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Old 11-15-2015, 05:34 PM   #1
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98 Boxster: Cat Delete Pipes Vs. Muffler Swap

Hi - Trust everyone is having a great weekend. I am looking to get a more aggressive sound note out of my Boxster and have spent time reading multiple posts with regard to the muffler options and cat delete pipes. Looking for some guidance as I embark on this mini project as I am not clear on a few things.

1) I have read feedback from some tenured members that starting out with the cat delete pipes and installing them before a muffler swap and trying out the sound. My only question for this option is if will trigger any CEL lights for my Boxster considering it is a 98 Reg.

2) If option 1 is going to trigger a CEL light, I would like to get some feedback on the Manzo vs. Top Speed Exhaust. There have been a few posts with regards to the Top Speed exhaust causing some drone so would appreciate some Top Speed owners feedback.

As always, appreciate the input.

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Old 11-16-2015, 12:28 PM   #2
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I have a 01 S and it had 4 cats.

The upstream cat on the header pipes is monitored with 2 O2 sensors.

The rear cat is not monitored.

I bought the Top Speed Muffler and with the rear cats still installed, it droned horribly and was unbearable in the lower rpm range.

Then I installed the Top Speed rear cat deletes pipe (a short section of pipe replacing the rear cat) and no more drone.

The sound they make now is pure sports car, louder than stock when hitting the gas and about the same as stock when idle/coasting/cruising.

It also has a very nice "gargle" sound when letting off the gas. Awesome for less than $500 and DIY easy.

If you only have the upstream cat by the headers then all you need it the Top Speed exhausts and you should be drone free and no change to your O2 monitoring either so no codes to worry about.

If you remove a O2 monitored cat from your system then you will have codes and worse the fuel mixture will not be optimum and likely run poorly.

Not sure how the racers get around the O2 monitor issue but you need at least an upstream O2 sensor for the engine to run right.
There are post cat O2 sensor devices that can fool the computer into thinking all is well and avoid the check engine light coming on.


Ray
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Last edited by jb92563; 11-16-2015 at 12:40 PM.
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Old 11-16-2015, 04:26 PM   #3
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Quote:
Originally Posted by jb92563 View Post
Not sure how the racers get around the O2 monitor issue but you need at least an upstream O2 sensor for the engine to run right.
The early 97-99 Boxsters only have one set of cats which are located separately downstream of the headers (non-integrated) and the cat delete pipes from Fabspeed have an O2 mount so the ECU will continue to monitor the exhaust and avoid any CEL issues from cat removal.

Porsche 986 Boxster Primary Catbypass Pipes (1997-1999) - Fabspeed Motorsport

I bought my TopSpeed cat back muffler after hearing how well they sound. It really sounds bad ass.

Please note that the TopSpeed + cat delete will be pretty loud. Its fine for my race car but it would be too loud for me (and my very quiet neighborhood) on a daily basis.

For daily driving, I would first try either the cat delete or the TopSpeed muffler and see how well you like the sound. You can always add the other component if you want it louder. I installed the muffler first and kept the stock cat's and had some drone. Removing the cat's eliminated the drone but the combination increased the loudness quite a bit over pure stock.

Here is a pic of my 97 Boxster with the TopSpeed muffler; stock cat on the left and the cat delete pipe on the right:



And here is the full cat delete and TopSpeed muffler installation:

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Last edited by thstone; 11-16-2015 at 04:46 PM.
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Old 11-16-2015, 05:49 PM   #4
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Gents - Many thanks for the detailed response. I will be trying out the Top Speed Exhaust. Hopefully I will be drone free as any drone in the cabin would be a deal breaker. I will also be ordering the 'Napa 2" Easy Clamps' as they seemed to have eliminated the drone issues for cases with drone.
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Old 11-17-2015, 12:46 AM   #5
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I went the opposite route to Tom - still using the Top Speed headers and cat delete pipes but I retained the original (heavy) rear muffler. No drone at all but a crisper sound over 3,500 rpm.
It loses a little low down torque (below 3,000 rpm) but makes up for it above 4,500 rpm due to the slightly larger diameter piping.

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