1st Gen R53 Cooper S Threw codes at the track

I spend Saturday and Sunday at VIR at the local BMW club's HPDE. Sunny, 70*F, slight breeze, awesome days. On Sunday afternoon, 2/3 of the way through the session, I'm heading up the bridge straight, supercharger is spooling up, maybe 5k rpm, and then the supercharger cuts out, boost drops to 0. I clutch in, coast, engine's still running, so I limp it around and pit out.

We checked the intercooler boots for a crack or hole, nothing. Bypass valve was moving, so it wasn't stuck open. Can't find anything loose or falling off or leaking. Car was making normal vacuum on idle. I was able to drive it unless I made positive intake manifold pressure, so I kept one eye on the boost gauge and one on the road, keeping the boost under 0 psi. Took a couple hours to get home, but the car seemed okay.

At Advance Auto, I read the OBD and got these codes: P1109, P1242, and P1688. In the parking lot, we noticed a burning smell coming from the back of the block. Any ideas what could have happened?

Limping home from the track sucks. :frown5::frown5:

 

I kept an eye on the oil and water temp, and nothing was too dangerous. But yeah, a friend told me the supercharger doesn't spin fast enough to run the water pump when the crank pulley fails. Luckily it was relatively cool out, and it got cooler while I was driving home.

The same friend pointed out that heat is not only the result of crank pulley failure but the cause, which made me remember that I have a brake duct running right next to my crank pulley, so the airflow to my pulley is already reduced. Tack on the 15% supercharger pulley I installed last weekend, and the big straightaways at VIR were probably cooking that thing.

Thanks for the diagnostic help, guys.

 

Yup, that was the OEM pulley. I haven't gotten under the car to examine it yet, but I think all signs point to the crank pulley. When I had the car apart to do the supercharger oil and oil pan gasket, I took pictures of random parts of the car. Here's the crank pulley before failure.



I think the rusty stuff on the outside is where the broken brake duct hose wire was rubbing. I had a hole in the duct that may have been inadvertently cooling the pulley, but I patched that up when I put the car together.

 

Good advice, thanks. I was exhausted last night after limping the car all the way home. A 60 mile trip took 2.5 hours, staring at the boost gauge all the way home. Also, I need to get an OBD code reader. Nobody in the paddock had one - too many E30's and E36's.

 

I think I've made a positive diagnosis. I pulled the wheel and fender liner, and I took the belt off. When I reached under the brake duct, I could wiggle the part of the crank pulley that has the belt grooves in it. I'm actually surprised I could drive the thing. I could spin the outer ring around the inner part of the crank pulley with little effort.

Look closely, I wiggled it one way, snapped a pic, then wiggled it the other way and snapped another picture.

 

OEM = not going on my car again

Heard about the RMW pulley; apparently it's stock size vs +1% for the ATI pulley (but that won't affect the belt choice). I like things like steel and rubber, the idea of a fluid filled damper just doesn't appeal to me. Not saying it's a bad product or that I did much research into it, just a simple human bias. So I went with the ATI damper. Apparently they're awaiting a new production run, so I had to call around a few places to find one, but it's in the mail.