OTT Downpipe for Hybrid 4Runner arrived

[jrdees916]

Great question I am actually sending mine back to wrapped with the heat shield material. They didn’t have that available when I purchased it but now they do.

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[tipsyjam]

Great question I am actually sending mine back to wrapped with the heat shield material. They didn’t have that available when I purchased it but now they do.

Sounds like a good move.

Sorry for hijacking your thread a bit with the questions. Your post is the first I've seen where someone actually received one in person and I got curious as to why certain OEM features were omitted.

 

[jrdees916]

No you’re good. Ask away

 

[JustDSM]

Actually have a couple more questions - it looks like the OEM downpipe is supported at about 3/4 of the pipe length with a "manifold stay" bracket that bolts onto the engine or transmission or something in that area. It looks like there is something similar on your GR pipe, but no support bracket for the 4Runner/Tacoma one.

How is the downpipe supported? It seems like it just hangs from the turbo and then uses the exhaust front pipe as support. Not sure this is the case but wanted to confirm as I am just looking back and forth at pictures of an OEM downpipe and this new one.

Is there also a solution from you guys that includes a support bracket for this new downpipe?

Good question!

Before getting into the Tacoma/4Runner/LC250 design specifically, just to clarify: the GR Corolla downpipe shown in some photos was not built by our fabricator. Our fabricator added shielding to an existing pipe provided to us for a project. So that example isn’t directly comparable from a structural design standpoint.

You’re absolutely correct that the OEM downpipe utilises a “manifold stay” support bracket. Toyota typically uses those stays because the factory pipe is quite heavy, incorporates a ball-and-socket junction, and does not include an integrated flex section near the point it fastens to the exhaust section. That combination increases bending moment and cyclic loading at the turbo flange and downstream connections, which justifies the additional support.

Our design takes a different approach. A few key factors influenced the decision to omit the stay bracket:

1.) Significant mass reduction
The OEM downpipe is comparatively heavy due to its construction and catalyst packaging. Our unit substantially reduces overall mass. The Lower mass directly reduces static load and bending moment at the turbo outlet flange.

2.) Addition of a flex coupling
We utilise and incorporate a flex section into the design. This allows the system to absorb engine movement, torsional vibration, and thermal expansion without transmitting that stress directly into the turbo flange or downstream exhaust. The OEM design relies more heavily on rigid geometry plus the stay to manage those loads.

3.) Elimination of the ball-socket junction
The ball and socket junction used in the factory configuration can create off-axis loading and localised stress during dynamic operation. Eliminating that junction and pairing the system with a flex section reduces stress concentration and cyclic fatigue loading at the ends of the pipe.

4.) Overall length and geometry
The GR Corolla downpipe (referenced above) is significantly longer, which increases its moment arm relative to the turbo flange. That length/geometry makes a stay more beneficial in that application.
The 2.4T Tacoma/4Runner/LC250 downpipe is notably shorter. With the reduced mass, shorter lever arm, and integrated flex section, the structural loading profile is materially different.

When we evaluated the system from a load-path and fatigue perspective, with the shorter length + reduced mass + controlled compliance via flex section, the additional stay bracket is no longer required for the intended application.

No, we do not currently offer an additional support bracket for this pipe, as it was intentionally engineered without one in accordance with the above criteria.

And just to be transparent, we are not a hard-parts manufacturer by trade. We specialize in Toyota ECU calibration. For this project, we partnered with a high end local exhaust fabricator who handled the mechanical design and engineering, and the stay omission was a deliberate design decision based on application analysis.

 

[tipsyjam]

Good question!

Before getting into the Tacoma/4Runner/LC250 design specifically, just to clarify: the GR Corolla downpipe shown in some photos was not built by our fabricator. Our fabricator added shielding to an existing pipe provided to us for a project. So that example isn’t directly comparable from a structural design standpoint.

You’re absolutely correct that the OEM downpipe utilises a “manifold stay” support bracket. Toyota typically uses those stays because the factory pipe is quite heavy, incorporates a ball-and-socket junction, and does not include an integrated flex section near the point it fastens to the exhaust section. That combination increases bending moment and cyclic loading at the turbo flange and downstream connections, which justifies the additional support.

Our design takes a different approach. A few key factors influenced the decision to omit the stay bracket:

1.) Significant mass reduction
The OEM downpipe is comparatively heavy due to its construction and catalyst packaging. Our unit substantially reduces overall mass. The Lower mass directly reduces static load and bending moment at the turbo outlet flange.

2.) Addition of a flex coupling
We utilise and incorporate a flex section into the design. This allows the system to absorb engine movement, torsional vibration, and thermal expansion without transmitting that stress directly into the turbo flange or downstream exhaust. The OEM design relies more heavily on rigid geometry plus the stay to manage those loads.

3.) Elimination of the ball-socket junction
The ball and socket junction used in the factory configuration can create off-axis loading and localised stress during dynamic operation. Eliminating that junction and pairing the system with a flex section reduces stress concentration and cyclic fatigue loading at the ends of the pipe.

4.) Overall length and geometry
The GR Corolla downpipe (referenced above) is significantly longer, which increases its moment arm relative to the turbo flange. That length/geometry makes a stay more beneficial in that application.
The 2.4T Tacoma/4Runner/LC250 downpipe is notably shorter. With the reduced mass, shorter lever arm, and integrated flex section, the structural loading profile is materially different.

When we evaluated the system from a load-path and fatigue perspective, with the shorter length + reduced mass + controlled compliance via flex section, the additional stay bracket is no longer required for the intended application.

No, we do not currently offer an additional support bracket for this pipe, as it was intentionally engineered without one in accordance with the above criteria.

And just to be transparent, we are not a hard-parts manufacturer by trade. We specialize in Toyota ECU calibration. For this project, we partnered with a high end local exhaust fabricator who handled the mechanical design and engineering, and the stay omission was a deliberate design decision based on application analysis.

I appreciate your explanation of the engineering intent behind the new design. Thank you for taking the time to address my concerns and answer all questions. This has been of significant help in my decision making process for a future upgrade.

 

[SC4Runner]

Mine is still in transit. I’m looking forward to seeing how this sounds before I decide to install it. If it’s too loud, my wife won’t be able to handle it, so I might bow out on the installation.

 

[xp0nex]

Will this be installed with the factory exhaust or going aftermarket?

 

[SC4Runner]

Will this be installed with the factory exhaust or going aftermarket?

My understanding is this will work with factory exhaust. I’m interested to hear what it sounds like with aftermarket too, but my understanding is that it’s pretty loud. However, I haven’t personally heard/seen clips from anything post down pipe installation.

 

[jrdees916]

I have to send mine back to get the heat shield put on. I was also just thinking of heat wrapping it. What do you all think? OTT didn’t offer it for me at the time but they are great and said they would but I have to send it back to them. I will be mounting mine to the AWE exhaust but I did see the downpipe does mount to the stock exhaust.

 

[xp0nex]

I have to send mine back to get the heat shield put on. I was also just thinking of heat wrapping it. What do you all think? OTT didn’t offer it for me at the time but they are great and said they would but I have to send it back to them. I will be mounting mine to the AWE exhaust but I did see the downpipe does mount to the stock exhaust.

Once you have everything installed, it would be great if you could share an update with some sound clips.

 

[jrdees916]

I promise I will do a before install and after install.

 

[SC4Runner]

Great question I am actually sending mine back to wrapped with the heat shield material. They didn’t have that available when I purchased it but now they do.

Did they mention the turnaround time for that? I’m starting to think I may have jumped the gun on this one. People are talking about how loud it will be, and now there’s discussion of a need to wrap the down pipe. The wrap will probably reduce the noise too.

 

[jrdees916]

I just mailed mine back today and John at OTT stated should be sometime next week. I do want it back so I can install it and give everyone a video

 

[Scrappopatamus]

I just mailed mine back today and John at OTT stated should be sometime next week. I do want it back so I can install it and give everyone a video

Be sure to tag everyone interested in this mod. I've performed several mods and am very happy how it performs and handles and it drives so well. I have to admit that having a vehicle like this that's pretty stealth is a plus. I'm very interested in hearing this mod and have someone confirm the gains. Thanks

 

[Scrappopatamus]

Anyone fitted their down pipe yet?

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