would not be located in the stock area, I want to do a custom section one with cats and resonators. Cats to get rid of the smell and resonators to quiet the car down. Also not sure how effective lambda control would be on a tuned car. I was under the assumption most tuners increase AFR to avoid lean conditions.

[maupineda]

You think any Euro 4 cats would do a good job of removing the smell regardless of the size?

You are missing the fact that the s54 exhaust is split, so you don’t need huge cats. If you look at each bank, is a 1.6liter 3 cylinder engine. So any Euro4, or LEV EPA approved cat will work.

all will smell a bit on cold start, but shall be fine after 2-3 mins. That is why US cars have the Cats on the manifold, to heat them up quickly.

[MC346]

You think any Euro 4 cats would do a good job of removing the smell regardless of the size?

They do a good enough job on my car (2005 EU4 variant) in stock form. HC emission limits got quite a bit strickter with the switch from EU3 to EU4 standard. Theoretically speaking, i would aim at replicating the EU exhaust setup by mounting a EU4 section 1. However, i have absolutely no clue about the compatibility with your headers and the software you are running, and whether the back pressure is to high.

Regarding position of cats: EU models run the cat in section 1 too, a few milimeters up and down should not hurt as long as O2 sensors are at a similar position relative to the cat. Compared to the stock US variant with its cat in the header it could influence the behavior of your lambda controller, but will probably not influence driveability too much.

Regarding your tune: Unless the lamda setpoints at part load have not been deliberately changed, it should strive for lambda = 1. I guess you are refering to high load/power areas in the operation map where you strive for a rich enough AFR to contain component temperatures. Your cats won't work in that area anyway, even in stock form.

[Gt4]

They need to be modified. If you can source a second hand one, you would have OE high flow cats to harvest.

actually, it would be rather simple as you may just need to shorten the header connections, and clock the flanges to the resonated section.

https://z4-forum.com/forum/viewtopic.php?t=137175

I have a set that I bought from a guy on Zpost and modified to fit E46 M3:

https://nam3forum.com/forums/forum/classifieds/members-parts-for-sale-wtb/e46/277810-custom-euro-cats-section-1-low-mileage