I just picked up for cheap a Nismo exhaust. It was heavily discounted because it was missing the y-pipe and the midpipe has a dent.
I bought the proper gaskets and a nismo y-pipe, but before installing it I was wondering if this dent on the mid-pipe would have any negative effects on the engine / power or if it's nothing tragic.

 

Very minor if anything.

Take it to a local muffler shop and have them weld in a straight piece of pipe in place of the dent

 

+1 This.

You *might* notice something amiss at high rpm but really doubt it's going to make much diff 99% of the time.

 

I like the muffler shop idea...but rather than splicing a hard pipe in I would splice in a flex hose section...

 

I don't think that is TOO bad. It may have just a minor effect on the flow of air, but I don't think it is dangerous for the engine to keep it like that.

 

This is hilarious. People pay ridiculous sums of money for mandrel bent piping because it has no kinks and flows better but this guy gets a big dent in his pipe and people shrug it off like it's nothing.

 

I bet a stud gun at a body shop can pull it out

 

I hear the closer the dent is to the headers the worse is for the engine and back pressure issues. The dent on my midpipe is after the resonator, closer to the muffler, I hope that's far enough not to create any loss of power or problems.

 

I wouldn't think that matters. Any restriction in the exhaust is a restriction, whether at the front or back of the exhaust. If the cat is clogged or the muffler is clogged, it will still have the same effect.

 

Just finished installing the Nismo kit and besides sounding great the car pulls way harder! I expected it to be louder with less power gain, pleasantly surprised it was the opposite. The only other mod I have is a 5/16 plenum spacer.

About the dent, I can't scientifically say it doesn't make any difference but it really doesn't seem to have any neg. effects on power/torque/sound.

 

I was referring to the irony of some of the conversations and arguments I've witnessed/been involved with regards to exhaust flow and bends in pipes.