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Technical Topics B58 6-Cylinder Turbo Engine / Drivetrain / Exhaust Modifications vrsf or active autowerks catless dp?

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      04-21-2020, 01:23 PM   #23
DG20
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My engine on my old 340i blew and after 2 MONTHS of diagnostics, they were out of ideas and blamed it on my catted downpipe. They claimed that it caused damage to the cylinder walls. It had 18,000 miles. Never tracked, never raced. I was on Eco-Pro on the hwy when it blew and the cylinders started misfiring. They didn't want to take the blame for their defective engine. It was out of the dealership's hands and it was corporate engineers who gave the final call.

They had the audacity to ask me for $20,000 to fix the engine. Lol. I told them to go take a hike. It's a shame how scumbag-ish and money hungry this company (BMW) is and has become.
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      04-21-2020, 02:13 PM   #24
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Quote:
Originally Posted by DG20 View Post
My engine on my old 340i blew and after 2 MONTHS of diagnostics, they were out of ideas and blamed it on my catted downpipe. They claimed that it caused damage to the cylinder walls. It had 18,000 miles. Never tracked, never raced. I was on Eco-Pro on the hwy when it blew and the cylinders started misfiring. They didn't want to take the blame for their defective engine. It was out of the dealership's hands and it was corporate engineers who gave the final call.

They had the audacity to ask me for $20,000 to fix the engine. Lol. I told them to go take a hike. It's a shame how scumbag-ish and money hungry this company (BMW) is and has become.
what was your eventual resolution? Did you buy a used engine etc..? Was your only mod a DP?

Thanks!

Last edited by chenry; 04-21-2020 at 02:21 PM.. Reason: typo
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      12-12-2023, 06:33 PM   #25
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Can anyone tell is there cell issue with vrsf catted do without tuned? Appreciate any reply!
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      12-13-2023, 02:52 AM   #26
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Quote:
Originally Posted by Jeff40 View Post
Can anyone tell is there cell issue with vrsf catted do without tuned? Appreciate any reply!
With an aftermarket downpipe - catted or not you WILL GET A CEL. Period!

The only exception is the AA downpipe as that uses more restrictive 400cel GESI cats. Whereas the others will use a 200cel high flow cat.

The AA are a lot more expensive and do not flow as good as a 200cel or catless, but still much better than stock. I wouldn't (didn't) bother with an AA, I got a 200cel and a tune for the same price as just an AA DP.

But to repeat this - YOU WILL GET A CEL WITH AN AFTERMARKET DOWNPIPE. (with above exception noted).
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      12-13-2023, 10:56 AM   #27
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Quote:
Originally Posted by cyam View Post
With an aftermarket downpipe - catted or not you WILL GET A CEL. Period!

The only exception is the AA downpipe as that uses more restrictive 400cel GESI cats. Whereas the others will use a 200cel high flow cat.

The AA are a lot more expensive and do not flow as good as a 200cel or catless, but still much better than stock. I wouldn't (didn't) bother with an AA, I got a 200cel and a tune for the same price as just an AA DP.

But to repeat this - YOU WILL GET A CEL WITH AN AFTERMARKET DOWNPIPE. (with above exception noted).
Agree with everything you said except the flow remark.

From the data I saw, the AA flows just as well if not better than the 200 CEL on the market. It uses GESI cats rated up to 850 whp.
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      12-13-2023, 07:00 PM   #28
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Quote:
Originally Posted by mike@x-ph.com View Post
Agree with everything you said except the flow remark.

From the data I saw, the AA flows just as well if not better than the 200 CEL on the market. It uses GESI cats rated up to 850 whp.
Mike, come on. Basic laws of physics says that is impossible. 400cell literally means 400 cells per square inch, 200cell is half that so all variables equal the 200cell would flow twice the 400 cell, because it has half the restriction. Other variables however modify that and the end result is not as dramatic.

No data I have seen shows a 400cell flowing higher that a 200cell :-D

What I HAVE seen are flow rate graphs on these downpipes. Wagner did some good tests. The 200cel flows slightly less than a catless, the 400 cell flows less again than the 200 cell by a slightly wider margin and the OEM 600cell flows quite a bit less (due also to the fact the OEM has 2 cats a 600 cell then another 400 cell post cat.)

Due to the large diameters of these downpipes (4-6") and other factors like maximum exhaust volume, the differences are not as linear as in a "lab test".

Bottom line, the AA with a 400cell certainly flows better than OEM but it does not flow as well as a 200cell, let alone a catless - although the differences are becoming smaller and would be hardly noticeable from a performance stand point, but audibly would be more obvious.
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      12-14-2023, 10:27 AM   #29
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Quote:
Originally Posted by cyam View Post
Mike, come on. Basic laws of physics says that is impossible. 400cell literally means 400 cells per square inch, 200cell is half that so all variables equal the 200cell would flow twice the 400 cell, because it has half the restriction. Other variables however modify that and the end result is not as dramatic.

No data I have seen shows a 400cell flowing higher that a 200cell :-D

What I HAVE seen are flow rate graphs on these downpipes. Wagner did some good tests. The 200cel flows slightly less than a catless, the 400 cell flows less again than the 200 cell by a slightly wider margin and the OEM 600cell flows quite a bit less (due also to the fact the OEM has 2 cats a 600 cell then another 400 cell post cat.)

Due to the large diameters of these downpipes (4-6") and other factors like maximum exhaust volume, the differences are not as linear as in a "lab test".

Bottom line, the AA with a 400cell certainly flows better than OEM but it does not flow as well as a 200cell, let alone a catless - although the differences are becoming smaller and would be hardly noticeable from a performance stand point, but audibly would be more obvious.
Im not disagreeing with the theory but there are more variables here than just the CEL count.

That said, I'm not saying you are incorrect, I'm only asking for the data comparing the two.

Also while one might flow more than the other, that does not automatically mean it makes more power. From the data I have seen, the GESI cat is more than enough for the stock turbo and makes the same power as the 200 CEL catted or the catless (1~2 whp difference).
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      12-14-2023, 08:44 PM   #30
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Quote:
Originally Posted by mike@x-ph.com View Post
Im not disagreeing with the theory but there are more variables here than just the CEL count.

That said, I'm not saying you are incorrect, I'm only asking for the data comparing the two.

Also while one might flow more than the other, that does not automatically mean it makes more power. From the data I have seen, the GESI cat is more than enough for the stock turbo and makes the same power as the 200 CEL catted or the catless (1~2 whp difference).
I do agree Mike, there is virtually no difference in peak power with any of these downpipes. But that's not primary the reason we get a mod'd downpipe.

We get a downpipe because of the increased flow. That increased flow means there is a greater pressure differential across the turbo, which means the turbo spools even faster (even less lag). That's the biggest benefit from a performance perspective. It makes the throttle response more immediate.

The other benefit is sound - and the cell count makes a direct correlation to sound. The lower the cell count the louder it will be.

So when you look at it from this perspective the cell count is very relevant and does make a difference.

As for data, Wagner did a test on flow rates on downpipes for this car and it shows exactly this regarding flow rates. I can't locate that graph though. But I did find one for a similar car, but the exhaust is different so the results are not the same as the M340i, but you get the idea from it. (attached)
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      12-15-2023, 09:36 AM   #31
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Quote:
Originally Posted by cyam View Post

But to repeat this - YOU WILL GET A CEL WITH AN AFTERMARKET DOWNPIPE. (with above exception noted).
You forgot to mention the Fabspeed 200 cell catted DP. They also guarantee no CEL but at $2k some might say it’s not worth it. I had one on my N55 for 5 years and not one single CEL and passed emissions every time. As far as sound I noticed the Fabspeed gets a smaller diameter post cat whereas the AA stays about 4in wide until the connection so even though it’s 400 cell I wonder if that helps with sound? Or will the 200 cell still sound better? I need a dp for my M440ix and I’ve pretty much boiled it down to these 2. For me honestly the price difference is not that major to defer me from the Fabspeed especially having experience with their product before and being extremely satisfied. However as me and Mike discussed before I’m not building anything in excess of 800hp maybe around 500 possibly so the AA should definitely be enough for me, but if one sounds better than the other then that might sway me. Pics of Fabspeed, AA, and OEM for comparison.
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      12-15-2023, 10:25 AM   #32
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Quote:
Originally Posted by cyam View Post

As for data, Wagner did a test on flow rates on downpipes for this car and it shows exactly this regarding flow rates. I can't locate that graph though. But I did find one for a similar car, but the exhaust is different so the results are not the same as the M340i, but you get the idea from it. (attached)
Since i agree with most of what you said, I'm only quoting the small part that i don't agree with.

Wagner did post the flow data, but that's not a valid comparison that would include Active Autowerke or Fabspeed or any other downpipe.

Since the CEL count is not the only factor, just because the downpipe wagner used in their test flowed a certain amount that certainly does not mean the active autowerke will flow the same even if they have the same CEL count.

For a valid comparison i would need to see the flow of the actual downpipe in question vs stock vs catless or any other downpipe we are comparing it to.
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