[XC3LLR8]

Curious why the Active Autowerke downpipe is frequently recommended as a high flow cat when the cell count is 400, which I believe is inline with the cell count in the OEM downpipe? If so, is there really that much difference in flow? Is this also why AA can pretty much guarantee it won't throw a CEL?

UPDATE: OEM cell count = 700

[Rdurty2]

Stock cell counts are usually around 800 if not higher.

I attached comparison photo of my aa to stock. It’s a good difference.

I love the aa downpipe. Zero cel, great sound, no smell, and noticeable power increase by itself.

It’s zero cel not just because of cell count but because of the amount of precious metals that make up the cat. Cheapo catted downpipes aren’t going to have even close to the amount of precious metal which will contribute to a cel.

[XC3LLR8]

Originally Posted by Rdurty2

Stock cell counts are usually around 800 if not higher.

I attached comparison photo of my aa to stock. It’s a good difference.

I love the aa downpipe. Zero cel, great sound, no smell, and noticeable power increase by itself.

It’s zero cel not just because of cell count but because of the amount of precious metals that make up the cat. Cheapo catted downpipes aren’t going to have even close to the amount of precious metal which will contribute to a cel.

With 1 being Easy and 5 Hard, what would you rate the install? Doesn't really matter either way, just curious on what to expect.

[Rdurty2]

It’s pretty easy. I did it on jack stands.

If someone would consider installing an intake a 1 then I think the downpipe install would be a 2/5

[XC3LLR8]

I called Fabspeed to inquire about their downpipe as they use a 200 cell. However, they did not list the G42, but they were curious if the downpipe for the M340i was the same. I called my BMW dealership and confirmed the downpipe part numbers for a G42 M240i and a 2022 M340i are the same.

Now it looks like the two top-tier downpipes - Fabspeed and Active Autowerke - are the ones I'd like to compare.

OEM = 700 cell
Active Autowerke = 400 cell / $1,500
Fabspeed = 200 cell / $1,996

Both guarantee no CEL.

"This downpipe feature German made HJS 200 cell EURO 6 compliant trimetallic catalytic converters. We use 4 in piping from the engine side to the cat, and 3 in tubing from the cat to the rest of the exhaust. Our larger catalytic converters are better because they allow for more exhaust flow and the increased catalysts surface area allows for better exhaust gas filtering which means emissions compliance that will NOT trigger a check engine light. Our Sport Cat Downpipe are a direct bolt-on replacement for the factory M340i catalytic converter.

When we looked at the factory 12” long 700 cell ceramic core cats we immediately found an opportunity for improvement. The OEM Cats restrict exhaust CFM flow, limit sound and worst of all, rob performance. Replacing the OEM cats for a set of Fabspeed Sport Catalytic converter will net you improved performance with absolutely zero fear of a check engine light."

I'm a little concerned I'd be overpaying for the Fabspeed name, as they're selling a $70 K&N drop-in air filter (labeled BMC F1) for $200. LOL

[Rdurty2]

Honestly there will be next to no difference between them. High flow cats are so efficient now that you are probably talking single digit 1-5 HP differences, if any difference at all. Nothing you would ever feel. Even the difference between high flow cats and catless is very minimal these days.

I see that fabspeed uses interlocking bellows for their flex section. I know that on other makes interlocking bellow flex sections can create some noise.

[XC3LLR8]

Originally Posted by Rdurty2

Honestly there will be next to no difference between them. High flow cats are so efficient now that you are probably talking single digit 1-5 HP differences, if any difference at all. Nothing you would ever feel. Even the difference between high flow cats and catless is very minimal these days.

That's a good point - I remember reading somewhere that a high flow moves something like 93% of the air a catless moves.

[Rdurty2]

Originally Posted by XC3LLR8

That's a good point - I remember reading somewhere that a high flow moves something like 93% of the air a catless moves.

Exactly, that's why I always have to laugh when people act like their catless gives them 245hp more than a catted downpipe. The difference is negligible.

[Rw-M240]

Originally Posted by XC3LLR8

With 1 being Easy and 5 Hard, what would you rate the install? Doesn't really matter either way, just curious on what to expect.

For me it was about a 3. The downpipe was hard to get from the midpipe once everything was disconnected. I had everything off and it didn't move an inch till I started hitting it with a rag and hammer on the midpipe. I got the Cg ds1 200 cell downpipe that's means for a 340i but I knew it would fit fine. It was 979$ and has a little smell to it but makes the car sounds amazing. No check engine light too.

[mike@x-ph.com]

The CEL count is not necessarily linked to the no-check engine light. The quality of the cats is the most significant factor.

Active Autowerke uses high-quality GESI cats (EPA Approved); they are the most popular because Active Autowerke will replace your downpipe for free if you get the CEL.

HJS cats are 300 CEL, also no check engine light.

You will get a check engine light if you get a lower quality 400 CEL or 300 CEL downpipe.

The same goes with the flow; a high-quality 300 CEL will flow better than a low-quality 200 CEL.

[dasistato]

Can someone post a link to the AA downpipe? I do not see one for g42 on their site.

[HawksG42]

Originally Posted by dasistato

Can someone post a link to the AA downpipe? I do not see one for g42 on their site.

I think you can refer to XC3LLR8 ‘s post about calling BMW and verify that the stock downpipe is the same for the M240i as it is for the M340i

[Rdurty2]

Originally Posted by HawksG42

I think you can refer to XC3LLR8 ‘s post about calling BMW and verify that the stock downpipe is the same for the M240i as it is for the M340i

You don’t need to call BMW. The m340 and m240 use the exact same downpipe.

This is the one you buy:

https://x-ph.com/active-autowerke-aa-bmw-supra-b58-catted-downpipe-fits-f-g-chassis-supra/

[mike@x-ph.com]

Originally Posted by dasistato

Can someone post a link to the AA downpipe? I do not see one for g42 on their site.

Originally Posted by Rdurty2

You don’t need to call BMW. The m340 and m240 use the exact same downpipe.

This is the one you buy:

https://x-ph.com/active-autowerke-aa...chassis-supra/

+1

[dasistato]

Originally Posted by mike@x-ph.com

+1

Ty ty! Looks like its even discounted a little more. Tempted to buy! Got anything else left in the bag to make it closer to 1k?!

[mike@x-ph.com]

Originally Posted by dasistato

Ty ty! Looks like its even discounted a little more. Tempted to buy! Got anything else left in the bag to make it closer to 1k?!

Check your inbox

[NaxG42]

someone use the Miltek catted downpipe ?

They don't specify anything about the cel on their site, I've already ordered the full catback, but I hesitate for the catted DP, it's about $400 (Canadian) cheaper than the Active.

I tend to tell myself that Miltek is a reputable company and that they make quality products.

What do you think ?

[MrPickles]

Originally Posted by mike@x-ph.com

Check your inbox

Mind sending something to mine? 😁

[mike@x-ph.com]

Originally Posted by MrPickles

Mind sending something to mine? 😁

Done

[NaxG42]

Mike, i sent you a message

[Rdurty2]

Originally Posted by mike@x-ph.com

Done

Good ol Santa Mike!

[mike@x-ph.com]

Originally Posted by Rdurty2

Good ol Santa Mike!