Stock exhaust restrictive?

s.myrr · 03-11-2010, 01:22 PM

Group buy!

ar design · 03-11-2010, 01:32 PM

Hehe... Not likely

Syndicategt · 03-11-2010, 01:39 PM

What's the difference btw the new HJS equipped DPs and my AR DP's with the magnaflow hfc?

ar design · 03-11-2010, 01:48 PM

Quote:

Originally Posted by Syndicategt

What's the difference btw the new HJS equipped DPs and my AR DP's with the magnaflow hfc?

$1,000.

The HJS cats will not throw codes on the new 2010s, and older cars that have the more sensitive software that BMW has released (presumably to combat exactly what we are doing

Syndicategt · 03-11-2010, 01:51 PM

Yikes, remind me to not get my ECU reflashed with a new software update.

ar design · 03-11-2010, 01:53 PM

Quote:

Originally Posted by Syndicategt

Yikes, remind me to not get my ECU reflashed with a new software update.

Yeah, HJS bends us over HARD for the cats.

D.B.S · 03-11-2010, 01:54 PM

Quote:

Originally Posted by ar design

$1,000.

The HJS cats will not throw codes on the new 2010s, and older cars that have the more sensitive software that BMW has released (presumably to combat exactly what we are doing

Now all you need to do is put out a version for the Xi's, and I'll buy some Catted DP's...

s.myrr · 03-11-2010, 02:02 PM

Not having to worry about CELs is definately worth a premium.

Fern8321 · 03-11-2010, 02:12 PM

Correct me if I'm wrong, but aresnt some of the fastest n54's still running the stock exhaust. EAS for example still has the stock exhaust on their project car(last I checked) and they're pushing out 420+whp. I thought the most restrictive part of the exhaust was the cats. Once they are removed, the exhaust should be ok. I have full bolt-ons and I'm still running stock piping w/straight pipes and magnaflow mufflers.

s.myrr · 03-11-2010, 05:27 PM

This is why I kind of want to leave the stock exhaust alone... It seems the gains are far greater w/ DPs. I actually kind of like the stock exhaust sound... or lack thereof. I just may jump on some ARs, unless there are any other catted options out there to compare to...? I don't want to worry about CELs or sims that may or may not work in the future.

FWIW - on an otherwise stock car, Eurotuner put on the BMW perf exhaust... it actually lost power on the dyno! Of course this was on a 135i... and that exhaust is mainly just mufflers.

cn555ic · 03-11-2010, 05:49 PM

Quote:

Originally Posted by Praemienhai

I got CEL after the update to v 36.x with the AR catted DPs.

Deleting with the BT tool didn't work in the long run, after rd about 50km I got a new CEL... With the older software versions I didn't had such problems.

That is one of the reasons why I will try to never get an update...

Praemienhai · 03-11-2010, 06:05 PM

Quote:

Originally Posted by Nando

Correct me if I'm wrong, but aresnt some of the fastest n54's still running the stock exhaust. EAS for example still has the stock exhaust on their project car(last I checked) and they're pushing out 420+whp. I thought the most restrictive part of the exhaust was the cats. Once they are removed, the exhaust should be ok. I have full bolt-ons and I'm still running stock piping w/straight pipes and magnaflow mufflers.

I think you are right.

I read an article in the German scientific journal MTZ from two engineers from Boysen (the company which developed and designed the exhaust system for the N54 engine, including downpipes, midpipes and the muffler with flap). They published some data and charts regarding the backpressure of the whole exhaust system. There you can see that the primary cats incl. downpipes are the most restrictive part of th exhaust system, followed by the secondary cats and the midpipes. The muffler itself isn't restrictive at all, less than 5% of the overall backpressure of the exhaus system.

Irishace · 03-11-2010, 06:46 PM

Quote:

Originally Posted by ar design

If you are worried about emissions, we now offer our downpipes with HJS motorsport catalysts - guaranteed NO CEL, even on 2010 models, and should have no issues with emissions. Usually takes me 2hrs on jackstands to install downpipes.

What kind of power gains are you seeing with this type of DPs?

s.myrr · 03-11-2010, 07:49 PM

Quote:

Originally Posted by Praemienhai

I think you are right.

I read an article in the German scientific journal MTZ from two engineers from Boysen (the company which developed and designed the exhaust system for the N54 engine, including downpipes, midpipes and the muffler with flap). They published some data and charts regarding the backpressure of the whole exhaust system. There you can see that the primary cats incl. downpipes are the most restrictive part of th exhaust system, followed by the secondary cats and the midpipes. The muffler itself isn't restrictive at all, less than 5% of the overall backpressure of the exhaus system.

Interesting stuff there - say you replace the midpipes and go to racing secondary cats, with stock mufflers will there be much of a change in sound?

ar design · 03-11-2010, 08:37 PM

Quote:

Originally Posted by Irishace

What kind of power gains are you seeing with this type of DPs?

We have not dyno'd it - however, our regular DP lose about 7whp vs the catless, and they are 300 cell.....

s.myrr · 03-12-2010, 09:23 AM

Is that to say the HJS cats will lose less hp?

03-11-2010, 01:22 PM	#23
s.myrr Lieutenant 13 Rep 499 Posts Drives: AW 335i E90 Join Date: Jul 2008 Location: Seattle, WA iTrader: (1)	Group buy!
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03-11-2010, 01:32 PM	#24
ar design 304 Rep 4,408 Posts Drives: 04 M3 Join Date: Jan 2008 Location: Denver, CO iTrader: (9)	Hehe... Not likely __________________ -Critter
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03-11-2010, 01:39 PM	#25
Syndicategt Brigadier General 164 Rep 3,730 Posts Drives: 335i Join Date: Sep 2009 Location: Nor Cal iTrader: (11)	What's the difference btw the new HJS equipped DPs and my AR DP's with the magnaflow hfc? __________________ 2008 BMW 335i e90 - Sold - Rob Beck Turbos / PROcede V5 / Aquamist HFS-4 / AR Downpipes / AE Exhaust / ER Comp FMIC / ER CP / TiAL BOV / Custom Intake / RPI Scoops / Quaife LSD / Swift-Koni Coilovers / DSS HS / Morr VS8.2 Sig Black / Michelin PSS / P3 Boost Guage / M3 body / M3 steering wheel / Adam's Rotors / Hawk HPS / SS lines /
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03-11-2010, 01:51 PM	#27
Syndicategt Brigadier General 164 Rep 3,730 Posts Drives: 335i Join Date: Sep 2009 Location: Nor Cal iTrader: (11)	Yikes, remind me to not get my ECU reflashed with a new software update. __________________ 2008 BMW 335i e90 - Sold - Rob Beck Turbos / PROcede V5 / Aquamist HFS-4 / AR Downpipes / AE Exhaust / ER Comp FMIC / ER CP / TiAL BOV / Custom Intake / RPI Scoops / Quaife LSD / Swift-Koni Coilovers / DSS HS / Morr VS8.2 Sig Black / Michelin PSS / P3 Boost Guage / M3 body / M3 steering wheel / Adam's Rotors / Hawk HPS / SS lines /
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03-11-2010, 02:02 PM	#30
s.myrr Lieutenant 13 Rep 499 Posts Drives: AW 335i E90 Join Date: Jul 2008 Location: Seattle, WA iTrader: (1)	Not having to worry about CELs is definately worth a premium.
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03-11-2010, 02:12 PM	#31
Fern8321 Captain 35 Rep 805 Posts Drives: X5 M60i Join Date: Sep 2009 Location: Naples, FL iTrader: (3)	Correct me if I'm wrong, but aresnt some of the fastest n54's still running the stock exhaust. EAS for example still has the stock exhaust on their project car(last I checked) and they're pushing out 420+whp. I thought the most restrictive part of the exhaust was the cats. Once they are removed, the exhaust should be ok. I have full bolt-ons and I'm still running stock piping w/straight pipes and magnaflow mufflers.
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03-11-2010, 05:27 PM	#32
s.myrr Lieutenant 13 Rep 499 Posts Drives: AW 335i E90 Join Date: Jul 2008 Location: Seattle, WA iTrader: (1)	This is why I kind of want to leave the stock exhaust alone... It seems the gains are far greater w/ DPs. I actually kind of like the stock exhaust sound... or lack thereof. I just may jump on some ARs, unless there are any other catted options out there to compare to...? I don't want to worry about CELs or sims that may or may not work in the future. FWIW - on an otherwise stock car, Eurotuner put on the BMW perf exhaust... it actually lost power on the dyno! Of course this was on a 135i... and that exhaust is mainly just mufflers.
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03-12-2010, 09:23 AM	#38
s.myrr Lieutenant 13 Rep 499 Posts Drives: AW 335i E90 Join Date: Jul 2008 Location: Seattle, WA iTrader: (1)	Is that to say the HJS cats will lose less hp?
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