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Discussion Starter · #1 ·
So, I am currently shopping for a downpipe and I have a few questions which through numerous searches, I can't seem to find an answer to.

1. Boost cut. It seems like a lot of people get boost cuts after switching to a downpipe. Does anyone know why this happens and how to cure it? I have read that an accessport helps to raise boost cut limits, but I'm don't want to purchase one any time soon. I want to get all my bolt-ons together before picking a tuning solution.

Are there certain situations where boost cut is more apt to appear than others? Accerlating in high gear? Certain loads/rpms? Temperature?

2. I want to go catted, but don't want to deal with codes. I understand that you run the chance of tripping a CEL after a downpipe install, even if its catted. So, is there anyway to get around this? In the domestic world people use O2 simulators. I've read a few posts about a diode trick? Anyone have a surefire way around this issue?
 

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i also want to know about N1.
 

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If you just have an intake and add a downpipe...you should not overboost and cut. Maybe if its really cold and you're catless

Little confused by number 2, you want to go catted but dont want to deal with codes, do you mean you want to go CATLESS? Most if not all downpipes come with an antifoulder/extender thing for the 2nd O2 which does a good job at tricking the ECU and not giving you a CEL. I drove catless for awhile and I got a CEL a few times here and there, but to me it was no big deal I would just clear it with my DH. I've also seen people put a diode into the wiring...but theres also some debate on whether or not the 2nd O2 affects fuel trims, so I personally wouldn't want to mess with that, I would just deal iwth the rare/occasional CEL.
 

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there is no debate, it doesn't mess with fuel trims, ask any vendor or company that makes parts for our car, after the car is warmed up it has no affect on the fuel trims at all
 

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Discussion Starter · #5 ·
[quote author=aaronc7 link=topic=138091.msg2977209#msg2977209 date=1236260944]
If you just have an intake and add a downpipe...you should not overboost and cut. Maybe if its really cold and you're catless

Little confused by number 2, you want to go catted but dont want to deal with codes, do you mean you want to go CATLESS? Most if not all downpipes come with an antifoulder/extender thing for the 2nd O2 which does a good job at tricking the ECU and not giving you a CEL. I drove catless for awhile and I got a CEL a few times here and there, but to me it was no big deal I would just clear it with my DH. I've also seen people put a diode into the wiring...but theres also some debate on whether or not the 2nd O2 affects fuel trims, so I personally wouldn't want to mess with that, I would just deal iwth the rare/occasional CEL.
[/quote]

I do want to go catted, but it is my understanding that sometimes people with catted downpipes still get the check engine light to illuminate. Even Cobb stated in their post, when they released their downpipe that there was still a chance of a CEL with their catted downpipe. Perhaps this is a rare occurance?

My understanding of OBD-2 computers is that the 2nd cat is only there to monitor converter efficiency.

Right now I'm looking at the CP-e and Stainless works downpipes. I will probably end up with one or the other as I don't like how the COBB necks down to 2.5"
 

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i'm going full catless (CS dp, and custom RP), only other thing is MSCAI.
So did anyone figure out how not to get a boost cut? (aside from AP and SB)
 

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BTW I've never noticed the rear 02 affecting LTFT, just throwing that out there too.

I would get the cpe catted dp personally
 

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cpe dp=$600 my set up $350. i think i'll go with $350. i know i know quality, but still. i'm not planning to keep this car for life, so maybe in a year or two changing it (335i ftw), so that $300 extra dollars are going into savings.
 

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Yes a CEL can happen on an catted aftermarket downpipe. It usually happens on warm up if the sensor does not see what it was expecting. The aftermarket cats warm up more slowly that the constrictive stockers, making the sensor think that the cat has malfunctioned.

I've had my CPe catted DP on for about 5k miles. I got one CEL around 2k miles for a warmup catalyst code. Cleared it and it never came back.

It's really nothing to worry about. Worst case you invest $100 in a good OBDII reader to clear the code.

I don't have an much experience with boots cut, but my car seems fine - I've got a SRI, inlet tube and full catted TBE.

Hope that helps.
 

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Boost cut is most likely when...

1. The more breather mods you have (Intake, DP, intercooler)
2. Colder weather (~20 degrees)
3. Higher gears (usually 4th and up)

With that said, it happens to some and not others. Depends on many other factors (individual car, humidity etc.). The MS3 ECU is very touchy.

Also, an upgraded fuel pump or internals seems to help boost cut.
 

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[quote author=HitIt link=topic=138091.msg2977909#msg2977909 date=1236281533]
Yes a CEL can happen on an catted aftermarket downpipe. It usually happens on warm up if the sensor does not see what it was expecting. The aftermarket cats warm up more slowly that the constrictive stockers, making the sensor think that the cat has malfunctioned.

I've had my CPe catted DP on for about 5k miles. I got one CEL around 2k miles for a warmup catalyst code. Cleared it and it never came back.

It's really nothing to worry about. Worst case you invest $100 in a good OBDII reader to clear the code.

I don't have an much experience with boots cut, but my car seems fine - I've got a SRI, inlet tube and full catted TBE.

Hope that helps.
[/quote]

The O2 needs to warm up....not the cat. The more free flowing the exhaust is, the more time it takes to warm up the O2. Is the mazda's 2nd O2 heated? if not, the solution is easy. Buy a heated O2 and wire it in place.
 

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^^ Right, sorta. The cat warms to a level that will burn off any unburned fuel. If it doens't do that in the time the o2 sensor is expecting, a CEL will signal.
 

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installed cs dp, no CEL no boost cuts (temp 50F, 60 miles).
 

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With your choice of DP, think about what are your future plans are going to be for the car.

Going with a larger turbo?

Keeping the stock turbo?


PS. if you planning on upgrading to a bigger turbo, hold out for the Medieval 3.5" DP
 

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[quote author=darkstarmotorsports link=topic=138091.msg2991713#msg2991713 date=1236922721]
Medieval 3.5" DP
[/quote]

O RLY?!?!

:eek:hsnap:
 

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[quote author=thapr3dat0r link=topic=138091.msg2992622#msg2992622 date=1236967839]
[quote author=darkstarmotorsports link=topic=138091.msg2991713#msg2991713 date=1236922721]
Medieval 3.5" DP
[/quote]

O RLY?!?!

:eek:hsnap:
[/quote]


http://www.mazda3forums.com/index.php?topic=138812.0
 

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I saw that last night. Great option for BT. Medieval is really coming out with some good $hit for this car.
 

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installed dp last week. over the weekend it was 30*F at night. had boost cuts. during the day, the car is spiking 21psi, and holding just below 18psi (17ish). At night, when it was cold, spikes to 22psi, holding 18-19psi, and bam, boost cut. car backfires like crazy, then get's back on it. next gear, same thing. (i was racing this poor 2dr altima 3.5 with exhaust and intake).
p.s. still smoked him
 
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