New exhaust system for 04 4Runner v8

j4x4v8

j4x4v8

Member
Hey folks. I've got an 04 4Runner v8 4WD @ 210k miles. I have a cracked manifold (typical cold start ticking), and it's possible a manifold cat is going bad (P0430 code).

I want to get a new exhaust, if not for a bit more power, but to solve any issues that could arise from dying cats or a cracked manifold. After a fair bit of research this is what I came up with for my new exhaust system. I also am putting in a K&N intake 77-9022KP.

Edit: I have updated my parts list to be current as of 6/11/20

PARTS LIST

HEADERS - Doug Thorley THY-564-SS-C Short Tube Headers
UNIVERSAL CATS - QTY 2 - G-Sport #50025
Y-PIPE / REAR CAT - MagnaFlow #93655
CAT-BACK - MagnaFlow #15781 & Vibrant 1141 Resonator
AIR/FUEL RATIO SENSOR - QTY 2 - UPSTREAM - Denso 234-4138
OXYGEN SENSOR - DOWNSTREAM LEFT - Denso 234-4261
OXYGEN SENSOR - DOWNSTREAM RIGHT - Denso 234-4260
MANIFOLD GASKET - QTY 2 - OEM 1717350021
HEADER BOLT KIT - Stage 8 (8919) 10mm Header Bolt Kit

Questions I have..

1. I am unsure if those universal cats can be welded onto the DT headers. They do say they're for "rear". Can they be used as manifold cats, though? The DT's are meant to be welded to the factory cats, so I am wondering if this means I would need to buy the full manifold catalytic converters only to cut off the manifold part?

Edit: I ended up going with the same cats JONBOY345 used: G-Sport #50025

2. Does my vehicle have (2) cats in the rear or (1)? I am pretty sure I have only (1) cat in the rear, as this isn't/wasn't a California car. I recently read that apparently some 4Runners have (2) cats in the rear. It's confusing because I need the (4) total O2 sensors.. or so that is my understanding.

Edit: I have only (1) cat in the rear! See this Walker exhaust diagram that Ed_C posted.

3. Is there any other element of the exhaust system I may be missing? Except for the Y-Pipe, that would still be OEM I assume. I will be taking all the parts to my mechanic who is enlisting the help of his guy who does exhaust. My underbelly has surface rust, as it's been an east coast car it's entire life. Should I provide new nuts/hardware/gaskets? I am really not sure what all is needed because I have limited knowledge when it comes to exhaust systems.

Edit: Yes, there is a "front pipe" that connects from the drivers side cat to the Y-Pipe. I also added OEM Manifold Gaskets and a Stage 8 (8919) 10mm Header Bolt Kit to the parts list.

I would really appreciate any info or advice for my situation :yo:
 
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Nice little rabbit hole your about to go down.
First of all, does VA have sniffer or visual tests for emissions? This will dictate if you can use aftermarket CATs and what you can use going forward.

Second, do not buy sensors from bargain sites, there have been boot leg part stories for Denso imitations flooding the market.

3rd use this search parameter and multiple threads will pop up. Type in your question, such as -Doug thorley short tube headers CAT install- and put the red text in after your question.
site:toyota-4Runner.org/4th-gen-t4rs/
So it would look like this in the search bar:
Doug Thorley Short tube headers CAT install site:toyota-4Runner.org/4th-gen-t4rs/
You can use the text in red to learn anything about your T4R. Read till they bleed is my motto.

I can't answer all of your questions about CATs as I live where there are no inspections and have LT headers. I do think if the CATs you have listed are for the rear, they won't work on the manifolds.
The 2 upstream sensors are actually air/fuel ratio sensors and are technically not o2 sensors, although they look the same and bolt in ahead of the CATs. They read the mixture in real time and send the ECU this information so that it can adjust parameters to the Mass Air Flow sensor so that your engine will have properly mixed fuel and air going into the combustion chamber for ignition. The two down stream sensors are actually the o2 sensors and give the ECU a constant reading of the Catalytic converters state of health and operation.

The rear CATs are really only effective for cold start operation as some pollutants get by the upstream CATs for the first few minutes. Once the system warms up the upstream CATs start to work properly. Unless you have a visual inspection, I think these can be eliminated. Also with headers the flow rate changes and you may have to put spacers on the o2 sensors to get them to read the flow properly and eliminate the CELs that other people have had to deal with, myself included.

And lastly, Get some Visine or Clear Eyes. Hopefully someone else will chime in with a lot more than my limited knowledge of Short Tubes and Good Luck!!
 
Thanks for the info man! I made an edit to my original post, looking at a different universal cat which may work better.

4RunnerAquasport said:
does VA have sniffer or visual tests for emissions? This will dictate if you can use aftermarket CATs and what you can use going forward
Click to expand...

After a quick Google it appears if my CEL is off, I will pass yearly inspection. I'm not in a county that requires emissions inspections every 2 years, either. I'd like to keep the cats but other than that all I need is no CEL .

4RunnerAquasport said:
Second, do not buy sensors from bargain sites, there have been boot leg part stories for Denso imitations flooding the market.
Click to expand...

Good to know!

4RunnerAquasport said:
Unless you have a visual inspection, I think these can be eliminated.
Click to expand...

That makes sense. I'm worried about if I move to another, non-Cali/NY/Maine state could I get it registered without my rear cat?

4RunnerAquasport said:
Also with headers the flow rate changes and you may have to put spacers on the o2 sensors to get them to read the flow properly and eliminate the CELs that other people have had to deal with, myself included.
Click to expand...

Oh boy, what a rabbit hole indeed!!
 
'03-'04 exhaust

YTQjT11.gif
 
Ed_C said:
http://www.dougthorleyheaders.com/images/documents/THY-564-SS-INST-REV-C.pdf

The headers already have the sensor bungs. If you're having a Y-pipe made you'll need the bungs for the post-cat O2 sensors, they're easily sourced.
Click to expand...

:thanks: That makes sense with the sensors. Do you know if DT makes a Y-pipe for my 4Runner? Or is that Y-Pipe only for the long tube headers? I was planning to stick with my stock Y-Pipe unless there's a better option. I know Jason Burtman sells the Y-Pipe for the long tube.
 
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j4x4v8 said:
:thanks: That makes sense with the sensors. Do you know if DT makes a Y-pipe for my 4Runner? Or is that Y-Pipe only for the long tube headers? I was planning to stick with my stock Y-Pipe unless there's a better option. I know Jason Burtman sells the Y-Pipe for the long tube.
Click to expand...

Yes DT makes a Y-pipe. The Y-pipe works with the Stock Manifolds. Make sure you specify your year. DT re-did the one for the 03-04 and brought it up higher to Not hang below the Frame.
 
[MENTION=75868]Ed_C[/MENTION] and [MENTION=74494]Az4runnin[/MENTION] Thanks for jumping in! This subject takes a village.
There has been several of us who had fitment issues with the DT Y pipe. Mine didn't match up to the drivers side CAT. I think others echoed the same problem. I could not afford Headers at first, so I had the Y installed to the factory Manifold/Cats, and we had to modify the Y to make it work. Then of course when we installed the LTs a year later, we had to modify the Y again lol. But, if you are having Cats welded to the DT ST headers, the installer might be able to mock it all up and weld the CATs to properly mate up to the Y from the get go. Also of note: The upstream sensors (A/F ratio sensors) DO NOT need spacers, just the o2 sensors downstream if the evil CELs show up.

If your worried about moving to a state where you have to go back down the rabbit hole again, this Y pipe might be a better choice because the rear CAT is included, and it's over $100 cheaper than the DT Y.
MagnaFlow HM Grade Federal / EPA Compliant Direct-Fit Catalytic Converter
 
Last edited:
j4x4v8 said:
Hey folks. I've got an 04 4Runner v8 4WD @ 210k miles. I have a cracked manifold (typical cold start ticking), and it's possible a manifold cat is going bad (P0430 code).

I want to get a new exhaust, if not for a bit more power, but to solve any issues that could arise from dying cats or a cracked manifold. After a fair bit of research this is what I came up with for my new exhaust system. I also am putting in a K&N intake 77-9022KP.

PARTS LIST

HEADERS - Doug Thorley THY-564-SS-C Short Tube Headers
UNIVERSAL CATS - QTY 2 - MagnaFlow #51005
Y-PIPE - Doug Thorley 89253
INTERMEDIATE PIPES, MUFFLER, TAILPIPE - MagnaFlow #15781
CATALYTIC CONVERTER - REAR - MagnaFlow #93655
MANIFOLD GASKET - QTY 2 - OEM 1717350021
OXYGEN SENSOR - QTY 2 - UPSTREAM - Denso 234-4138
OXYGEN SENSOR - DOWNSTREAM LEFT - Denso 234-4261
OXYGEN SENSOR - DOWNSTREAM RIGHT - Denso 234-4260
HEADER BOLT KIT - Stage 8 (8919) 10mm Header Bolt Kit

May need even if I keep cats(?) BLOX Racing Check Engine Light Eliminator Adapter BLO BXFL-00108-SS

Questions I have..

1. I am unsure if those universal cats can be welded onto the DT headers. They do say they're for "rear". Can they be used as manifold cats, though? The DT's are meant to be welded to the factory cats, so I am wondering if this means I would need to buy the full manifold catalytic converters only to cut off the manifold part? ($$$) See Edit

2. Does my vehicle have (2) cats in the rear or (1)? I am pretty sure I have only (1) cat in the rear, as this isn't/wasn't a California car. I recently read that apparently some 4Runners have (2) cats in the rear. It's confusing because I need the (4) total O2 sensors.. or so that is my understanding.

3. Is there any other element of the exhaust system I may be missing? Except for the Y-Pipe, that would still be OEM I assume. I will be taking all the parts to my mechanic who is enlisting the help of his guy who does exhaust. My underbelly has surface rust, as it's been an east coast car it's entire life. Should I provide new nuts/hardware/gaskets? I am really not sure what all is needed because I have limited knowledge when it comes to exhaust systems.

I would really appreciate any info or advice for my situation :yo:

EDIT: Just realized the universal cats I bought are 2.5" inlet/outlet and the headers are 2.25". I found this post by [MENTION=102822]JONBOY345[/MENTION] where he used G-Sport high performance cats. I wouldn't mind getting those, but will that keep my check engine light off? Also how do the O2 sensors attach? I think I'll get MagnaFlow #51065 instead, which are 2.25", and have a spot for O2 sensors. Or do my O2 sensors not attach that way?

EDIT 2: MagnaFlow 99205HM might be the right one after seeing this post, however their model was a 05 v8.
Click to expand...

I have an 07, so slightly different engine - but I can give you what I learned when sourcing my parts (I didn't do the install myself).

-Cats - Magnaflow 59956 (2.5" inlet/outlet).
-Blox Spacers - I DID need those to eliminate the check engine light.
-With 210k miles on the east coast, definitely recommend AT LEAST the stage 8 bolt kit that you've mentioned - good piece of mind. That is what I got as well.

Good luck! It was a bit of a pain sourcing the parts and finding someone to install for me, but well worth it in the end!
 
j4x4v8 said:
Hey folks. I've got an 04 4Runner v8 4WD @ 210k miles. I have a cracked manifold (typical cold start ticking), and it's possible a manifold cat is going bad (P0430 code).

I want to get a new exhaust, if not for a bit more power, but to solve any issues that could arise from dying cats or a cracked manifold. After a fair bit of research this is what I came up with for my new exhaust system. I also am putting in a K&N intake 77-9022KP.

PARTS LIST

HEADERS - Doug Thorley THY-564-SS-C Short Tube Headers
UNIVERSAL CATS - QTY 2 - MagnaFlow #51005
Y-PIPE - Doug Thorley 89253
INTERMEDIATE PIPES, MUFFLER, TAILPIPE - MagnaFlow #15781
CATALYTIC CONVERTER - REAR - MagnaFlow #93655
MANIFOLD GASKET - QTY 2 - OEM 1717350021
OXYGEN SENSOR - QTY 2 - UPSTREAM - Denso 234-4138
OXYGEN SENSOR - DOWNSTREAM LEFT - Denso 234-4261
OXYGEN SENSOR - DOWNSTREAM RIGHT - Denso 234-4260
HEADER BOLT KIT - Stage 8 (8919) 10mm Header Bolt Kit

May need even if I keep cats(?) BLOX Racing Check Engine Light Eliminator Adapter BLO BXFL-00108-SS

Questions I have..

1. I am unsure if those universal cats can be welded onto the DT headers. They do say they're for "rear". Can they be used as manifold cats, though? The DT's are meant to be welded to the factory cats, so I am wondering if this means I would need to buy the full manifold catalytic converters only to cut off the manifold part? ($$$) See Edit

2. Does my vehicle have (2) cats in the rear or (1)? I am pretty sure I have only (1) cat in the rear, as this isn't/wasn't a California car. I recently read that apparently some 4Runners have (2) cats in the rear. It's confusing because I need the (4) total O2 sensors.. or so that is my understanding.

3. Is there any other element of the exhaust system I may be missing? Except for the Y-Pipe, that would still be OEM I assume. I will be taking all the parts to my mechanic who is enlisting the help of his guy who does exhaust. My underbelly has surface rust, as it's been an east coast car it's entire life. Should I provide new nuts/hardware/gaskets? I am really not sure what all is needed because I have limited knowledge when it comes to exhaust systems.

I would really appreciate any info or advice for my situation :yo:

EDIT: Just realized the universal cats I bought are 2.5" inlet/outlet and the headers are 2.25". I found this post by [MENTION=102822]JONBOY345[/MENTION] where he used G-Sport high performance cats. I wouldn't mind getting those, but will that keep my check engine light off? Also how do the O2 sensors attach? I think I'll get MagnaFlow #51065 instead, which are 2.25", and have a spot for O2 sensors. Or do my O2 sensors not attach that way?

EDIT 2: MagnaFlow 99205HM might be the right one after seeing this post, however their model was a 05 v8.
Click to expand...


Just wanted to chime in and say that the GESI cats I have are awesome. I had my mechanic weld on a SS 3 bolt flange to the DT Headers and then to the top of the GESI cats as well. So that if in the future for whatever reason I need to replace the cats, it's a simple process.

I did the GESI cats, DT ypipe, and Magnaflow cat back and love it. No check engine lights either...

The GESI cats are pricey, but they'll outlast the truck for sure... Keep your factory parts and sell them to RRcats.com for about $350 back (according to market prices about a month ago when I sent mine out).
 
Thanks everyone for your input! This is helping me tremendously. :happy:

4RunnerAquasport said:
[MENTION=75868]Ed_C[/MENTION] and [MENTION=74494]Az4runnin[/MENTION]But, if you are having Cats welded to the DT ST headers, the installer might be able to mock it all up and weld the CATs to properly mate up to the Y from the get go.
Click to expand...

4RunnerAquasport said:
If your worried about moving to a state where you have to go back down the rabbit hole again, this Y pipe might be a better choice because the rear CAT is included, and it's over $100 cheaper than the DT Y.
MagnaFlow HM Grade Federal / EPA Compliant Direct-Fit Catalytic Converter
Click to expand...

Wow, that Y pipe you sent is what I already had on my parts list, but because of my limited exhaust knowledge, I thought that it wasn't the same Y-pipe that goes to my upstream cats. I thought it went `Headers -> Upstream Cats -> OEM Y-Pipe -> Some Exhaust Piping -> Rear Cat -> ??`

I don't know what I thought. But this makes so much more sense now. I agree that since I'm trying to not remove any cats I should ditch the DT Y-pipe and use that MagnaFlow.

JONBOY345 said:
The GESI cats are pricey, but they'll outlast the truck for sure... Keep your factory parts and sell them to RRcats.com for about $350 back (according to market prices about a month ago when I sent mine out).
Click to expand...

That's great to know! If I don't use the DT Y-Pipe, and use this MagnaFlow #93655 Y-pipe/cat like [MENTION=119302]4RunnerAquasport[/MENTION] mentioned, is it even more pointless to get the GESI cats? Because the Magnaflow cat built into the Y-pipe will act as a bottleneck?

I'm really looking at getting the GESI's, not because I like throwing money away, but because they do seem solid. Like you said, buy once, cry once. :crybaby:
 
j4x4v8 said:
Thanks everyone for your input! This is helping me tremendously. :happy:





Wow, that Y pipe you sent is what I already had on my parts list, but because of my limited exhaust knowledge, I thought that it wasn't the same Y-pipe that goes to my upstream cats. I thought it went `Headers -> Upstream Cats -> OEM Y-Pipe -> Some Exhaust Piping -> Rear Cat -> ??`

I don't know what I thought. But this makes so much more sense now. I agree that since I'm trying to not remove any cats I should ditch the DT Y-pipe and use that MagnaFlow.



That's great to know! If I don't use the DT Y-Pipe, and use this MagnaFlow #93655 Y-pipe/cat like [MENTION=119302]4RunnerAquasport[/MENTION] mentioned, is it even more pointless to get the GESI cats? Because the Magnaflow cat built into the Y-pipe will act as a bottleneck?

I'm really looking at getting the GESI's, not because I like throwing money away, but because they do seem solid. Like you said, buy once, cry once. :crybaby:
Click to expand...
OK I think I was wrong about the cost, sorry about that. There doesn't seem to be ANY cheap alternatives to do this legally. And it appears there are 4 CATs total on our trucks I just couldn't remember. [MENTION=212541]doofenshmirtz[/MENTION] put the magnaflow rear CATs on his with the LT headers. His post is linked below. You would still have to have the primary CATs welded on your STs to be compliant. Like I said Read till they bleed lol. You should give Magnaflow a call and make sure of all this before pulling the trigger.
https://www.toyota-4runner.org/3414058-post28.html
 
I believe doof has a '05-on, OP's stock system has a single cat after the Y instead of one each after the manifolds.

Here's the breakdown using Walker exhaust parts...

0WclEtD.png


The universal replacement for that Y-pipe converter is a the same ones Walker uses for their 05-on Y, except it uses two.
 
j4x4v8 said:
The pipe labeled “front pipe” in that diagram is piping I would still need to buy, right? I tried searching it doesn’t seem like there’s a part number for it. Something like this, and cut/weld to fit? MagnaFlow 3 in 1 Multi Bend Stainless Steel Pipe
Click to expand...

Looks like you reuse the existing OEM pipe, in the other illustration I posted it's called the "Exhaust Front Pipe Assy". Walker doesn't offer a replacement part but Rock Auto lists two brands that do

Xb0I3lU.png


Here's a thread about the 2003-2004 style Magnaflow Y-pipe by the way Worst Y-pipe Design ever - 2003 V8 4runner

I saved a photo from the thread before Photobucket decided to charge people - OEM setup vs. Magnaflow
5k1nVfw.jpg
 
Updated Parts List

Big thanks to everyone who has chimed in helping me figure this thing out :hug:

[MENTION=102822]JONBOY345[/MENTION] I ended up going with the same cats you got.

I have updated my original post to reflect my updated parts list:

HEADERS - Doug Thorley THY-564-SS-C Short Tube Headers
UNIVERSAL CATS - QTY 2 - G-Sport #50025
Y-PIPE / REAR CAT - MagnaFlow #93655
CAT-BACK - MagnaFlow #15781
AIR/FUEL RATIO SENSOR - QTY 2 - UPSTREAM - Denso 234-4138
OXYGEN SENSOR - DOWNSTREAM LEFT - Denso 234-4261
OXYGEN SENSOR - DOWNSTREAM RIGHT - Denso 234-4260
MANIFOLD GASKET - QTY 2 - OEM 1717350021
HEADER BOLT KIT - Stage 8 (8919) 10mm Header Bolt Kit
Click to expand...

I believe I have found an exhaust shop who is willing to do the work. I will keep everyone posted with updates!

Ed_C said:
Looks like you reuse the existing OEM pipe, in the other illustration I posted it's called the "Exhaust Front Pipe Assy".
Click to expand...

After talking to the exhaust guy, I won't need to buy that "Front Pipe" / "Exhaust Front Pipe Assy" which I believe would be the only thing left OEM, but they said they are more than able to put a new stainless steel pipe in there, including the hole for the O2 sensor.
 
j4x4v8 said:
Big thanks to everyone who has chimed in helping me figure this thing out :hug:

I believe I have found an exhaust shop who is willing to do the work. I will keep everyone posted with updates!

After talking to the exhaust guy, I won't need to buy that "Front Pipe" / "Exhaust Front Pipe Assy" which I believe would be the only thing left OEM, but they said they are more than able to put a new stainless steel pipe in there, including the hole for the O2 sensor.
Click to expand...

Excellent! The shop-fabbed will probably have smoother bends, those two listed in Rock Auto are all crinkled.
 
New Exhaust Installed

Got my 4Runner back from the exhaust shop :tongue:

It sounds so much better, especially paired with the K&N!

I do get the droning at ~2100 RPM which is unfourtnate for going around corners and stop/go traffic, and also when going 70-80MPH. But everywhere else it sounds perfect. I'm willing to bet other people wouldn't even consider what I am talking about as 'droning' at all.

Here's what my mechanic said about the headers:

  • 2 studs broke off in head and had to be extracted
  • Header holes not lining up with head
  • Had to remove headers 4 times on drivers side to get all studs to start
  • Passenger side header also had fit issues

He did the install solo to my knowledge. He opted to not put the locks on the stage 8 header bolts until after I drive it a few hundred miles and it needs to be re-torqued.

I am getting a dreaded CEL: P0154 - O2 Sensor Circuit No Activity Detected Bank 2 Sensor 1. That's the upstream A/F sensor for the passengers side header I believe. So I don't think I need the O2 spacers, which are for downstream (as [MENTION=119302]4RunnerAquasport[/MENTION] pointed out). I'm hoping the sensor just needs to be wiggled or something.. maybe I got a bad Denso? Not sure.

Video 1 - Startup / idle sound - YouTube

Video 2 - Phone on dash; all windows down - YouTube

Hey [MENTION=102822]JONBOY345[/MENTION] do you have that Vibrant Resonator right before the Magnaflow muffler? How's the sound? Is it just as loud everywhere else for the most part, and the resonator gets rid of the droning? Would love your thoughts since I realized we have a pretty similar exhaust setup minus the Y-Pipe.

P.S. I sold my old cats to RRCats, $103/ea for the manifold cats and $73 for the Y-Pipe cat.

Ed_C said:
Excellent! The shop-fabbed will probably have smoother bends, those two listed in Rock Auto are all crinkled.
Click to expand...

Pictures of the welds & underside coming very soon :)
 
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