Doug Thorley headers...successful install stories.

[DoctorPopcorn]

I ended up going with the 05+ Long Tube headers. Probably the best option for my case.

On a related note, I went with the URD O2 simulator and with a little adjusting I was able to eliminate the ‘catalytic converter efficacy’ code. But only since installing the DT headers I sometimes get a P0172 & P0175 code ‘System too rich bank 1 & 2’

Hey, thanks for the quick response, Dabsalot, and 05+ LTs make the most sense. That's also super helpful to note you went with the URD O2 sim and the intermittent rich codes. Hope the LTs are treating you well & you're enjoying them.

The O2 sim seems like the best route, rather than monkeying with rear O2 spacers, but I've seen and heard URD's stock is off & on. I think they used to have a plug & play specifically for the 4th gens, then had a universal sim, and now I can only find the O2 sim as a purchase option with their headers.

 

[JONBOY345]

Please know that I haven't replaced my headers with DT, but with all of the info that I've poured over from a ton of super helpful folks on T4R, I can offer this:

DT longtube headers (deleting upstream cats, connect straight to the Y pipe): you will either need an O2 simulator (URD sometime has one on their website), or space out your downstream 02 sensors with something like this. With LT headers and deleting the upstream cats, can't recall anyone getting around either of these 2 options.
.

Great info, just wanted to toss out another option in addition to the ones you listed.

I've recently moved to LT headers from ST headers due to less than stellar work by my mechanic's fabricator. In doing so, I wanted to retain catalytic converters because tread lightly. If I'm rolling through a national forest and stinking up the place, I'm not being a very good steward of our resources or a very good neighbor to those I'm passing or near...

Anyways, here's what I did.

I moved the GSport cats from their original location in front of the y-pipe, to the DT Y-pipe. Specifically, I removed the resonators in the y-pipe and replaced them with the cats. I plugged the O2 sensor bung just behind the flange of the DT y-pipe and had my fabricator weld in new O2 bungs behind the cats that are now installed in the y-pipe for the downstream O2 sensors.

It does take a little bit longer for the cats to warm up and start working, but I've not gotten any codes since completing the work. Few pictures showing what I did in case the above is clear as mud. lol.

Showing the DT y-pipe with O2 bung plugged and comparing the size of the resonator to GSport Cat.

Driver side with GSport cat replacing resonator and new O2 bung for downstream OS sensor.

Passenger side finished as above.

One of the most interesting things I noticed, is that now at about 70 MPH, I'm running 100-150 fewer RPM than before when I had the short tube headers.

 

[DoctorPopcorn]

Great info, just wanted to toss out another option in addition to the ones you listed.

I've recently moved to LT headers from ST headers due to less than stellar work by my mechanic's fabricator. In doing so, I wanted to retain catalytic converters because tread lightly. If I'm rolling through a national forest and stinking up the place, I'm not being a very good steward of our resources or a very good neighbor to those I'm passing or near...

Anyways, here's what I did.

I moved the GSport cats from their original location in front of the y-pipe, to the DT Y-pipe. Specifically, I removed the resonators in the y-pipe and replaced them with the cats. I plugged the O2 sensor bung just behind the flange of the DT y-pipe and had my fabricator weld in new O2 bungs behind the cats that are now installed in the y-pipe for the downstream O2 sensors.

It does take a little bit longer for the cats to warm up and start working, but I've not gotten any codes since completing the work. Few pictures showing what I did in case the above is clear as mud. lol.

Showing the DT y-pipe with O2 bung plugged and comparing the size of the resonator to GSport Cat.


Driver side with GSport cat replacing resonator and new O2 bung for downstream OS sensor.

Passenger side finished as above.


One of the most interesting things I noticed, is that now at about 70 MPH, I'm running 100-150 fewer RPM than before when I had the short tube headers.

Jonboy, that's a sweet setup, and another slick way to go! Agreed on removing cats vs being a good steward, but that's a whole other discussion. Also pretty sweet that you're not throwing any codes, even during warmup. I've got the URD Y-pipe and would consider this same setup if I were doing DT LTs, BUT, I had my driver stock DS cat cutout last September by cat thieves. We've got a 1-stall garage that houses the 3rd gen, and the 4th gen and fiancé's Crosstrek sit out in the elements on the parking pad on the alley. So, I settled on the URD Y-pipe with no resonators, because I thought cat thieves might come back and cut the DT Y-pipe, thinking the resonators are cats, like the stock pipe.

This is a great option for folks with LTs that don't mind a set of cats in their Y-pipe, no other monkeying with fooling the DS 02s, and don't have to worry about their cats getting cut out.

 

[JONBOY345]

Jonboy, that's a sweet setup, and another slick way to go! Agreed on removing cats vs being a good steward, but that's a whole other discussion. Also pretty sweet that you're not throwing any codes, even during warmup.

From what I can tell, it may take just a few more minutes for them to warm up. It's nothing significant in the grand scheme of things. From start to them being at operating temp isn't more than 5 minutes.

 

[4RunnerAquasport]

Bump, hopefully good fortune for the 2UZ owners.

 

[Az4runnin]

Bump, hopefully good fortune for the 2UZ owners.

I wonder what part of Arizona

 

[Gamblin4Runner]

No cats

Question 1...did you change out the cats?

Eliminated all four entirely

Question 2...did you use an O2 simulator or spacer?

Sure didn't. Got a YotaWerx tune that took care of all of it (I don't have emissions testing to worry about)

Question 3...did you put a cat back exhaust system on?
Gibson Elite Exhaust:
Gibson Performance Exhaust 618815B Gibson Elite Series Cat-Back Exhaust Systems | Summit Racing

Here is what she sounds like:

4.7L V8 4Runner | 2UZ-FE | Doug Thorley Headers & Gibson Elite Exhaust - YouTube

 

[cyclingtrav]

Finished Install of Shortie Headers, Successful California Smog

Hey y'all- just finished a detailed write up of my shortie header install and California smog experience. Check it out here:

Doug Thorley Shortie Headers 4.7L V8 - My Experience w/ Install & CA Smog

TL;DR- my mechanic is a gangster (shout out to Mark @ Auto Tech in San Ramon) and successfully installed my DT headers. I went on to get SMOG cert and registration completed. Be sure to replace things like the air tube gaskets, O2 sensors, and motor mounts.

 

[parsky1]

Would this job be any easier with the Struts out? I gotta do the suspension anyway. Also, can anyone confirm if the magnaflow high flow cats cause a CEL with the shorties?

 

[Zero0575]

Would this job be any easier with the Struts out? I gotta do the suspension anyway. Also, can anyone confirm if the magnaflow high flow cats cause a CEL with the shorties?

Yes, you will get a CEL. Easy to fix by adding O2 spacers to the downstream sensors. I had to stack 2 spacers to get rid of CEL.

 

[Coolbeans_T4r]

Follow Up on this set up after 4 years

Great info, just wanted to toss out another option in addition to the ones you listed.

I've recently moved to LT headers from ST headers due to less than stellar work by my mechanic's fabricator. In doing so, I wanted to retain catalytic converters because tread lightly. If I'm rolling through a national forest and stinking up the place, I'm not being a very good steward of our resources or a very good neighbor to those I'm passing or near...

Anyways, here's what I did.

I moved the GSport cats from their original location in front of the y-pipe, to the DT Y-pipe. Specifically, I removed the resonators in the y-pipe and replaced them with the cats. I plugged the O2 sensor bung just behind the flange of the DT y-pipe and had my fabricator weld in new O2 bungs behind the cats that are now installed in the y-pipe for the downstream O2 sensors.

It does take a little bit longer for the cats to warm up and start working, but I've not gotten any codes since completing the work. Few pictures showing what I did in case the above is clear as mud. lol.

Showing the DT y-pipe with O2 bung plugged and comparing the size of the resonator to GSport Cat.

Driver side with GSport cat replacing resonator and new O2 bung for downstream OS sensor.

Passenger side finished as above.

One of the most interesting things I noticed, is that now at about 70 MPH, I'm running 100-150 fewer RPM than before when I had the short tube headers.

I’m really stoked I found your exact post. I just wanted to ask a follow up of how this set up has treated you now that’s it been 4 years from 2021.

My situation is that I have had DT LT headers and the DT Y-pipe w/ resonators stored in my storage for the past 2 years - having put the project on the back burner for sometime now.

In an exact thought process as you described and from what was explained to me, I came to the conclusion having 2 cats was good - so I second guessed, should I buy the ST headers instead and have cats welded on (in going about a set up that would be “most-logical”) but then go through the whole hassle of selling the DT OR keep what I have and have welded in news cats to the DT Y-pipe in place of the resonators. It wouldn’t be a waste to have the DT Y-pipe all cut up and modified?

Anywho, my thought process now is that it would be cool to keep the LT Headers and have welded in cats in the Y-Pipe.. as way to meet in the middle, as you described in this post. I really liked to hear that you had experience with both configuration set ups of ST and LT.

Could you share with me your long term thoughts of pros & cons for both set ups?

If its just running slightly longer warm up times (but ultimately the truck is the same once at operating temps) - results in lower rpms at higher speeds even, and no CEL from your set up, sounds like a total green light for me!

LTs are more power than the ST (even if not significant). No issues with running too lean or too rich?


Also btw, I finally made my first account of this forum just so I could respond. Great info man, thanks


2006 V8 4Runner

 

[JONBOY345]

I’m really stoked I found your exact post. I just wanted to ask a follow up of how this set up has treated you now that’s it been 4 years from 2021.

My situation is that I have had DT LT headers and the DT Y-pipe w/ resonators stored in my storage for the past 2 years - having put the project on the back burner for sometime now.

In an exact thought process as you described and from what was explained to me, I came to the conclusion having 2 cats was good - so I second guessed, should I buy the ST headers instead and have cats welded on (in going about a set up that would be “most-logical”) but then go through the whole hassle of selling the DT OR keep what I have and have welded in news cats to the DT Y-pipe in place of the resonators. It wouldn’t be a waste to have the DT Y-pipe all cut up and modified?

Anywho, my thought process now is that it would be cool to keep the LT Headers and have welded in cats in the Y-Pipe.. as way to meet in the middle, as you described in this post. I really liked to hear that you had experience with both configuration set ups of ST and LT.

Could you share with me your long term thoughts of pros & cons for both set ups?

If its just running slightly longer warm up times (but ultimately the truck is the same once at operating temps) - results in lower rpms at higher speeds even, and no CEL from your set up, sounds like a total green light for me!

LTs are more power than the ST (even if not significant). No issues with running too lean or too rich?


Also btw, I finally made my first account of this forum just so I could respond. Great info man, thanks


2006 V8 4Runner

Hey man, welcome to the forum.

So, unfortunately, I did start seeing some CEL for P420 and P430 with my setup. It will happen almost exclusively after the truck has been running for a while, I turn the truck off for a a short duration, then get back in and immediately run it pretty hard.

Typical example of this would be after stopping at a rest area on a road trip. Once back in the truck and after accelerating up to speed, the CEL would pop on. I have a head unit with an Idatalink Maestro installed, so I could clear those codes from the head unit without any issue.

I did run some spark plug defoulers for a while, and that made the issue go away.

I recently started testing some Catalytic Converter mat style heat shielding, as I think the codes are caused in that scenario due to the cats cooling faster than OEM, thus on restart, the ECU going into closed loop due to higher water temps on restart vs cold start. This has certainly helped reduce the rate of CELs on warm starts, but hasn't totally eliminated them. Next step is to test some clamp on style heat shields that are made of sheet metal to see if that makes a difference too.

But, other than just tinkering for my own curiosities sake, the setup in my OP with the addition of the Spark Plug Defoulers on the down stream O2 sensors is the set it and forget it option. Long term fuel trims are good. Low single digits, with .5-1.0% difference bank to bank.

Once it's warmed up, exhaust smells "clean", no rotten eggs smell, etc.. Under hard acceleration and the back window down, I can smell the engine, but it smells like any other OEM vehicle under heavy load.

My next step is a tune, so will let you know how that goes when I get it done.

 

[VortepJ]

Interesting thread. Thanks for the info!

 

[mafern21]

HP and Torque Increase

For those who installed the Thorley short pipes, what is the average HP and torque increase if any?

 

[mafern21]

HP and Torque Increase

For those who installed the Thorley short pipes, what is the average HP and torque increase if any?