[fast_lap28]

Originally Posted by Ultimate Racing

Everyone always seem to forget that our downpipe (catless and catted) dyno results are with stock catback!



Darryl
www.ultimate-racing.com

Darryl,

So the HF catted pipes are with stock exhaust and no tune? If I want this setup (stock exhaust + HFC DPs) I am essentially eliminating the primary cats for HFC and keeping the secondary cart? Or can I do w/o secondary cats...I just don't get why we have to keep secondary cats in the first place

Definitely interested in HFC because of NC strict emissions laws....so I have to have some cats.

(plan on Dinan flash in future)

[Sniz]

Investigating the same thing myself. My understanding is that if you go with the HFC DP's you could eliminate the 2nd cats in the exhaust. Or you could go with catless and keep the stock cats in the exhaust which would then become your primary cats. At that point you would need to do something to fool the ECU to keep from throwing codes. I have procede so I plan on using shiv's built in O2 simulator. With the Dinan tune I'm assuming you would need to explore another option to keep from getting codes.

Originally Posted by fast_lap28

Darryl,

So the HF catted pipes are with stock exhaust and no tune? If I want this setup (stock exhaust + HFC DPs) I am essentially eliminating the primary cats for HFC and keeping the secondary cart? Or can I do w/o secondary cats...I just don't get why we have to keep secondary cats in the first place

Definitely interested in HFC because of NC strict emissions laws....so I have to have some cats.

(plan on Dinan flash in future)

[e90AW335i]

Originally Posted by fast_lap28

Darryl,

So the HF catted pipes are with stock exhaust and no tune? If I want this setup (stock exhaust + HFC DPs) I am essentially eliminating the primary cats for HFC and keeping the secondary cart? Or can I do w/o secondary cats...I just don't get why we have to keep secondary cats in the first place

Definitely interested in HFC because of NC strict emissions laws....so I have to have some cats.

(plan on Dinan flash in future)

You should be able to do without the secondary cats....

[Ultimate Racing]

Originally Posted by fast_lap28

Darryl,

So the HF catted pipes are with stock exhaust and no tune? If I want this setup (stock exhaust + HFC DPs) I am essentially eliminating the primary cats for HFC and keeping the secondary cart? Or can I do w/o secondary cats...I just don't get why we have to keep secondary cats in the first place

Definitely interested in HFC because of NC strict emissions laws....so I have to have some cats.

(plan on Dinan flash in future)

Correct. The only mods done to this 335i are the downpipes. Everything else is 100% stock. You can do without the secondary cats if you want. Nothing stopping you. The secondary cats are in the exhaust midpipes so they don't have anything to do with the downpipes.

Darryl
www.ultimate-racing.com

[fast_lap28]

Originally Posted by kyleh4852

You should be able to do without the secondary cats....

I have been under the car already but didn't remove the plastic panels to reveal where the cats meet up to the turbos. So if I do the Dinan flash and I install the HFC's is removing the 2nd cats a quick unbolt or is it necessary to "cut" the secondary cats off?

Also, if removing the 2nd cats with Dinan flash require an ECU trick? or will flash recognize and adjust properly?

So many options that you go crazy trying to figure out how to do the right thing!

[fast_lap28]

funny but just earlier on seperate post we started on the same road...

http://www.e90post.com/forums/showpo...6&postcount=10