[studio54]

Originally Posted by vadonchez

yes it's certain now that they are not exactly the same.

I think that design is not the same even if total cells number is the same.

This is why bmw talk about difference between 1M/35is and 135i/335i

Yes, I read somewhere that yours should be lighter than mine. That's would make a final conclusion that yours is more empty than mine. I can weight it in a few moment if you can too.

[The_E92_Fan]

I can weigh my 335is cats too, for science

[studio54]

yeahh science... !

my right primary (shorter one, used on this thread for pictures) weights 3.5 kilograms.

[The_E92_Fan]

I think measuring down to the gram would be the best option here

[studio54]

Originally Posted by The_E92_Fan

I think measuring down to the gram would be the best option here

I have no precise balance, but it can give a starting point.

I may consider buy a Z4 or 1M set of downpipe, if it flows better than stock, so I don't have to care about emissions tests/bad smells at startup anymore and still have decent airflow.

[vadonchez]

I don't think that's an accurate way to proove anything because of teh difference in flange and maybe in lenght between Z4/135i and 335i design.

But for information mine weight 3.5kg too without VBAND :

[studio54]

Originally Posted by The_E92_Fan

I think measuring down to the gram would be the best option here

Maybe you have a good phone to take a picture of the honeycomb, I think the 335is have the same catalytic converter as 135/335 so it should be circles like mine.

[studio54]

Hehe it will be hard to compare anyway because of the difference between cats is so light..

BOYSEN reference is , to my understanding, the catalytic converter itself, the ceramic.

BOYSEN 603201 (1M / Z4) : 405 grams
https://metalsprice-lb.com/product/7...-603201-boysen

BOYSEN 579902 ( 135 / 335 ) : 438 grams
https://metalsprice-lb.com/product/7...-boysen-579902

[vadonchez]

Anyway, bmw should'nt have purchased two different reference from boysen without good reason.

1M and 35is reach more boost , i imagine bmw tried to keep reliability same as 135i/335i that's why DP are a little bit less restrictive.

But it seem's that's not night and day....

Could be interessant for science to have a picture from 335is honeycomb and 35i too!!

[studio54]

Yes, I am now convinced the 1M/Z4is has better flowing. Like you said, it does have same cells amount, surface look similar until you look closely. Honeycomb is different when you zoom it, less dense and squared holes, and maybe inside there are differences in the ceramic too.

Even german themselves says 1M and 135 cats are differents and 1M have a better flow :
https://www.1erforum.de/threads/3-ve...npipes.148876/

So good for you ! Will you keep the catless or reinstall OEM back ?

I wish I could find some 1m/Z4is primaries for cheap, but it seems hard to find...

[vadonchez]

yes I will probably put back my oem DP , VRSF DP are too loud for me.

If i was 25 years old again, i have been fallen in love for that noise but now it's too loud for me especially below 2000rpm and I'm often below 2000 RPM in 7 gear when I'm crusing...

[studio54]

Originally Posted by The_E92_Fan

I think measuring down to the gram would be the best option here

Hey,

I am curious to know if 335is (326hp instead of 306) have also a better flow cats than regular 335i ?

Since you have one, can you tell me what's the case number on yours ? The BOYSEN reference on the catalytic converter case.

Can you also takes a very close picture of the honeycomb to see if the pattern is circle or squared?

Thanks if you could !

[vadonchez]

bump!

[TiAgAu]

Originally Posted by studio54

Hey,

I am curious to know if 335is (326hp instead of 306) have also a better flow cats than regular 335i ?

Since you have one, can you tell me what's the case number on yours ? The BOYSEN reference on the catalytic converter case.

Can you also takes a very close picture of the honeycomb to see if the pattern is circle or squared?

Thanks if you could !

I'd say the cats are the same. The difference in power is only the tune.

Slightly more boost and leaner fuelling up top for the 335is

Left is 335i <--> Right is 335is.

[studio54]

Originally Posted by TiAgAu

I'd say the cats are the same. The difference in power is only the tune.

Slightly more boost and leaner fuelling up top for the 335is

Left is 335i <--> Right is 335is.

Yes, and 335i and 335is seems to have the same lastest updated part number.

I say "updated" cause the part number for the downpipe changed at the LCI time I think.

For example, today front downpipe part number (18307587609) is the same for 335i/335is/335xi while it was 18307553594 in the past, that came with first 335i in 2006 and 135i n54:

https://www.realoem.com/bmw/enUS/par...609&series=E92

It will fit 335is, 335i and 335xi, but won't fit my 135i for example according to realoem ?

Back in the time 18307553594 was ok for both 135i and 335i.

It could also be a mistake from realoem and 18307587609 will fit a 135i too.

And I have no clue what is the difference between 18307553594 and 18307587609. New design? better flow, or just new part number (different supplier or something).

The only thing sure for now, is that the z4 35 and the 1m have the same downpipes that are different from 135i/335i.