Over the past few years, the most common topic in regards to the S65 and aftermarket performance has been "Which Supercharger kit is better" (or something along those lines). It has been discussed so much it's turning into one of those topics that you do not discuss among friends such as politics and religion as it could quickly ruin a friendship.
I am confident in saying that i doubt anyone has had more experience with the two most popular candidates than I have.
Over the past few years I have had countless hours of direct contact with both the AA Systems as well as the ESS Systems. Everything from have hours of seat time behind the wheel of E92's equipped with both kit down to the packaging of each kit and everything in between. I would like to touch on a few topics while I post the differences of both systems.
The list of similarities is pretty short, both are supercharger systems applied to the S65 engine. Thats might just about be it.
Power and Power delivery:
Horsepower and Torque gains are just about the most discussed aspect of the systems. **If anyone has any questions or would like to discuss any points of my post please do so and i will answer to the best of my ability.
Dyno Charts used for reference:
As far as horsepower goes, without a doubt a comparable ESS system will make more horsepower. It has been proven countless times with dyno charts from both companies as well as from customers and other types of individual testing. I will post two charts below as it will refer to them a few times through out my post.
Other than the chargers there has not been much discussion as to "why" one kit makes more power. It has been attributed to "one charger is larger than the other" but it actually goes much deeper than that. I will do my best to explain.
Boost: it is no secret that the charger makes boost etc... which allows us to make more power from an S65.
Once the air is compressed it has to makes it way into the intake manifold and then to the engine. The ESS system has a very short amount of travel between the charger and engine, the fastest path between two points is a straight line.
While the AA system requires the compressed air to travel quite a bit before entering the intake manifold, it much travel around a few 90 degree bends and actually go full circle before reaching the intake manifold, if you study physics you will see why this is not ideal.
A little background on superchargers: they take power to make power (we can go deeper into this by request but it has been discussed many times over).
Considering above, the ESS system does not have to work as hard to make the required boost to achieve the required power output; however, the AA system not only has to travel much longer distances but it also have to enter the intercooler half way between it's travel. During testing the AA system has to actually make a few extra pounds of boost to compensate for the few pounds of boost that are lost during the travel and from the intercooler. Which in turn forces the engine to work harder because it has to create more boost and is actually forced to work harder to compensate for a less efficient system.
Charge cooling: I want to be the first to recognize the improvements of aftercooling as an effective method of charge cooling, i have been a long time believer of intercooling and refused to admit aftercooling could be efficient.
The method of charge cooling should dictated by the platform and the system to find the most efficient method. In our case, space is an issue which is probably a big reason improvements in aftercooling have been addressed over the past few years. For example: the N54 which was the first recent turbo model by BMW was intercooled; however, the S63TU found the M5 is aftercooled and makes more power. Which makes my point that the method should be dictated by the platform.
Going back to the Boost section above, running an aftercooler allows the compressed air to reach the engine with less restriction and at the same time placing less load on the engine to make power.
Tuning: Tuning is just as important as the hardare as it needs to be perfected to allow the car to make power and make it safely but tuning also plays a hand in regards to power delivery and the overall user experience provided by the system.
The two largest things i've noticed after having been behind the wheel of both systems.
The first is the throttle response. The ESS system feels like a wire, the response is instand and smooth but powerful, with traction off and street tires on a 20" wheel the car will get away from you in third gear if you allow it too.
The AA system is smooth but it has a weird hesitation around 3K which could be attributed to the design of the system since the compressed air has to travel quite a bit (compared to the ESS System) or it could be software. This hesitation can be exaggerated based driving style or not be noticed at all based on driving style.
Second is the power delivery at redline. The ESS system revs cleanly to redline. If anyone has driven a stock E92 M3, you know that as you approach redline the throttle starts to close and if you hit redline it's a soft redline, you dont bang on it like the E46 M3. It seems AA has not figured this out and it gives the driver a weird drop off as you close in on redline, where the ESS system feels like it just wants to keep going. The only thing possible is to shift early once you've become accustomed to the system however, you are then missing out on a few hundred RPM of the power band given AA lowers the redline and you still need to shift early. This dip/drop off is seen on all dyno charts.
The system as a whole and going back to stock: Both systems can be installed by the end user; however, the AA system requires more parts due to the systems design. It also requires quite a bit of cutting compared to the ESS system. The ESS system includes any factory parts that require cutting so you actually retain the stock part that is modified instead of actually modifying your actual stock part. This plays a big role in going back to stock as with the AA system you will need to purchase a few parts to successfully put your car back to 100% factory form.
Meth: Meth has been one of the quickest ways to make more horsepower and provide an edge to anyone looking for one. However, i am not sure if requiring your system to use meth is the best method of making power. The ESS systems make more power without meth while the comparable level 2 AA system makes less power with meth. It is an added piece of the system which add to the systems install difficulty and could be a turn off for the DIY member. It is also something else that requires maintenance. Some other aftermarket systems come with some sort of light or gauge when your tank is empty, hopefully AA can add this to their system as it should have already been included.
Price: There is a difference of $2,225.00 between the AA Level 2 and the ESS VT2-625 (comparable systems) in ESS's favor. Where there is efficiency there will be savings without sacrifice.
Both charts were done at the same Dyno Jet. How do i know? Like Chris Berman would say on Sports Center "because we were there". Both posted in SAE and Smoothing 5.
ESS VT-625 System with full exhaust and no meth:
AA Level 2 System with full exhaust and meth: