psdguy95
New member
Anyone who has a 4 inch down pipe on there obs can you post up some pics please? I'm curious to see how it looks.
4 inch down pipe pics please
- Thread starter psdguy95
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7.3psd97444
New member
Like a 4 inch downpipe. lol
3 inch, maybe 3.5 inch is the biggest you can fint on an OBS. Without major firewall modification and/or a body lift.
Just FYI a 3 inch down pipe to either 4 or 5 inch exhaust(which ever you prefer) is perfectly fine.
3 inch, maybe 3.5 inch is the biggest you can fint on an OBS. Without major firewall modification and/or a body lift.
Just FYI a 3 inch down pipe to either 4 or 5 inch exhaust(which ever you prefer) is perfectly fine.
psdguy95
New member
I know the 3inch is good. I didn't know it was that hard to get a bigger one in it.
Cat_rebel
New member
On some trucks a 3" is enough of a chore. I've seen a 4" pipe on a buddy's 94.5 with a 5sp but all the stars lined up perfectly to make his fit. Another buddy had one but he also had a 3" body lift & still had to massage it a little. FWIW I went from a 3" DP to a 4" on my 00 & I didn't make a 50* difference. Just sounds deeper. People have made 500hp+ with OBSs running a 3" DP & EGTs were fine towing in daily trim. Why bother creating more of a headache?
7.3psd97444
New member
Yeah 3 inch are a pain as is. No real point in anything bigger IMO
powerstrokenstang
New member
I have a 4" and its tight. It was homemade many years ago not by me.
7.3psd97444
New member
How much firewall modification did it take?
i'm in the process of gathering all the parts to put on a garett 38. exhaust outlet is bigger than the stock. I either need to put on the 4" or find just the flange and weld it to the 3" downpipe. So I'm also interested in fit. I haven't been able to find just the flange. Anyone have any ideas other than buying the 4" downpipe and cutting off the flange?
powerstrokenstang
New member
3" body lift , removed firewall insulation and a sledge hammer. But i traded a h max down pipe that fit mine perfect yet didn fit good on the guys that ran the 4" one w/o a body lift and had no issue. I am feedin the fuel rails from the back though so that dont help.
Cat_rebel
New member
The flange will be the same as a stock 99-03 7.3L 3" factory down pipe. Someone has to have one laying around in a scrap pile.
Guess I'll go junk yardin!! The yards around here are pretty spotty for diesel parts Thanks
Strokersace
Well-known member
You want a 4" dp without a body lift???
Here's my SD 1-piece 4" dp. My opinion... Not worth it other than to do something different. That's the only reason I did it.
Here's my SD 1-piece 4" dp. My opinion... Not worth it other than to do something different. That's the only reason I did it.
psdguy95
New member
You want a 4" dp without a body lift???
Here's my SD 1-piece 4" dp. My opinion... Not worth it other than to do something different. That's the only reason I did it.
Nice work man! :thumbup:
tocker5691
New member
i put a 3.5 incher on mine just got under the truck with an air hammer and worked the firewall back, took 20minutes of hammering and fitting beats trying to swing a hammer in there or prying on ne thing.
Old OutLaw
New member
I don't have any pix, but we put a 4" in mine....no body lift, sawed out the firewall up as far as we could go, and about 10 inches wide, installed the pipe (takes a SHORT 90* up at the turbo, and a LONG 45* down by the trans) and then built a steel cover for it ....worked out well....
would I do it again ? yes, definitely...if you stop and think about it, you're trying to exhaust a Turbocharged 445 cubic inch engine thru a 3 inch pipe, and IMO, it ain't gonna work very well.....I do think it's ok if you're fairly stock, stock injectors, particularly on the 97's and older. If you're running bigger injectors, and towing, I don't believe it will get rid of the heat fast enough.....
thats all I do with my truck is tow (20,000 lbs gross) and I needed all the cooling I can get....
and Yes, it did help, especially down lower in the RPM range, from about 1500 to 2100, more torquey, and I can run more boost @ the same Pyrometer reading....probably took about 150 degrees off the pyro everywhere....
just my opinion....
would I do it again ? yes, definitely...if you stop and think about it, you're trying to exhaust a Turbocharged 445 cubic inch engine thru a 3 inch pipe, and IMO, it ain't gonna work very well.....I do think it's ok if you're fairly stock, stock injectors, particularly on the 97's and older. If you're running bigger injectors, and towing, I don't believe it will get rid of the heat fast enough.....
thats all I do with my truck is tow (20,000 lbs gross) and I needed all the cooling I can get....
and Yes, it did help, especially down lower in the RPM range, from about 1500 to 2100, more torquey, and I can run more boost @ the same Pyrometer reading....probably took about 150 degrees off the pyro everywhere....
just my opinion....
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Strokersace
Well-known member
In relation to what did it help? From the stock squash downpipe, or a round 3" aftermarket downpipe?
Old OutLaw
New member
from a 3" DP W/4" exhaust, to the 4" DP and got rid of all the transition pipe...
Strokersace
Well-known member
Cool. That's a great comparison then. I modded my firewall more, but wanted to be able to run an "off the shelf" aftermarket 4" dp just in case I changed between turbos down the road. Otherwise, I'd have made a custom one like you did.
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