4" exhaust?

[bobracing]

This weekend my brother took the truck which involved a trailer, Bronco, 3 engines, and a trans to load it down. The end result, 35mph up tiger mountain and about the same peaking Snoqualmie Pass. I figured the truck is hauling about ~7500# and runs the flats fine at 60-65 loaded and just the trailer at 70 without a problem.

I know the truck (see sig below) is very restricted right now with the stock intake and a N/A stock 2.5" exhaust with the stock muffler I believe, and where ever the fuel was set on the very stock truck it came out of. I can't hardly get the thing to puff black smoke. No pyro or boost gauges, so no playing with the fuel yet.

So, with a better intake for fresh air (have a hypermax cowl intake but not sure I want to listen to it), and ATS 3" turbo housing and downpipe, is a 4" exhaust worth it or would 3" be just as good? It would be a straight pipe to begin with and if to loud a muffler added.

And while at it, how much of a difference does a flat on the fuel screw make for the butt dyno or even dyno numbers if someone has them?

 

[Devon Harley]

One flat does alot but idk if anyone has dynoed a single flat at a time. It will add a good bit more. Im running 35%wvo an rest #2 diesel so the smoke level is down a lil as well as egt's I max my pump out an I have a 3in dp 088 ATS nongated turbo an 4in straight pipe an runs great with a turbo no need to add a soot trap on it there not loud. 3in would be fine to but 3.5 or 4in have a lil better tone imo than 3in is a lil to tight sounding but could just be me. If I were to run 3in it would be straight. I would say with the factory turbo you could max your pump out an not blow alot of nasty black smoke while driving it will puff at rev though.

 

[Exekiel69]

Go with 4" all the way if You can, it will make a difference over a 3".

 

[90ididoorguy]

I had a straight through muffler on my 3 inch and it was really quit. So I cit the 3 inch out and from the so back went with a straight 4" dump right in front of the rear tire. Was really loud at first so either I've gotten a little deaf or its gotten a little more quite not sure which. But it has mad a difference on my rig with a 088 ats 60-1 compressor wheel

 

[War Wagon]

A 4" system will be easier to come by as you can use a system for a OBS PSD. The 3" systems are not offered by many unless you just had the exhaust shop build it, but then it would not be a mandrel bend system. If you shop around online you can probably find a good deal on a OBS PSD 4" system that can be easily adapted to fit an IDI.