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4" Exhaust at My Mod Level

3K views 28 replies 9 participants last post by  csp 
#1 ·
I have the Full Force Stg1 injectors, Tymar intake, TS Chip, 3" Downpipe, and no cat. Would a 4" with muffler delete do anything for me except make more noise?
 
#2 ·
Imo, you won't see a appreciable difference.
Maybe lower EGT'S.

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#3 ·
I would just install a muffler delete pipe.
 
#5 ·
I got about 8hp more switching from a modified exhaust with the stock muffler to a true 4" with muffler at the 400hp level. Using a straight pipe without a muffler probably gains nothing except more noise over using a 4" muffler.

Modified exhaust was gutted EBPV, downpipe, factory cat delete test pipe, stock muffler and 3-1/2" Banks tailpipe. Did 399.8hp with it and 408hp with the true 4" exhaust with muffler.
 
#7 ·
So I may see some benefit from a non muffler 4" system. Maybe a little power, better sound, slightly lower egt's.
 
#11 ·
In that line of thought, well why do they make anything bigger than the collector? Heck why even bigger than the exhaust ports? Lol

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#12 ·
Actually it does make a difference. My modified exhaust retaining the use of the stock muffler was a Banks exhaust system. Going to a full 4" past the downpipe gave me 8hp over the Banks exhaust setup.

Gutted EBPV, 3" downpipe, cat delete (factory cat delete test pipe), factory straight through muffler and 3.5" tailpipe changed to 4" past the downpipe, 4" muffler and tailpipe. The power difference would have been larger had I compared the 4" to a real stock exhaust.
 
#19 ·
You are correct when saying there is a point of diminished returns but it is not at the point of switching from a 3” exhaust to a 4” exhaust. A stock OBS PSD goes from 175RWHP to about 195hp when installing a 4” exhaust, something I saw a dozen times at dyno meets. That's over a 10% increase in my book. My truck went from 400hp to 408hp when switching from a 3” exhaust to a full 4” exhaust. Others have posted no power gains when switching from a 4” system to a 5” system just a change in tone. That’s where there is no increase.

Banks sold the 3” exhaust saying that was, economically speaking, the best bang for the buck. However, it left some stuff on the table. Their system was a 3” downpipe retaining the stock muffler and using a 3.5” tailpipe. I added the factory cat delete test pipe to my Banks system. As close to a 3” system as you could find except for the 3.5” tailpipe.

When I installed the full 4” system including the 3” downpipe, the truck gained 8hp, going from 400hp to 408hp at the rear wheels. So, there was a power gain with no other changes to the truck.

I did over 90 dyno runs on my truck as I did various mods mainly using an inertia type DynoJet 248 with no load cell (5000# roller) and atmospheric data correction for consistent comparable results over the five years I spent modding my truck. One thing about a DynoJet without a load cell is that there is no fudging of the results, something I saw when using several load dynos. The DynoJet’s internal weather station supplies atmospheric data to the dyno programming correction factors.

So, if you want to argue with the facts (in this case empirical data), count me out. I come from the school of not arguing against the facts. Just join up with the engineers who once proved that bumble bees couldn’t fly.
 
#22 ·
I'm not "admitting" there is a increase in power in going from a 3" pipe to a 4" pipe, its a fact. you are the one who said there isn't a difference when in fact there is. And the 5" pipe is just the point where there is not a significant gain in results. Anyone knows that if you exhaust into atmosphere then there is no backpressure. Thats the ultimate "big pipe" (ignoring tuning lengths). You are just turning around what I said to suit your own means.

Maybe you should consider just what you are saying when you refer to laminar vs turbulent air flow and why the larger 4" pipe does increase horsepower (as an analog to improved flow). I think there is a big difference when considering fluid flow when dealing with imcompressable fluids vs compressable fluids like exhaust gases.

About drag (friction), consider this:

https://en.wikipedia.org/wiki/Darcy%E2%80%93Weisbach_equation
 
#24 ·
So 5" exhaust with no muffler it is!!!!! Only if I can keep my spare tire under the truck?
 
#25 ·
Haha or the rear tank.

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#26 ·
I'd like 400 to the rear tire, 1000 degrees max egt's pulling 15,000 lbs up a 10 percent grade, 14 mpg pulling that 15,000 pound trailer, and 20mpg unloaded.?????
 
#27 ·
Not in this world with the usual 400 hp mods. Under those conditions you will burn down your entire powertrain.LOLLOLLOL

This was demonstrated by a poster named Charles who did just that many times a few years ago with his twin turbo 7.3 towing super heavy. Regular semis have much bigger powertrains than our pickups to stand up to high continuous loading and horsepower. Our stuff is light duty pickup rated.

And a 5" pipe or no muffler adds nothing over using a 4" system with a muffler except irritated neighbors.

.
 
#28 ·
Yeah, I ordered a 4" today. I'm adding an IC, T500 pump, E-Fuel, and maybe some meth.
 
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