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down a dark alley of turbocharging.

Not sure exactly what happened, but I'm happy to say that everything appears OK right now.....any thoughts, suggestions, and flames are always welcome....



Popped the hood the other day to change the oil and filter, hoping to fix the slow oil pressure light issue that I posted about recently. I had also noticed a new oil leak, and needed to take a closer look. After buttoning up the rear main and retorquing the valve cover, I enjoyed a few thousand miles of leak free operation, and was bummed to see and smell oil again. The car has been so reliable that I rarely pop the hood. (that's foreshadowing, folks)

Hood came up...oh crap, the oil cap wasn't there. Well that explains the leak. Clearly my fault, since the cap was sitting on the intake manifold. So I pulled off the intercooler, and was checking out the piping and wiping things dry, and making sure things were goodntight, when I noticed the air intake tube had popped off the inlet side of the turbo.

OH CRAP!

Ok, don't panic...the hose clamp is just dangling there...maybe I just pulled it out while I was cleaning. Maybe not....oh crap oh crap. I know that in the 5-7K miles I've had the turbo, I have been under the car and visualized that everything was tight and in the proper place...so worst case would be running around with that pipe off for maybe 1000 or so miles.

Well clearly the oil cap and the intake tube is not related to the long oil light problem, and the car had seemed to be running fine.

Hmm now I'm fearing a JBort situation...how to alleviate this panic? Ok, I'll button it up real tight, do a compression check, and hopefully all will be good. I had a feeling when I was putting this together that I should flare the edges of the tube just to be sure they don't pull apart. I did that on the coupler I had made between the intercooler and throttle body since there was very little room to get a good bite with the clamp. I also know that when those intake tubes get a little oily, they can tend to slip apart.

Replaced the oil with 20/50, and a new WIX filter, which ended up not improving the long oil light. Next for that issue will be the spray bar banjo bolts, then possibly look for a bad checkvalve/anti-drainback valve, if it exists on this motor, which still isn't clear after a little poking around past posts.

Nervously checking the compression, I was relieved to see 150-155 in cylinders 2-6, and cylinder 1 pushing 165. This was a hot, dry test. Phew!! I did read, though, that dust contamination can take a long time to show up in the compression test, so I'm keeping my fingers crossed for the next check down the line. Snapped a pic of the plugs:



Buttoned back up, I take it for a test drive. Not sure what to expect in terms of now knowing that the intake pipe was properly connected...but something seemed different. The woooooshing of the air upon boost seemed a little muffled, and it seems like the boost is building a little slower, like it takes a few more hundred RPM to build to the max of 9. Hmmm...not good. Also, the engine almost dies when I come to a stop...and the AFR gauge confirms that I am having a very rich low-speed running condition. Crap...does this support the idea that the air intake tube was, in fact, disconnected?

Ok, well either way, its properly fitted now, and I need to work with my RRFPR to get the low speed mixture back into spec.

A look under the hood at idle...my fuel pressure gauge is pinned! The gauge maxes out at 65, and I know I initially set the gauge to be around 50 at atmospheric, and had seen the gauge at that reading many times along the way. How in the hell is the RRFPR suddenly pushing so much pressure?? I had to back the mix screw out about 10 turns before the reading came into range, and the locknut was tight when I started.

WHAT HAPPENED AND WHODUNIT?

I would have expected a rich mix if the air intake tube had been off when I initially set the mixture...but the air intake tube certainly would make no difference in the pressure that the RRFPR was pushing.

So, I'm back to square zero. Turbo is working great and just slightly muffled from previous, car runs great and the AFRs look good at idle, cruise, and WOT; I now have a compression baseline...but I'm still not sure if I knocked the air intake tube loose when I was messing around....or if the BEGI 2025 RRFPR had a jam and suddenly required, out of the blue, and radically different atmospheric mix adjustment.

If that wasn't enough, I discovered that my intercooler pump crapped out. Which I'm sure happened only very recently. A slightly used Bosch Mercedes OEM pump is on the way.

And if that wasn't enough......I ordered a 12psi wastegate spring over a month ago, and the guy's second attempt to ship one to me failed as of today. Is that a sign?

And if that wasn't enough..I couldn't sound out Albuquerque, and had to google it

Your mixture was rich because your elevation was 5500ft and the air contains 20%+ less oxygen.

Nice read. I guess the moral of the story is user error is always the primary suspect.

So, you car doesn't compensate for altitude? I think my 745 drove just fine over the Rockies.

demetk wrote:Nice read. I guess the moral of the story is user error is always the primary suspect.

So, you car doesn't compensate for altitude? I think my 745 drove just fine over the Rockies.

Your 745i is programmed for boost and air density is measured by the AFM.

BEGI adds fuel pressure via boost regardless of air density.

Todd, I'm at sea level, and always have been.

I still don't know how the BEGI turned itself up 20+ psi since the last time I fudged with the tuning, when the center screw was locked tight. Do you think the unit may be malfunctioning?

My general thought is that even if the tube had popped off the inlet, it would likely hold itself closed under engine vacuum. Short of popping it off, and seeing how it runs, I still don't know exactly what happened.

Question: If there wasn't much intake air coming through the AFM, would the motor still run? If not, then I assume that I was the one to pop the tube out when I was messing under the hood.

I don't know. Keep an eye on it.

Interesting read. Sounds like you've got a handle on things though. A turn of the RRFPR, free-air calibrating your o2, checking oil pressure to the turbo, and you'll be fine.

Good luck!