97 LX450 / 80 Series - Inside Frame Rail Exhaust Using 105 Series Downpipe

[bonestock]

The time has come, the parts are starting to arrive. I am deleting my OEM Cats and moving the whole exhaust inside the frame rails. Ordered the 105 Series Down Pipe from Partsouq (Part# 17401-66140) based on this thread. Ordered a small universal Cat from Summit found here and weld-in bungs found here. I am working with a local exhaust shop to fit everything.

Expected improvements in order of importance
1.) Stop bashing exhaust on rock when wheeling
2.) Eliminate fitment issue with PEM Cats and WKOR sliders

3.) Performance improvement

More to follow.

 

[bonestock]

This thread was also helpful (mostly!)

Custom Inside the Frame Exhaust using 105 header

I always hated how the factory exhaust placed the cats outside the frame and looped under. For such a beast of an offroad machine it always felt like a dumb oversight that I wanted to change. After smashing my cat on my last wheeling trip, I decided I needed to reroute the exhaust this time...

forum.ih8mud.com

 

[Tennessee80]

This looks like it's going to be an awesome improvement!!

 

[JoeCova]

My exhaust rattles and whistles so, I’m on the edge of replacement. Was gonna go with a 95+ downpipe and cat then run and exhaust dump behind the tcase.

I have a 94 so I’ll get creative. I’ll look into the 105

 

[bonestock]

Thanks for the reminder to update. I went by the selected muffler shop local to me and talked through the disassembly of my armor so that the install could flow correctly. I reviewed all parts in hand (105 down pipe, universal catalytic converter and enough OEM hardware to replace everything on a stock setup). Guy claimed to understand the process, know Toyotas and be ready to get it done.

Pretty excited here about the prospect of a permanent solution using OEM exhaust manifolds and downpipe.

Got a group trip in about 3 weeks and want to have the exhaust and a valve adjustment completed by then.

Updates to follow.

 

[bonestock]

Got the 105 downpipe installed and only had to drill/tap one of the manifold studs. Seems a bit loud but we will see how it sits.

Had to remove the heat shield from the down pipe to avoid clearance issue in the passenger seat.

More to follow.

 

[CrabCake]

Nice progress...and it's great to have a shop that is actually competent (and willing!) to do this type of project. I have an exhaust shop here in MD that has done several projects like this for me on various cars. I never understood why they looped the exhaust into an obvious bash point on the later trucks...I have a '94, so at least no issues there for me, but still nice to see what you are working on that is pertinent to so many in this forum.

 

[voodu3]

What muffler are you going to use?

 

[bonestock]

What muffler are you going to use?

It was something that muffler shop had. I think it came off a BMW? There isn't much room to add anything large. May need to rethink it a bit from the cat back.

 

[bonestock]

From the noticeable side. Pretty sure I need to add a resonator to the mix.

Still need to weld in the o2 sensor bungs. Tough time of year to make room for the ol girl.

 

[mudgudgeon]

There isn't much room to add anything large

There's a stack of room IMHO

This was a 3" system for my 105 series. I did similar under an 80.

Muffler is a full flow 6x9x16" in a 3" system.
Rear muffler was 6x14 3" from memory.

Full offset muffler at the front would have packaged in easier. I used a half offset.
Could have increased the length and thicknesses too.

This was for a turbo diesel, but with full flow 3" system, it was very quiet

 

[bonestock]

There's a stack of room IMHO

This setup is premium looking. I opted for a more methy, bubble gum approach to welding. Primary goals have all been achieved. Just need to get the O2 sensor bungs welded up and hit the trails to see how much better my life actually is. Not a ton of time to spend between now and EOY. Thanks for chiming in!!

 

[mudgudgeon]

Many ways to skin a cat, as always.

Post pics of your finished result?

 

[bonestock]

For sure will post. Want to get the sensor extensions made and the sensors installed, clear codes and see how she sounds. The horsepower increase has been noticeable but not game changing.

 

[JoeCova]

There's a stack of room IMHO

View attachment 3796211View attachment 3796212

This was a 3" system for my 105 series. I did similar under an 80.

Muffler is a full flow 6x9x16" in a 3" system.
Rear muffler was 6x14 3" from memory.

Full offset muffler at the front would have packaged in easier. I used a half offset.
Could have increased the length and thicknesses too.

This was for a turbo diesel, but with full flow 3" system, it was very quiet

How is this routed on the 80?

 

[mudgudgeon]

How is this routed on the 80?

Stock exhaust path on a diesel 80 is basically the same as gas.
It passes through front wheel well, outside the frame, then back over the frame to a large muffler, then inside the frame the rest of the way back. All of them have the pipe crushed flat where it passes over the rear cross member.

No idea what Toyota was thinking.

There's room for a full 3" system on the inside of the frame all the way front to back.
It's a bit tight getting past the transfer, but with the right bends it's doable.

I built a very similar system for my diesel 80

 

[JoeCova]

Stock exhaust path on a diesel 80 is basically the same as gas.
It passes through front wheel well, outside the frame, then back over the frame to a large muffler, then inside the frame the rest of the way back. All of them have the pipe crushed flat where it passes over the rear cross member.

No idea what Toyota was thinking.

There's room for a full 3" system on the inside of the frame all the way front to back.
It's a bit tight getting past the transfer, but with the right bends it's doable.

I built a very similar system for my diesel 80

Ya I was laying under the frame yesterday and I think I can run that 105 downpipe then straight down the frame. I’m just debating whether to run an OEM cat or just pick up an aftermarket like this, or none at all

 

[mudgudgeon]

Ya I was laying under the frame yesterday and I think I can run that 105 downpipe then straight down the frame. I’m just debating whether to run an OEM cat or just pick up an aftermarket like this, or none at all

There's some pics under my 105 showing my system in place, starting here . . .

Rolling the dice - slow moving turbo HZJ105 project - https://forum.ih8mud.com/threads/rolling-the-dice-slow-moving-turbo-hzj105-project.967105/post-10790602

The first section of mine is 4".

There's two spots clearances are tight. Getting past the transfer case, and getting over the frame above the rear diff.

A little bump up and back down could help get past the transfer case.

 

[JoeCova]

This may be a dumb question but why do the 95+ have two cats? I get the 94 because the exhaust is split but why two in line?

 

[bonestock]

O2 sensors plumbed. Just need to extend my harness to match the new locations.

Edit: ordered these to make my own extensions.