Back pressure

[rmb1393]

I cut off my muffler and noticed when I start the truck it revs the engine for a second then back to idle but I hear a slight knock. Im just wondering if my 2002back f350 7.3 needs the back pressure from a muffler or not. Cause I was thinking of welding. Straight pipe off the down pipe.

[mxfever090]

Back pressure is the enemy of a turbo.

A gas engine needs backpressure to run efficiently. Not so with a turbo diesel.

I'm lost as to why your engine would rev up now. Hopefully others have an idea

[Galaxie]

Your turbo is your motors back presure. The turbo doesnt like backpresure.

So, I have a feeling you are hearing the motor start and rumble before the turbo starts spinning at speed.

[JEL]

Could just be a little injector noise. These engines can have noisy injectors at times.