3.5 or 4 inch downpipe
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3.5 or 4 inch downpipe
I was wondering how much advantage I would get by going with a 4 inch downpipe vs. a 3½ inch downpipe? Would a 3½ inch be sufficient or should I go with a 4 inch? Would a 4 inch even fit?
Any suggestions on exhaust systems to go with? It is a 2002 PSD.
Thanks
Any suggestions on exhaust systems to go with? It is a 2002 PSD.
Thanks
Last edited by Andywk; May 3, 2003 at 09:42 PM.
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Joined: May 2002
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From: East Texas
3.5 or 4 inch downpipe
my 2001 already has the 3.5 downpipe stock, I would thank the 2002 would also. When I inquired about it, the responce that I got back was to upgrade to 4" from 3.5" wasn't worth it. Everything from the downpipe back is 3" and there is where the benefit came in.
over and out
gseeders
over and out
gseeders
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From: C H I C A G O
3.5 or 4 inch downpipe
So , from what I am reading , going to a larger downpipe really isn't worth the money ? I mean , if the stock size is 3.5 and an aftermarket one is 4'' , the gains would be very small, if any, i would think.
It is about time for me to look into downpipe's and exhaust , so I kinda need to get a straight answer on this before I spend my cash......
It is about time for me to look into downpipe's and exhaust , so I kinda need to get a straight answer on this before I spend my cash......
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3.5 or 4 inch downpipe
Well if this is true than I only need to worry about from the downpipe back if it already is 3½ inches. I am just trying to do my homework before making a purchase. This would explain why some 4" systems that I see have a 3½" downpipe.
Any other feeddback or comments out there? It is all helpfull!
Any other feeddback or comments out there? It is all helpfull!
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Joined: Mar 2003
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From: Oxford, Alabama
3.5 or 4 inch downpipe
I went with the 3.5 down pipe. Somebody said that the stock was a 3.5 and I think they had better check. Mine 03 is a 3 so I gained .5 inch. it may not make that big a diffrence but any little thing helps and adds up. The flange on the trubo is the trick, I went with another compamy just because it was the one my local shop had connections with but I wish that I had gone with the Site store or Ken. I had to have 3 diffrent down pipes sent in the flange was wrong on everyone. The final one they got right. what a mess. The rest of the system is 4 inch with a 5 inch tip. Looks awesome. I've had people in a parking lot's stop and stare. They don't believe its real until I fire it up. Then they believe. I don't think that I am supposed to say the name if not (ken just Blip me out) its Western Deisel. 
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Joined: Nov 2002
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From: Mansfield, TX USA
3.5 or 4 inch downpipe
Many people just run with a low restriction muffler, like the Walker BTM. The main restrictions in the system are the turbo outlet and the muffler. Not much you can do with the turbo outlet except replace the turbo. The BTM is <$50 and reduces THE major restriction in the system.
A larger downpipe will help some too, but I have read that Banks Engineering does not recommend anything larger than a 3.5" downpipe. I think because they did not feel that anything larger did you any good. Haven't confirmed this anywhere.
The 4" will move your torque up a few 100 rpm's (3.5" will do this a little too). Make you think that you have lost power off the line. It really just moved up the tach.
A larger downpipe will help some too, but I have read that Banks Engineering does not recommend anything larger than a 3.5" downpipe. I think because they did not feel that anything larger did you any good. Haven't confirmed this anywhere.
The 4" will move your torque up a few 100 rpm's (3.5" will do this a little too). Make you think that you have lost power off the line. It really just moved up the tach.
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From: Denton,TX
3.5 or 4 inch downpipe
Originally posted by bricot
And also remember that even though the stock pipe was 3" it was squashed pretty flat, which I believe would cause the restriction/back pressure to be greater.
And also remember that even though the stock pipe was 3" it was squashed pretty flat, which I believe would cause the restriction/back pressure to be greater.
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From: Salem USA
3.5 or 4 inch downpipe
Volumes are interesting things too. They don't necessarily follow the common logic one may think, like a 7" pipe would have twice the flow as a 3.5". I know that a 3.5" hose with double the flow rate of a 2.5" hose due to friction loss, etc. I would assume these downpipes follow the same principle so even though the changes in diameter/shape sound small, I think they will make a big difference.
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3.5 or 4 inch downpipe
Well I am just trying to do my homework b4 making a purchase. I see that there are true 4 inch systems out there from the turbo back. It looks like that is what I will go with. Now I just need to decide with SS or aluminum. I would like to go with SS but it is expensive. Can you guys convince me that SS is the way to go vs. aluminum. The site store has a 4 inch SS that looks pretty good but is over 800 dollars. Thanks
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From: Oxford, Alabama
3.5 or 4 inch downpipe
I went the way of the aluminum. The stainless looks really nice but after a year it looks just like the other. I had the stainless on my last truck and figured out that I wasted money..Less money means less toys.. Just my way of thinking.