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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > N55 down pipe fix found!



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      02-23-2015, 12:40 PM   #45
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very interesting discussion, thanks for enlightening us. Just so I can follow along better... The "IAT" that I'm reading off JB4 logs, is that Temp at the intake (before IC) or at the CP/throttle body area (after IC)? Thanks
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      02-24-2015, 01:29 AM   #46
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Definitely just learned a ton....thanks guys!!
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      02-24-2015, 06:25 AM   #47
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Quote:
Originally Posted by wgknestrick View Post
A MAF sensor has a temperature sensor already in it (it has to have one to even function). That's how they work. They have a heater that heats a known size block that is located in the center of the pipe. It is set to keep a constant temp on that block in closed loop. Airflow correlates to the voltage required to keep that block at known temp (assuming laminar flow). More flow, more heat lost in flow, ie more voltage required to heat. That process correlates airflow directly to voltage. Turbulent flow uses a different equation for convective cooling so this is how MAF can break down and give improper readings once flow turns turbulent.

Speed density cars need IAT because there is no inherent compensation for changing ambient temps like you have in MAF cars. Speed density is generally a less desirable (IMO) way of loading because it does not adapt well to changes in volumetric efficiency like MAF does, and can have poor resolution during low rpms. It can be much smoother (on boost) in a turbo car, but a more efficient intake/exhaust can shift the entire fueling map quite a bit requiring a re-tune. It doesn't necessarily matter where the IAT temp is (before compressor inlet or after IC), just as long as it is tuned per that location.

The reason that IAT don't matter as much in turbo cars is that the IC is usually capable of cooling a slight difference in IAT anyway (they have some cooling headroom). Sure the air coming in is 10F hotter, but the IC just cools it down so it's only approximately 2F hotter when it goes into the engine. It is theoretically better to have lower IAT, but not as much as what you think. Generally, flow optimization is more important for max HP. A short ram intake almost always flows significantly better than a longer, serpentine CAI routed to the fender area.

It's better to get ALL 100% of the air to compress, than it is to get 90% of the cold air. Just pulling numbers out of my posterior, to illustrate my point. Stock intakes on these cars are horribly designed from BMW with respect to flow. Once big turbos are norm, you will see well designed intakes making big power IMO. I don't feel we have well designed intakes yet because they mostly keep the stock elbow at the compressor inlet, and have a great deal of bends in the piping. They are fine for most stock turbo cars, but will restrict HP as bigger turbos come onto the market.

E90 Packaging is horrible on these cars around the turbo, so I see why various companies did not want to relocate everything to fit an uncompromised intake solution in them. It doesn't mean that "intakes don't make power". It just means that the average turbo (ie oem) is too small to realize significant intake gains with aftermarket intakes.....that re-use most of what makes the stock intake a poor design with respect to HP.
Ignoramis I am.

So, stock intake is crap. Long, serpentine CAI are crap. Wonderful. (I know you didn't say crap but I can temper that with less desirable).

Not too many good options on our cars since the intake does wrap around the engine and frankly it's got to go somewhere to take advantage of FMIC.

So, after installing a CAI and a FMIC would you say a tune or adjustment is a good idea to compensate for the changed variables? I would think for those minor changes compensation would happen in it's own no?
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      02-24-2015, 06:48 AM   #48
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Is this a intake thread or a N55 downpipe CEL fix thread???????
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      02-24-2015, 07:19 AM   #49
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Air turbulence will screw up a maf's reading so its less accurate than IAT's. Thermodynamics doesn't change.

It comes down to what you prefer for tuning and what is available for a given car.
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      02-24-2015, 09:52 AM   #50
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Quote:
Originally Posted by timothy2001 View Post
Ignoramis I am.

So, stock intake is crap. Long, serpentine CAI are crap. Wonderful. (I know you didn't say crap but I can temper that with less desirable).

Not too many good options on our cars since the intake does wrap around the engine and frankly it's got to go somewhere to take advantage of FMIC.

So, after installing a CAI and a FMIC would you say a tune or adjustment is a good idea to compensate for the changed variables? I would think for those minor changes compensation would happen in it's own no?
I agree with others that this got off track, and I apologize. If you want to create an intake design thread, I can move the posts in there.

Back on catless CEL track:

Do we have any update on the N55 CEL fix for catless downpipes? I am very skeptical of the solution posted working long term because I know how hard it can be to fool the electronics. We probably need someone with a scope-meter to see the transient voltage the ECU wants to see (and when) from the O2 sensor(s). I would LOVE to find something that works though. It would also help if BMS could help share their past efforts here and why they didn't work. I would guess they spent a good deal developing their N54 solution and just tried that on the E9x N55. It didn't work and they probably scrapped it due to low volume.

The path I see a solution developing is to scope the O2 voltage on a stock car and then compare that transient graph with a catless O2. Once we know the offset, then we can start to develop an electronic solution to shift the V waveform.

for example:


Generally the voltage interceptors work best IMO over the mechanical. The mechanical tend to have too much delay (longer wave periods) in V readings. They don't always shift the waveform (up or down) into the acceptable zone.
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      02-26-2015, 04:20 PM   #51
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Okay so I know this is for folks wanting to pass emissions. But searching the last few days between a few threads and its confusing lol.

Does the JB4 delete the CEL from the Downpipe? Or do I have to use my CAN tool to delete it like on my previous car? Thanks.
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      02-26-2015, 05:58 PM   #52
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Been covered countless times. Yes, it can. However, the cel will come back shortly after. Deleting will not aid you in passing emissions.
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      02-26-2015, 06:10 PM   #53
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Perfectly fine I plan to use the CAN tool then it'll keep it off. Thanks.
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      02-26-2015, 10:55 PM   #54
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Sorry, should've mentioned that the JB4 can also keep it off. Just leave auto-clear on. It'll clear other codes too though
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      02-27-2015, 12:53 PM   #55
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Quote:
Originally Posted by CantCatchMe View Post
Perfectly fine I plan to use the CAN tool then it'll keep it off. Thanks.
CAN tool will not get rid of the light very long. JB4 constantly deletes the code.
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      02-27-2015, 12:55 PM   #56
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Quote:
Originally Posted by JETmn View Post
CAN tool will not get rid of the light very long. JB4 constantly deletes the code.
Is that something different going on the 335? Cause my MINI kept it off always, it never appeared with my CAN tool off setting it?
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      02-28-2015, 09:19 AM   #57
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Can the mods close this thread?

It is a complete waste of time, and extremely misleading for anybody that had any shred of hope of a downpipe fix.

Please delete it or close it, for the love of God already.
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      02-28-2015, 02:22 PM   #58
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Originally Posted by Dark_Knight_335 View Post
Can the mods close this thread?

It is a complete waste of time, and extremely misleading for anybody that had any shred of hope of a downpipe fix.

Please delete it or close it, for the love of God already.

+1
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      03-07-2015, 01:24 PM   #59
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since my emissions are up this march.
i've been trying all of feb. there is no work around to pass emissions on a c a t less dp for n55.

i have turned off jb4 aka set it to map0. which you will also need to turn off the auto clear in jb4 as well. found that out the hard way. aka wasting time driving around in just map0.

i perform the bmw drive cycle which turns me cat to ready status...the very second they hit ready. my cel comes on. tell me about the dps. i delete...drive nice as pie. 2nd time. same result. i'm using a canbus scan tool to watch my cats, evap, etc.
with jb4 autoclear on....it just sets all emissions to pending/not ready status. there is no way to get around this.

so now i will go with an extension and have to become a dp unbolting and bolting master. since i kept my stock cat...incase there was no way around it. for us n55...i see no other way. i have a spacer on and it doesn't do shit. with jb4...and even stock cat...you must go to map0 and turn autoclear off. also delete the pending code for the cat in there. pass test....bolt your fav dp back up.
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      03-19-2015, 07:54 AM   #60
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Ok sorry this post has caused a lot of debate. The truth is with the dp fix o2 spacer i first posted it works fine until you get on it heavy. Soft driving it will stay off. Hard driving it comes right on. For some reason the intake from bms triggers it alot quicker. For emissions this year i plan to just exempt it because i have other cars to keep the miles down on my 335. Plus i am a technician i hate getting my car dirty.

Just everyone go go get a shitty beat around car and dont drive your car more than 5k since your last inspection 😂😂
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      03-19-2015, 08:39 AM   #61
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Thanks for the tips kevbquick. I've been trying to get my readiness to set for a week on map 0 and they continue to read not ready. I thought setting it to map 0 would turn off that function. I'll change it today and see if I can get it to set. I swapped my Cat back on last night so it should be fine once I turn auto clear off.
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      04-08-2015, 07:50 AM   #62
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Cel has been off for a while now. At Least since my last post and I've been driving it hard...hope i don't jinx myself
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      04-08-2015, 09:39 AM   #63
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I ended up finding a muffler shop that can do DP swaps for $100. I removed the DP and drove for 50-60 miles this weekend with the jb4 in map 0 and auto clear off. I passed emissions with no problem (intake and CP still installed) and will have the DP back on by tomorrow. That seems to be the easiest course of action for now. I really miss my DP right now : For anyone that can't do it themselves, call around to nearby muffler shops. The bmw performance shops like Cobb tuning wanted $400-500 per swap.
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      04-08-2015, 10:31 AM   #64
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Quote:
Originally Posted by Johnny Boost View Post
I ended up finding a muffler shop that can do DP swaps for $100. I removed the DP and drove for 50-60 miles this weekend with the jb4 in map 0 and auto clear off. I passed emissions with no problem (intake and CP still installed) and will have the DP back on by tomorrow. That seems to be the easiest course of action for now. I really miss my DP right now : For anyone that can't do it themselves, call around to nearby muffler shops. The bmw performance shops like Cobb tuning wanted $400-500 per swap.
Thanks man, not sure what state you are in but I am having a heck of a time finding anyone to swap out my catless. I'll keep looking but anyone I have talked to say it's illegal and wont' touch it.
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      04-08-2015, 10:55 AM   #65
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Quote:
Originally Posted by Johnny Boost View Post
I ended up finding a muffler shop that can do DP swaps for $100. I removed the DP and drove for 50-60 miles this weekend with the jb4 in map 0 and auto clear off. I passed emissions with no problem (intake and CP still installed) and will have the DP back on by tomorrow. That seems to be the easiest course of action for now. I really miss my DP right now : For anyone that can't do it themselves, call around to nearby muffler shops. The bmw performance shops like Cobb tuning wanted $400-500 per swap.
Can you PM me the shop? I think you are near Austin right? The place that installed my DP charged me $300 so I doubt they would do a swap for that price haha.
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      02-02-2016, 08:34 PM   #66
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I'll be installing VRSF catless downpipe in a few days on my 2012 N55 335i.

All those opposed to the non-fouler on the 02 sensor I can let you know that I've used this method for years and passed emissions (in New York) with readiness every time even being catless.

I ordered 42 Draft Design 02 Spacer (link below) for this install. I'm going to try it out and see what happens, I have high hopes of it working since these have worked for me countless times in the past. I'll keep you posted if it works or doesn't work for me.

http://www.42draftdesigns.com/o2-sensor-spacer/
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