what are you running for exhaust?

[Can30Diesel]

3" pipe off the stock Y pipe then into a 3" cherry bomb and out the passenger side just in front of the rear tire.

 

[chris142]

mine has an obnoxious rap from 1600 to 1900 rpm.its livable since my tailpipe exits after the rear axle and i keep the rear window shut. people often turn around to see what all the noise is.

 

[dunk]

What is the point of going from a 3" or smaller down pipe out through a 4" or larger to the back of the truck? Seems like a waste of space and money since the restriction is the down pipe size and any bend right off the turbo.

Anyhow mine is the ridiculously long Banks pipes up to the turbo and 3" off that ending behind the cab. Gonna get more pipe and exit in front or right rear tire to keep the soot from accumulating underneath and cut down on cab noise.

 

[Dieselcrawler]

bigger the diameter pipe, the lower the tone. my dually has a very distinct sound to it, never heard any other IDI sound like it. ask Subway, he has ridden in my truck.

 

[PwrSmoke]

What is the point of going from a 3" or smaller down pipe out through a 4" or larger to the back of the truck? Seems like a waste of space and money since the restriction is the down pipe size and any bend right off the turbo.

Anyhow mine is the ridiculously long Banks pipes up to the turbo and 3" off that ending behind the cab. Gonna get more pipe and exit in front or right rear tire to keep the soot from accumulating underneath and cut down on cab noise.

You bring up a good point, Dunk. Exhaust gasses have a volume. The hotter they are, the more volume they have and the larger the pipe needed to not create restriction. That means the front of the system, where the gasses are hottest, is where the bigger pipes need to be. As the exhaust moves downstream, it cools and contracts so it needs less pipe to carry the flow. You see some factory systems like that, with bigger front pipes to the muffler and smaller after. This is done to maximize scavenging and inertia. Most aftermarket or home built systems are the reverse of that, small up front and big out back, indicating the important thing for many is sound and looks, not maximum performance. There is also a science to selecting the size of pipe exiting the turbine and it's based on the turbo. Changing the pipe size changes the performance of the turbo and not always for the better. To build an optimal exhaust system, you need to know a lot of parameters and then you can only tune to optimize for one particular rpm range or situation. A big system will move the power band to the upper rpm ranges at the cost of the lower rpm range and a smaller one does the opposite. There is a balance where you can gain some in both areas but that's generally at the smaller pipe sizes; ~2.5-3 inches or so for an NA and ~3-3.5 for a 10-15 psi turbo.

 

[PwrSmoke]

ATS full 3" dp to 3.5" pipe off an OBS powerstroke. muffler replaced w walker 21470. Dumped straight down right before the axle. I think it sounds great.

Could you tell us more about using the OBS PSD system. I guess yours in a '92 and mine is an '86 but a 3.5" system is pretty close to optional on my setup and If I could find a used PSD system to install and it fit without major mods, I'd like that.

 

[sjwelds]

Well back when I got the truck, I knew opening up the exhaust was needed lol. Went over to my diesel mechanic down the street and poked thru his pile of take-off exhaust systems, and found one that he claimed was off an OBS PSD. I just modified the pipe at the time (truck was still N/A) and that system even lined up quite well with the factory hangers. Later I changed out the muffler for the one currently on the truck, as well as made a custom 2-into-1 smoother y-pipe junction. Then when I turboed the truck, just cut all the y-pipe mess off and added some straight pipe to connect to the downpipe, with a stainless seal clamp so I can disassemble if needed. Also added a hanger on the driver side of the muffler to help with rotational weight. I feel it sounds and works great.

Hope this helps. Your truck may have the hangers in totally different places tho... Just bring it to my shop and I'll fix you up lol. 10% discount for OBN members !!

 

[Black dawg]

What is the point of going from a 3" or smaller down pipe out through a 4" or larger to the back of the truck? Seems like a waste of space and money since the restriction is the down pipe size and any bend right off the turbo.

There has got to be more to it than that though. We are not talking a short exhaust system, what is it like 15 feet on a crew cab? And with a turbo, all the tubing after the turbo is doing is getting rid of the exhaust, no tuning.

 

[IDIoit]

I tried to make a 4" up pipe. But extensive remodel of the firewall and transmission was needed.
3" fit perfect with just enough room after I cut the firewall to floor pan seam.
No, I did not run numbers on the stats ofy turbo,
Because 1, I'm not trying to make thousands of ft/lbs, and 2, I spent 85 dollars on 10 feet of 4" and a 90 degree bend.
This truck was a 6.9 NA. And I don't think the 2 " exhaust would cut it.
Seems like a lot of you are running pretty much what I installed.
Mabe I should install a whistle tip to keep me out of the norm!
Relax, I'm kidding!

 

[truckermark]

4 inch straight pipe on my N/A 7.3 works and sounds pretty good

 

[jhenegh]

......Seems like a lot of you are running pretty much what I installed.
Mabe I should install a whistle tip to keep me out of the norm!.......
Relax, I'm kidding!

https://www.youtube.com/watch?v=JZD-ADArwXo

Enjoy!

 

[IDIoit]

wooo wOOOOOO!
people make me laugh...