4" or 5" exhaust - Diesel Forum - TheDieselStop.com
'99 & up Upgrades and Aftermarket - 7.3L Engine Upgrading or adding OEM or aftermarket equipment to your 1999-Up Super Duty or Excursion with 7.3L Power Stroke diesel engine. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

 
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post #1 of 9 (permalink) Old 01-09-2010, 10:05 PM Thread Starter
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4" or 5" exhaust

I plan to put a new exhaust system on my 2000 F250. One shop says 4" from the turbo is plenty and another shop says 5" is the best.

They both say I won't see a performance difference with a straight through muffler or straight pipe, just more noise.

Alll I know is I just want to spend the money once.

2000 F250 XLT, 7.3L, 6 speed manual, 2 wheel drive, extended cab, short bed
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. The truck is for pulling our 24' Cougar 5th wheel and taking my sweetie and our 2 Italian Greyhounds on vacation.
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post #2 of 9 (permalink) Old 01-09-2010, 10:16 PM
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Unless you are going crazy for power and mods, the 4" should be sufficient. Try a 3.5" straight pipe (OE diameter) first and see if that satisfies you. That setup on mine pulling a 9,000# TT all over the country has been quite sufficient with no chips, tunes or expensive mods.

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post #3 of 9 (permalink) Old 01-09-2010, 11:00 PM
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Quote:
Originally Posted by FleetMan View Post
Unless you are going crazy for power and mods, the 4" should be sufficient. Try a 3.5" straight pipe (OE diameter) first and see if that satisfies you. That setup on mine pulling a 9,000# TT all over the country has been quite sufficient with no chips, tunes or expensive mods.
Unless you want to spend the money, go w/3.5" straight through. My current truck came w/4", otherwise I would be w/the $80 3.5" straight. Those shops don't make any money going this route. I once was talked into going from my 3.5" to the 4"kit, I noticed no power improvements at all and maybe, 50 degs out of my egt's pulling hard and heavy up hill. If you can weld or know a friend, a 10' stick of 3.5" probably cost you $20.
W/ all you $avings, you can get a DP or TS chip too and be 10x better off!

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post #4 of 9 (permalink) Old 01-09-2010, 11:31 PM
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4 is the way to go. You can't fit a bigger downpipe in anyway.

2011 F350, CC, SB, Lariat Ultimate, Chrome Package, 4x4, FX4, White Platinum, 6.7L (SOLD)

2001 F-250 CC Lariat, LB, 4x4. 205K and Traded in
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post #5 of 9 (permalink) Old 01-10-2010, 11:37 AM
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As FleetMan noted, unless you plan to spend over $10,000 on engine mods plus another $5,000 for a bulletproof automagic tranny that can live with those horses, then you won't gain any benefit from a 5" exhaust system. Except braggin' rights at the local pub. In fact, you won't even gain any benefits from a 4" exhaust system. 3.5" is all you need for up to about 400 horses from a 7.3L engine.

A straight pipe puts out obnoxius racket and is illegal in most jurisdictions. So the least-expensive but good mod is to replace the stock muffler with a straight-thru diesel performance muffler, and keep the rest of your stock 3.5" stainless steel exhaust system. The most popular straight-thru diesel performance muffler for the last dozen years has been the Walker Big Truck Muffler (BTM) # 21470, also known as the Dynomax RV muffler. You can buy one from Summit Racing for about $54, and your Midas Man will probably charge you about $60 to install it.
Walker/Dynomax RV muffler - SummitRacing.com
Plus you'll also need two 3.5" muffler clamps that are not available at most auto parts stores or muffler shops, so get them at a big-truck parts store.

You'll gain very little more benefit from replacing the downpipe with a 3.5" mandrel-bent performance downpipe. Replacing the 3.5" exhaust pipe and tail pipe won't gain you anything, but some folks like to replace the whole shebang. Because of all the hype that "bigger is better", there is almost no demand for performance 3.5" exhaust systems, so most of the ones available at competitive prices are so-called 4" performance exhaust systems, including a 4" performance straight-thru muffler. The downpipe begins at 3" coming out of the turbo but quickly expands to 3.5" or 4". So a 4" downpipe actually begins at 3" on the hot end.

In my case, I had a 3.5" Walker BTM for over a year. I was pleased as punch with it. But a sponsor offered me a deal I couldn't refuse on a 4" performance stainless exhaust system, so falling for the hype that bigger is better, I took him up on it. I was disappointed at how little gain the high-priced exhaust system made compared to the BTM. My seat-of-the-pants estimate is that the $100 (installed) Walker BTM gave me about 80 percent of the benefit of the $1,000 aftermarket system. (Performance exhaust system prices are about half that much now.)

Quote:
They both say I won't see a performance difference with a straight through muffler or straight pipe, just more noise.
They're wrong. Depending on how you define "performance difference", you'll definitely achieve reduced EGT with either the straight thru muffler or the straight pipe. And a performance straight-thru muffler is very little louder than the stock muffler, while the straight pipe is a lot louder. From the front seat with the windows rolled up for the AC or heater to work good, you can't tell the difference in sounds between the stock muffler and a straight-thru performance muffler. But the straight pipe is obnoxiously louder.

As far as "performance difference" is concerned, a straight pipe, or a performance muffler or entire turbo-back performance exhaust system will not give you significantly more power than the stock exhaust system. Maybe a little faster spool-up of the turbo. The reason to replace your stock muffler is to be able to go faster when towing up a mountainside, or pull a heavier load up the mountainside, or climb a steeper grade without busting the pre-turbo EGT red line of 1,250. Dragging my 8,000-pound trailer over the interstate mountain passes, I can go about 5 to 10 MPH faster without exceeding 1,250 EGT than I could with a stock muffler.

So you'll get more towing power at the 1,250 red line, but not more power when unloaded. Increased power comes from your tune, not from your exhaust system. But even a mild performance or towing tune bumps up against the EGT redline too quickly with a stock muffler. So replace that stock muffler so your tune can produce more horses without exceeding the 1,250 EGT redline. That's not literally "lower EGT", but that's what folks call it.





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My Sierra Blanca (Spanish for White Mountain) in the sig pic was a great pickup for 11.5 years. I sold it several years ago. I drove a hand-me-down 2003 F-150 SuperCrew 4.6L 2V for a while, but it was unacceptable for towing more than a rowboat. Replacement is a 2012 F-150 EcoBoost SuperCrew Lariat that tows my 5,000-pound TT like a dream. Replaced the 2012 with a 2019 F-150 3.5L EcoBoost with max tow.
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post #6 of 9 (permalink) Old 01-11-2010, 05:15 PM
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so let me make sure i'm understanding what you're saying smokey... i think in a different thread i posted about exhaust you said something about our trucks 99 and up have a stainless 409 exhaust already right? and in this one you are also saying that a 4in exhaust isn't necessarily the way to go? take me and my psd for instance, i am planning on a tuner, some mild bolt on turbo up grades, and an exhaust system. thats about it. my rig is a daily driver/ family hauler; so... in your opinion i should just stick with a piece of 3.5in pipe and call it good?
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post #7 of 9 (permalink) Old 01-11-2010, 09:52 PM
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this is an interesting thread

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post #8 of 9 (permalink) Old 01-12-2010, 02:41 PM
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Who sells a 3.5" downpipe? I just cut out my muffler, pickup sounds much better.

2002 F350 CC 4x4
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post #9 of 9 (permalink) Old 01-13-2010, 01:49 PM
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4" is all you really need, but 5" does look and sound great. It is all personal preference really. I find that most people who just do an aftermarket muffler end up buying a full kit shortly thereafter. Get one the first time and be done with it. We have everything from budget kits to full blown show truck kits. Check our site, we currently have a special on MBRP and Magnaflow kits. Feel free to give me a call if you have any questions.
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