hey to everyone out there, i'm new to the diesel world and was wondering about an exhaust upgrade for my 1993 f-350 7.3. i have read many threads and articles saying not to go bigger than a 3 inch exhaust on a non turbo because the muffler and smaller pipe causes back pressure that is needed. but on a turbo it is ok to go big because the turbo causes the appropriate back pressure needed. so i would like to know is this true or is this all just a folk lure. i would really like to stack my truck. thanks for any and all help.

 

That is true on the IDI's. I have ran 3" to 5" stacks on them and been fine on a non turbo'd IDI. We used a y pipe as well. I have had friends that had 4" and bigger on them and they have had valve train problems sooner or later with them. Basically burning valves.

 

to DB..

 

I dont buy the whole backpressure theory as I never run mufflers on anything and have never had any problems or lost any power doing it. On my IDI I run a 3" down pipe into a 4" straight pipe that splits in the bed into 5" stacks. Anything bigger than 3" really isn't going to help anything but the sound quality though. For the N/A trucks, most guys run 2.25" or 2.5" duals or will run them into a single 3" pipe.

 

Sycostang; you have a turbo so that gives you the needed back pressure, with out one you do need something for back pressure. I tried just the y-pipe and about a foot of the intermediat pipe before my turbo was incstalled, loss of power and about 50 miles later it would fill a 5 lane road with blue smoke going 35mph... So in conclusion you do need some back pressure, a 2.5 inch cherry bomb seems to be enough though. my 7.3 had one and my cousins 6.9 still has one. Also watched as we burned out the valves on a Hough model 120 front end loader from lack of back pressure, so yes some is needed.

 

Hey everyone, thank you for the information on my question so i will probably stick with the back pressure and go to the 2.5" dual setup but i want to run a few more tanks of fuel through her to get a good base line for my mileage and power. right now with a dirty air filter and synthetic oil no other mods have been made and i am averaging just over 20 mpgalso thanks for the welcome aboard, i am sure i will have plenty of more questions in the future but for now i just want to start out kind of simple with the upgrades. once again thank you all.

 

Maybe it's different for the N/A diesel motors, but I've never had issues with a gas motor. My last truck had a 460 with straight 2.5" true duals into 5" stacks and my mustang has long tubes with an X-pipe and straight 2.5" exhaust as well. I'll be picking up an 86 N/A 6.9 shortly, maybe I'll tinker just to satisfy my own curiosity.

 

It's something that diesels need, try running a gasser with open heads (no headers) and you will notice a little loss in low end tourque, all our engines have is low end torque. Or you could take that snail shell shaped restriction out of your exhaust and give it to me so that you can experiment with your 7.3.

 

That had crossed my mind because I miss the sound of my 460, but I think I would rather have the extra power from the turbo.

 

Trust me, you would.