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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > High Flow Cats. The Deal?



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      07-28-2013, 04:06 PM   #23
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I really believe downpipes are overkill on this platform at 15-17 PSI and that 350 WHP level.

Last edited by Jnat; 07-29-2013 at 07:29 AM.
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      07-29-2013, 04:23 AM   #24
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Quote:
Originally Posted by jnat View Post
That's what I'm talking about, for a DD, that's the ticket! I really believe downpipes are overkill on this platform at 15-17 PSI.
Perhaps, but why is there so much more to be had from upgrading the downpipes & losing the cats? What you're saying is that we could all just fit an intercooler and then map the car to an FBO tune. Has anyone tried running a Cobb Stage 2+ or equivalent JB4, Vishnu etc map with the stock downpipes? I sure haven't seen it and I wouldn't feel comfortable pushing that amount of flow through the stock downpipes without some sort of tests showing the effect on longevity of parts. There are a lot of tuners offering downpipes for this engine and sure, they are in the business of making money but they don't do their R&D for fun.

You mention in your previous post that you don't think running factory DP's at 350whp is a problem and you are right. However, 350whp is basically a Stage 1 + FMIC tune which does not require downpipes at all.

Last edited by Cozy; 07-29-2013 at 04:36 AM.
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      07-29-2013, 07:05 AM   #25
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Quote:
Originally Posted by Cozy View Post
Perhaps, but why is there so much more to be had from upgrading the downpipes & losing the cats? What you're saying is that we could all just fit an intercooler and then map the car to an FBO tune. Has anyone tried running a Cobb Stage 2+ or equivalent JB4, Vishnu etc map with the stock downpipes? I sure haven't seen it and I wouldn't feel comfortable pushing that amount of flow through the stock downpipes without some sort of tests showing the effect on longevity of parts. There are a lot of tuners offering downpipes for this engine and sure, they are in the business of making money but they don't do their R&D for fun.

You mention in your previous post that you don't think running factory DP's at 350whp is a problem and you are right. However, 350whp is basically a Stage 1 + FMIC tune which does not require downpipes at all.
Btw Cobb recommends highflow catted or cattless downpipes to run with there race maps.

I am surprised you mention JB4, Terry has been supporting lots of vehicles running 19 PSI on an all stock car

As for Vish, well, never seen him condoning such a thing. Perhaps I pay less attention to his tuning, but never heard of him doing this.

Everything about this platform and the community is about the "cheapest" alternative for max power gains so that is why cattless DPs have a larger presence over highflow catted DPs. Balance and efficiency is so much ignored it has no value or merit.

The difference of power gains between cattless and catted (highflow) are only a 5-8 whp difference and for some that is just not worth the sacrifice.
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      07-29-2013, 07:39 AM   #26
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I'm not even looking at it from a money stand point. I'm just thinking about what we have on our platform and what others have on theirs. I'm also taking into consideration years (like most of you) of research, reading and modding. Speaking of vendors, tuners, there are several that think on this platform with using two downpipes (three cylinders per) we are fine up to 400 WHP. At some power level, I'm in total agreement that you need to upgrade but if you look at our stock downpipes, there actually designed very well in comparison to some stock downpipes on other makes. The gains in our case are from loosing the kitties, not the downpipe design. Lastly, as referenced above, the gains are minimal and not much 'bang for buck'. My point is very arguable, just food for thought!
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      07-29-2013, 07:47 AM   #27
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As far as I know ALL tuners recommend that you use high flow downpipes (catted or not) with an FBO tune. If 5-8whp is all we can get between catless aftermarket and stock catted downpipes then why do we all bother?

I have never seen a tuner say that you can use an FBO tune with stock downpipes. If that was the case I'd be very happy and I'd go right outside now and change my tune from Cobb Stage 1+ to Stage 2+ and save a heap of cash.
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      07-29-2013, 10:20 AM   #28
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Quote:
Originally Posted by Cozy View Post
As far as I know ALL tuners recommend that you use high flow downpipes (catted or not) with an FBO tune. If 5-8whp is all we can get between catless aftermarket and stock catted downpipes then why do we all bother?

I have never seen a tuner say that you can use an FBO tune with stock downpipes. If that was the case I'd be very happy and I'd go right outside now and change my tune from Cobb Stage 1+ to Stage 2+ and save a heap of cash.
I agree but then there are some that do the contrary as they are suppose to lead by example.

Its because it is a cheaper solution. If catted DPs were less than $100 more than a cattless DPs then people would buy them more. However there is an average $400+ difference between the two.

I can show you worse, a tuner condoning a completely stock car running PSI that is suppose to be ran on a FBO car; however common sense says its wrong period
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      07-29-2013, 04:39 PM   #29
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Then why do we all bother is exactly my point! On other platforms, if you look at dyno plots, the difference between the stock pipe and any aftermarket is 35-50 WHP (with tune). On ours, the difference is up to 8 WHP, doesn't that raise a eyebrow or two? My read on that is our stock downpipes are not bottlenecks, they're fairly efficient and flow well. Again, at higher power levels, they're needed but not at DD power levels or what we all refer to as FBO. It's another personal preference. If I saw an incredible difference in dyno plots, I'd do it, but I don't. I'm going to stay away from the 'every tuner recommends' statements because it's not my point. I like to look at the results and again, IMHO the results say that at 350-400 WHP, our stock downpipes especially since we have two work well.
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      07-29-2013, 04:45 PM   #30
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Difference between catless and high flow catted downpipes is 5-8 whp. Difference between OEM and catless is much higher.

Quote:
Originally Posted by jnat View Post
Then why do we all bother is exactly my point! On other platforms, if you look at dyno plots, the difference between the stock pipe and any aftermarket is 35-50 WHP (with tune). On ours, the difference is up to 8 WHP, doesn't that raise a eyebrow or two? My read on that is our stock downpipes are not bottlenecks, they're fairly efficient and flow well. Again, at higher power levels, they're needed but not at DD power levels or what we all refer to as FBO. It's another personal preference. If I saw an incredible difference in dyno plots, I'd do it, but I don't. I'm going to stay away from the 'every tuner recommends' statements because it's not my point. I like to look at the results and again, IMHO the results say that at 350-400 WHP, our stock downpipes especially since we have two work well.
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      07-29-2013, 04:54 PM   #31
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The way I see it is cat less helps turbo longevity.
So I'd rather pay 800 bucks to help the turbos spool better and gain more power
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      07-29-2013, 05:02 PM   #32
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This is directly off the Cobb web site on an N54.
06-15-2012 11:02 am 328 hp 388 ft/lb Stage 1 Agr. Baseline
07-11-2012 06:00 pm 339 hp 400 ft/lb Stage 2 Agr Baseline
Stage one is a tune plus FMIC and Stage two adds kittiless downpipes/DCI.
I don't see it and again, it's personal preference.
Also, real world feed back from members.
1)Yea I didn't feel much of a difference going from stage 1+ to stage 2 + the boost is just a little higher up top but there is no point to really rev that high on stock snails
2)I briefly ran the OTS Stage 2+ Sport map when I first installed my downpipes and was still running straight 91 octane pump gas. I was actually a little disappointed. I thought going from Stage 1+ to Stage 2+ would be a substantial jump. If anything, I thought Stage 2 felt slower.

Last edited by Jnat; 07-29-2013 at 06:13 PM.
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      07-29-2013, 05:06 PM   #33
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Quote:
Originally Posted by jnat View Post
This is directly off the Cobb web site on an N54.
06-15-2012 11:02 am 328 hp 388 ft/lb Stage 1 Agr. Baseline
07-11-2012 06:00 pm 339 hp 400 ft/lb Stage 2 Agr Baseline
Stage one is a tune plus FMIC and Stage two adds kittiless downpipes/DCI.
I don't see it and again, it's personal preference.
Do you have a tune? Are you able to or have you dyno'd on an FBO tune with your stock DP's? I'd be interested to see your logs or a dyno plot.
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      07-29-2013, 05:18 PM   #34
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My set up is very basic, just a JB4/G5-DCI-secondary kittyless-E25-30. My next very soon mod is an upgraded FMIC and an OCC. I'm leaning towards the Wagner FMIC I like that step up design. I'm really not interested in a dyno at this point as I'm personally not chasing a number. If I had dyno'd prior to any mods for a baseline then maybe it would make sense but I did not. I'm just looking to add useable power to my DD and add (like the OCC) preventative measures where possible. Walnut blasting is on my to do list also 45k miles (a little off topic).
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      02-23-2018, 03:38 PM   #35
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Anyone running the AR catted DPs on N54? I'm considering these for a stock turbos setup with JB4, ER CP, WMI meth, haven't yet decided on the FMIC, but close. I'm just trying to plan things out and budget for what's needed and want to know if this is needed. I want my less than legal mods to be as stealthy as possible so I don't have to swap things out when passing smog in CA.

Thank you
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      02-23-2018, 09:59 PM   #36
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its pointless. Go catless or stay stock
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