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Old 04-19-2018, 06:39 AM   #1
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NHP headers - brought back to life

So I've been looking for high flow cat headers for a while and bought the used NHP 200 cell cat headers from rfuerst911sc (thanks!) to replace my restrictive stock headers.

I installed them yesterday and wow

My exhaust setup now consists of NHP 200 cell cat headers, circuit works secondary bypass pipes and a Borla muffler.

Here's how I they started:



There was obviously quite a bit of corrosion and tarnish, so I started off with using a SS wire brush on my electric drill, then I cleaned them with CLR to remove the rust. Here's the left side compare to the right side after wire brush:



Then I wet sanded using WD40 using progressivley finer grit aluminum oxide sand paper, from 220 to 1,200. After wet sanding, I would spray down with some Meguiars Ultimate Wheel Cleaner and wipe off with a damp microfiber rag. Then, for the final cycle, I wet sanded with the Wheel cleaner (using rubber gloves!). This cleaner contains some acid (hydrochloric I believe) and does a decent job at removing light corrosion and stains, but elbow grease is what is still needed.

Here's how it looked at the end:



A few notes:

I tried various products and techniques. The baking soda and lemon juice home made paste can work ok only if the corrosion if very superficial since it contains nitric acid. I tried this and there was not much improvement. Also, as an alternative to SS wire brush, I found that power wet sanding with a rotary sanding flapper wheel work very well for removing heavy oxide and tarnish.

I realize the headers are not mirror polished like new, but for me this was an acceptable finish. When I get a chance, I'll take pictures of the install. In the meantime, I went for nice spirited drive last night and noticed a noticeable increase in torque over the entire RPM band, but even more at the high end. The noise level is just a tad higher than with the factory headers, still has the burble, zero drone, and when you apply WOT, it is music to the ears! Some say it sounds like a GT3, and I do concur with that opinion. I also did not get any CEL codes and the Long Term Fuel Trims now are at about 2.0%. I just hope that I can pass the 94 DB noise limit at AMP next month

Edit: LTFTs are now in the 3% to 7%, so that looks good. These headers are definitely louder, but I love the sound...
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2002 Boxster S - NHP 200 Cell Headers,test pipes,Borla CatBack,Competition Plenum,74 mm TB, EVOMS Tune,Tarett UDP,Eibach Swaybars,H&R Sport Springs,TuneRS rear toe links,wheel studs,15 mm wheel spacers on all 4,EBC yellow stuff pads,Sebro rotors, EBS oil baffles,160 deg Thermostat,2 quart Accusump,full filtration remote oil filter,rad fan switch,custom gauge/switch plate, Race Capture data logging, 80K miles

Last edited by AZ986S; 05-14-2018 at 06:50 PM.
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Old 04-19-2018, 07:27 AM   #2
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Very nice, I always wanted a set like that.
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Old 04-19-2018, 08:47 AM   #3
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Very nice looking!
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Old 04-19-2018, 12:20 PM   #4
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They look great and good to hear that they make the engine feel stronger. Nicely done.
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Old 04-19-2018, 08:22 PM   #5
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I would ceramic coat these babies........when you have them off again
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Old 05-07-2018, 07:20 PM   #6
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Some photos of the header installation.
I had to add a heat blanket to protect the oil lines since the new headers are larger and much closer.

Passenger side:



Driver side:



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2002 Boxster S - NHP 200 Cell Headers,test pipes,Borla CatBack,Competition Plenum,74 mm TB, EVOMS Tune,Tarett UDP,Eibach Swaybars,H&R Sport Springs,TuneRS rear toe links,wheel studs,15 mm wheel spacers on all 4,EBC yellow stuff pads,Sebro rotors, EBS oil baffles,160 deg Thermostat,2 quart Accusump,full filtration remote oil filter,rad fan switch,custom gauge/switch plate, Race Capture data logging, 80K miles
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