I have had my muffler off for 24,000 miles, and when I did my side pipes I gutted the cat and ran a 5" pipe through it. Has run fine, and I like the sound. If I was towing all the time it might be a bit loud, but it runs fine. I had a cat test pipe and didn't want to fool with putting it in and out if I had to go the dealer. You cant tell by looking it has a pipe through it. I have a test pipe someone could have if they are in CO or want to pay the shipping. Levi

 

I've had my exhaust with no cat( and you can look straight through my muffler) on for 25,000 miles and no problems!!!backpressure? what backpressure.....

 

"...i dont know how much of an argument you want to get into...but if you want to get into technicals we can...

the VGT system of a 6.0 runs exclusivly off of backpressure to controll boost. just because you have not "seen" problems doesnt mean they dont exist, and ESPECIALLY with 6.0's, each motor reacts differently to different conditions, so you cant bundle the all together and say "well it worked on mine".....on the 03-04.25 motors the latest programming uses an inferred backpressure reading based off of MAP and BARO readings....the 04.5-07 motors use the EBP sensor along with the readings from the Map and Maf sensors....that alone makes it a completely different ball game between the two builds. there are even more differences between even more years we can go into if you want to as well....

The vaines in the turbo dont "open for less boost and close for more boost" like most people want to think...they open and close to controll BACKPRESSURE, thus controlling the exhast side turbine based on how fast the air has to flow out of the turbo, and if you open up the exhaust pipe side, you have changed the airflow out of the turbo, which changes its operating charactaristics, and not for the better.... if you reduce the exhaust side backpressure too much, even if the truck seems to be driving fine, you can actually reduce its performance. on a wastegated style turbo, like the newer 7.3's have...none of this holds true...but on a 6.0, you are 100% wrong....if you want to get more technical and deeper into it we can... ..."


https://www.ford-trucks.com/forum/99-03-7-3l-general-discussion/13862-back-pressure.html<!-- / message --><!-- edit note -->

 

and as quoted on that same thread:
You are talking about the VGT and its use and function. On the 6.0L PSD there is nothing that monitors backpressure in the exhaust... no pressure trasnducer or any other way. There is a reason for the VGT, it is DRIVE PRESSURE. Back pressure is always a bad thing... But...

If your non VGT turbine were set up to maximize resonse in the upper 1/2 of the RPM range... what would the drive pressure do with the turbine at say 1/4 of the RPM's? Not a **** thing. The turbo would be extremely unresponsive and "laggy". The ECM knows the RPM's, load, throttle position, and a whole bunch of other things..... and this is some of the collective information used to determine how to actuate the VGT turbine.

It is not triggered off of back pressure.

As you straight pipe a 6.0 it does run and sound better. We have also done this to a large handfull of 6.0L and a crazy amount of 7.3 trucks as well as duramax and cummins trucks... and I have never seen a customer that felt that the straight pipes were bad for performance.

When you decrease exhaust back pressure (Think of back pressure as a traffic jam in the exhaust... the air wants out and more air is coming...but the traffic jam keeps stacking) you allow the given DRIVE PRESSURE to have a greater effect on the turbine... no matter what the current pitch or variable geometry is set at. The VARIABLE GEOMETRY TURBINE allows your turbine to make the best use of the available DRIVE PRESSURE (Drive Pressure is the pressure feeding from the exhaust manifolds) by optimizing the vane pitch to the conditions at hand. It works very well.....

The sad part is that so many get carboned and stuck.....boo-hiss. The good thing is that you can get a modded stock VGT turbo that has been rubbed on to prevent this... and also flow a crap load more air with a hybrid compressor...and its a direct bolt in.

So, back pressure is bad.
Drive pressure is good
Back pressure that nearly equals or exceedes drive pressure is VERY bad.
The VGT system does not know what back pressure is.
Straight pipes save lives
If its too loud, your too old.

 

no mufflers!! no kittys!!

 

Interesting you should quote Marc on this. I know him personally as a matter of fact. He put an injector in my truck 10 days ago at SSS in Winston-Salem. The exhaust thing has always been a matter of contention about HP and spool-up time. Personally I've had no issues except for lower EGT's with my straight-piped exhaust, but I can't speak for anyone else. I'm sure there will be more opinions and facts on this thread.

 

I believe class is dismissed!

 

Yes I agree with denman81. If the turbo was being controlled by backpressure then they would have put the EBP sensor on the output side of the turbine not on the input side.

 

Umm... YEAH! What Tim said! Ummkay?

 

I like how this site is directly named in that thread. lol Marc is a great, smart guy. cleaned my turbo for me. funny that guy copied and pasted what he said. whatever backpressure is needed is not worth it to lose my whistle. whistel>backpressure. lol

 

Generally speaking, less restriction in a 4 stroke exhaust means higher RPM performance and loss of low end performance. I can't think of any reason why that wouldn't work the same way for the PSD.

 

If the powerstroke 6.0l was not a turbo engine I would agree about the loss of low end torque but because your forcing air into the engine that rule no longer has the that same effect. The more air you force in the more horse power. the turbo is doing the forcing that is being driven by the exhaust from the manifolds. If there is resistance to the output of the turbine it will not spool up as quick or fast. That resistance can be in the form of back pressure.