Exhaust

[J DeMaio]

Well, I was wondering how much of a difference a new performance exhaust made on the 92' 4X4 trucks with the muffler removed, I love to hear a straight piped cummins. The main thing I was wondering about was how much do these exhausts help out with the turbo lag. With the exhaust installed will this cure the need for a new turbo housing? If I installed the exhaust I'd probably advance the timing of the pump or turn up the pump. What is the best route to go, I don't really want to spend money on the turbo housing if I don't have to. What does this do to your fuel mileage with the pump turned up.

 

[Scot]

TST says that there was no noticable performance difference except on the later model trucks with the catalytic perverter, unless you go with large mods to pump and injectors.

I pulled the 18cm off of mine and installed a 16cm. There was not a lot of difference except for the turbo spooling noticably faster.

Turning up the pump was like night and day. There is NO noticable change in fuel economy. Just follow the instructions in the archives. I get 24lbs WOT and 1150 deg uphill loaded. Spend the money and buy a pyro and boost gauge.

If you want to go to the 18cm, you can have mine for $5+shipping

 

[J DeMaio]

Are you sure the exhausts don't help? My downpipe and intermediate pipe seem very restrictive and small. The muffler also lookls restrictive, well I might just have to become a member of the straight pipe club, straight piped Cummins 5. 9L sound so sweet don't they? What is the best thing to do to the injection pump: Advance the timing or turn the screw? If I had any pump enhancements done I would probably take it to someone who knows what they are doing, I would hate to have to buy a new one. How long will these pumps last for? Mine has 173,500 miles on it and hasn't been touched. I replace filters on it every 15,000 miles and usually run fuel conditioner in it. Thanks for the input

 

[Doug]

The exhaust on the W250 has a number of "kinks" that do restrict exhaust flow. From what I have read, I don't think that there is much difference between a quality 3" exhaust with muffler and with going without a muffler. Most after market exhaust systems are 3" to the muffler and 3. 5" from the muffler back.
Doug

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91. 5 D250 5 speed, 16cm2 housing, gauges (EGT, boost, tach), BD exhaust brake (w/ 60lb springs)

 

[J DeMaio]

Well thanks for the information. How much do these exhausts help on the turbo. What I mean by this is how much turbo lag will still be left after the exhaust install? Thsi truck is bone stock. If I upgrade the exhaust and adjust the fuel rate how much more power will I make? I don't really want to spend the money on the turbo housing. Any tips will be appreciated.

 

[Scot]

When I did mine, I installed the housing first and then installed the boost, and pyro gauges. Boost was the same but comes on quicker. That gave me a base line to work with.

Using the instructions found in the archives here, I turned the pump up as suggested. The most difficult part was removing the stop collar on the full fuel screw. TST suggests removing it, which I did. Mark it with a dab of whiteout between the nut and screw. I ground the collar off with the bench grinder.

The most frustrating part was setting the idle back down. Some here have had trouble breaking the jam nut loose. I took a good tight (10mm?) wrench and just used it at a severe angle and stuck a screwdriver in the box end. That was easy. Turning the idle screw was the frustrating part. The paint made it tight.

It was all fairly simple and straight forward. Tools are few and if you record what you do, it can be undone.

The increase in performance was large and noticable. Before it would not hold speed in 5th with 1500 lbs trailer on a long grade. Yesterday I pulled a heavy 8 1/2'X16' trailer with a '79 Ford F250 4x4 about 250 mi. I could run it at any speed I cared. I never let off and was on cruise most of the time. Never saw over about 1150 deg. This is the first time I have had a good load on it since turning it up.

The main thing that has stopped me from losing the muffler is finding the pipe and

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