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      06-04-2015, 10:23 AM   #23
JNoSol
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Quote:
Originally Posted by dmk08 View Post
I have heard a lot of conflicting reports around this lately. My friend installed downpipes on his car and really didn't pick up anything on the dyno. It was ~20 degrees warmer when he dyno'd with the DP vs without but the same dyno. I expected at least some gains.

I would assume the reason to stay catted is smell and volume.
Cat Converters are very restrictive, even for N/A cars. The E9x M3 guys pick up 20HP and 20lb of TQ from just test pipe upgrades alone. For turbo charged cars, the gains should be even higher (more exhaust gas flow = quicker the turbine spins = quicker and higher boost).

If you run JB4 the same map, with and without Catless DPs there should be a big jump.

Something isn't right with your buddy's test, maybe he should let the car acclimate to the change (a week) before testing again at the same base temp.

http://www.m3post.com/forums/showthread.php?t=756575

Those who ran catless DPs didn't report any smell in the cabin. Obviously the users have to use common sense and not idle a car for long periods in a garage. Volume shouldn't be an issue, stock exhaust sounds like a kitten pur.
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      06-04-2015, 10:27 AM   #24
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Quote:
Originally Posted by JNoSol View Post
Cat Converters are very restrictive, even for N/A cars. The E9x M3 guys pick up 20HP and 20lb of TQ from just test pipe upgrades alone. For turbo charged cars, the gains should be even higher (more exhaust gas flow = quicker the turbine spins = quicker and higher boost).

If you run JB4 the same map, with and without Catless DPs there should be a big jump.

Something isn't right with your buddy's test, maybe he should let the car acclimate to the change (a week) before testing again at the same base temp.

http://www.m3post.com/forums/showthread.php?t=756575
He ran the car for multiple weeks w/ the DP before testing. No indications of issues from the curve etc.

I have been told by a well known tuner that DP have varying results. Not sure why some cars seem to respond better than others. Both the cars i have seen local have had issues. Either breaking up on the dyno up top or no power gain really. Remember JB4 and these other solutions are just removing the CEL and letting the computer compensate.

That and the environmental concerns Dave 90TT mentioned have kinda turned me off downpipes.
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      06-04-2015, 11:02 AM   #25
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Quote:
Originally Posted by dmk08 View Post
He ran the car for multiple weeks w/ the DP before testing. No indications of issues from the curve etc.

I have been told by a well known tuner that DP have varying results. Not sure why some cars seem to respond better than others. Both the cars i have seen local have had issues. Either breaking up on the dyno up top or no power gain really. Remember JB4 and these other solutions are just removing the CEL and letting the computer compensate.

That and the environmental concerns Dave 90TT mentioned have kinda turned me off downpipes.
Interesting on the testing, that is very odd and contradicts with everything else I've heard. Maybe he needs to run 93 octane, poor fuel cause the engine to stall out at 6,000rpm with JB4 + DPs. He may need send in his JB4 logs.

Agree with you about the environment and JB4 is just suppressing the CEL vs dealing with it.

I haven't considered DPs, but if I do it would be Zima catless (high quality, ceramic, and flex pipe at a reasonable price). Otherwise just leave it alone vs high flow cats. Our OEM DPs do just fine, it makes plenty of power with tunes and piggy.
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Last edited by JNoSol; 06-04-2015 at 11:14 AM..
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      06-04-2015, 02:05 PM   #26
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High flow cats can burn out after a while, I had them on on my n54, 3000 miles in I threw a cel.

The secondary cats take care of practically all the smell, I haven't noticed anything. The power is def there, I have a hard time accepting that they don't yield power. Plus later if you are think stage two, primary cats need to be deleted.

As far as the environment goes, well, that's an entirely whole other discussion. There's a ton of multinational companies who could cut their profits and executive bonuses to make HUGE impacts on the world, a lot more than my two cats would make. But again, that's a whole other discussion.
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      06-04-2015, 02:19 PM   #27
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I am very pleased with the effectiveness of the secondary Cats. They are doing a great job working overtime with the DP's in place. Here is my baseline in comparison to Zima DP's with Active 8 module. Car is much much smoother now, and obviously stronger everywhere.


http://5252motorsports.blogspot.ca/2...s-for-bmw.html

Quote:
Originally Posted by dmk08 View Post
He ran the car for multiple weeks w/ the DP before testing. No indications of issues from the curve etc.

I have been told by a well known tuner that DP have varying results. Not sure why some cars seem to respond better than others. Both the cars i have seen local have had issues. Either breaking up on the dyno up top or no power gain really. Remember JB4 and these other solutions are just removing the CEL and letting the computer compensate.

That and the environmental concerns Dave 90TT mentioned have kinda turned me off downpipes.

Last edited by VCP; 07-06-2015 at 03:04 PM..
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      06-08-2015, 01:01 PM   #28
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How are you liking the DP's so far?



Quote:
Originally Posted by tareemaa View Post
High flow cats can burn out after a while, I had them on on my n54, 3000 miles in I threw a cel.

The secondary cats take care of practically all the smell, I haven't noticed anything. The power is def there, I have a hard time accepting that they don't yield power. Plus later if you are think stage two, primary cats need to be deleted.

As far as the environment goes, well, that's an entirely whole other discussion. There's a ton of multinational companies who could cut their profits and executive bonuses to make HUGE impacts on the world, a lot more than my two cats would make. But again, that's a whole other discussion.
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      06-08-2015, 05:53 PM   #29
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Quote:
Originally Posted by VCP
How are you liking the DP's so far?



Quote:
Originally Posted by tareemaa View Post
High flow cats can burn out after a while, I had them on on my n54, 3000 miles in I threw a cel.

The secondary cats take care of practically all the smell, I haven't noticed anything. The power is def there, I have a hard time accepting that they don't yield power. Plus later if you are think stage two, primary cats need to be deleted.

As far as the environment goes, well, that's an entirely whole other discussion. There's a ton of multinational companies who could cut their profits and executive bonuses to make HUGE impacts on the world, a lot more than my two cats would make. But again, that's a whole other discussion.
Love them, the car is a different beast. It has def scratched my new exhaust itch. I wasn't looking forward to paying 3-4k for an exhaust.
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      05-19-2017, 05:12 PM   #30
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Anyone have a video review with zima DP on stock exhaust?
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