4” VS 3.5” DownPipe - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 16 (permalink) Old 10-18-2011, 03:19 PM Thread Starter
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4” VS 3.5” DownPipe

So here’s the deal. I currently have a 4” turbo back exhaust. The down pipe fits like S#!T. It beats against the spring shackle and the trans dipstick tube. It is driving me crazy. A friend of mine that works for Dynomax got me a stainless turbo back system but the down pipe is only 3.5” and it necks down to 3” at the “cat” flange. The other side of the flange is the omit pipe and it goes up to 4” and that’s how big it is the rest of the way back to the tail pipe and then it has a five inch tip. I am definitely going to fix it where it necks down to 3” but the question is how much am I going to lose going to a 3.5” downpipe from the 4”? Would it be worth getting a 4” downpipe from another vendor and if so, who makes one that fits half way decent? Or should I just through the 3.5” Dynomax downpipe on and go with it? Decisions decisions.

2004 F-350 CC/SB 4" downpipe and exhaust and thats it 220,000 miles strong
2002 F-350 CC/LB AFE Cold air, 4" turbo back, Rosewood Stage 2 Sticks and supporting chip. 4" lift on 35s. 150,000 miles strong
Just another Duramax guy seeing what the competition is raving about.

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post #2 of 16 (permalink) Old 10-19-2011, 12:31 PM Thread Starter
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Re: 4” VS 3.5” DownPipe

Wow. Either this was a retarded question or you people dont like me that much. lol Ya know the forum name is suposed to be funny, not offensive lol

2004 F-350 CC/SB 4" downpipe and exhaust and thats it 220,000 miles strong
2002 F-350 CC/LB AFE Cold air, 4" turbo back, Rosewood Stage 2 Sticks and supporting chip. 4" lift on 35s. 150,000 miles strong
Just another Duramax guy seeing what the competition is raving about.

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post #3 of 16 (permalink) Old 10-19-2011, 12:43 PM
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Re: 4” VS 3.5” DownPipe

Unless your pushing crazy power your only gonna hurt yourself with 4in. Some people notice a low end power loss with 4in. I would do the 3.5 or just keep the stock boy there really no need to have a down pipe bigger than you exhaust housing of the turbo.

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I know you said you wouldnt turn it up..... but come on.... its like saying "I promise I will only stick the tip in" never happens like that
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post #4 of 16 (permalink) Old 10-19-2011, 02:47 PM
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Re: 4” VS 3.5” DownPipe

I have a MBRP 4" turbo back and was told there is no benefit to a 4" down. Mine came with a 3.5" down, runs and sounds great.
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post #5 of 16 (permalink) Old 10-19-2011, 03:05 PM Thread Starter
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Re: 4” VS 3.5” DownPipe

thanks guys

2004 F-350 CC/SB 4" downpipe and exhaust and thats it 220,000 miles strong
2002 F-350 CC/LB AFE Cold air, 4" turbo back, Rosewood Stage 2 Sticks and supporting chip. 4" lift on 35s. 150,000 miles strong
Just another Duramax guy seeing what the competition is raving about.

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post #6 of 16 (permalink) Old 10-23-2011, 09:09 PM
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Re: 4” VS 3.5” DownPipe

This is a never ending debate it seems but the 4 diamond eye do I have fits terribly

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post #7 of 16 (permalink) Old 10-23-2011, 09:21 PM
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Re: 4” VS 3.5” DownPipe

my diamond eye was a PINA to put in...4" and saw no real change...maybe a little lower egt's

2005 F350 ex-cab long bed, 4x4. SRW. Big tires, bolts here and there...deleted a few things, added a few others, a couple monitoring devices.
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post #8 of 16 (permalink) Old 10-23-2011, 10:33 PM
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Re: 4” VS 3.5” DownPipe

I have a 4in down pipe from diamond eye it fits good but uses junk style clamps...

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post #9 of 16 (permalink) Old 10-24-2011, 02:36 AM
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Re: 4” VS 3.5” DownPipe

I never noticed any loss in low end power, going from stock to 4" downpipe and 5" system, but I certainly wouldn't argue any benefits over a 3.5" downpipe.

Mine is from Magnaflow and I have never had an issue with the downpipe fitting except for where it comes to the transmission crossmember, it rubbed the first bolt for a little while after it was first installed.

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post #10 of 16 (permalink) Old 10-24-2011, 06:32 PM Thread Starter
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Re: 4” VS 3.5” DownPipe

I'll be installing the Dynomax downpipe this week sometime. Its seem to be the general concesus that it wont effect anything enough to notice. And I can get rid of that piece of s#!t thats on the old girl at the moment. Thanks for all the help fellas.

2004 F-350 CC/SB 4" downpipe and exhaust and thats it 220,000 miles strong
2002 F-350 CC/LB AFE Cold air, 4" turbo back, Rosewood Stage 2 Sticks and supporting chip. 4" lift on 35s. 150,000 miles strong
Just another Duramax guy seeing what the competition is raving about.

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