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I recently removed the stock muffler and put on a straight through magnaflow, but otherwise the exhaust is stock. Is it worth my effort to put on a 3.5 inch down-pipe and if so, who sells one? I know a 4" exhaust would be the best, but I don't want to spend that much and I also don't want to lose much on the bottom end. Also, I'm trying to cut down my egt's a bit, while keeping it relatively cheap and quiet. Currently I have stock tuning, but might add in a mild tow or economy tune....Keeping the focus on a daily driver and towing
 

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Discussion Starter #3
I went out ant measured it at the turbo, as well as on the underside of the truck where it meets the rest of the piping, and it's definitely a 3" down-pipe that meets 3.5" pipe the rest of the way out.
 

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Stock exhaust is a 3" downpipe to a 3.5" dp back exhaust. I'm not sure how much your budget actually is, but I am guessing if you had not bought the magnaflow muffer, then you could've spent about the same and got a Diamond Eye full 4" exhaust for around $400.
 

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I definitely don't have anywhere near $400 wrapped up in a muffler, but I agree, 4" wouldn't be a bad option.....It's just not the way it's gonna happen at this point in time. I'm just curious if anyone has experience running a 3.5" dp and if they have, where did they get it from?
 

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A 4" turbo back exhaust is only like $230.00 on amazon, $250 for a diamond Eye on Riffraff. You might be able to get a 3.5 downpipe for $75 but I think it would be a waste of money verses the 3" pipe.

Also you are not going to lose that much on the bottom end with 4" and the egt's will be better especially when towing.
 

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That's even better pricing than I realized.

OP: what I meant was that with purchasing the muffler and then also buying a downpipe and related hardware, etc., then you would have been close to just buying a whole 4" system. You might be saving a hundered or so dollars now, but if you still end up with a 4" system, then you are paying even more. Not saying this will happen to you, but we see it a lot when people are trying to do upgrades. The ol' "Buy Once. Cry Once" philosophy.
 

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I'm looking at doing the same thing, a 3.5" down pipe on my 2000 F250 farm truck when I fix some valley oil leaks. The best thing I've found so far is the Magnaflow stainless 3.5" down pipe assy. #15459 for $118 on several sites. Diamond Eye makes an aluminized version but the rest of my exhaust is in good shape and will probably out last it. I pulled the stock muffler and installed an 4" Aeroturbine muffler so when the rest of the exhaust is gone I can transfer it to a new 4" system. The Magnaflow down pipe is mandrel bent and 1/2" bigger so it should help the turbo spool a bit easier with lower EGT and not get in the way of moderate power increases done by compressor wheels and daily/tow tunes. Anyway that's my theory, we'll see how it works out a little later this year.
 

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Project Shamu
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Hell OBS trucks can only fit a 3" downpipe and they work just fine, several guys running 600+hp with them. Might as well just leave your 3" in there.
 

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Another thing to consider is that the T-4 kits come with a 3.5" mandrel bent down pipe and they flow considerably more air than the stock set up. Our stock 3" down pipe is slightly kinked due to the bending method used in manufacturing, thus it isn't a true 3" radius. I've seen estimates ranging from 2.75" to 2.9" with the attendant flow disruption. As I said , you pays your money and you takes your chances.
 

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sooty
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Wow. I can't believe what I am reading.

Firstly, you won't lose any "low end" by upsizing the downpipe. These are turbo diesels not naturally aspirated gassers.

Secondly, whoever said a minor change in down pipe would help spool up is FOS.

Lastly, you have many more things to address/upgrade before downpipe diameter is a limiting factor of any sort...

Sent from my SM-G955W using Tapatalk
 

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2000 F350 SuperDuty 4x4
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... and I also don't want to lose much on the bottom end. Also, I'm trying to cut down my egt's a bit, while keeping it relatively cheap and quiet. Currently I have stock tuning, but might add in a mild tow or economy tune....Keeping the focus on a daily driver and towing

A smaller or bigger downpipe will have no effect on your bottom-end torque. If the engine were naturally-aspirated, had headers, etc., then maybe... but turbo-diesels aren't gassers, so exhaust size can only be too small, not too large.



Exhaust restriction can dramatically effect your EGT's, however. [As with many things...] Bigger is almost always better...



If you're stock-tuned, stock-turbo'ed, have a stock intake, etc., you probably won't see much change/improvement. Start adding more fuel (chip, injectors, etc.), then you will need more air flow, both in and out (intake, turbo, CAC, exhaust). It's always a package deal...


~Al
 
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