I have a 2006 350z 6MT with about 55k miles on it. Lately I have been noticing that whenever I get into the throttle moderately-to-heavily, I smell a slight burning smell. Oil level is good last time I checked. Mods are JWT Popcharger, Motordyne 5/16 spacer and MREV2 lower plenum, Invidia Gemini cat-back. I have a mail-in UpRev tune as well.

Is there anything obvious that I should be checking, or asking a shop to check out?

It may be placebo, but I swear the car started feeling more sluggish when I swapped my JIC y-pipe and Fujitsubo exhaust for the Invidia Gemini. After that I got the UpRev mail-in tune but I don't really feel like it made a difference. By the way, I smelled the same slight burning smell when logging my WOT runs for the mail-in tune.

Any suggestions would be appreciated, thanks!

 

Burn off from the new/newish exhaust?

 

watch for clutch slippage...could possibly be clutch burning???

 

If it smells like a old truck/old muscle car with shitty exhaust, its your car running rich at wot.
If it smells like burning plastic or a house fire its the gaskets and or the new exhaust burning in which will go away after a few weeks.
If it smells similar to sulfur or hot metal it could be your clutch slipping.

If you smell the "old truck" smell it could be your car running rich, or it could be the stock cats have gone bad and are not filtering right anymore, depending on if you have them i didnt see any mods to that area in your list.

Is it any of these?

I'm going to place my bet on car running rich at wot, mine has an uprev dyno tune and high flow cats and i get the unburnt fuel smell at wot just because my car is tuned a little rich cause it didnt like to be on the lean side of tuning.

Im betting its rich also due to the mail tune which i would guess they set it a little rich just to be safe because they cant monitor afr's through the mail :P

 

Could be, but I have probably ~1000 miles on this exhaust system and I do remember a different unpleasant smell from the first couple hundred miles, which has since gone away.

That was my first thought. When I'm really getting into the throttle I try to glance down at the tach to make sure that the engine speed is increasing proportionally to the wheel speed, i.e. to make sure the clutch is not slipping, and it appears not to be.

It's definitely not the old truck / muscle car scent...I know that one very well from my old Subaru with catless downpipe and off-the-shelf Cobb stage2 (pig rich) tune.
It's somewhere between plastic / house fire and hot metal. But the exhaust system has ~1000 miles on it so I would be surprised if that's it. Maybe it's the clutch.

Is there anything bad that could be happening inside the engine that could cause this? That's what I'm really worried about. To be honest, I wouldn't be heartbroken about a worn clutch....need an excuse to upgrade anyway!

 

when i had that exhaust it took mine a while for the smell to go away, mine also had a sticker on a resonator that took longer to burn off. also make sure you didnt run over a plastic bag, what will happen is it will melt, and sling back melting somewhere else on the exhaust til it is gone...

 

Hmmm alright, thanks for the input. Part of me wants to just beat the hell out of it for a while to run it real hot and burn off whatever's on there....the other part of me thinks something could be wrong internally in the engine that is causing the smell and I shouldn't beat on it at all. I guess the only thing I can really monitor as far as engine health goes is oil consumption. I think I'll top it off this week and do some heavy pulls and check the level each day. Maybe it's burning oil that I'm smelling....I'm just not sure what that smells like

 

Rise, Zombie thread, RISE!

Was the cause for this found? I'm having the exact same issue in my '06 350z 6MT.

 

check this

 

I would agree if it wasn't also sticking at high rpms.

 

I never got to the bottom of it, and come to think of it I haven't driven the car very hard (if at all) recently. I still have all of the mods listed in the OP except I removed the UpRev tune. If I get a chance today I'll take it out for a good rip and see if I get the smell. In any case, I wish I still had my JIC y-pipe and Fujitsubo exhaust. It sounded better and I swear it was faster. Maybe true-dual systems like the Invidia Gemini are better suited for forced induction builds.