[BWilson263]

Originally Posted by Kriz2fer

They don’t really help. Go catless or stay stock

I can't stay stock and go to BM3 Stage 2.

[540iSUP]

Guys, swapping the cat on a 540i literally takes 30 mins as long as everything is cool to the touch. I don't know about the 550, but you can reach everything from above and below the car and you don't need to remove anything. That is as long as you have an aftermarket intake.

I'm in California and I've driven the car in both LA and SF with police driving behind me on the freeway and city streets. I can smell the exhaust, but it seems to not bother any law enforcement. For emissions I'm planning on swapping the OEM cat back in and flashing a stock tune.

[thecooltype]

Originally Posted by Kriz2fer

If your doing downpipes, I would go catless or leave it stock. Catted downpipes don’t net much gain over stock. It’s a pain to install those. Make it worth it.

No disrespect but this is non sense... I have high flow catted.. It's only about 10 to 15 hp difference with the catless

Mine smells also. I cannot rev in the garage. The entire den area inside will smell of gas. I cannot even begin to imagine how much the catless smell then

[thecooltype]

Originally Posted by Kriz2fer

They don’t really help. Go catless or stay stock

false again... my car is night and day from stock to the high flow catted dp

[Kriz2fer]

Originally Posted by thecooltype

No disrespect but this is non sense... I have high flow catted.. It's only about 10 to 15 hp difference with the catless

Mine smells also. I cannot rev in the garage. The entire den area inside will smell of gas. I cannot even begin to imagine how much the catless smell then

So if catless only gains 10-15 hp that mean catted is only gaining 5hp? Lol

[mike@x-ph.com]

Originally Posted by Kriz2fer

So if catless only gains 10-15 hp that mean catted is only gaining 5hp? Lol

catted and catless net the same gains on the stock turbos.

[BWilson263]

I'm having a Evolution Racewerks catted downpipe installed this Tuesday. I will be going BM3 stage2. I know by using BM3 it won't throw a CEL. For those that have installed a Evolution catted downpipe when you went through motor vehicle inspection did you pass emissions? Active Autowerke Catted Downpipe claims no CEL any truth to this?

[Kriz2fer]

Originally Posted by mike@x-ph.com

catted and catless net the same gains on the stock turbos.

Have you seen a dyno comparison?

[540iSUP]

Originally Posted by BWilson263

I'm having a Evolution Racewerks catted downpipe installed this Tuesday. I will be going BM3 stage2. I know by using BM3 it won't throw a CEL. For those that have installed a Evolution catted downpipe when you went through motor vehicle inspection did you pass emissions? Active Autowerke Catted Downpipe claims no CEL any truth to this?

The BM3 tune just has a parameter that can disable the post cat O2 sensor from triggering a CEL. It will show up on an emissions test as monitors not ready. So technically, you are throwing a silent or blind CEL. ER sells a very high quality Cat so I doubt you will throw a CEL anyways. AA is on the same level and they actually guarantee you won't throw a CEL.

In CA, these newer cars should not go through the sniffer, just a simple OB2 read to make sure monitors are on, no CELS, and a quick visual inspection. They will see the DP, but if it looks like the Cat is still there, you'll be good.

[2022M550i]

All dyno's aren't created equal. Too many variables. I'd prefer to see ET & MPH differences.

I know this is like comparing apples to oranges. I put high flow cat's on my Viper. Stock set up was 4 large cats, the high flows eliminated 2 cats and the hi flo cats themselves were smaller units. Probably because of the 512 ci displacement, that was the first exhaust mod that I actually felt a seat of the pants difference. I couldn't believe it. The good thing is that they do their job well and I don't smell any gas. It's louder than hell though...from the factory, there are no mufflers on the car, just resonators.



Found a decent video of a M550i downpipe install. Don't mind the dude with the weed shirt. I can't imagine the heat on the top of this thing...between those cats and turbos. No wonder why they had issues with baking oil on the valve stems on the earlier N63's. It's my understanding that baked oil on the stems shredded the valve guide seals and that was why they consumed oil.

[thecooltype]

Originally Posted by Kriz2fer

Mine smells also. I cannot rev in the garage. The entire den area inside will smell of gas. I cannot even begin to imagine how much the catless smell then

So if catless only gains 10-15 hp that mean catted is only gaining 5hp? Lol

lol I see we have a clown troll here... If your catless is gaining only 10 to 15 hp with a stage 2 tune then you must be doing something wrong. However, I see that your are a troll with all your comments all over the forum.
I gain 30hp with catted and a tune...Catless is estimated to be an additional 10hp

[thecooltype]

Originally Posted by BWilson263

I'm having a Evolution Racewerks catted downpipe installed this Tuesday. I will be going BM3 stage2. I know by using BM3 it won't throw a CEL. For those that have installed a Evolution catted downpipe when you went through motor vehicle inspection did you pass emissions? Active Autowerke Catted Downpipe claims no CEL any truth to this?

I have gone stage 2 with catted for two months now and car still not showing emissions ready. I have until next February to sort it out so I am good for now. I partly suspect it's because I have not gone through the drive cycles.

[540iSUP]

Originally Posted by thecooltype

I have gone stage 2 with catted for two months now and car still not showing emissions ready. I have until next February to sort it out so I am good for now. I partly suspect it's because I have not gone through the drive cycles.

Yeah, you need to drive for like 30 mins and Start/Stop the car about 3 times. Easiest way to get monitors ready is to drive to the gas station, fill up, go for a nice scenic drive, or a fun little canyon run and by the time you get home you'll be good.

[mike@x-ph.com]

Originally Posted by Kriz2fer

Have you seen a dyno comparison?

I have not seen any dyno comparison showing otherwise.

[BWilson263]

I got mine Evolution Racewerks catted downpipe installed today and flashed BM3 stage 2. No CEL but there's a noticeable difference from stage 1 to stage 2. There is a slight fuel smell but, I can live with that since there's a nice low end boost in speed. Not much difference in sound from stock so I will most likely install a Dinan catback or if someone can suggest a better sounding catback.... please not too loud.

[Kriz2fer]

Originally Posted by thecooltype

lol I see we have a clown troll here... If your catless is gaining only 10 to 15 hp with a stage 2 tune then you must be doing something wrong. However, I see that your are a troll with all your comments all over the forum.
I gain 30hp with catted and a tune...Catless is estimated to be an additional 10hp

No Im saying if your going through all the trouble of installing a downpipe why not get the full bang? Why miss out on even 10 hp which is a lot when talking about a 25-30 ho net gain. I drive a 2022 m550 not 540. It is a long process to install them. I'm not missing out on 10 an extra 10 hp.

[2022M550i]

I think the main question here is if you live in an emissions testing state, do the high flow cats even do the job? I can't imagine if you're still smelling gas with the high flows, that they will pass emissions. If they don't do the job, then the juice isn't worth the squeeze and you stay with factory. I wouldn't want to go through that tedious BS replacing those things and swapping them out every two years for emissions testing. If you're in a non-emission state, then go catless….

You guys are lucky, exhaust and tune… And you're all set. In my time, major work was required to get 50 to 75 hp…. Heads, cam, exhaust, intake, fuel injectors, fuel pump, larger mass airflow etc. If you threw a supercharger on there (getting another 75- 150 hp), you almost guaranteed were destroying the engine…. At some point detonation would rear its ugly head. There weren't any knock sensors to retard timing.. and you would either squeeze out a head gasket or put a hole in the pistons….back in my day, I had to walk to school both ways uphill in the rain and snow.

[BWilson263]

Originally Posted by 2022M550i

I think the main question here is if you live in an emissions testing state, do the high flow cats even do the job? I can't imagine if you're still smelling gas with the high flows, that they will pass emissions. If they don't do the job, then the juice isn't worth the squeeze and you stay with factory. I wouldn't want to go through that tedious BS replacing those things and swapping them out every two years for emissions testing. If you're in a non-emission state, then go catless….

You guys are lucky, exhaust and tune… And you're all set. In my time, major work was required to get 50 to 75 hp…. Heads, cam, exhaust, intake, fuel injectors, fuel pump, larger mass airflow etc. If you threw a supercharger on there (getting another 75- 150 hp), you almost guaranteed were destroying the engine…. At some point detonation would rear its ugly head. There weren't any knock sensors to retard timing.. and you would either squeeze out a head gasket or put a hole in the pistons….back in my day, I had to walk to school both ways uphill in the rain and snow.

In my case to go with Evolution Racewerks catted downpipe was to be able to go BM3 stage2. I'm also waiting for my Dinan catback exhaust. I'm thinking a catless downpipe would be too loud for my taste. I have a 540 so doing a downpipe is no big deal to install. Hopefully with the downpipe, exhaust, cold air intake and tune I should be pushing near 400 hp or a little more.

[540iSUP]

I can't speak on any of the G30 High Flow Cats, but I had a 1990 RX7 with a High Flow Cat and passed CARB every time. It did smell a bit, but I never had any issues. This is assuming that you purchased a DP that specifically states it will pass emissions. Usually the more expensive ones will do this. The cheaper ones will pass emissions, but they most likely will not pass CA emissions testing after about a year of use.

I fig that the 550 guys have enough cash to spend on quality high flow cats and would rather go that route if emissions is a concern, due to the complexity of the install. For us 540 guys, its like a 30 min job to swap out DPs.

Another thing to consider is whether or not you plan on using any Ethanol blends above E10. Ethanol will coat the honeycomb material in the Catalytic converter and fudge it up. So in that case, a catless DP would be more ideal, although again, the more expensive units will be able to handle this due to them being made of metal.