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      11-19-2017, 10:52 AM   #1
Mandinca
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Modding questions

Hi guys, new owner here with a stock E88 (N54) and looking to get into some modding.
Starting with a charge pipe, BMS DCI, FMIC, BOV and downpipes.

Question, what would be the best way to go, catted downpipes or catless ?
I'm trying to avoid changing the downpipes every time I want to go through emissions because thats just too much of a PITA.

Any thoughts on the differences between being catless or going with a high flow catted set up ?
Power, drivability, sound, smell of gas ?
Or, does anyone know if emissions centers will allow catless downpipes in CT ?
Any friendly ones ?

What about the BOV ? I see the usual Tial BOV's being used but also saw a video for Lucas BOV's that are like replacement cartridges. Any pros and cons for either that anyone knows of ?

Last, what charge pipe does everyone recommend.
If I've broken any forum rules with my downpipe question I apologize....a previous forum I was in for my last car was a bit touchy about that.

Thanks in advance.

Last edited by Mandinca; 11-19-2017 at 11:16 AM.
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      11-19-2017, 12:49 PM   #2
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When it comes to catless downpipes and emissions, changing the aftermarket to stock is usually one of the aspects that comes with it, especially with myself being in Cali. Catless Downpipes are going to yield you the most power as far as bolt ons go. I don't have any experience or know of the power difference between catless and high flow but I do know of some friends who can't pass smog even with their high flows. And smog here is bi-annually so I usually just suck it up and swap out the pipes when the time comes.

Having just catless downpipes IMO didn't have too much of a sound increase unless I was WOT and the smell wasn't too noticeable.

For BOV I also see most people using the Tial BOV, with little to no issues. I personally use the HKS SSQV BOV and love it. Has that signature "flutter" sound which I like. I don't think there's any pros and cons when it comes to a reputable, proven BOV brand. Just a difference in sound really.

For the chargepipe my stock one broke under stock boost and I replaced it with a VRSF chargepipe with no issues at all. Most if the older heads I see use an ER chargepipe
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      11-20-2017, 11:48 AM   #3
Mandinca
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Swap them out every 6 months.....then back again two hours later. What a pain. Do you do it using a lift or on stands ?
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      01-11-2018, 08:17 AM   #4
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Dunno why no one has reccomended a dp fix. Not to hard to install and you donít have to change out your downpipes. I have one and havenít had trouble with inspection and what not.
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      01-13-2018, 12:44 PM   #5
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In CT itís all about obd2 compliance. No codes, no problems. With no other changes running catless you will throw a cat efficiency code. Running high flow, you may throw a cat code. The fix is to flash (not 100%) this works, or change the rear sensor in some way. I will let you search.

FYI, running completely catless sucks imo. Stinky exhaust, spew emissions and not much more power than hfc. If n55 I would go hfc. If n54, you could go catless dp but leave the factory mid pipe with cats.

Factory cats not the best for power

No cat is not good either.

Some cats are just right.
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      01-21-2018, 12:18 PM   #6
Mandinca
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Quote:
Originally Posted by Apex1.0 View Post
In CT itís all about obd2 compliance. No codes, no problems. With no other changes running catless you will throw a cat efficiency code. Running high flow, you may throw a cat code. The fix is to flash (not 100%) this works, or change the rear sensor in some way. I will let you search.

FYI, running completely catless sucks imo. Stinky exhaust, spew emissions and not much more power than hfc. If n55 I would go hfc. If n54, you could go catless dp but leave the factory mid pipe with cats.

Factory cats not the best for power

No cat is not good either.

Some cats are just right.
I have n54, I was planning catless DP with factory mid pipes. Everything I have read says to use JB4 or MHD tune with catless DP's and a FMIC. Are you saying I would actually be better off with HF DP's. I don't mind the smell so much unless it's really bad. I was catless on my Mazdaspeed6 and hardly noticed it unless it was idling somewhere which was rare. That said, swapping the DP was an hour job....LOL

As for emission inspection, I understood that OBDII replaced the sniffer but that there was still a visual inspection for cats in the downpipes. Do they even bother or are the inspection stations satisfied with mid pipe cats ?
Where do you take yours for inspections ?
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      01-23-2018, 11:25 AM   #7
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There is a visual inspection, so you need to have some cats. The secondary mid-pipe cats should serve this purpose. If you go with catless DP, the DME will throw a cat efficiency code. You may be able to flash this away, but I am not sure that will still be OBD2 compliant. Your IM monitors need to be in ready status to complete the emissions test. This is why you have to drive the car some time after disconnecting the battery. Flash aside, there are other ways to deal with the rear O2, but again I will let you search that out.
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      01-23-2018, 11:36 AM   #8
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Performance wise, moving the flow restrictions away from where the exhaust gasses are hottest will have the most impact on performance. Improve flow closest to the turbo should be the priority.

Regarding all the cats, just an estimation but if would guess 85-95% of the performance gain would come from replacing the DP cat, 5-15% from replacing the secondary cats.
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      01-23-2018, 02:18 PM   #9
Mandinca
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Quote:
Originally Posted by Apex1.0 View Post
There is a visual inspection, so you need to have some cats. The secondary mid-pipe cats should serve this purpose. If you go with catless DP, the DME will throw a cat efficiency code. You may be able to flash this away, but I am not sure that will still be OBD2 compliant. Your IM monitors need to be in ready status to complete the emissions test. This is why you have to drive the car some time after disconnecting the battery. Flash aside, there are other ways to deal with the rear O2, but again I will let you search that out.
Thanks for the info, I think the Mazdaspeed group used an extender that screwed into the downpipe then the O2 screwed into that...just took the sensor out of the gas flow so it worked, but didn't throw a code.
I'll read up on it - good to know that the mid pipe cats pass the visual inspection.
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      01-23-2018, 04:45 PM   #10
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You are on the right track.
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      01-23-2018, 05:04 PM   #11
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Quote:
Originally Posted by nyak View Post
Dunno why no one has reccomended a dp fix. Not to hard to install and you don’t have to change out your downpipes. I have one and haven’t had trouble with inspection and what not.
+1 on this. I use VRSF DP fix and get right thru MA inspection 3 years in a row now
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      01-25-2018, 02:25 PM   #12
Mandinca
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Thanks to all for the advice - much appreciated.
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