I just bought a 1988 745 Turbo, and according to the service records the car has the Turbo+ system. Unfortunately accoring to the records the PO declined replacing a leaking Turbo+ "acculator", which I'm guessing is a service manager's creative spelling of "accumulator". So now I have 2 questions: Is there an accumulator in the system and where would it be, and how can I tell by looking whether the Turbo+ components are still installed? I see the turbo, the air connections, and a valve that I think is for the wastegate - is there something that would confirm whether it's the Turbo+ system?

Thanks

Zack
1980 245DL M46 272k
1988 745Ti M46 186k

Turbo + was a system that "fooled" the wastegate by bleeding some of the actual turbo pressure before reaching the wastegate diaphragm. It really only has two parts: The system controller (brain) that got 12V and engine speed info at the ignition coil, and a connection to the normally unused wide open contacts of the throttle sensor. It operates a 3-way solenoid teed into the wastegate hose. Both components are mounted on the frontside of the air filter box by one philips screw each. Besides the presence of these, finding two push-ons at each terminal of the ignition coil would be a clue that it's still connected.

At wide-open throttle, at engine speeds over (I think) 3,700 RPM, some pressure to the wastegate is vented to atmosphere causing the controlled boost pressure to be higher than its actual setting. After 11 seconds of raised boost at WOT, the system will go back to normal and lower boost to standard setting to prevent engine damage.

It's easy to see if it works on the road. Mash the gas and watch the gauge, let the pedal up just a fraction (maybe 1/4") and you'll see the gauge drop a bit. Stepping hard should cause the gauge to return to the higher boost level.

The dealer maght have called the wastegate diaphragm an accumulator, or the Turbo+ plus solenoid an actuator.

accumulators were installed on the oil cooled side of the turbos. the idea is to fill the accum. while running, then after shut off, the accum. empties the cold oil past the hot turbo. this was not part of the turbo plus package. i forget exactly what was in the turbo+ kit. the box was a little bigger than a radio box and had a harness and some other stuff, i think a new brain, too. been a looong time. hopefully, dick in falls church will see this and jump in. he knows far better than i do. good luck, chuck.