RESPONSE:
First of all, I have an ESS SC on my '97 540iA. Second, according to Dinan's price list, the 9/98-2001 540i Supercharger Kit is still "Under Development". Are they ready for prime time and what's the price?

For most of us, the $7K-$9K (inc labor) delta *does* weigh heavily on our decision. But for this discussion, I'll ignore the price and appearance factor.

Dinan Pros

• Uses the very well-revered and popular Vortech V-2 SQ (Super Quiet).
• Dealer network in the US.
• Dinan has a reputation to uphold in the picky US market, so their products tend to be well engineered. Usually, you can't go wrong using Dinan equipment.
• Many board members are familiar w/ Dinan products, so "unofficial" support and news is much easier to come by.
• DanB and Jimmy have dyno'd and proven that the 9/97-8/98 Dinan setup works well, seems reliable, and produces more HP than the ESS kit.
• You get the cool "DINAN 5" badge.
• Dinan sometimes works in conjunction with your factory warranty. It looks like SCs are an exception. From Dinan's website:

  "Dinan's warranty matches whatever period remains on the individual New Vehicle Limited Warranty for up to 4 years or 50,000 miles. Exceptions are turbocharged, supercharged or stroker engines for which a Dinan Drivetrain Warranty is available."

  Hmmm, so you have to pay extra to have the rest of your drivetrain covered if you install a SC?

ESS Pros

• ESS has been supercharging BMW's in Europe for many years.
• I can't think of a BMW SC tuner that has a better mastery of ECU reprogramming. That's why they tend to come out w/ SCs for new BMWs faster than other tuners.
• Their 540i kit is well engineered and has a rock-solid mounting bracket system.
• ESS has probably exceeded 200 540i installs worldwide with 50+ in the US. I've personally been in contact w/ 5 people in North America alone.
• ESS tends to tune their system conservatively by only raising the US rev limit 100RPM and running 7PSI boost. Less HP, but it may positively affect reliability.
• The Powerdyne's intake and exhaust ports match up well to the V-8's normal intake track, making the install easier and allowing smoother airflow.
• The non-oiled Powerdyne SC is extremely quiet and cool running.
• Without the need for oil plumbing, the ESS kit can be removed w/ nearly no indication that it was ever there.
• Installation time is 50-75% of the Dinan install time. It's not an easy install, but I'm pretty sure it's easier than Dinan's kit.

Dinan Cons

• The Vortech intake and exhaust locations result in extra intake plumbing.
• The Vortech is somewhat audible, which is only bad for those of us who prefer "stealth mode".
• Install time is longer and more complicated.
• The 9/98-2001 kit @ 384HP has 20HP less than the earlier kit due to (possibly) more restrictive intake/pre-cats/ECU programming difficulties. The HP and torque curve isn't as nice as before. If all this equates to better reliability, it would be a Pro instead of a Con. In contrast, ESS claims their newer kit adds 2HP (417 engine HP), but I haven't seen an independent dyno yet to back that up.

ESS Cons

• They are in Europe so everything has taken much longer than expected to get across the pond. They recently changed shipping carriers, so this might be moot.
• Support would be harder to come by due to the distance. Regardless, the ESS install and design is relatively simple. If my SC dies, I can unbolt it myself in less than 45 minutes and ship it off for warranty repair, with the car still being drivable. Having the Dinan dealer a tow-truck ride away and a fully working car in a matter of days might be nicer. So far, ESS has been exemplary in providing any service necessary so it's not a real "Con" yet.
• The Powerdyne unit is frowned upon by some tuners, including Dinan. ESS reworks the Powerdyne unit and claims no significant failures to date. My buddy w/ a Mustang has 70K miles on the same stock Powerdyne SC w/ no problems. I have yet to hear any reports of issues w/ this model. Still, the Vortech has a safer reputation.

Verdict

Without money as an issue I agree w/ RevHigh, especially if your car is still under factory warranty. The Dinan uses a proven SC, has (depending on where you live) local warranty service available, and has produced a good product.

I chose ESS because my car is only under CPO warranty, money was a partial issue, and I got a good feeling about the company via e-mail and in person. The Powerdyne BD-11A hasn't been proven to be unreliable and provides quiet and smooth power. I'm very happy w/ my decision, just as the Dinan owners are. Get whichever you are most comfortable with - both are good products. Anyone going to Bimmerfest (West Coast) might be able to see and hear both systems side-by-side.

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