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Old 04-20-2008, 06:47 AM   #1
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Secondary Cat Bypass Pipes Installed

Finally got around to installing bypass pipes on my 2002 S. My car already has a custom sport muffler (Pedro style) and an Evo Hi-Flow. I was hoping for a bit more music and the pipes have not disapointed. They were quite straight forward to install and the bolts/clamps all loosened easily. The big clunky cats are now gone, saving considerable weight in the process (still don't know why our cars needed two sets of cats?) The car is a little louder at idle, but nicely so. Where I really hear the difference is as soon as the tach his about 3600 rpm...the car just screams. The sound is pure Porsche, like a baby GT3. I highly recommend this mod to anyone looking for some sound out of their car, without a huge investment. I bought my Fabspeed pipes (slightly used) from another member for $300, including shipping. Also, no CEL, as I re-set the DME before starting.

Sorry, I forgot to take pictures during the install, but it sure cleaned up the underside of the car and I anticipate it will run a little cooler.

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Old 04-20-2008, 08:11 AM   #2
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I'm unfamiliar with the particulars of bypassing the cat converters on a street car. I assume the oxygen sensors are removed? How is the ECU and resultant mixture affected?
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Old 04-20-2008, 11:40 AM   #3
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The first set of cats are in the headers, with a pre and post O2 sensor in the header also. This is why you can remove the secondary cats with no ill effects to the DME.

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Old 04-20-2008, 06:23 PM   #4
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Got it, makes sense, thanks.
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Old 04-20-2008, 09:14 PM   #5
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Very interesting! Can you elaborate a little more?

You write:

Quote:
Originally Posted by jmatta
Also, no CEL, as I re-set the DME before starting.
Did you doing this by disconnecting the battery or different?
I am assuming you did this just ONCE not every time before you start the car?

Will you still pass smog?

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Old 04-21-2008, 04:46 AM   #6
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Quote:

"Also, no CEL, as I re-set the DME before starting."

Posted by jmatta.

With only the second set of cats (no O2 sensors) bypassed, this step should not be needed, right??
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Old 04-21-2008, 05:26 AM   #7
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The reason I did this (re-set by disconnecting battery) is the back pressure is affected by removing the cats. This was strictly precautionary, as I wanted the DME to read the set-up and not notice the change. I also did this when I changed to the Evo Hi-Flow. You only need do this once so the system learns from here. It's going to be 72* in Chicagoland today, so I will need to get the car out for a drive...so much for work!
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Old 04-21-2008, 06:56 AM   #8
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Benefits?

Aside from the sound - and we all love these sounds - are there any performance improvements i.e. power or fuel savings?
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Old 04-21-2008, 07:44 AM   #9
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If there is any gain, it is probably minimal. The car does seem to rev a bit easier on downshift throttle blips...could be my imagination, too. Where I really notice the difference is in the mid rpm range when the varioram comes on.
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Old 04-21-2008, 07:59 AM   #10
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i've just bought some of ebay (item number 370043175082) you may still be able to view them. they state 12-25 bhp?!?! but it's prob more like 10 bhp, also they say no remapping of ecu and no CEL probs, they cost me 289 ($580ish) but they are stainless and there is quite a big weight saving. BUT just changing the rear silencer (muffler) does'nt seem to give me the sound i'm looking for (i've listened to loads) they don't scream enough, go on you tube and listen to the 987 going round the nurburgring now THATS the sound i want ps yes i know it's a 987 and not our beloved 986's but surely that sort of sound is achievable?
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Old 04-22-2008, 06:14 AM   #11
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Quote:
Originally Posted by jmatta
It's going to be 72* in Chicagoland today, so I will need to get the car out for a drive...so much for work!
I'm also in the chicago area, and if i install these, will it affect emissions testing? I would assume not because it does not delete any of the cats. btw, I agree, i've enjoyed driving my boxster in the last few days in this awesome chicago weather. makes up for it for the nasty winter we just had
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Old 04-22-2008, 09:29 AM   #12
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I would be very surprised if you would still pass smog after installing a secondary cat bypass. You take 50% of your cats out of commission. I am sure Porsche put them there for a reason. You will not throw a CE light as the O2 sensors measure before and after the primary cats, but smog is measured after the secondary cats.
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Old 04-22-2008, 09:37 AM   #13
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Quote:
Originally Posted by ChrisZang
I would be very surprised if you would still pass smog after installing a secondary cat bypass. You take 50% of your cats out of commission. I am sure Porsche put them there for a reason. You will not throw a CE light as the O2 sensors measure before and after the primary cats, but smog is measured after the secondary cats.
I still have all my cats. Here in AZ, all they do during a smog inspection is to hook up to the OBDII port, see if there are any codes, and then they do a gas cap pressure test. No underside or topside inspection. I'm pretty sure that a car with bypassed secondary cats would pass.
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Old 04-22-2008, 09:45 AM   #14
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passed smog in ca

I replaced the cat's on my Cayenne S (not my box... yet) it passed ca smog w/o a problem...
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Old 04-22-2008, 12:08 PM   #15
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cool

i stand corrected
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Old 04-22-2008, 12:11 PM   #16
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You will definately hear a difference with the bypass pipes...it was quite noticable on my 3.2. Again, I feel the biggest difference before and after is the throttle response. On heel/toe downshifts, there was always a slight hesitation on the throttle blip, even with e-gas. The response is pretty instantaneous now; I wasn't imagining it, now that I have had some more seat time.
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Old 04-22-2008, 12:30 PM   #17
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what's the difference in the exhaust note?


Quote:
Originally Posted by jmatta
You will definately hear a difference with the bypass pipes...it was quite noticable on my 3.2. Again, I feel the biggest difference before and after is the throttle response. On heel/toe downshifts, there was always a slight hesitation on the throttle blip, even with e-gas. The response is pretty instantaneous now; I wasn't imagining it, now that I have had some more seat time.
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Old 04-24-2008, 08:55 AM   #18
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Exhaust note is a little louder/deeper at idle. Where it really sounds different is above 3600-3800 rpms; the mid range just opens up with an aggressive howl. I'll have to record some, as I have difficulty describing the sound. I spend a lot of time at the track and it is similar to the sound a GT3 makes when heavy on the throttle.
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Old 04-24-2008, 09:36 AM   #19
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Quote:
Originally Posted by ChrisZang
cool

i stand corrected
Nope you were correct.

Technically,in CA you CAN'T remove any OEM engine related parts unless they are C.A.R.B. exempt.

That being said,most shops have no clue what they are looking at(or don't care) and as long as you stay within max measurements you would more then likely pass.

I've taken my 986 w/ a Top Speed exhaust(not C.A.R.B. approved) and it passed,the shop didn't say anything before the test. Afterwards they said I need to careful on the road though,apparently cops are cracking down on aftermarket stuff. If your pulled over your supposed to present documentation that the parts are C.A.R.B. approved or your car can be towed away.

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