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Old 04-03-2011, 08:24 AM   #12
McSpeed
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Join Date: Nov 2009
Location: Connecticut
Posts: 1,073
My Ride: 2005 ZHP TT Stg 1
Quote:
Originally Posted by MasterC17 View Post
I presume the lock-tite nuts on the later cars are still very much prone to this problem?
The two things the later cars have going for them:
  • a different P/N vibration damper that lists a slightly wider range of harmonic damping frequencies - I posted pics in some thread around here in response to azzy's question about it
  • a sprocket nut (aka OPN) with factory applied loctite
Do they make a difference? Although I can't recall a post about a newer car (IIRC 9/2003 onward) losing its sprocket, I doubt it. I think it's just a matter of time- tracktime that is. Really hanging out above the 6K mark is going to create wild crankshaft harmonics that will eventually loosen the nut or break the sprocket shaft. These are street cars and I guess BMW doesn't expect revving like that. When the harmonics get going your crankshaft starts to become much less a solid piece of forged steel and much more a really long tuning fork. Especially if you're making more power than stock and/or running a lightweight flywheel. The oil pump sprocket is chained to the crankshaft and gets abused by the thrashing harmonics. To address this nonsense I installed Greg's upgraded pump, an ATI Super Damper and stuck with the stock DMF when I replaced my clutch. The perceptible upshot is that now when I rev over 6K it's completely butter smooth (this is pretty much due to the Super Damper). Before, it was kind of angry-feeling. The more imperceptible upshot is total peace of mind about tracking it.

One simpler alternative might be replacing the stock vibration damper at a conservative interval - TxZHP04 did this and said it felt a lot smoother. I think older cars tend to see more OPN trouble primarily because their vibration dampers wear out and usually go unreplaced for years. The problem is that, like a bushing, they can look ok but not work well. Whatever the car's year, they're made of rubber and ~5 years is a reasonable street driving lifespan for them IMO. Infamous racer mrshelley replaces his vibration damper(s) after every 1-2 GA events(!). The more robust and better damping ATI Super Damper is rated for something like 5-10 years depending on how much track you're doing, but it's not allowed in some racing classes.

Can you get by tracking the car without the upgraded pump if your harmonic damping is good enough? Maybe. Time will tell. But if you're really hanging out above 6K regularly I wouldn't risk it myself.

Fwiw my OPN was on super tight after about 75K of spirited street driving including about 3K miles turboed. Did I rev above 6K much? Sure. Did I hang out there much? No.

Quote:
Originally Posted by PEI330Ci View Post
The biggest pain is the that you have to drop the front subframe: Disconnect steering shaft and hydraulic lines, disconnect the brakes, and drop the struts. You'll have to have an engine support from the top, as you'll be dropping the engine mounts as well. Pulling the pan and pump in comparison is pretty easy.
When I did it I didn't disconnect any hydraulic or brake lines or drop the struts. To get the subframe out I popped the control arm connections out of the wheel hubs, moved the steering rack forward, undid the lower motor mount nuts, undid the subframe bolts and voila. This was all per BMW TIS. Not easy at all either. And I wouldn't trust an engine hoist if you're leaving it over night- I used a screw jack under each motor mount to be safe.
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Technique Tuning Stage 1 Turbo w/ Greddy Profec B Spec II | 3.07 Quaife
ATI Super Damper | Vaio Oil Pump | VAC Pan Baffle | SRE Organic Clutch
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Turbo Driveability Video

Horsepower vs. Torque

Last edited by McSpeed; 04-04-2011 at 08:53 AM.
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