[AndyR83]

I currently own a bone-stock E92 335. I'm about to buy a JB4/DCI combo and start getting some mods done. One of the things that seems to be an early mod is the installation of downpipes. I'm all for this, but I have one problem: I need my car to still pass emissions testing. My state (PA) doesn't have a "sniffer" test, they just check for codes. Since I want to stay legal, I've been looking at the catted downpipes instead of traditional catless. They seem to be a lot more expensive, which makes sense I suppose. Can anybody comment on the performance gains achieved with catted downpipes as compared to the catless kind? I'd hate to drop a wad of money on something that won't have much impact on performance.

Thanks!

[gzim335]

Originally Posted by AndyR83

I currently own a bone-stock E92 335. I'm about to buy a JB4/DCI combo and start getting some mods done. One of the things that seems to be an early mod is the installation of downpipes. I'm all for this, but I have one problem: I need my car to still pass emissions testing. My state (PA) doesn't have a "sniffer" test, they just check for codes. Since I want to stay legal, I've been looking at the catted downpipes instead of traditional catless. They seem to be a lot more expensive, which makes sense I suppose. Can anybody comment on the performance gains achieved with catted downpipes as compared to the catless kind? I'd hate to drop a wad of money on something that won't have much impact on performance.

Thanks!

get catless with dp fix n ull pass emissions testing.

[AndyR83]

I searched and read about the dp fix for a long time the other day but was still unable to determine exactly what it is/how it works. Can you use a dp fix with a JB4? Is it something I can easily install myself?

[gzim335]

Originally Posted by AndyR83

I searched and read about the dp fix for a long time the other day but was still unable to determine exactly what it is/how it works. Can you use a dp fix with a JB4? Is it something I can easily install myself?

u can use dp fix with or without a tune,bms sells it u can check for instruction on there website.

[gzim335]

Originally Posted by AndyR83

I searched and read about the dp fix for a long time the other day but was still unable to determine exactly what it is/how it works. Can you use a dp fix with a JB4? Is it something I can easily install myself?

u can use dp fix with or without a tune,bms sells it u can check for instruction on there website.

[AndyR83]

From the BMS website:

"The JB4 tuning system includes this functionality built in so a DPFIX is not required if you are already running a JB4 Performance Tuner!"

So, does this mean I don't need it?

[BES335xi]

Originally Posted by AndyR83

From the BMS website:

"The JB4 tuning system includes this functionality built in so a DPFIX is not required if you are already running a JB4 Performance Tuner!"

So, does this mean I don't need it?

No you still need it, that just means that the JB4 will not allow to throw a SES light when driving when youre catless but you wont pass emissions with that. So yeah just get dpfix for about 80$ or whatever it is, and pretty much just set it and forget it type of thing.

[benzy89]

ONLY have the DP fix set up when you're getting your emissions testing done. IF you left it after you've passed your emissions test, you will mess up the AFR sensor readings & the tune will impact the performance of your car FTL

[ar design II]

It depends on how your car reacts to the DP. Some cars with catted DPs will never throw a code and be just fine passing all emissions testing, other cars you still get the CEL and would pass a sniff test but need a DP fix to pass for OBD2 readiness. PM me if you have any questions!

As far as performance, the car only uses the front o2 for tuning and the DP fix only adjusts the rear so there should be no effect on the performance of the car with the DP fix installed.

[E90Company]

Originally Posted by benzy89

ONLY have the DP fix set up when you're getting your emissions testing done. IF you left it after you've passed your emissions test, you will mess up the AFR sensor readings & the tune will impact the performance of your car FTL

That's not right, it won't affect your performance.

[ar design]

Originally Posted by E90Company

That's not right, it won't affect your performance.

Correct, it will not effect performance.

[Quebequer]

I personnaly have catted downpipes on my car, and used to have catless. Yes they are more expensive, but the smell is a thing of the past, and there is almost no wastegate rattle anymore. Didn't notice a big loss in power whan I swapped them. Really like catted ones.

[MDORPHN]

Originally Posted by ar design

Correct, it will not effect performance.

According to the BMW, the post cat sensors do in fact have some relation to long term fuel trims (due to catalyst aging), although their primary purpose is a functional check of the cats.

I have also spoken to experienced tuners who have told that running with dp fix in place will affect air-fuel, and for that reason should only be used to pass emissions tests.


Neil

[benzy89]

Originally Posted by MDORPHN

According to the BMW, the post cat sensors do in fact have some relation to long term fuel trims (due to catalyst aging), although their primary purpose is a functional check of the cats.

I have also spoken to experienced tuners who have told that running with dp fix in place will affect air-fuel, and for that reason should only be used to pass emissions tests.


Neil

THANK YOU

[E90Company]

Originally Posted by MDORPHN

According to the BMW, the post cat sensors do in fact have some relation to long term fuel trims (due to catalyst aging), although their primary purpose is a functional check of the cats.

I have also spoken to experienced tuners who have told that running with dp fix in place will affect air-fuel, and for that reason should only be used to pass emissions tests.


Neil

Originally Posted by benzy89

THANK YOU

They don't. Any proof?

[benzy89]

Originally Posted by E90Company

They don't. Any proof?

BMW Service Foreman who has a 1M and knows a LOT more than either me or you, agreed that while BMW has never officially stated that the secondary o2 sensors adjust anything, that they do have some influence on AFRs/Fuel Trimming/etc

There's also NO reason to have an o2 SIM in when it's not being used, just unnecessary filters for DME data to go thru

[t3t5]

Do you guys know if you ran catted downpipes (i.e. ar catted dp's) with a catless exhaust system (i.e. Vanguard v2), this will pass California Sniffer? Not concerned about visual inspection, just need to pass the sniffer.

[FirstBMWLA]

Originally Posted by benzy89

BMW Service Foreman who has a 1M and knows a LOT more than either me or you, agreed that while BMW has never officially stated that the secondary o2 sensors adjust anything, that they do have some influence on AFRs/Fuel Trimming/etc

There's also NO reason to have an o2 SIM in when it's not being used, just unnecessary filters for DME data to go thru

This is also supported by the fact that Vishnu recommends you remove the O2 simulator wiring if you do not need it and they updated the harness long ago to do so.
I forget all Shiv's reasoning but I think you basically are feeding the DME only 1 signal when running it.

[BQTuning]

Have catted highflow DPs. So glad I didn't go catless for couple of reasons:

Exhaust sound with the catted DPs alone doubled my exhaust sound. Catless would have made even more louder.

No smell with the catted vs the gamble with the catless

Absolutely no rasp with the catted vs the gamble with the catless of having rasp

[gangzoom]

I have Catted AR DPs. Here in the UK new laws means a fail on emissions if the tester spots you've removed any factory fitted cats regardless of exhaust gas readings!!

I have a JB4 tune, and have recently started to run map 1 instead of 2 (also have intercooler) mainly because at map 2 the car was able to get to liscence lossing speeds so quickly I felt the car had almost too much power for public roads. Even on map 1 I'm pretty sure I can still give a E90 M3 a scare!! So although I have no dyno figures Im pretty sure your not going to be dissapponted by Catted Downpipes!!

[AlterZgo]

Originally Posted by Quebequer

I personnaly have catted downpipes on my car, and used to have catless. Yes they are more expensive, but the smell is a thing of the past, and there is almost no wastegate rattle anymore. Didn't notice a big loss in power whan I swapped them. Really like catted ones.

Did switching from catless to catted DPs also reduce the amt of exhaust soot on your rear bumper? My car is white and I'm concerned about excessive exhaust dust with catless DPs. Thanks.

[Quebequer]

Originally Posted by AlterZgo

Did switching from catless to catted DPs also reduce the amt of exhaust soot on your rear bumper? My car is white and I'm concerned about excessive exhaust dust with catless DPs. Thanks.

Didn't notice anything, maybe because my car is black...
The only things I noticed when switching were no more anoying rasp (mine was really loud rasp), no more smell and almost no drone anymore.