We have developed both 1.9 liter and 1.8 liter BMW kits available for the Z3 and 3-series automobiles. Performance from both kits is very similar, with zero to sixty mph times in the 7.0 second range and under. While we are still in the final fuel curve calibration stage, our horsepower figures thus far are over 200 hp. Fuel mileage is essentially unchanged with our test cars achieving stock highway fuel mileage. This is attributable to our unique bypass system that will be explained later in this text.

Our design consists of an Eaton sixty-two cubic inch Roots-type supercharger mounted directly onto a proprietary cast aluminum intake manifold that replaces the stock intake manifold. All of the variable intake length gizmos from BMW are eliminated - when you pressurize the intake air to over seven psi of boost, tuning tricks such as those become moot.

We use the stock belt run to drive our blower, including the stock tensioner (exception: early 318i engines). The supercharger is supported by the new manifold and by under braces that connect to the engine block. Stock items on the engine are still accessible such as the oil filter and engine dipstick.

The stock fuel injection system is used unchanged save for a DowningAtlanta-designed "downstream" fuel pressure regulator
that is boost sensitive. No chip, EPROM, or other electronic changes are necessary - an important reliability point our engineers were careful to adhere to.

Our kit is built to BMW factory standards using the highest quality materials and components throughout. Our kit is comprised of high quality castings, laser cut high grade steel brackets which are heavily zinc plated for underhood longevity, high grade silicon hoses and gaskets, high quality fasteners, stainless steel clamps. No expense has been spared in making the entire kit as solid as the car it is going on.

We use the world-renown Eaton supercharger for its superior quality, low noise levels, and superb output characteristics. In fact, we are the only company approved by Eaton to engineer and design aftermarket kits for many applications, of which our BMW kit is one. The "partnership" between Eaton and DowningAtlanta has produced some excellent kits thus far of which there are over 1,100 now in daily use around the world.

Eaton has put hundreds of thousands of superchargers on the road since the start of their factory programs five years ago. The performance and longevity data from the field is phenomenal. Units regularly exceed the 120,000 mile life target and pressure output shows no degradation over time. This sort of reputation solidly reinforced our decision to use the Eaton design over other options: No other company has the sort of hours of research and real world testing to back up their claims of performance. The last thing we wanted was to ship systems that were simply another aftermarket supercharger kit. Using similar criteria to their successful Jaguar, Aston Martin, Buick, Mercedes Benz, and Ford programs, the Eaton engineers were able to provide the perfect blower for our BMW program that would exceed all factory quality levels for longevity and performance. These special blowers have become our competitive edge in the forced induction tuning field.

Just as Mercedes has chosen to use an Eaton supercharger on their new SLK roadster, you can now increase the performance of your four cylinder engine in the same fashion. Mercedes choose to use a force induced four cylinder for weight and performance reasons, actually surpassing their six cylinder engine in power, weight, and fuel consumption targets. We are purchasing identical displacement superchargers from Eaton, and using the same factory levels of engineering, have applied it to the BMW four cylinder. Just as Mercedes has done, we have exceeded six cylinder performance levels and ended up with a better balanced automobile thanks to the lower weight penalty.

What exactly is a supercharger doing to help make more power? Your engine, as designed by BMW, relies on the downward movement of a piston in a cylinder to suck fuel and air into the combustion chamber. The limits of power come from how much mixture can be sucked in given the time allotted by an open intake valve. By pressurizing the air, more can be forced in during a given period of time. Matching this with the appropriate amount of fuel makes more power across the board.

Our kit puts out linear boost by design - it is a belt driven air pump tied to the engine's crankshaft. For each increase in engine rpm, there is a correct and proportional increase in supercharger low. This trait maintains your BMW's carefully developed "feel" as you run up the gears.

The manner in which the Eaton Roots blowers make pressure is its own trick-of-the-trade. Boost comes in very low with these units, there is no need to wait for the supercharger to "spool up" or get into its sweet spot. We are able to create 2 psi of boost at 1000 rpm. While the M series BMW engines get a lot of great press, their horsepower numbers are peak values that occur at much higher rpm levels than with the DowningAtlanta supercharger.

The key to acceleration performance is the area under the torque curve. With a boost level coming in so low and staying strong up to redline, the entire torque curve is moved drastically upward with a DowningAtlanta supercharger. At every rpm point, the engine can do more "work" (i.e. accelerating the mass of the vehicle). When you only spend a few seconds in each gear, making each rpm segment do more work means much greater and more satisfying acceleration. You will never need to wait for your engine to "get up on the cam" with this sort of system. Exiting corners from a hot apex become an instantaneous exercise in motion. You go forward right now, right when you open the throttle. Launching from a standing start begins strongly from the first rotation of the tires. Passing on the road occurs immediately - you are up to speed instantly.

Our unique bypass system loops the supercharger output back into itself under part-throttle operation, effectively cutting the supercharger off. This maintains idle quality and highway fuel mileage, and reduces engine loading. In practice, your Eaton supercharger will be "engaged" no more than 25% of the time on your BMW, even with spirited driving. This is opposed to all other supercharger applications that drain power 100% of the time. This bypass system greatly reduces the load on your engine and drivetrain - you produce power only when you ask for it with the gas pedal.

We relocate your throttle upstream of the supercharger. We have the only kits on the market with this sophisticated feature combined with the bypass system. When you close the throttle, you are starving the blower for air, minutely controlling the amount of power you need or don't need. With a throttle downstream of the blower (as some manufacturers do), a closed throttle jams the supercharger with high pressure shock waves and spiking boost levels. If you immediately crack open your throttle after shutting it in this sort of system, the traffic jam of air between your blower and throttle can cause chronic driveability problems. We move the throttle upstream as a better solution. All of Eaton's factory systems utilize this same upstream throttle and bypass system for perfect levels of driveability and performance.

We have created dedicated fuel management schemes that perfectly match the needs of the BMW engine under boost. This is one of the most critical areas for a supercharger designer. Pushing in more air can be a matter of plumbing, up to a point. Meeting that air with the proper amount of fuel is a very complicated task, one that we performed on over hundreds of hours in our lab. Before you buy a kit, inquire about the test procedures used to validate the kit maker's fuel maps. Few have the resources to perform advanced engine dyno work or intensive on-road instrumentation, most rely on "seat of the pants" testing and some simple mathematical formulas.

Unlike a turbocharger, the Eaton supercharger does not contribute to underhood heat. Our kit only increases the intake charge air by 69 degrees even when underhood temperatures are over 150 degrees Fahrenheit. Because our supercharger is hung off of the engine in a position that receives large amounts of airflow, our total system efficiency is very high. It is not a stretch to state that the Eaton supercharger in our application acts as a sort of intercooler itself. We did not need to add the expense or complication of a flow-through intercooler and the loss of boost that comes with its use.

Our BMW kit installs in a straightforward fashion. The major component to be replaced is the stock intake manifold. No drilling or welding is required. The only part of your BMW that will be modified from stock is a housing box that the engine wiring harness routes through (no wires will need to be cut). A realistic length of time to install this kit yourself is from four to six hours. Some folks take all day, others might do it in two hours. If you are paying a mechanic to do it, budget five hours since he will need to spend some time checking out your car first.

When considering adding any performance item to your BMW, ask the manufacturer how many he has sold or has in stock. We build for large production runs of at 50 to 100 pieces of each part. This requires that our designs are well thought out and functional. Many companies in the aftermarket literally hand-make each part as orders come in. This may sound quaint and craftsman-like, but the variation in kit to kit is creating nightmares for the installers and owners.

We are geared up for high volume production which means a well proven and trouble free system will be under your hood. You won't be driving around with "Prototype #21" under your hood, playing test engineer for free for the kit maker.

Some final notes: The DowningAtlanta 1.8/1.9 liter BMW supercharger kit is undergoing certification to be 50 state legal by the EPA and California Air Resources Board. The supercharger unit comes with a full one year replacement warranty. Eaton blowers regularly exceed a life of 120,000 miles. No maintenance is required for our kit or for the supercharger itself.

We hope this review of our kit is helpful in your decision making process. Thanks for your interest! If you have any questions about the DowningAtlanta Supercharger, call us at 770-457-BMW2.

For Pricing and further information, Contact: Jim Goodroe at Downing Atlanta Inc.