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Hello, I am interested in purchasing the Doug Thorley long tube headers.

I've done quite a bit of research and I have found a few things out. Forgive the layout of this, just trying to make it easy to follow.

1. The old model (ceramic coated) seemed to have issues with rusting. I read the 12 pages on the forums hear of racers debacle

2. the 2010 edition came out and is stainless steel (probably because of the mentioned rust problems)

3. If you want long tube headers for your fj you don't have another option.

So these are the headers I have in mind. Underdog Racing Development

the THY-515-LS-C Thorley Header, 2010+ FJ Cruiser, 4Runner 4.0L V6

it says 2010+, yet on a posting i read before they came out it said "they are planning to have them compatible with other years as well"

so my questions are these.

1. Will these work on 2008 fj cruiser, or is it only for the 2010 models and up.
2. How difficult are these to install
3. if you have them, how long, and how are they/how are they holding up.

Thank you.
 

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it been a week since I installed my long doug Thorley headers.
The headers long tube suppress the first catalysts.
We must add the wiring for rear co2 not that you have started the engine Tcheck on.
There are not too noisy, I could feel a big improvement in the low-end torque.
To install you must disconnect the battery, remove the air cleaner and disconnect two switch have room for, so no problem right.
To the left it will loosen the bolts on the transmisson because not much room but overall maximum of 2 hours work, not complicated.
 

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and yet, they have the same reference THY-515-LS- C
 

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These are for the 07-09 (was not clear from your post what year you have):

Underdog Racing Development

I have had them for a few months. No rust; not sure of performance gain because I also added the UCON, Supercharger and a smaller pulley.

Previous to putting them on I installed the URD y-pipe, AFE catback and AFE CAI.
you could mount the Headers+Y pipe ?
So most of resonator, you had the engine Tcheck ?
 

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I read a bit of info as well on the forum and on URD site. I know I will increase low end torque, but will I lose high end? Any fuel mpg decrease with adding these? What type of gains are expected?
 

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Yes. I do not have a check engine code because the UCON overrides it. You can also buy O2 sensors from URD to override it.
Sorry I do not speak much English and I am still a novice with the FJ.
What UCON ?
As you climb the Thorley Headers ago the original location of the probes upstream so as catalyst removes one connects the rear O2 harness to fool the ECU.
So if we add the Y should be added O2 or even a beam that is in my setup I just add the Y ?
 

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if you have a complete system you'll necessarily gain the top and bottom.
Doug Horley said that with headers you can win a 16 hp, personally I do not think, but 8/10 certainly cv.
Example, I measure my TRD Fj with CAI, and Magnaflow exauhst Unichip, I was at 288 hp.
I have my Unichip remaper now because I add Headers
 

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Sorry I do not speak much English and I am still a novice with the FJ.
What UCON ?
As you climb the Thorley Headers ago the original location of the probes upstream so as catalyst removes one connects the rear O2 harness to fool the ECU.
So if we add the Y should be added O2 or even a beam that is in my setup I just add the Y ?
UCON is an engine management system that can take over the fuel injection, comes with new timing gears and a new thermostat (you can find it on URD's website). It can optimize the performance of your FJC and the associated modifications you have made.

Yes, you put in a new O2 sensor in the DT headers to fool the ECU. The y-pipe will get rid of the second set of cats.
 

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I read a bit of info as well on the forum and on URD site. I know I will increase low end torque, but will I lose high end? Any fuel mpg decrease with adding these? What type of gains are expected?
No, you will not lose high end HP. If anything, you would risk losing low end (unlikely though). By doing LT headers, I would expect something around 10-20 HP increase (nothing to substantiate though). The OEM manifolds are very constrictive vs. the DT headers and removing the cats will increase flow as well.
 

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1. Will these work on 2008 fj cruiser, or is it only for the 2010 models and up.
2. How difficult are these to install
3. if you have them, how long, and how are they/how are they holding up.

Thank you
.

There is now only one part number for all 4.0's. The new part number has
1 5/8" dia tubes and has two sets of mounting holes that will cover all years.

Easy to install, you reuse the factory metal manifold gaskets, but make sure you have new header to Y pipe gskts. Just make sure to spray your manifold studs etc, with penn fluid such as Blaster before hand.

I am upgrading from 1 1/2" primary pipes to the new larger Thorley's, and am waiting for new flanges and O2 bunges to be welded on.
Also I would suggest purchasing O2 sensor extensions to re-locate the O2's in the collector instead of in the center tube.
Good luck with the install.:cheers:
 

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UCON is an engine management system that can take over the fuel injection, comes with new timing gears and a new thermostat (you can find it on URD's website). It can optimize the performance of your FJC and the associated modifications you have made.

Yes, you put in a new O2 sensor in the DT headers to fool the ECU. The y-pipe will get rid of the second set of cats.
Ok thanks !
Unfortunately for now there is not much for 2010, I want a TRD compressor :(
 

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.

There is now only one part number for all 4.0's. The new part number has
1 5/8" dia tubes and has two sets of mounting holes that will cover all years.

Easy to install, you reuse the factory metal manifold gaskets, but make sure you have new header to Y pipe gskts. Just make sure to spray your manifold studs etc, with penn fluid such as Blaster before hand.

I am upgrading from 1 1/2" primary pipes to the new larger Thorley's, and am waiting for new flanges and O2 bunges to be welded on.
Also I would suggest purchasing O2 sensor extensions to re-locate the O2's in the collector instead of in the center tube.
Good luck with the install.:cheers:
Uh I do not know if I understood everything but the extension Urd must be plugged into the back on how you plug the headers?
From the beginning we had aillor loose, he had been connected upstream and we had the engine shek
 

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Free Doug Thorley Headers
Any 2013/ 2014 fj owners in Southern California . I just got off the phone with sAles at Doug Thorley 1800 347-8664. They are looking for a 2013 and a 2014 fj to make a set of long tube and shorty headers. Donor vehicle gets free headers!
Will some one please help us all out and go for this deal until someone goes there will be no headers from DT for the rest of us.
 

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so anyone who have done this mod b4 can help me with this ?

I want to know , how to install o2 sensors , does DT has the mount or cutting and welding needed ? and when u install o2 sensors that check engine failure will gone ? or better to use an urd 02 simulator ? I'm about to spend about 1.5K so I really need to be sure about this stuff.

Thanks in advance
 

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