Is there such a thing as too big of an exhaust? - Ford Powerstroke Diesel Forum
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post #1 of 16 Old 08-27-2012, 01:22 PM Thread Starter
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Is there such a thing as too big of an exhaust?

Looking at exhaust systems and trying to decide whether I should go 4" or 5".

In a turbo application back pressure /scavanging is not really a concern.

Does it really come down to a sound preference? 5" can lower EGT's a bit more correct?

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post #2 of 16 Old 08-27-2012, 01:54 PM
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Usually larger pipes will lower egts. You can go too big though, the velocity of the exhaust gasses are important too. What do you have done to your truck? Do you have future upgrade plans?


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post #3 of 16 Old 08-27-2012, 01:55 PM
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I wish I would have gone with a 5"....

They sound Sick

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post #4 of 16 Old 08-28-2012, 04:47 AM
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No you cant go "too big" on an exhaust. The bigger the better. Deeper sound, louder turbo, more responsive turbo, lower egt's. This is exacerbated with more modifications, also.
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post #5 of 16 Old 08-28-2012, 04:51 AM
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5" and LUVIT....and yes you can go to big but 5 is not too big

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post #6 of 16 Old 08-28-2012, 04:56 AM
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Originally Posted by kinnisoj View Post
and yes you can go to big but 5 is not too big
Maybe in your opinion of the sound quality, but in terms of technicalities, there is no "too big".
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post #7 of 16 Old 08-28-2012, 05:50 AM Thread Starter
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Quote:
Originally Posted by Jrz13 View Post
Usually larger pipes will lower egts. You can go too big though, the velocity of the exhaust gasses are important too. What do you have done to your truck? Do you have future upgrade plans?
Nothing really yet. When I got the truck it was bone stock minus someone cutting th muffler out and replacing with straight pipe.

I plan to do some intake/exhaust/intercooler mods to help her breathe better. Maybe one day I will upgrade turbo/injectors/valve train but for now I want to keep her as dependable as possible.

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post #8 of 16 Old 08-28-2012, 07:10 AM
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Originally Posted by 85_305 View Post
Maybe in your opinion of the sound quality, but in terms of technicalities, there is no "too big".
Yes you can go to big technically. You seem to spread a lot of info that is just hear say or bad.

If the pipe is too big, the air inside will get lazy (slow down) and actually create resistance. This is why "velocity" was mentioned.

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post #9 of 16 Old 08-28-2012, 07:20 AM
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Originally Posted by Turbostang500 View Post
Yes you can go to big technically. You seem to spread a lot of info that is just hear say or bad.

If the pipe is too big, the air inside will get lazy (slow down) and actually create resistance. This is why "velocity" was mentioned.
Really? So what size is "too big" then, where the numbers begin to reflect upon your statement?

A turbo diesel doesn't need "velocity"... theres a fat ****ing garrett turbo pushing the exhaust out


A turbo wants the least amount of resistance and restriction in the path of the intake and exhaust. Why do you think sled pullers run a filter clamped to the turbo and the biggest exhaust they can fit with the shortest path routed?


Here's a nice little article written by a former Garrett development engineer, on how scavenging and velocity theory goes out the window with a turbo:
http://www.tercelreference.com/terce...st_theory.html






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Last edited by 85_305; 08-28-2012 at 07:35 AM.
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post #10 of 16 Old 08-28-2012, 07:45 AM
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I can't give you an exact size because I don't know the math and it would depend on a lot of other factors.

Pulling trucks are a very different senerio! They are forcing a ton more air through the engine so they NEED larger exhaust to vent it all. Also, as you mentioned, these "pulling" exhaust are as short as possible. If you understood fluid dynamics you would also understand that the length of the pipe largely impacts flow velocity.

I didn't read your article so I don't know what was talked about. I am talking about velocity after the turbo.

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