[quenotte]

Hello,

To complete AnooooOH review of LightWeight Exhaust + HJS catted DP, here is my review of newly introduced HJS EU6 catted downpipe.

My M235i is my daily car.

Basically, I mainly focused on the reliability and on improving throttle response before carrying out any ECU tuning.

Aim would not be to have the better power or torque absolute values but the best power delivery (from idle up to 7000RPM with no max HP at 5000RPM and nothing after) with less turbo lag as possible and reliability not altered over stock.

All mods should work without triggering any CEL, nor soft error, nor not correct car behaviour.

Mods so far:

• M Performance Exhaust
• M Performance Rear Diffuser
• Air box from F3x MPPK (Removed: triggered DME soft errors and odd/jerky motor behaviour, especially on startup and light throttle load).
• M4 shift paddles (Stock ones are way too short and not convenient to trigger)
• M550d ZF8 shifter insert (To add THE missing M logo to car )
• ER IC to TB charge pipe
• ATM FMIC (To be replaced with Wagner EVO2 Competition when available since it flows better and thus should have better throttle response and reduced weight).
• Challenge stainless steel brake hoses (the fixed ones, not the former too long with incorrect rear lines bolt pattern with no lock from first batch).

Last mods:

• HJS EU6 catted downpipe
• GFB DV+ (installed after HJS DP)
• ER Turbo To IC charge pipe (Fixed one installed)

As I said, I'm quite sensitive to throttle response.

There is a very small lag from factory, a little increased with ATM FMIC. So aim of DV+ would be to reduce On-Off-On throttle issue and sport cat to have turbo spool faster and cooler.

I've measured my factory catalyst at 975°C so I'm not quite confident with its reliability on the long term...

So why HJS? Because they are the best catalyst core manufacturer. I'm quite confident with them since they are makers of brands such as Alpina and some BMW sport cats.

So I've been waiting HJS downpipe since mid January when I was aware that HJS was working on an ECE homologated catted downpipe for M235i.

I contacted HJS and product was forecast for March and then June.

I ask to HJS the following:

• Is it an ECE homologated device?
  Yes
  
  
• Will it keep the car Euro 6 compliant?
  Yes
  
  
• Will you guarantee that no Check Engine Light (CEL) / MOT / EOBD issue occurs with it like with standard OEM catalytic converter?
  Yes
  
  
• Will it have the same lifetime as OEM catalyzer with no CEL/MOT/EOBD hard/soft errors?
  Yes!
  
  
• Do you have some figures on how much noise level is increased?
  +1dB
  
  
• Is your downpipe made of stainless steel?
  Yes!
  
  
• Is cat integrated in your downpipe the same as fabspeed one?
  No! For the HJS DP we use a special 2 chamber ECE homologated catalyst. This catalyst is exclusive for the HJS DP.
  
  
• Is it a 200-cell cat or a 300-cell cat?
  It is a 300 cpsi catalyst
  
  
• Do you have a version for 3.5” flange (for M135i before 07/2013) on top of this design with 4.0” flange for M235i and post 07/2013 M135i?
  No. So only available for EWG cars.

And mid June, product was announced HJS website and HJS listed N55 F2x/F3x EWG supported cars. And then available to sale mid July.

I ordered HJS 90 81 2010 EU6 catted downpipe to Marc @ Lightweight Performance. Very nice and professional guy, quick shipment.

I ordered to my local BMW dealership clamps and gaskets in order not to have any leak:

• Downpipe to turbo V-Clamp:
  BMW Ref: 1x 18 30 7 606 136 (20€).
  Tightening torque: 13 Nm.
  BMW indicates in ISTA to replace it each time.
  
  
• Downpipe to turbo Gasket ring:
  BMW Ref: 1x 18 30 7 581 970 (15€).
  
  
• Downpipe to exhaust V-Clamp:
  BMW Ref: 1x 18 30 7 620 349 (15€).
  Tightening torque: 30 Nm.
  To my mind, needed to be changed because the seal part of clamp is damaged when removed from OEM downpipe.
  
  
• Downpipe bolts/nuts on its holder:
  Tightening torque: 28 Nm.
  
  
• Exhaust on aluminium holder:
  Tightening torque: 28 Nm.
  
  
• Lambda probes on downpipe:
  Tightening torque: 50 Nm.

Some photos of HJS downpipe:







Installation was straightforward. Most difficult part was to put in place exhaust V-Clamp correctly (its gasket part...).

There is no need to remove exhaust. Only need to release it at its next mount point after downpipe.


So far, I'm very happy with this downpipe. It's as quieter as OEM one in comfort mode while cruising. So perfect for a daily driver car.
It adds a very nice note when throttling. It's less raspy, more clear/vocal.

Throttle response is clearly improved and what annoyed me has disappeared.

It's even better with GFB DV+ installed. Perfect combo. On/Off/On are now stellar.

There is no soft error/CEL or anything.

[Turbo-N55]

Nice, post a vid if u can !

It doesnt look like the one on their website.


Also , how much was it ?

[CSL335i]

I have already purchased HJS downpipe. Actually it has 300 Cell cats (information confirmed by Lightweight). As i suspected the downpipe, it has two cats installed after each other in the downpipe. One is after second lambda sensor. Maybe an additional few HP/NM if you remove the second cat.

Fitment was perfect, installation was straight forward.
I also have ER charge pipes (turbo to intercooler, intercooler to intake manifold), but not yet installed. Also purchased Challange SS brake lines, but not yet installed. Will go with Motul RBF660 brake fluid.

I also has Awron display and some BMW Performance goodies.

Other power up modification is under consideration.

As for the HJS downpipe, it has a little bit more smell than OEM downpipe in some circumstances, but its ok for me.

[alz0rz]

How are you measuring the catalyst temp? The car does not have an actual temperature sensor. Any temperature reading you are getting is a approximation. Also, I would not be quick to discount the OE design based on the temperatures you are seeing. Many hundreds of hours going into designing stuff like this. You not liking the temperature does not mean it is not within operating parameters.

[quenotte]

Originally Posted by alz0rz

How are you measuring the catalyst temp? The car does not have an actual temperature sensor. Any temperature reading you are getting is a approximation. Also, I would not be quick to discount the OE design based on the temperatures you are seeing. Many hundreds of hours going into designing stuff like this. You not liking the temperature does not mean it is not within operating parameters.

I used M Performance Drive Analyzer for catalyst temperature. I don't know how accurate it could be. I guess it uses lambda sensors temperature info.

I didn't think that stock design is a flaw. I just prefer to have less constrainst on turbo, lower temperature. But the key element is clearly the better throttle response.

[quenotte]

Originally Posted by Turbo-N55

Nice, post a vid if u can !

It doesnt look like the one on their website.


Also , how much was it ?

Thanks

I will try to post some video.

To my mind, it's the same device as on their website!

Price was 1150€ Net, same price as Fabspeed downpipe delivered here and ECE homologated so no problem with emissions.

Car is still Euro6 compliant.

[quenotte]

Originally Posted by CSL335i

I have already purchased HJS downpipe. Actually it has 300 Cell cats (information confirmed by Lightweight). As i suspected the downpipe, it has two cats installed after each other in the downpipe. One is after second lambda sensor. Maybe an additional few HP/NM if you remove the second cat.

Fitment was perfect, installation was straight forward.
I also have ER charge pipes (turbo to intercooler, intercooler to intake manifold), but not yet installed. Also purchased Challange SS brake lines, but not yet installed. Will go with Motul RBF660 brake fluid.

I also has Awron display and some BMW Performance goodies.

Other power up modification is under consideration.

As for the HJS downpipe, it has a little bit more smell than OEM downpipe in some circumstances, but its ok for me.

Aim was to have an emissions compliant, euro6 homologated, downpipe so yes it has, like stock downpipe, two catalyst parts, one between the two lambda probes and the second after the second lambda probe.

I've ask HJS to confirm if this is a 200-cell cat or 300-cell one.

I also had some sporadic smells with stock downpipe, as with HJS one. To my mind, nearly the same.

[quenotte]

I had the confirmation, you're right, it's a 300-cell cat

I've updated the first post.

[CSL335i]

Originally Posted by quenotte

I had the confirmation, you're right, it's a 300-cell cat

I've updated the first post.

Thanks. Within the 200 cell and 300 cell cat there is just a few psi back pressure, therefore I assume that the HP differences would be 2-5HP for the 200 CELL.

I am very happy with HJS downpipe. I already ordered GFB DV+ to my car.

[AnooooOH]

Great review!!

The first hjs 200cell have exactly the same power output as the newer 300cell cats.

[KAY-OS]

Great write up quenotte!

Have a question to those who have installed the DP. Is it necessary to purchase new clamps and gasket for install? Have any of you installed the DP with the original stock clamps/ gaskets? Any problems?
Thanks!

[AnooooOH]

Originally Posted by KAY-OS

Great write up quenotte!

Have a question to those who have installed the DP. Is it necessary to purchase new clamps and gasket for install? Have any of you installed the DP with the original stock clamps/ gaskets? Any problems?
Thanks!

You should get new gaskets. The stock ones.

No Problems!

[quenotte]

Originally Posted by KAY-OS

Great write up quenotte!

Have a question to those who have installed the DP. Is it necessary to purchase new clamps and gasket for install? Have any of you installed the DP with the original stock clamps/ gaskets? Any problems?
Thanks!

As I wrote in first post and AnooooOH just pointed out, you should change clamps and gaskets.

Turbo clamp because BMW indicates to change it each time (low tightening torque and exposed to lots of heat).

Exhaust clamp because gasket is integrated in the clamp so that it's very difficult not to damage it when removing it from stock downpipe.

In the first post, I've mentioned all clamps and gaskets parts that must be changed to have a trouble free install. I'll will emphasis that more. It's a 50€/USD ticket compared to 1150€/USD downpipe cost...

[KAY-OS]

Originally Posted by quenotte

As I wrote in first post and AnooooOH just pointed out, you should change clamps and gaskets.

Turbo clamp because BMW indicates to change it each time (low tightening torque and exposed to lots of heat).

Exhaust clamp because gasket is integrated in the clamp so that it's very difficult not to damage it when removing it from stock downpipe.

In the first post, I've mentioned all clamps and gaskets parts that must be changed to have a trouble free install. I'll will emphasis that more. It's a 50€/USD ticket compared to 1150€/USD downpipe cost...

Originally Posted by AnooooOH

You should get new gaskets. The stock ones.

No Problems!

Thanks guys for the info.

[Jeff Valo]

Hello everyone,
I own a M235i 2015 and it's equip with the Dinan Stage II, Dinan Cold Air Intake, Dinan highflow exhaust, Go Fast Bits Diverter Valve + and just had the Fabspeed HighFlow Downpipe. My question is, two days after I got the downpipe install at my BMW dealer, the check engine light turn on ! I was under the impression that these kind of Downpipe were design to not turn any lights on ! Is it the downpipe or the DV+ that turn it on ? Because I got them install at the same time. I was also thinking that the Fabspeed DP and the HJS DP were the same !?
Thanks

Thanks.

[quenotte]

HJS is manufacturing cats for various applications/customers.

Then, those customers like Fabspeed, integrate HJS cats in their products (downpipe for instance for Fabspeed).

HJS on their side, launched their own downpipes, with specific and dedicated dual chamber cat to have their downpipe to keep car ECE (EURO6 for M235i) homologated and CEL free.

There is no integrated lambda spacer in HJS downpipe like it is in Fabspeed one for secondary lambda sensor.

So NO, HJS downpipe and Fabspeed downpipe are not the same ones.

I've a GFB DV+ and HJS EU6 downpipe and I didn't have a CEL since installed (+2500 km ago).

But, first thing to do will be to read what error code triggered CEL.

[quenotte]

I've installed ER Turbo to IC charge pipe two weeks ago.

Installation was OK with no issue.

Quite happy with the result.

Update of OP.

[Jeff Valo]

Thanks, can you give me the link for the proper HJS downpipe for Canada ?

[quenotte]

To my mind there is only one reference of HJS downpipe for M235i: HJS 90 81 2010

See this page for HJS downpipe products.

Contact HJS Customer Service to ask them their distributor in Canada.

[KAY-OS]

I recently installed the HJS downpipe. So far so good!

Sound : increased volume of about 10%, more aggressive tone, backfire a bit louder and a bit more frequent. Perfect.

Performance : pulls harder in low to mid rev range (less laggy) and it feels it wants to rev more.

No check engine light.

Here's a quick clip of the sound. Near the end of the clip, there's a shot of the exhaust sound with standard OEM downpipe for comparison.

Very happy with this HJS downpipe.

[SeanWRT]

OP, is there any noticeable smell with Euro 6 downpipe, just like CSL335i mentioned earlier? Thanks.

[EBM235]

I have the HJS catted DP and I haven't noticed any additional smells