7.3L IDI diesel not very loud without exhaust.

[GJCAT427]

My 95 F350 has a little over 200,000 on it, It was 4yrs old when I got it with 74,000 miles. I`ve put 3 valve cover units on it between 80,000 and 190,000 and a HP pump in around 100,000. Its seems to be loosing some power and I want to get into the injectors next. Still gets 20-22 mpgs at 2000 rpms and 15 mpgs towing at 2000 rpms. Its got 3.55s in it and its a rebuilt factory E4OD in 1999. Gail Banks torque converter with Trans command that upped the lockup and mileage. Now it needs a new exhaust from frt to back. Oh ya It has a full flow snake head too.

[Hemi Joel]

I had a 93 with a glass pack muffler, no turbo, pump turned up a little. People said they could hear it coming from blocks away.  Some of you are talking about motors with turbos. The 1990 IDI did not have a turbo. There is a big difference in the sound, as the turbo acts as somewhat of a muffler.

[cleandan]

I built the exhaust and it is pretty good so far.
I used the factory manifold to Y-pipe connectors with about 8" of factory pipe left on them...basically to the bottom of the oil pan.
From there I built a merge collector to a 3" pipe for the rest of the Y-pipe.
The (Y) connection is no longer a right angle because I built a proper angled merge from the passenger side manifold into the Y-pipe...A nice smooth transfer of flow now.

The rest of the system is a single 3" pipe using a big Dynomax Super Turbo muffler (3" in/out)
There is a full tail pipe over the rear axle that exits about midway between the rear wheel well and the rear bumper, out the passenger side of the truck.
I installed 3 bolt flanges so I can remove the system in three sections.
The Y-pipe flange is just in front of the frame crossmember.
The center section is from the Y-pipe flange to just after the muffler where there is another flange.
The last part is the tail pipe.
The "best" part is I built this whole thing from extra 3" pipe pieces and setions I already had in the garage. I just happened to have plenty of mandrel bends and such to get the job done.
Cut, shape, weld = nice exhaust system.
I got a new exhaust for my truck, and cleaned up some crap from my garage too.

The sound now has a bit of a V8 rumble at full throttle...NOTHING loud though. Otherwise it is really quiet.
Remember, "quiet" is a relative term with a 7.3L IDI diesel because the engine itself make a LOT of noise simply running...Not exhaust noise but engine noise. I think most of that noise comes from the injection pump and compression ignition.

Anyway, I built what I think is a nice "performance" exhaust for a bone stock 7.3L IDI and it seems pretty good.

It got tested right away too as I just towed my 26 foot enclosed trailer 700 miles round trip.
Much of that was foot to the floor, up highway hills in WI, bucking a strong headwind.
At night, when the wind dies down and things got calm I was able to maintain 65 MPH without issue (I don't tow any faster than that)
But MAN, I got to tell you, the truck was working to maintain 55-60 mph in the wind. My trailer is a pretty good air brake too.

[RustyCrankshaft]

The IDI's are basically the equivalent to a similar era big block gas engine for power, they just get better mileage while going over the pass at full throttle and 20mph with the enclosed race car trailer.....but with a little maintenance they do last a long time. The brown 86 I posted a picture of had a replacement 6.9 done under warranty when the truck was a year old with about 22k miles on it. Current 6.9 has around 290k on it.

They don't make enough power to hurt themselves unless someone has turned the pump up or put a turbo on a 7.3. If you do turbo a 7.3 I like to sleeve them and use 7.3 turbo rods on 6.9 pistons, the whole thing lives a lot longer. Late 6.9 blocks became the 7.3 just with a bigger bore and much like some factory displacements in the FE lineup, 7.3IDI's are prone to thin walls and to suffer from core shift. If you don't run an SCA in the coolant they pinhole pretty easy.

As a side note, Dynomax still makes a full manifold back exhaust kit for the NA IDI trucks. They list it as only fitting 7.3's, but it fits any of them. The difference is on 6.9 trucks you'll have to build your own exhaust hangers as the kit is set up for the rubber bayonet style hangers like the newer trucks had. Thru Summit it's still only a little over 300 bucks I think and comes with a muffler and tip.

[70tp]

We had some idi 7.3 and a decent big block would out power one easy.   I was using a 350 k30 chev at the time and a 7.3 non turbo and weak 350 was a very close match.  My guys tried the 7.3 one day without a muffler, they were pulling a gooseneck trailer with a medium size back hoe on it.  They were very glad to put the muffler back on it at the end of the day.   It wasn’t bad unloaded , but virtually foot to the floor for a while gets old real quick.  They get decent fuel mileage is all I give them credit for.