Engine: BMW 'M20B25', 2.5 liter originally natural aspirated, but now intercooled and turbocharged inline six.

One might question, is the engine in question capable of handling increased power level, and how much it can handle reliably ?

About 'M20B25'..

* pistons seems quite good in increased 'brake mean effective pressure' vice, since these do not contain steel 'thermal expansion control' section and oil ring area cuts often found on natural aspirated engine pistons.

* connecting rods, good for 300 hp, also rod end cap mounting uses bolts not weak bolt and nut combination.

* oil to air engine oil cooler standard.

* I've helped a guy to install a genboard v3 in a car like this, we are currently boosting 1.3-1.4 bar on that one, only mod to the engine is machined pistons to lower compression, He is using a garrett GT37 turbo (similiar to holset HX40) and 465 cc injectors, recently drove 11.7 down the quarter mile //Emil

However, there is an caveat emptor 'as always' :)

* coolant circulation in standard form 'sucks' in this type engine, somewhat limiting amount of power level.

* valve rockers are made of aluminium, limiting maximum revolutions per minute (std redline near 5600 1/min).

* standard rod and big end bearings are 'quite soft' to handle increased bearing loads.

* no piston cooling oil spray nozzles.

* clutch needs to upgrade also, fex...

** Sachs '88 3082 999618' pressure plate

***Max. transmittable engine torque:

***Organic facing: 415 Nm

***Org. special facing: 480 Nm

***Sintered plate: 530 Nm

Hence, goal was set to 300 hp max and also limiting torque (to around 400 Nm) with electronic boost control, partly to save driveline (gearbox, propellel shaft and rear differential).

Original components (from Motronic 1.3 installation) used are

* Crankshaft Speed/Angular Position Sensor (CS)

* Idle Air/Speed Control Valve (IAS)

* Ignition Coil

* fuel pump

* Coolant temperature sensor (CLT)

Components in VEMS installation:

* Crankshaft Speed/Angular Position Sensor (CS)

** Standard BMW/Bosch (E30, M20B25) 60-2 trigger wheel with variable reluctance (magnetic type) sensor. Standard BMW item manufactured by Febi-Bilstein - AB Technik.

** 510 ohm +/- 5%, measured 531 ohm from mine.

** for connector pinout, see the wiring diagram MembersPage/BengtR/BMW/WiringDiagram

* Manifold Absolute Pressure sensor (MAP)

** Genboard mounted (VEMS internal) Motorola (MPX4250AP) (2.5 kg/cm2) absolute pressure sensor.

* Coolant temperature sensor. (CLT)

** Standard Bosch item: 0 280 130 026

* Inlet Air Temperature sensor (IAT)

** FAE 33180

** Installed to throttle body immediately at 'upstream' of airflow on low throttle opening.

** Note ! In 'original' BMW Motronic 1.3 ECU installation, IAT is inside Air flow meter.

* Throttle Position Sensor (TPS)

** Standard OEM spare part 'SE04-M'. 2.6 - 0.88 kOhm angular potentiometer, without idle and full throttle microswitch.

** Adaptor plate to mount resistor TPS needed, lasercut it from 3 mm aluminium.

** ISO Din G-code (Bystronic) MembersPage/BengtR/BMW/TPSSensorAdapterPlate

** Note ! In Motronic throttle position is just idle, 'in between' and full throttle ie. contains two microswitch.

* Idle Air/Speed Control Valve (IAS)

** Standard BMW/Bosch item 0 280 140 509 (rotary valve type).

** for connector pinout, see the wiring diagram MembersPage/BengtR/WiringDiagram

** for driwing it, see MembersPage/GergelyLezsak/IdleControl

* Lambda Sensor (LS)

** Wide-Band Lambda Sensor (Bosch LSU4). 5 wire special connector, ordered this with the wiring loom connector from VEMS shop.

** LSU4 Bosch item 0 258 007 057.

* Ignition Coil (Coil)

** <WAS>Standard spark delivery via distributor with original BMW/Bosch 'TZI' coil</WAS>. Actually did not work at higher revolutions than standard maximum revolution is.

** Now -> * MembersPage/BengtR/BMW/Ignition

* Ignition module (IgnMod)

** <WAS>'dummy' (no dwell control in module) Bosch '0 227 100 124' ignition module, originated among others from Peugeot 605 V6 3.0 SV.

** Using 'IGN 00' channel to drive. -> Actually coil was driven directly, after few misfires at higher revs, without separate ignition module.

</WAS>

* Boost control valve (BCV)

** Standard wastegate actuator control 'so called' 'N75' valve, VW/Audi origin; turbo control valve VW part code: '0589 062 83F'

* Turbo Control

** Turbocharger Holset HX30 center core with custom compressor and turbine, without variable nozzle turbine. Hence not needing control device.

* Injectors

** Bigger injectors than in standard naturally aspirated BMW engine were selected to cope with increased power level (from 170 PS to around 250-300 PS).

** For maximum fuel vaporisation modern 2 to 6 hole injectors are preferable.

** Bosch: B 280 431 824/20 item. Has four spray holes with wire splitter, four 'atomization helper' air channels, high impedance (~ 16 ohm). 261 g/min approx. 351 cc/min (N-Heptane).