Quote:
Originally Posted by 3GFX
Hi All...I know there have been other threads on this topic but I wanted to start an opinion and factual thread in one spot for my own benefit 
Purpose: Motor work for a track orients street M54 powered BMW.
I'm slowly turning my non-M Z4 into a dual purpose track and street car. I've done suspension, brakes and now seats, to my liking. I'll be investing in track rubber shortly. Now my attention turns to engine work. Summary: I want more power. I have headers, intake and a tune. Roughly 280 at crank dyno'd. I'm planning on upgrading my water pump (metal impeller) and will also be looking to take car of the oil pump nut issue in one way or another (was thinking cotter pin).
I was considering a VF supercharger, but I've read and been told multiple ways that the heat generated will quickly ruin gains from forced induction on the M54 on a track day. I'm still leaning this way.
The other option is cams, which might be a little cheaper and easier on the wallet if not as much power. I'd like to get over the 300 crank mark in all honesty. I know an S54 motor needs to have the valves checked quite often. Would this be something of a concern with aftermarket cams?
Chime in your thoughts and experiences. I welcome all. 
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With headers, intake, and a tune, you're probably closer to 250 bhp in all honesty. Your mods + aggressive cams will not get you to 300 bhp either (270 bhp is more realistic). A 300 bhp / 252 rwhp build looks like
this. Dynos can be made to read however the customer desires. Fortunately, a VF kit will get you well over 300 bhp.
A supercharger can increase the magnitude of crankshaft vibrations, theoretically making oil pump failure more likely, although there isn't enough data out there to show that FI cars are more prone to failure. The cotter pin method isn't a reliable fix for the oil pump problem, as the oil pump's shaft can shear. The ATI super-damper and an upgraded oil pump are the only methods I know of that truly minimize the problem.
I highly recommend an LSD, even before supercharging. Be careful of going too aggressive on the final drive, as your car will require more shifts (potentially mid-corner). I've been thrilled with my Quaife LSD and 3.46 final drive. I had a 3.64 open diff before picking up the 3.46 Quaife, and it made the car a whole lot more fun too. However, it had traction problems coming out of corners with the supercharger. The Quaife made a night and day difference in corner exit speed.
As Dave pointed out, cams aren't really worth it on these motors any more. Previously, hotter cams could partially bridge the gap between the M54 and S54 at a fraction of the cost of moving to a Z4M or M3. These days, you can buy a whole ZHP motor for $1200, and a Z4M is <$20k. With aggressive Schrick cams, you will pick up 15-20 hp, but only at the very top of the rpm band. Cams essentially move the powerband, meaning cam choice is a compromise between power at low rpm and power at high rpm. Aggressive cams make less power than stock at low rpm.
If you do install a VF kit, WMI is great for cooling the intake charge, but I wouldn't recommend having a custom tune that
requires WMI on the track. As the water/meth is used, the remainder sloshes around in the tank, and the pump doesn't provide reliable flow under high cornering loads. Therefore, I wouldn't use it for anything beyond supplemental cooling, and a lot of track guys don't recommend it at all.
Your best bang for the buck is going to be moving up to a Z4M, which is nearly track ready. I fully understand wanting a unique car; just be aware that it will be much more expensive in the long run if you try to mod your car into Z4M territory (let's not forget that a Z4M can be modded into supercar territory). You'll spend $6k on a supercharger after all is said and done, and it won't add to the resale value of the car. It will be a hassle to pull the supercharger off to sell for half of what you paid, and in the meantime you'll need to store all your stock parts. Consider it a sunk cost. I'm not saying don't do it, but take into account the true lifecycle cost.
The S54 is a better track motor. While they do fail from time to time and suffer from a handful of Vanos / rod bearing issues, the S54 is still pretty stout. The M54 is a great commuter motor that can be modified to impressive power levels. On the track, the oil pump issues make it a timebomb, and the fixes cost half as much as it would be to upgrade to the more powerful S54. Therefore, I don't recommend a supercharger for an M54 track car, but not because the supercharger itself will cause any problems. They're reliable on the street, but the M54 isn't track-ready.