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Old 10-21-2020, 03:19 AM   #1
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Year: 1998
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Engine: 7.3 Powerstroke
Stock Exhaust Diameter

Looking to put an exhaust tip on the 16 powerstroke with stock exhaust. I was not sure if a 4 or 5 inch inlet is needed for the exhaust. Also I consider some exhausts that you can see here. Are they good in terms of high performance? Any help would be great.
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Old 10-21-2020, 08:16 AM   #2
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ive read a lot on this for in terms of my T444E.. from what all the people who have tried various things say is that keeping a 3 inch downpipe is ideal. (possibly the only pipe that fits in a van chassis). and then going up to 4, if you are really going to turn up your power and install a bigger turbine'd turbo then the argument could be made for a 3.5" or 4" downpipe but for anything stock or even mildly tuned it seems 3" downpipe going to 4" exhaust.. some like 5" after the muffler (or last couple feet when straight piped.). i think for look and sound more than function..



this all changes if you are going to performance build the engine..
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Old 10-22-2020, 02:11 AM   #3
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Here is a related question ... just how much performance enhancement might a change in exhaust piping produce?
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Old 10-22-2020, 06:15 AM   #4
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Here is a related question ... just how much performance enhancement might a change in exhaust piping produce?
For a stock diesel not particularly much, it may pick up some responsiveness. Exhaust Gas Temperatures could be reduced. I'm not fully familiar with the 7.3l in the Super Duty or E-series chassis, but in the Old Body Style trucks the downpipe is regarded as very restrictive due to its flattened shape and replacing it with something else allegedly picks up a rather notable amount of power. I've not done this to mine yet so I can't verify with personal experience.

In a full size bus I would not expect any performance gains as the exhaust on a bus is generally a nice large diameter throughout and would do it purely for sound. I've also heard a school of thought that Variable Geometry Turbos require some backpressure for proper operation, ultimately the DPF in a modern setup provides plenty.
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Old 10-22-2020, 08:25 AM   #5
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some of the guys with 7.3's installing 4 inch or 5 inch down-pipes reported less lower end torque but some gains in lowering EGTs and and a bit of high end gain..



we used to deal with this on gas engines too.. everyone was about "let it breathe!" yet exhaust back pressure esp in a turbo environment is very definitely something to read up on as opposed to just installing the biggest pipe..



as a kid all the old guys told us just to go big... and perhaps thats true for non tuirbo engines. but scavenge flow, siphon effect and air turbulence in the pipes is something that needs addressed when dealing with forced induction..



the ford powerstroke threads are good reads as there is lots of data from lots of people. so you dont have to just go on what pne or two people say.. while every engine is different, the concepts in a powerstroke will apply to all forced induction diesels..
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Old 10-22-2020, 10:25 AM   #6
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In most cases, the down pipe is fine. A few rare examples is on the IDI engine in ford pickups. In that scenario the factory had a limited amount of space to work with and did the best they could.

So unless you upgraded turbochargers and are flowing more air, you likely won't see a gain by going with a bigger downpipe. It has to do with gas velocity and heat loss.

An upgrade every diesel would benefit from would be to apply some sort of coating or wrap to your up-pipes and manifolds before the turbo. That will help keep the heat and energy in the exhaust, which allows more of it to be applied to the turbo.
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Old 10-23-2020, 02:12 AM   #7
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Ah, I did wrap the downpipe, but have not ventured into doing so in the manifold.
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Old 10-23-2020, 08:20 AM   #8
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I knew of wrapping the up-pipes ive never wrapped a down-pipe..



my EGTs run a bit high on my 444 so I havent wrapped any pipes yet.. id rather lose a little performance to keep my EGTs down until I update my turbo to get a little more low-end Boost.
-Christopher
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Old 10-23-2020, 08:56 AM   #9
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They wrap downpipes for a couple reasons. One is because it's easy to do, at least compared to the manifolds and up-pipes. Another is to lower underhood temps, and a third is to keep the velocity up in the pipe to increase performance.

Same reasons people use turbo blankets.

Wraps can hold moisture, so sometimes you'll see manufacturers void warranties if a wrap is used. I plan on cerakoting my manifold and turbine housing before I install them.
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Old 10-23-2020, 09:06 AM   #10
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Originally Posted by cadillackid View Post
I knew of wrapping the up-pipes ive never wrapped a down-pipe..



my EGTs run a bit high on my 444 so I havent wrapped any pipes yet.. id rather lose a little performance to keep my EGTs down until I update my turbo to get a little more low-end Boost.
-Christopher
Wrapping doesn't increase the heat being made, it better preserves that heat up until the turbo and then out of the engine. If your pyrometer is reading high now, any increase to your pyro temp that wrapping causes only better shows your combustion temps.
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Old 10-23-2020, 04:14 PM   #11
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They wrap downpipes for a couple reasons. One is because it's easy to do, at least compared to the manifolds and up-pipes. Another is to lower underhood temps, and a third is to keep the velocity up in the pipe to increase performance.

Same reasons people use turbo blankets.

Wraps can hold moisture, so sometimes you'll see manufacturers void warranties if a wrap is used. I plan on cerakoting my manifold and turbine housing before I install them.
I wrapped the downpipe for the heat. It runs right down under the passenger side floor at the firewall and was too close for me. When I wrapped the pipe, I applied a heavy coat of high-temp silicone paint (made for the wraps) to seal the pipe and wrapping. If I ever get adventurous enough to wrap the manifold, I may look into cerakoting.
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