1st Gen R53 Cooper S What am I smelling when I stomp on the gas?

last night I went for a spin and decided to do a little research on the smell thing. Since the last hard pull the car has been driving around town a few times, maybe 40 miles total of short and easy trips, so it was time to clear the pipes again.

First pull was 2nd gear, full throttle up to about 55k rpm at 14.5psi boost. The roof was cracked open and we were headed into the wind. The smell that got into the cabin was so strong we had to open the windows. My son said that a few weeks ago when we drove home from Road America, his friends who were driving behind us also smelled it. Conclusion from all that - the smell comes out of the exhaust and depending on turbulence, speed, open windows, gets sucked into the car. Scary to know that some exhaust fumes actually get into the car even when every window is closed, but there's no other explanation. If we had such an exhaust leak for fumes to come from the front of the car through the hood to the fresh air intake, that would be audible.

After the first pull, we did a few 6psi runs with less throttle. No more smell. Next open stretch of clear road, one more hard pull at full throttle and boost in second gear, almost exactly like the first one, but in a different direction to the wind, and no smell.

I figured if this is a leak in the intake system, rpm should not matter, but boost should, so we did three more pulls in 4th and 5th gear full throttle from lower RPM, boost at 10-11psi, climbing slowly with the rpm building before lifting. No smell. One more hard pull to 6k rpm, and again, no smell.

Conclusion - crap builds up on the IC surfaces or other areas of the intake, and if not driven hard for a while, the first hard pull will suck much of that gunk into the engine, it burns the oily mess and what we smell is a puff of smoke coming out of the exhaust.

So for next season, I've added a catch can to the shopping list. The smell clearly was "exhaust flavor" with a blend of some real icky stuff in it, probably exactly what come out of a crank case and builds up in the IC. Everyone who ever smelled it agrees that it doesn't smell like rubber, just some real rank exhaust.

 

15% pulley
new belt, ATI damper, idler and tensioner this summer

I did completely clean my IC this summer in a bath of Simple Green, so it doesn't have long-term gunk caked on the inside. The boost reported to the ECU is 14.5 psi at about 5k rpm when I had a chance to glance at the numbers. Might even go higher, but I don't like getting near redline.

Everyone's rear hatch seal not working?

I am wondering if smell enters through about those rear vent holes below the hatch for cabin air exit. Those may actually suck air in if the sunroof is open and creates negative pressure in the cabin.