Settle this for me

[Lancer250]

A friend and I have been debating exhausts. I say that by doing a delete pipe and keeping the stock exhaust it would run the same as a down pipe back 4" exhaust with a muffler. He says I'm all wrong. Please don't be afraid to hurt my feeling just please give me the real answer. Thanks.

[jesilvas]

Stock is 3.5 or 4?
It all depends on what muffler? Stock muffler is restrictive. But a free flowing 4" is just sound absorption material in a free flowing cylinder. So with or without muffler doesn't matter as long as it is straight through.

[Checkmat3]

I would think that the 4" exhaust would be better being that forced induction needs air in and air out.however im new to this diesel thing so who knows?

[deamsphelps]

I thought that the stock muffler is just a resonator. I don't know what it looks like in there. It's pretty small. If he went with down pipe back, he should consider no muffler because it isn't that loud and it would be cheaper. He could just do the cat/dpf delete and stock then later do dpf back if he wants more sound. That way he has the flexibility to go back to stock but have a better looking tailpipe. But some like the sleeper stock tailpipe. Decisions decisions. Been there.

[INJEKTER1]

my stock muffler was straight through, no restrictions.... DPF.... plenty of restrictions....my aftermarket muffler is the same .. straight through.... your delete pipe with stock muffler is going to be about the same as an aftermarket set up performance wise... technically the bigger aftermarket pipe will be better performance....you probably wouldn't be able to tell much except for the sound....just race him, and settle it that way...