[SeanWRT]

I figure there is no need for further description of this downpipe, given the title, other than the manufacture part reference number: HJS 90 81 2010, fitting all N55 powered 35i and M2. Also find another review on M235i application at: http://www.2addicts.com/forums/showthread.php?t=1160714

It isn't as popular as HJS 200 cell Euro 5 high flow downpipes, so I had no luck sourcing it from USA. Fortunately my wife travelled to Oberkochen, Germany in early Dec and got this thing from Lightweight Performance. I cannot think of a better Christmas Gift And special thanks to Marc with Lightweight Performance for getting everything ready in advance.

If I want cat, I want THE best cat, hence HJS Euro 6 it is. The reasons why I chose it over the 200-cell one (Fabspeed, Supersprint, Miltek branded) are as following:

1) Flow capacity difference is minimal. 90% with 200 cell, vs 80% with 300 cell, according to HJS.

2) Emission Compliance guarantee. The Euro 6 cat, not only 100 cell denser, but also twice as long thanks to dual chamber design, makes three times as much catalyzing area in total (1.5 times in density, multipled by 2 times in length) as a 200 cell does. Provided catalyst can fail overtime, 300-cell should be more reliable in long term. The tradeoff is 10% less flow that most cannot even take advantage of.
See the attached dual chamber vs single chamber comparison picture (OEM vs Fabspeed)

3) Minimal Smell. I don't know what it would be like with 200 cell, this is my experience with 300 cell:
At cold start, there is a little smell if you stand close behind looking for it. To be fair, stock cat was every bit the same. There is no increase in smell whatsoever.
When warmed up, it's ZERO smell.
And more, HJS metallic cat warms up much faster than stock ceramic one, which means overall it OUTPERFORM stock cat in term of smell.

Box open, HJS screams Akrapovic quality. BTW, there is a Akrapovic branded 300 cell Euro 6 dp as well with same design, same details, same spec, same certificate, same everything. Most certainly made by HJS.

Needless to say, the fit is Akrapovic spot on. My mechanic, one man, did it effortlessly in less an hour after engine cooled down. To ensure no leakage, I bought all the associated clamps & bolts - the turbo end clamp is not reusable in replacing downpipe for its prone to getting loose according to BMW.

HJS downpipe instantly felt very "OEM" on the car with the silver heat wrap matching surrounding nicely, making the stock DP it replaces look like just a good quality aftermarket part...

The car started with clearly a louder roar with rawness. In driving to warm the thing up, I noticed turbo response is sharper. Not to mistake with throttle response, it's the less time it took to spool up to give you SERIOUS push. I did a few WOT pulls when car's fully warmed up. The torque in middle and low end is noticeably improved. Unfortunately it still falls at top end like stock.

Now the sound. The freer flow cat really opens it up and gets it significantly louder throughout the rev band. The best part is revving it up to above 5k and hear a higher pitch sounding where stock system gets just muffled. And it definately burbles and cracks louder at mid and low end. In hidden exhaust (MDM+sequential) mode, it sounds just too good for a turbo engine burbling from 1500rpm. Overall, I reckoned the dp makes a 30% louder exhaust system.

I met another m2 guy at car wash the other day and confirmed everything I felt. Comparing my car to his side by side, what a big difference in sounding... Then I took his car out for a joy run and he took mine. Well, I clearly noticed the stock m2 of his is less torquey!

My MPE is coming and will be installed in 2 weeks. Can't wait to see how HJS works with MPE! Will post a good sound clip.

Thanks for reading! Happy New Year to you and your beloved ones!

Sean

Update: review and sound clip of MPE cat back + HJS DP:
http://f87.bimmerpost.com/forums/sho....php?t=1346405
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[marcusfva]

Thanks Sean for your review, I've got the same dp and I hope to put it on the car soon.

[JKen_0115]

Do u know how I can buy this DP from US?

[SeanWRT]

Originally Posted by JKen_0115

Do u know how I can buy this DP from US?

Ask Fabspeed the only distributor of this particular part in US to my knowledge.

[JKen_0115]

Originally Posted by SeanWRT

Ask Fabspeed the only distributor of this particular part in US to my knowledge.

Thank u Sean

[mike@x-ph.com]

Originally Posted by JKen_0115

Do u know how I can buy this DP from US?

We offer the Fabspeed catted downpipe, as mentioned above it uses the same cats

[metrickid]

Originally Posted by mike@x-ph.com

We offer the Fabspeed catted downpipe, as mentioned above it uses the same cats

But the 200 cell version.

[mike@x-ph.com]

Originally Posted by metrickid

But the 200 cell version.

We have not had a single issue with the 200 CEL yet, it also flow more air ... I see no reason to go with the more restrictive 300 CEL at this time

[Fabspeed Motorsport]

No issues on our end either with our HJS 200-cell cats.

[Benef1cient]

@Sean
Where is the promised sound clip?

[SeanWRT]

Originally Posted by Benef1cient

@Sean
Where is the promised sound clip?

MPE delay in custom clearance as we speak. Trying to avoid paying unreasonably to get this thing released.

Will install hopefully next week.

[SeanWRT]

Originally Posted by mike@x-ph.com

We have not had a single issue with the 200 CEL yet, it also flow more air ... I see no reason to go with the more restrictive 300 CEL at this time

300 cell is higher level confidence inspiring on CEL free when you run with bolt on mods, hard enough and for years. Plus you have much less smell to deal with. And most likely will pass smog test.

Truly a OEM like mod, install and forget it.

All it take is 10% less flow over 200 cell, it's not much more restrictive and what it reflects on power gain difference is negligible. Granted, it's more expensive and the availability in USA could be an issue.

To each their own though.

[M2wolf]

Should be interesting.. might be following this route to go CEL free.

http://www.babybmw.net/forum/viewtopic.php?f=74&t=84130

MPE has been ordered but available from March onwards... love to heard the combo with the HJS downpipes..

[SeanWRT]

Originally Posted by M2wolf

Should be interesting.. might be following this route to go CEL free.

http://www.babybmw.net/forum/viewtopic.php?f=74&t=84130

MPE has been ordered but available from March onwards... love to heard the combo with the HJS downpipes..

Got to read this already. The m235i dyno readouts show a 11WHP gain from DP only on stock configuration (jb4 disabled) and that is prior to DME's adaption to the freer flow DP. Make sense to expect delta be slightly bigger when tuned up but unfortunately the car wasnt given any miles to adapt new bolt ons so no luck to see a proper comparison on map5 (autotuning map, sometimes problematic). Though on map7 targeting an absolute 18.5psi, the car performs well with DP and make 406hp on the wheel. To be realistic, from this dp, 15whp gain in top end is expected with m2.

I am not going to remove DP and do the test. But I will install FBO in a few weeks and dyno it with Dinantronic on and off.

[SeanWRT]

Originally Posted by Benef1cient

@Sean
Where is the promised sound clip?

http://f87.bimmerpost.com/forums/sho...5#post21159765

[Louzy77]

After Sean I too was inspired and installed the HJS 300 cell catted DP.
It really opens up the N55 and even the stock exhaust sound is augmented beautifully.
Best mod for sure as others have attested too!

[PiK]

Just a heads-up guys. According to one of dealers by installing a custom downpipe you lose the warranty for two components:
1. Exhaust (no big deal).
2. Engine :/

[omasou]

What is stock cell count? I've read 700 and 400.

[omasou]

Looks like Fabspeed has the same dp? This will fit the M2 right?

http://www.fabspeed.com/bmw-m235i-f2...tted-downpipe/

[XutvJet]

Yes, that's the same DP. I'd much rather have the HJS 300 cell catted DP because of lack of CEL, higher quality build, and most importantly, it looks like an OEM part. FS pushes their DP obviously so that they can get more money selling your their own part.

[LBBDrew]

Originally Posted by XutvJet

Yes, that's the same DP. I'd much rather have the HJS 300 cell catted DP because of lack of CEL, higher quality build, and most importantly, it looks like an OEM part. FS pushes their DP obviously so that they can get more money selling your their own part.

Not the same. 200 cel vs. 300 cel

[Fabspeed Motorsport]

Originally Posted by omasou

Looks like Fabspeed has the same dp? This will fit the M2 right?

http://www.fabspeed.com/bmw-m235i-f2...tted-downpipe/

The downpipe between the M235i and the M2 is the same.

Originally Posted by XutvJet

Yes, that's the same DP. I'd much rather have the HJS 300 cell catted DP because of lack of CEL, higher quality build, and most importantly, it looks like an OEM part. FS pushes their DP obviously so that they can get more money selling your their own part.

Our Sport Cat Downpipe utilizes a HJS, 200-cell cat core as well. This also does not trigger a CEL, and provides all the necessary benefits from a high-flow downpipe. The difference between the 300-cell and the 200-cell is very marginal and in my opinion, not worth the difference in cost.