986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - NHP headers

AZ986S · 04-19-2018, 07:39 AM

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:dance:

Edit: LTFTs are now in the 3% to 7%, so that looks good. These headers are definitely louder, but I love the sound...

04-19-2018, 07:39 AM	#1
AZ986S Registered User Join Date: Jun 2016 Location: Arizona Posts: 379	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:dance: Edit: LTFTs are now in the 3% to 7%, so that looks good. These headers are definitely louder, but I love the sound... __________________ 2002 Boxster S - NHP 200 Cell Headers,test pipes,Borla CatBack,Competition Plenum,74 mm TB, EVOMS Tune,Tarett UDP,Eibach Swaybars,BIlstein PSS9s,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, 90K miles Last edited by AZ986S; 05-14-2018 at 07:50 PM.