Ar Downpipe

[supercarfreak]

I notice there are 3 types of downpipe on the ar website. Does anyone know the difference between the normal one, one with race cat, and the resonator?.

Also would it give me a CEL if I install it (although I do have a jb4). Just incase if I ever turn off the jb4 it wouldn't show up.

Thanks for the help!

[jts1981]

One version is catless so it will fail emissions. The race cat version is claimed to be street legal and should pass emissions. At least thats what they say on one of these websites. The resonator is an add on to keep things quiet.

Im looking into them as well. I was curious about the O2 bungs. Not sure why there is an option to add 2nd one .

[nicknaz]

I believe the 2nd O2 bung is to have the option for an aftermarket wideband O2 sensor.

Depending on how far the cat is from the exhaust side of the turbo it could still fail emissions (cold start up test).

it is technically not allowed to modified the location/type of emissions control equipment so if you have a very savvy LEO who is looking for more reason to ticket that could be an issue for you.

some cars have stock heat shielding on the OEM downpipe, and if you can bolt those on to the aftermarket downpipe that would be good

[supercarfreak]

Originally Posted by jts1981

One version is catless so it will fail emissions. The race cat version is claimed to be street legal and should pass emissions. At least thats what they say on one of these websites. The resonator is an add on to keep things quiet.

Im looking into them as well. I was curious about the O2 bungs. Not sure why there is an option to add 2nd one .

Thanks bro, yeah I'm probably get one soon and update soon. At the same time I don't know which one to get

[Gunzaro]

I got the AR catted version because I didn't like the sound without the cats and also it keeps it legal. Sounds too farty without the cats. Noticed improvements in power, sound and throttle response.

[supercarfreak]

Originally Posted by Gunzaro

I got the AR catted version because I didn't like the sound without the cats and also it keeps it legal. Sounds too farty without the cats. Noticed improvements in power, sound and throttle response.

So how much power do you think you gained?. Also how does it sound (louder and deeper?) and does it give u a CHECK ENGINE LIGHT?.

[Gunzaro]

No CEL at all.

The sound is more racy - more aggressive without being overly so. Minor increase in volume of the stock 35is exhaust, few more pops and bangs on overrun. On one 1-2 gearchange I get a loud crack of a bang that sounds vicious!

Power has increased in conjunction with my EES stage 2 tune. After a few 3 rd gear adaptation runs I noted more power. IN cold weather it really flys.

[Hujan]

I think catless would be a little raspy/loud with the 35is exhaust, but I wonder if it would be okay with the 35i exhaust, which is more tame.

[supercarfreak]

Originally Posted by Gunzaro

No CEL at all.

The sound is more racy - more aggressive without being overly so. Minor increase in volume of the stock 35is exhaust, few more pops and bangs on overrun. On one 1-2 gearchange I get a loud crack of a bang that sounds vicious!

Power has increased in conjunction with my EES stage 2 tune. After a few 3 rd gear adaptation runs I noted more power. IN cold weather it really flys.

thanks bro for your input, i'm really consider cattle version but the same time i want to gain as much power as i can.

[Vintage]

Originally Posted by Gunzaro

I got the AR catted version because I didn't like the sound without the cats and also it keeps it legal. Sounds too farty without the cats. Noticed improvements in power, sound and throttle response.

Same for me - AR cats and ceramic coated - in love with them. This should be done before buying exhaust; save the money. Buy these DPs and a good tune.

[Hujan]

Any concern that the ceramic cats in the AR catted DPs will melt from high heat and eventually block the exhaust? The fact that they are not metallic cats is what has me concerned.

I talked to the AR guys and it sounds like they're able to do them with Magnaflow metallic cats instead of the Magnaflow ceramic cats for, I think, $400 extra. For $800 extra, I think you could get a set of HJS metallic cats in either 100 or 200 cpsi.

[Mak135i]

OP: I've had both types of AR DP on a 135i (N54). Honestly, there was no benefit to having the catted variety. It still threw a CEL and would not have passed inspection because of error codes. Of course, the JB4 takes care of that and I also have a BT cable with which to delete all codes right before I take it in for inspection (if you decide to remove JB4).

The smell and noise issues are greatly exaggerated in my experience. There was virtually no difference between the 2 in those regards (my car was a convertible, so it should have been very obvious if there were differences)

My recommendation is go catless with a tune.

[Hujan]

Originally Posted by Mak135i

OP: I've had both types of AR DP on a 135i (N54). Honestly, there was no benefit to having the catted variety. It still threw a CEL and would not have passed inspection because of error codes. Of course, the JB4 takes care of that and I also have a BT cable with which to delete all codes right before I take it in for inspection (if you decide to remove JB4).

The smell and noise issues are greatly exaggerated in my experience.There was virtually no difference between the 2 in those regards (my car was a convertible, so it should have been very obvious if there were differences)

My recommendation is go catless with a tune.

This is the only concern with catless for me: Too much noise. The Z4 is our "tame" car so drone/too much noise at cruising is a no go. Whichever DP I get, I plan to keep the remainder of the exhaust stock from the downpipe back (i.e., keeping the OEM secondary cats, resonators, and muffler). (I also plan to delete the cold start cycle since I know that can be loud with any kind of HFC or catless setup.)

If catless/catted are about the same in the noise department, then that makes it an easy choice.

[Alext]

I have not heard of anyone melting their AR cats. The main reason why a cat will melt is if your tune/sensors are totally out of sync.

Catted will provide a much more refined sound. This is why AR also released RESONATED downpipes that are catless but for people that want max flow and less sound.

However I had someone local PM me to say that even with the resonated pipes you will still get some farty sound and of course the smell. To me you want to avoid all chance of your car sounding like a Honda. It's a top of the line BMW Z4.

The difference in HP isn't much between catted and non-catted - like 5+ RWHP depending on level of tune.

[Mak135i]

The Catless DP set up DOES NOT drone...assuming you keep everything else stock. It is certainly more raspy and somewhat louder under acceleration. The typical "ricer" sound comes from the muffler or the silly "hissing sound" from a BOV (turbo cars).

I suggest you try to listen to both in real life. I could not tell much difference at all and like them both better than stock.

[Lambobimmer]

IMO, I would not spend the money for catted DP's. The exhaust is only slightly louder and you can hear the turbo's a little more with no Cats. I have them on my Z4 and I've also had them on my previous 135i. I pass NC emissions every year with my Cobb tune running only the secondary cats. I have also passed emissions without the secondary cats as well but I would not do that mod because of the smell.

[nicknaz]

Originally Posted by Lambobimmer

I have them on my Z4 ... I have also passed emissions without the secondary cats....

Did you need to use an "additive" or are there more cats in the Z4?

[Hujan]

Originally Posted by nicknaz

Did you need to use an "additive" or are there more cats in the Z4?

Not Lambo, but I believe there are only four cats in the Z4: One primary in each downpipe and two secondary cats.

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[Lambobimmer]

Yep, the primary cats are in the DP's. If you remove them you will get a lot more power with your tune with little to no smell compared to the OEM DP's. The secondary cats are in the exhaust and you will get significant amount of smell if you remove them with not much added power.

[Gunzaro]

I went for a drive with the 35is + AR catted DP's to test the sound once warm.

NB: the 35is exhaust is a lot louder than the standard 35i exhaust so I cant comment on that - the 35is exhaust is more like the 335is version but not quite as loud.

Now with my car (stock 35is exhaust) and catted AR DP's it sounds farty when cold that is for sure. When warm there is only a slight rasp at mid-high RPMS at full throttle that I can hear when I drive close to another car or wall.

Here is a very good vid of the actual sound of a 335is with stock exhaust and catless DP's - the rasp is similar to what I get but obviously much more pronounced with the catless.

Here is another vid of a 335is with catless DP's. Not such a good vid but when he goes WOT in the second part of the vid you can actually hear the terrible rasp @ 30secs (although some love it ...I don't) as he goes thru 1st and 2nd gear.

And I'll say again the 335is exhaust is similar to the 35is but a little more aggressive.

Catted definitely smooths out that rasp. Decision is up to you. Sound vs a little more power.

[supercarfreak]

Originally Posted by Gunzaro

I went for a drive with the 35is + AR catted DP's to test the sound once warm.

NB: the 35is exhaust is a lot louder than the standard 35i exhaust so I cant comment on that - the 35is exhaust is more like the 335is version but not quite as loud.

Now with my car (stock 35is exhaust) and catted AR DP's it sounds farty when cold that is for sure. When warm there is only a slight rasp at mid-high RPMS at full throttle that I can hear when I drive close to another car or wall.

Here is a very good vid of the actual sound of a 335is with stock exhaust and catless DP's - the rasp is similar to what I get but obviously much more pronounced with the catless.

Here is another vid of a 335is with catless DP's. Not such a good vid but when he goes WOT in the second part of the vid you can actually hear the terrible rasp @ 30secs (although some love it ...I don't) as he goes thru 1st and 2nd gear.

And I'll say again the 335is exhaust is similar to the 35is but a little more aggressive.

Catted definitely smooths out that rasp. Decision is up to you. Sound vs a little more power.

thanks buddy i will take everything in consideration.

[supercarfreak]

If the catted sound anything like this ill probably get it. Any thought?.