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DT Headers on '03 S/C - DONE

53K views 108 replies 30 participants last post by  fatkid_UH-60 
#1 · (Edited)
DT Headers on '03 S/C - DONE & FINALLY W/ SOUND CLIP!

I hope i never have to replace headers on any vehicle again! It turned out that both of my OEM manifolds were cracked, so i needed to do this anyhow.

I installed the DT headers and a Nismo catback, i finished it last night. The SES light came on, but I am assuming that is due to the elimination of the primary cats. I'll get the code pulled today. It runs and sounds great! I'll post sound clips soon. There is no degradation of performance from the s/c, before i had only 2 lbs of boost max, it seems to be back to normal now.

To everyone worried about the backpressure issues, can a more open header really be that less restrictive than a manifold that is almost cracked in half?

Anyhow, I just wanted to post that it does work, and i will never do it again. It's not that hard, but it is a PITA to get in there, there is no room.

A few notes:

The Driver side comes with 2 02 mounting locations, but the secondary cat has the factory location of the second o2, so i just plugged the second opening in the header.

jack up the truck, i dont have a lift, but i jacked up the front and took off the front wheels. When you remove the rubber fender liners, you can get to 90% of the bolts you need.

You can only reuse half of the factory studs. The OEM manifolds use 3 short and 3 long studs into the block, the long ones are too long, so we bought 6 more short from a nissan dealer for about $2 each.

There are 2-3 bolts on each side that are impossible to get a socket on the DT headers, the pipe goes directly in front of the mounting hole and the stud is just long enough to block getting a socket on them, unless i missed something.


Other than that, it went ok, just took forever. I didn't worry about a how-to because i was following other people's how-tos and it was pretty much the same. I did pull and install most of the parts through the wheel well rather than through the engine bay though.

 
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#2 ·
Looking forward to hearing the results.

Yes a performance header is MUCH less restrictive than factory headers. With most factory manifolds, the exhaust has to "share" the path of escape which inhibits the maximum power it can achieve. The first cylinder pushes out the exhaust on it's exhaust stroke which means that the 2nd cylinder has to push out the exhaust from its cylinder along with the exhaust from the 1st cylinder and so on and so on with the following cylinder(s). With performance headers, each cylinder has it's own dedicated "escape" and eliminates back pressure from the manifold.
 
#6 ·
Nice!!!
 
#8 ·
I'm in the process of writing up a DIY for AC header installation and I see that you had basically all the same issues and the install seems to be similar. Justageorgiaguy Do you have a 2" BL?
Just by looking at the truck/steering shaft i'd say no...
 
#9 · (Edited)
no, suspension is stock, unless the 4wd is any higher than 2wd.

after driving about 100 miles, i'll be installing some dynamat or something in the cabin. There is a drone from the nismo around 2500 rpms, not deafening but it wears on you. Performance wise, it responds nice, but since the SES code is thrown, the s/c is being bypassed again, so i don't have the full effect.

edit: one other thing i noticed but didnt really cause any issues was on the passenger side header, the rear flange (closest to the cab) is opposite from the stock manifold. It doesn't cause any issues, the gasket is square on that end and can accept bolts in any corner. Not sure why it is different, but I did notice it. I believe the driver side matched up with the stock studs.
 
#10 ·
no, suspension is stock, unless the 4wd is any higher than 2wd.

after driving about 100 miles, i'll be installing some dynamat or something in the cabin. There is a drone from the nismo around 2500 rpms, not deafening but it wears on you. Performance wise, it responds nice, but since the SES code is thrown, the s/c is being bypassed again, so i don't have the full effect.
Yeah the 2" body lift makes all the difference in the world, much easier to get at every thing.

I have the Nismo cat back as well and I agree that between 2500 to 3000 rpm the drone can be annoying. My muffler may be going bye bye, but I want to get the larger down tubes fabbed up before I do that. I have a theory that the larger down tubes may help to bring the drone back down to the sound levels they were at before the headers.

My guess is the code will be an O2 sensor being caused by the elimination of the cats. Did you install any CEL's?
 
#11 ·
Here's the codes i am throwing:

P0037 HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
P0158 Oxygen Sensor Circuit High Voltage (Bank 2 Sensor 2)
P0328 Knock Sensor 1 Circuit High Input

Now I know about the knock sensor issues on the s/c and i've debated on the relocation techniques

As far as the O2 sensor codes, Are these the codes I will keep throwing unless i install an O2 sim or did i damage the sensor wires when i installed the headers possibly?
 
#12 ·
Here's the codes i am throwing:

P0037 HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
P0158 Oxygen Sensor Circuit High Voltage (Bank 2 Sensor 2)
P0328 Knock Sensor 1 Circuit High Input

Now I know about the knock sensor issues on the s/c and i've debated on the relocation techniques

As far as the O2 sensor codes, Are these the codes I will keep throwing unless i install an O2 sim or did i damage the sensor wires when i installed the headers possibly?
Possibly, maybe. What I can tell you for sure that it will throw O2 codes without the CEL's installed.

Mine through code P1148 the first time I drove it after installing the headers and CEL's but after going through the process of getting rid of the learned data in the ECU it has been fine since. I have been driving it like a stolen Ferrari on the way to work and a few *cough* high speed runs on the highway *cough* and no check engine light.
 
#13 ·
stupid question but what are CELs? whenever i saw that I thought it meant Check Engine Light. I read on another board about using spark plug spacers between the o2 and the cat and I've seen electrical sims, what is better, or what works is all that really matters.
 
#14 · (Edited)
CEL (Check Engine Light Eliminator) basically fools the rear O2 sensor into thinking the cat is still in place and functioning by pulling the rear O2 sensor out of the exhaust stream.

Could you use something else as a spacer to fool the sensor, I guess so but there will be a lot of trial and error to get the length correct.

CEL


CEL installed on drivers side. Ignore the circles and arrows there for another thread.

 
#16 ·
You might also want to double check the placement of the driver's side O2 sensor as the DT headers were built for N/A Xterra's that have a EGR tube that connects to the exhaust manifold. From the looks of your pictures you may need to relocate the sensor to the lower hole. Looks sweet though. Hope to get a pair soon.
 
#18 ·
i would love a sound clip!! I would love to do headers into a nismo...but also get some down tubes!!
Towards the end of my build thread are some Iphone videos of my truck with headers and Nismo cat back but before I put in the larger down tubes.
One video idling and one run up through the gears.
 
#20 · (Edited)
Sounds awesome!!!!!!! Exactly everything I want...Were the headers a direct bolt on application? Total cost for them? How do you like the pulley??? Any problems from the pulley?
 
#21 ·
Headers were a direct bolt on, not hard, but aggravating. I bought them from Rugged Rocks, so they were $456.

No problems with the pulley, well actually i bought one, but the pulley installer didn't stop when it reached the s/c shaft like the instructions said so it went on too far, binding up the s/c. The puller cracked the pulley trying to back it off, so I had to reorder another pulley. so I ran w/o a s/c belt (and w/o a/c) for a week or two before i got a chance to install the new pulley.

I'm finally done, but I bought a CC Insert for the exhaust. The drone is pretty bad from 2500-3K RPMs, i'm sure it'll kill some of the sound and hp but should increase a little of the low end torque lost from the mods...
 
#22 ·
I have a nismo exaust installed this past summer. And right now i have one cracked manifold. I was looking to do the headers in the spring if the stock one doesnt get too bad. My question for any of you is do the headers bolt straight to the y pipe? Obviously they delete the cat but far enough to reach the y pipe flange? Maybe a picture from your truck. Or do i need a short peice to connect header to y pipe. Thanks guys.
 
#23 ·
I have a nismo exaust installed this past summer. And right now i have one cracked manifold. I was looking to do the headers in the spring if the stock one doesnt get too bad. My question for any of you is do the headers bolt straight to the y pipe? Obviously they delete the cat but far enough to reach the y pipe flange? Maybe a picture from your truck. Or do i need a short peice to connect header to y pipe. Thanks guys.
Not sure on the DT's but on the AC headers they bolt to the down tubes that in turn lead to the Y pipe, at least on my 2000.
 
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