SMG Components for the HPF M3 Turbo System

Many of you may or may not know how the SMG works, so I'll explain some of the things we've learned along the way. There is a separate computer that controls when the car shifts in an SMG M3 as opposed to a manual M3. The transmission and clutch are basically the same in the SMG M3 as in the manual M3. The main difference is that a separate computer is doing the shifting and there is no clutch pedal.

The SMG computer determines when the car should be shifted and actuates the slave cylinder to disengage and re-engage the clutch. As shifting can occur when the accelerator pedal is on the floor as well as part throttle, the SMG computer must tell the DME that it is time to shift, and how quickly it is doing the shifting. If this doesn't occur, the RPM's would go sky high any time the computer shifts as the load is immediately gone when the clutch is disengaged.

In order to provide similar shifting with an aftermarket turbo system and engine management a few things had to be engineered and produced. For starters, the SMG clutch fluid normally is housed in a section of the factory intake manifold however the factory intake manifold is not designed to hold boost pressure and must be replaced. In order to run boost, we designed our own intake manifold which did not include an area to hold SMG fluid. That container had to be designed to fit within the limited space available, be resistant to clutch fluid, hold the required amount of fluid, and have fittings and a cap that can vent but not leak as well as attach to the factory clutch lines. The container we designed is shown below.

The second major component is the communication between the SMG computer and our EMS. This required the creation of a separate SMG controller box (pictured below). The controller box must allow the SMG transmission to effectively communicate what it's doing to the EMS otherwise RPM's will not be controlled properly on acceleration and deceleration.