Q&A

Where can i get spare parts for 745i turbo?

There are several online retailers selling OE/OEM parts, here are some i have used:

autohausaz.com
bmw2002.com
wallothnesch.com
shop.bmw-classic.com
schmiedmann.com/

For correct part numbers online go to see realoem.com

I have searched succesfully used parts from following sites:

ebay.de
ebay.com
ebay-kleinanzeigen.de
bimmerforums.com

How much boost can a stock M106 engine handle?

First thing likely to fail is old headgasket past 1 bar of pressure. It can be avoided with head studs and/or special headgasket. Then again stock fuel pump and turbocharger do not follow up.

What are main differences between M102 and M106 turbo engines?

Obvious are  displacement, compression, digital motor electronics and electric 4-spd transmission. Minor changes were made to turbocharger, intercooler, charge piping, piston cooling and boost pressure level.

How much it costs to rebuild engine parts by a professional workshop?

Here are some five years old prices from top of my head:

Short block without parts 1300 euros
Turbocharger 500 euros
Cylinder head 700 to 1000 euros
Fuel injectors 200 euros

What ways there are to identify my wastegate?

M106 parts sometimes have punched b-letter in cast iron part, with M102 part it is not true. M102 spring is much harder and you need two thumbs pushing it down, as M106 spring is “soft to touch”.

How using bigger fuel pump instead affects fuel pressure?

Fuel pressure is controlled by regulator in end of fuel rail. Regulator only adjusts pressure according to manifold air pressure. High capacity fuel pump can be loud though.

Can Nimonic exhaust valves be machined?

Yes, as long minimum edge thickness of 2 mm is respected. Valve must be replaced when minimum edge thickness cannot be held. Single OE exhaust valve is over 100 euros from BMW.

Is there online E23 repair manual available?

Yes — go to see http://repair.bmw-e23.com/

What is stock boost pressure in 745i turbo?

According to BMW documents it is 0.7 bar for M102 engine (tolerance +0 -0.1 bar ) and  about 0.4 bar for M106 engine. Often something else can be seen on M102 because of wastegate spring wear over times.

How many times can i resurface M30/M106 cylinder head?

Head with thickness of 128.1 mm was run many miles with Ross pistons. This was with thick OE head gasket. Ross spec for piston to valve cleareance is 2.3 mm on intake and 2.8 mm on exhaust.

Why there is no bypass valve in 3.4L engine?

With automatic transmission throttle plate is always open in acceleration. When throttle closes, position sensor signals computer to open wastegate solenoid, decreasing boost pressure to minimum.

How can i get 745i chip so i may increase my boost?

Chip can be done with PC, eprom burner, empty chip and binary file. Make your own binary as instructed in REPROGRAM-page. See CHIP-page for reference.

Is it possible to make +400hp from M106 engine with only chip and wastegate mod?

No — boost pressure of 1 bar should yield max. 350hp on crankshaft.

What happens if i install M102 wastegate to M106 engine?

Spring rate is three-fold and control line disconnect makes boost go dangerously high. In general boost comes sooner and boost level is set to 0.6 bar, shortcutting to much better performance. Chip is needed to avoid dreaded fuel/boost cut.

What happens if i install 024 ECU or Chip to my engine? 

024 ECU was for emission controls with EGR system (exhaust gas recirculation). Installing 024 ECU instead of 013 corresponds to EGR delete. Part throttle improvements (spark timing, boost control) are shadowed by downside (lean mixture).

Where are ground straps located in E23 745i engine bay?

First is on engine hood right hinge, the second on cyl. head end on firewall side and third from AFM to cyl. head. Battery negative connects directly to left engine feet (and splits from battery terminal to fuse box bottom). Also alternator is grounded to oil filter head.

Is there any discussion forum dedicated to E23 745i?

Yes — go to visit: http://bmwturbos.scottiesharpe.com/